Scholarly article on topic ' Regiospecific Anomerisation of Acylated Glycosyl Azides and Benzoylated Disaccharides by Using TiCl 4 '

Regiospecific Anomerisation of Acylated Glycosyl Azides and Benzoylated Disaccharides by Using TiCl 4 Academic research paper on "Chemical sciences"

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Academic research paper on topic " Regiospecific Anomerisation of Acylated Glycosyl Azides and Benzoylated Disaccharides by Using TiCl 4 "

CHEMISTRY _

A EUROPEAN JOURNAL

DOI: 10.1002/chem.201302572

¿fcVChemPubSoc

rf* Europe

Regiospecific Anomerisation of Acylated Glycosyl Azides and Benzoylated

Disaccharides by Using TiCl4

Mark Farrell, Jian Zhou, and Paul V. Murphy*[a]

Abstract: Chelation induced anomerisation is promoted when Lewis acids, such as TiCl4 or SnCl4, coordinate to the pyranose ring oxygen atom and another site, giving rise to endocyclic cleavage and isomerisation to the more stable anomer. In this research regiospecific site-directed anomerisation is demonstrated. TiCl4 (2.5 equiv) was employed to induce anomerisation of 15 glycosyl azide and disaccharide sub-

strates of low reactivity, and high yields (> 75%) and stereoselectivies (a/p > 9:1) were achieved. The examples included glucopyranuronate, galactopyra-nuronate and mannopyranuronate as well as N-acetylated glucopyranuronate

Keywords: anomerisation • glycur-onic acid • Lewis acids • protecting groups • regioselectivity

and galactopyranuronate derivatives. A disaccharide with the linkage

found in polygalacturonan was included. The use of benzoylated saccharides was found to be important in disaccharide anomerisation as attempts to isomerise related acetyl protected and 2,3-carbonate protected derivatives were not successful.

Introduction

Glycosides are ubiquitous and important to life, health, food, materials, energy and the environment. Despite progress, it is still viewed as being important to improve the ste-reoselective synthesis of glycosides.'1,2] Previous studies from our laboratory have shown that the presence of a carboxylic acid or a derivative (e.g., ester or amide) at the C-5 of a sac-charide, as found in glycuronic acids, leads to a significant increase in the rate of anomerisation promoted by Lewis acids, such as TiCl4 or SnCl4.'3' This is explained by chelation of the pyranose ring oxygen atom and C-6 carbonyl group to the Lewis acid facilitating endocyclic cleavage and consequent glycoside bond isomerisation to the thermodynamical-ly more stable anomer (Scheme 1). A study of factors influencing anomerisation of glucose and galactose derivatives'4' has been carried out, with the impact of protecting group (e.g., benzoylation>acetylation) and promoter (TiCl4> SnCl4) on the rate and stereoselectivity of the reaction being

S-glycoside A = aglycon a-glycoside

Scheme 1. Lewis acid promoted anomerisation by endocyclic cleavage.

[a] M. Farrell, Dr. J. Zhou, Prof. Dr. P. V. Murphy

School of Chemistry, National University of Ireland Galway University Road, Galway (Ireland) E-mail : paul.v.murphy@nuigalway.ie □ Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/chem.20132752.

established.'5' In previous studies the presence of an azide or a saccharide residue at the anomeric carbon led to a significant reduction in reactivity of the linkage towards anomerisation. Herein we now report the generation of a-configured acylated glycosyl azides and benzoylated disaccharides using TiCl4 promoted anomerisation of the corresponding p-linked precursors. This study shows that anomerisation is induced in a regiospecific manner at the glycuronic acid anomeric carbon, providing additional evidence for the significant rate enhancement for the Lewis acid in the presence of the C-6 carbonyl group. In the case of the disaccharides the use of benzoylated substrates was found to be important in achieving anomerisation.

Results and Discussion

This study commenced with the synthesis of a variety of gly-cosyl azide and disaccharide substrates. The methyl ester 1 was prepared as previously reported.'6' Its analogous allyl ester 2 was generated via 1 by saponification, which was followed by the base-mediated allylation of the carboxylic acid and subsequent acetylation.'3' The bromide 3 was prepared from D-galacturonic acid through acetylation,'7' subsequent methyl ester formation and then treatment with HBr/AcOH (Scheme 2). Treatment of this bromide with sodium azide in DMF in an ultrasonic bath gave the azide 4.'6' The p-manno-pyranosyl azide 6 was prepared from 5 via a glycosyl iodide.'8' This azide 6 was then subjected to Zemplen deace-tylation followed by one pot silylation-benzoylation to give the TBDPS derivative 7. Removal of the the silyl protecting group, followed by oxidation and base-mediated esterifica-tion gave 8.

©WILEY %

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FULL PAPER

AcO AcO

1. LiOH, THF, H20,

MeOH, RT 16 h, 93% -►

'3 2. NaHC03, ally I iodide, DMF, RT 16 h 3. Ac20, DMAP, RT 16 h, 71% (two steps)

AcO AcO

C02Allyl

H?C02H 1. HCI04, Ac20,

0 °C to RT, 3 h HO^^^fcA 2. NaHC03, Mel,

\ | DMF, RT, 16 h, 71%

H0OH -

3. HBr in AcOH, CH2CI2, D-Galacturonic acid 0 °C to RT 5 h, 65%

Ac? C02Me

AcO^^^A AcO ¿r

NaN3, DMF

Sonication 92%

AcO co2Me

AcO AcO AcO

cO—y OAc

1. I2, Et3SiH, CH2CI2, 40 °C, 20 min

AcO AcO „ AcO

cO—y OAc

' 2. Bu4NN3, CH2CI2 UAC RT, 16 h

84% over 2 steps

1. NaOMe, MeOH RT 1 h, 94%

2. TBDPS-CI, pyridine, 0 °C to RT, 16 h, then BzCI, pyridine, 0 °C to RT, 16 h, 76%

TBDPSO

BzO BzO

1. HF, pyridine, THF, RT

16 h, 85% -3

2. TEMPO, BAIB ACN/H20 (3:1) RT, 5h

3. Mel, NaHC03 DMF, RT 16 h 24%, 2 steps

Me02C OBz BzO-BzO-

Scheme 2. Synthesis of p-azides 2, 4 and 8.

An approach similar to that used for the mannuronic acid derivative 8 was adopted for the preparation of the 2-deoxy-N-acetyl-glycuronides (Scheme 3). The a-glycosyl bromides 9 and 10 were converted to the corresponding p-azides using

AcO Ac

.OTBDPS

1. Bu4NN3, CH2CI2, RT Bz0

9 (Glc)

10 (Gal)

2. NaOMe, MeOH, RT, 1 h

3. TBDPS-CI, pyridine, 0°C to RT, 16 h, then BzCI, 0°C to RT 16 h

11 Glc 37%

12 Gal 35%

1. HF-pyridine, THF, RT, 16 h -1

2. TEMPO, BAIB, MeCN/H20 (3:1), RT, 5h

3. p-TsOH, MeOH, RT, 16 h

BzO BzO

13 Glc 42%

14 Gal 47%

Scheme 3. Synthesis of p-azides 13 and 14.

tetrabutylammonium azide in CH2Cl2.[9] These azides were then treated with sodium methoxide in methanol to bring about O-deacetylation and this was followed by one pot sily-lation-benzoylation to give 11 and 12.[10] The TBDPS group was removed from 11 and 12 using HF/pyridine and the resulting primary alcohol was oxidised to the carboxylic acid using TEMPO/BAIB. Initial attempts to prepare the methyl ester by base-mediated esterification as described for other acids above gave low yields. However, the esterification with p-toluenesulfonic acid in MeOH gave the desired azides 13 and 14 in improved yields.

The preparation of the disaccharide 20 was carried out from azide 15.[11] Deacetylation followed by treatment of 1,3-dichloro-1,1,3,3-tetraisopropyldisiloxane (TIPDSCl2) in the presence of pyridine gave 16 in which both 4- and 6-OH groups are protected. The TIPDS group was then rearranged, using p-toluenesulfonic acid in DMF, so as to protect the 3- and 4-OH groups.[12] Then oxidation of the primary alcohol to the acid using TEMPO/BAIB followed by esterification gave 17. Glycosidation using the trichloroaceti-midate donor 18 gave 19.[13] The TIPDS protecting group was removed using HCl/MeOH and subsequent treatment with benzoyl chloride and pyridine gave the disaccharide 20 (Scheme 4).

Scheme 4. Synthesis of 20.

Scheme 5. Synthesis of 27.

The synthesis of disaccharide 27 began from the allyl glycoside 21 (Scheme 5).[14] Deacetylation followed by treatment with TBDPSCl in the presence of pyridine and subsequent benzoylation gave 22. Removal of the TBDPS group followed by oxidation and esterification gave 23. The allyl group was removed using PdCl2 to give a hemiacetal. Subsequent treatment of this hemiacetal with trichloroacetonitrile in the presence of DBU gave donor 24.[15] The disilyloxy derivative 25, prepared from 16 (Scheme 3), was used to give acceptor 26 through regioselective acetylation at the 6-OH. The glycoside bond forming reaction between 24 and 26 then gave the disaccharide 27.

The glucosyl azide 28, prepared by deacetylation of 15, was next regioselectively silylated using TBDPSCl. The remaining hydroxyl groups were benzoylated and removal of the TBDPS group with TBAF gave acceptor 29. The glycoside coupling reaction of 29 with 24 gave disaccharide 30 (Scheme 6).

The diol 16 was used to prepare 31 and 32 (Scheme 7). Thus, the treatment of 16 with acetyl chloride in the presence of collidine led to the regiose-lective introduction of an acetyl group at the 2-OH.[16] Subsequent glycosidation of this acceptor with 24 gave 31. Removal of the disilyloxy group using HCl/MeOH also led to the selective removal of the acetate from 31 but not the benzoate protecting groups.

The subsequent benzoylation Scheme 7. Synthesis of 32.

/' Pr \

/Pr —Si-\

/'Pr I

Si —/'Pr

оЛЬ

Scheme 6. Synthesis of 30.

of the free OH groups in the aglycon of the intermediate gave 32.

Azide 28 was used to prepare 34 and 35. Treatment of 28 with dimethoxypropane under acidic conditions led to intro-

1. AcCI, collidine, 16 h

-35 °C to RT, 78% -►

2. 24, TMSOTf, 4 Â mol. Me02C sieves, CH2CI2, 0 °C to BzO RT, 1 h, 82% BzO

1. HCl/MeOH, RT 16 h -1

2. BzCI, pyridine, 0 °C to RT, 16 h, 67%

Me02C BzO " BzO

duction of an acetonide group at the 4- and 6-OH groups. Then treatment with TIPDSCl2 in pyridine placed the TIPDS protecting group onto the 2- and 3-OH groups. Removal of the acetonide and regioselective acetylation gave 33. The glycoside coupling treatment of 33 with 24 gave di-saccharide 34. Concomitant removal of the TIPDS protecting group and the acetate using Amberlyst-15H+ in methanol followed by benzoylation of the free OH groups gave 35 (Scheme 8).

Scheme 8. Synthesis of 35.

OH 1. TrCI, pyridine,

i ^OH 80 °C, 3 h

HOA^^X^OH 2. BzCI, pyridine,

\ 0°C, 16 h

0H 3. H?S04, CHoCI

D-galactose

i2ou4, L/n2oi2, 1 h, 61%, 3 steps

1. TEMPO, BAIB

2. Mel, NaHC03 DMF, 2 h, 78% over 2 steps

3. HBr/AcOH, 6 h

4. Ag2C03, acetone/H20 16 h, 73%, 2 steps

5. DBU, CCI3CN, CH2CI2, 5 h, 61%

Bz? C02Me

BzO ' 37

1. PhCHOMe2 CSA, CHCI3, 92%

2. BzCI, pyridine, 16 h, 95%

hoA^^X

HO I 3. pTsOH, MeOH, OMe 16 h 90%

1. 31, TMSOTf -5 °C, CH2CI2 1 h, 77% Bz0

2. BzCI, pyridine, 24 h, 90%

Bz? C02Me BzO

Scheme 9. Synthesis of 39.

41 with the galactose acceptor 42 gave the disaccharide 43 in good yield.[17] Then the removal of the TBDPS, followed by oxidation, esterification, removal of the benzyl groups and finally benzoylation gave 44 (Scheme 10).

With a series of disaccharides based on glucuronic acid in hand, our attention next turned to preparation of disaccha-rides based on galacturonic acid. Hence, the donor 37 was required and its preparation was commenced from D-galac-tose which was first tritylated at the 6-OH group and then the remaining hydroxyl groups then benzoylated. Acid catalysed hydrolysis of the trityl group gave 36. Subsequent oxidation of the primary alcohol and esterification followed by glycosyl bromide formation and silver ion promoted hydrolysis of the bromide gave a hemiacetal. Treatment of the hemiacetal with trichloroacetonitrile in the presence of DBU gave 37. The acceptor 38 was prepared from methyl a-D-galactopyranoside by introduction of a benzylidene at the 4- and 6-OH groups, benzoylation of the 2- and 3-OH groups and then removal of the benzylidene. The glycoside coupling reaction of 37 and diol 38 was regioselective with bond formation occurring at the primary alcohol. Subsequent benzoylation of the initially formed glycoside gave 6-O-linked 39 (Scheme 9).

The 4-O-linked disaccharide 44 was prepared starting from thioglycoside 40. Deacetylation of 40 followed by selective introduction of the TBDPS group at the primary alcohol and subsequent benzoylation gave 41. The coupling of

Scheme 10. Synthesis of 44.

CHEMISTRY

P. V. Murphy et al.

A EUROPEAN JOURNAL

The anomerisation study commenced with a range of substrates in hand. This began with the azide 1 (Table 1, entry 1), which when subjected to treatment with SnCl4 (0.5 equiv) was only partially converted (~ 5% conversion)

Table 1. Anomerisation of glycosyl azides.'a'

Entry Substrate (ß-anomer) Product (a-anomer)

Reagents, conditions[b]

a/ß ratio (yield [%])

AcO AcO

oX^L- N

AcO' AcO.

C02Me 45 AcO¿

AcO AcO

C02Allyl

2 AcO AcC>C02Me

Me02C OBz Bzo—¿~L-o BzO-X-Jfci^N

BzO BzO.

13 AcHN °C02Me

BzO' BzO' BzO

iS^OBz

Ac^^Me

Me02C OBz BzO—t-L -0 BzO-X-J«^

Bzo^-^L-o 49AcHN1

Bz°C02Me

BZO-^0' BzO'S/^OBz

[a] Experimental and analytical data of all compounds are available in the Supporting Information. [b] A: SnCl4 (0.5 equiv) CH2Cl2, 20°C, 24 h. B : TiCl4 (2.5 equiv) CH2Cl2, -15 °C, 48 h.

to the a-anomer 45 after 24 h. This observation is indicative of a slow anomerisation reaction as reactions of simpler ace-tylated-O-glycosides were complete under these conditions.'5' However, when 1 was left to stand in the presence of TiCl4 in 2.5-fold excess (entry 2) in a freezer at —15 to -18 °C for 48 h then 45 was isolated in high yield (94%) and with high stereoselectivity (ratio of 1/45 = 19:1). The use of TiCl4 under these conditions was found to be successful for a range of the glycosyl azides (Table 1, entries 2-8). The yields of the products (> 82%) and stereoselectivities (a/p > 9 :1) were high. The glycosyl azides successfully anomerised included glucuronic acid, galacturonic acid, mannuronic acid and 2-deoxy-2-acetamido-D-glucuronic acid and 2-deoxy-2-acetamido-galacturonic acid derivatives. In the latter two examples the presence of the acetamido group in 13/14 did not impair the glycosyl azide isomerisation which gave 49/50 ste-reospecifically (entries 6 and 7). The regiospecific anomeri-sation of the glycosyl azide linkage in disaccharide 20 was also achieved (entry 8), which demonstrated clearly the rate enhancement brought about by the presence of the glucur-onic acid carboxylate leading to the site-directed anomerisa-

tion. The excellent stereoselectivities observed are in part due to the use of 2.5-fold excess TiCl4. In an earlier study on O- and S-glycosides the use of 2.5-3.0 equivalents of TiCl4 was found to be optimum in terms of maximizing the a/ p ratio. The impact of Lewis acid concentration on stereoselectivity of the glycosyl azides is explained by coordination of the Lewis acid at higher concentrations to the anomeric azide, which influences the anomer equilibrium. It is proposed that coordination at this site leads to enhancement of the anomeric effect. The use of TiCl4 at lower or higher amounts gives rise to a reduction in stereoselectivity. The use of TiCl4 at higher concentration than 0.5 equiv also enhances the rate, which is most likely important to induce isomerisation of the less reactive substrates as is the case with the glycosyl azides.

Having successfully achieved the anomerisation of the glycosyl azides, we next turned our attention to disaccharide linkages. In previous research we observed the partial anomerisation (~ 33 %) of an acetylated disaccharide using 0.5 equiv TiCl4 after 24 h in nitromethane. Encouraged that use of 2.5 equivalents of TiCl4 facilitated the rearrangement of glycosyl azides we explored these conditions with the series of disaccharides shown in Table 2 (entries 1-8). Gratifyingly, these disac-charides were all successfully isomerised to give the 1,2-cis glycosides 52-59. The yields were > 75% and the stereoselectivity greater than 9:1. In a number of cases the selectivity was > 95:5, with the p-configured starting disaccharide not being detected in the product mixture by 1H NMR spectroscopy. In the case of the reaction of 44 conversion of its methyl glycoside to the corresponding glycosyl chloride occurred to a degree (~ 15%), explaining the lower yield of 56. Anomerisation of disaccharides with a variety of glycosidic linkages (1^6, 1! 4, 1 >3 and 1!2) were all achieved and the successful examples included both glucuronic acid and galacturonic acid linkages. In contrast with the azides in Table 1, the glycosyl azide group in each disaccharide in Table 2 did not anomer-ise. Anomerisation occurred only at the site where efficient chelation to the C-6 carbonyl group could occur. The regio-specific nature of the reaction is worth noting and this provides additional convincing evidence for the rate enhancing effect of the C-6 carbonyl group. The TIPDS protecting group (Table 2, entries 6-8) was also highly compatible with the reaction conditions, especially when located on the agly-con. This contrasted with attempted anomerisation of the azides 17 and 19 (Scheme 4), which were not successful. The TIPDS group may hinder the approach of the Lewis acid in 17/19. The disilyloxy group would be less likely to cause steric hindrance at the chelation site when placed on the aglycon.

The results described herein demonstrate a broader application of anomerisation for acylated substrates than hereto-

5:95 (90)

95:5 (91)

94:6 (82)

> 97:3 (93)

> 95:5 (90)

> 95:5 (90)

9:1 (87)

> 90:10 (94)

Table 2. Anomerisation of disaccharides.

Substrate (ß-anomer)

Product (a-anomer)

Reagents, conditions'''

a/ß ratio (yield [%])

'Pr, (Pr

/Pr-Si-o. /Pr

O-V^ „

-Si—o^ \

Me02C BzO BzO'

—fA^O BzO-. r-OBz BzC) N3

?°2C\ O n T~Of\c BzO y SLn

i Pr' \ -Si-

39 BZ° Bz0^feö\)Me

-Os ./Pr

> 90:10 (92)

95:5 (94)

95:5 (87)

tion would have been fast in these cases given that they contain both the 2,3-trans carbonate and C-6 carbonyl group, both of which promote endocyclic cleavage. However, the reaction of 61-65 led to intractable products when subjected to various Lewis acid promoters. Anomerisation of more reactive saccharides (e.g. , benzyl protected saccharides) without the 2,3-trans carbamate or 2,3-trans carbonate, including that promoted by TiCl4, have been carried out

> 90:10 (92)

95:5 (94)

95:5 (90)

[b] B: TiCl4 (2.5 equiv) CH2Cl2, -15°C, 48 h; C: TiCl4 (2.5 equiv), CH2Cl2, -20°C, 36 h.

fore described. The presence of the benzoyl groups in the saccharides in which anomerisation takes place is important as the anomerisation reaction of 60 under the conditions described were not successful. Anomerisation with weaker Lewis acids and also SnCl4 has been reported for pyrano-sides which have 2,3-trans carbamate or 2,3-trans carbonate groups, which demonstrate increased susceptibility to endo-cyclic cleavage and anomerisation due to inherent strain.[18, 19] The disaccharides 61-65 were also investigated as part of this work as it had been anticipated that anomerisa-

previously and this has included some examples of disac-charide anomerisation.'19,20' There are reports in which anomerisation with benzylated saccharides give high yields but in other cases they proceed with low yield (< 50%). It is possible that TiCl4 could cause the removal of benzyl groups, which would complicate the anomerisation of benzylated substrates. In our hands acetyl and benzoyl groups have been found to be stable to TiCl4. Although benzoyl groups are more electron withdrawing than benzyl groups and acetate groups they still confer sufficient reactivity to enable the >95:5 (92) anomerisation and they are faster than for acetylated substrates. In a previous study the SnCl4 promoted anomerisation of 2,3,4-tri-O-benzoylated glu->90:10 (75) curonides were 2-3-times faster than corresponding tri-O-acetylated analogues. This contrasts with impact of ben-zoate groups compared to acetate groups on reactivity in other carbohydrate-based model systems.'21' It is not clear yet why it is the case that anomerisation becomes possible for the benzoylated disaccharides compared to acetylated derivatives. Aside from our own investigations and that shown herein there has been limited investigation to date on anomerisation of acylated disaccharides.'22'

In terms of application there is potential for anomerisa-tion of glycuronic acids and some applications have been recently described, such as the synthesis of S- and O-glyco-lipids.'23' Importantly, homogalacturonan is a major pectic

polymer of a-homogalacturonan and compounds related to 59 could be envisaged as building blocks for the synthesis of homogalacturonan fragments, which would be important for plant scientists.[24] The conditions described herein provide an alternative access to a-glycuronides.[25] a-Glycuronides are components of bacterial polysaccharides and hemicellu-loses, providing a range of interesting target molecules. Although the presence of the uronate is necessary for the most efficient anomerisations,[26] it is possible to subsequently chemically transform the carboxylic acid group of the uro-nate (e.g., reduction) to increase the diversity of products that can be obtained. The azide group is the precursor to tri-azole-based conjugates prepared by metal catalysed alkyne-azide cycloaddition reactions.[27] Glycosyl triazoles have been prepared from the corresponding azide and a-glycosyl azides have also been used for the synthesis of a-glycosyl amides.[11b,28,29] The number of a-glycosyl azides is limited in the literature and, until now, these have usually been prepared by nucleophilic substitution of the b-glycosyl halide.[30] In summary, we have described chelation-induced anom-erisation of acylated glycosyl azides and disaccharide substrates. The work has included regiospecific or site-directed anomerisation. Further exploration of this reaction, in terms of understanding how the rates can be enhanced, including improving the activity of the promoter is under way. There are intriguing possibilities if regioselective or site-directed anomerisation of higher-order oligosaccharides or polysac-charides can ultimately be achieved. Understanding factors that influence rates of anomerisation will help chemists to achieve isomerisation of glycosidic linkages in increasingly complex substrates.

Experimental Section

Methyl 2,3,4-tri-O-acetyl-1-azido-1-deoxy-ß-D-galactopyranuronate (4):

The bromide 3[31,32] (0.25 g, 0.63 mmol) and NaN3 (0.41 g, 6.3 mmol) were placed in a Biotage microwave vial and then DMF (2.5 mL) was added and the vial was sealed and the resulting suspension was placed in an ultrasonic bath and then sonicated for 15-20 min. The vial was opened and the solution was poured on H2O (15 mL) and extracted twice with EtOAc (15 mL). The combined organic extracts were washed with H2O (40 mL), brine (40 mL), dried over Na2SO4, filtered and the solvent was

removed under diminished pressure. Flash chromatography of the residue (petroleum ether/EtOAc 1:1) gave 4 (0.21 g, 92%) as a white solid; [a]D = 16.3 (c 0.6, CH2Cl2); 1H NMR (500 MHz, CDCl3): d = 5.74 (dd, 3J-(H,H) = 3.5, 1.4 Hz, 1H; H-4), 5.19 (dd, 3/(H,H) = 10.4, 8.8 Hz, 1H; H-2), 5.09 (dd, 3/(H,H) = 10.4, 3.5 Hz, 1H; H-3), 4.67 (d, 3/(H,H) = 8.8 Hz, 1H; H-1), 4.39 (d, 3/(H,H) = 1.4 Hz, 1H; H-5), 3.78 (s, 3H; CO2CH3), 2.13 (s, 3H; COCH3), 2.09 (s, 3H; COCH3), 2.00ppm (s, 3H; COCH3); 13C NMR (126 MHz, CDCl3): d = 170.1 (CO2CH3), 169.8, 169.4, 165.9 (3x COCH3), 88.6 (C-1), 74.2 (C-5), 70.5 (C-3), 68.1 (C-4), 67.8 (C-2), 53.1 (CO2CH3), 20.8, 20.7ppm (2s) (3xCOCH3); IR (film): n = 2980, 2119, 1771, 1737, 1273, 1239, 1210, 1051 cm1; ESI-HRMS calcd for C13H17O9N3Na 382.0862, found m/z (%) 382.0866 [M+Na] + . 2,3,4,6-Tetra-O-acetyl-p-D-mannopyranosyl azide (6): Penta-O-acetyl-a-D-mannose 5 (3 g, 7.7 mmol) was dissolved in CH2Cl2 (80 mL), I2 (2.74 g, 10.8 mmol) was added followed by the slow addition of Et3SiH (1.72 mL, 10.8 mmol ; warning exothermic). The reaction was heated at reflux for 20 min and was then cooled to room temperature, diluted with CH2Cl2 (80 mL) and washed with satd. aq. NaHCO3 (150 mL) containing 10% Na2S2O3. The aqueous phase was further extracted with CH2Cl2 (50 mL) and the combined organic extracts were dried over Na2SO4, filtered and the solvent was removed under diminished pressure. The residual glyco-syl iodide was taken up in CH2Cl2 (60 mL) and tetrabutylammonium azide (3.3 g, 11.6 mmol) was added. The reaction mixture was stirred, overnight, before being diluted with CH2Cl2 (50 mL) and extracting with 1 m HCl (100 mL). The aqueous phase was further washed with CH2Cl2 (30 mL) and the combined organic extracts were dried over Na2SO4, filtered and the solvent was removed under diminished pressure. Flash chromatography of the residue (petroleum ether/EtOAc 1:1) gave 6 (2.1 g, 64%) as a white solid; [a]D = -70.6 (c 0.3, CH2Cl2); 1HNMR (500 MHz, CDCl3): d = 5.44 (dd, 3/(H,H) = 3.3, 1.3 Hz, 1H; H-2), 5.26 (aptt, 3/(H,H) = 10.0 Hz, 1H; H-4), 5.04 (dd, 3/(H,H) = 10.1, 3.3 Hz, 1H; H-3), 4.73 (d, 3/(H,H) = 1.3 Hz, 1H; H-1), 4.28 (dd, 2/(H,H) = 12.4 Hz, 3J-(H,H) = 5.7 Hz, 1H; H-6a), 4.20 (dd, 2/(H, H) = 12.4 Hz, 3J(H,H) =

2.5 Hz, 1H; H-6b), 3.76 (ddd, 3/(H,H) = 10.0, 5.7, 2.5 Hz, 1H; H-5), 2.20 (s, 3H; COCH3), 2.11 (s, 3H; COCH3), 2.05 (s, 3H; COCH3), 1.99 ppm (s, 3H; COCH3); 13CNMR (126MHz, CDCl3): d = 170.6, 169.9 (2s), 169.5 (each COCH3), 85.1 (C-1), 74.6 (C-5), 70.9 (C-3), 69.2 (C-2), 65.3 (C-4), 62.3 (C-6), 20.7, 20.6, 20.5 ppm (each COCH3); IR (film): n = 2115, 1744, 1366, 1238, 1209, 1038 cm-1; ESI-HRMS calcd for C6H15N4O5 391.1465, found m/z (%) 391.1469 [M+NH4] + .

6-O-teri-ButyldiphenylsHyl-2,3,4-tri-O-benzoyl-p-D-mannopyranosyl azide

(7): Azide 6 (1.8 g, 4.8 mmol) was taken up in MeOH (20 mL) and NaOMe (0.05 g, 0.96 mmol) was added and the mixture was stirred for 1 h. Dowex 50WX8 H+-resin (500 mg) was then added and the resulting suspension was stirred until the solution was neutral. This was then filtered and the solvent was removed to give the deprotected intermediate (0.93 g, 94%) as a white solid; [a]D = -42.6 (c 0.2, CH3OH); 1H NMR (500 MHz, D2O): d = 4.87 (d, 3/(H,H) = 1.1Hz, 1H; H-1), 3.03 (dd, 3J-(H,H) = 3.2, 1.1Hz, 1H; H-2), 3.96 (dd, 2/(H,H) = 12.3 Hz, 3/(H,H) = 2.2 Hz, 1H; H-6a), 3.77 (dd, 2/(H,H) = 12.3 Hz, 3/(H,H) = 6.4 Hz, 1H; H-6b), 3.67 (dd, 3/(H,H) = 9.7, 3.2 Hz, 1H; H-3), 3.61 (aptt, 3/(H,H) =

9.6 Hz, 1H; H-4), 3.49 ppm (ddd, 3/(H,H) = 9.5, 6.4, 2.2 Hz, 1H; H-5); 13C NMR (126 MHz, D2O): d = 87.2 (C-1), 78.3 (C-5), 72.7 (C-3), 71.0 (C-2), 66.4 (C-4), 60.9 ppm (C-6); IR (film): n = 3332, 2886, 2113, 1739, 1370, 1243, 1053, 1008 cm-1; ESI-HRMS calcd for C8H13N3O6Na 228.0596, found m/z (%) 228.0600 [M+Na]+. This intermediate (0.9 g, 4.4 mmol) was dissolved in pyridine (50 mL) and the resulting solution was cooled over an ice-bath. TBDPSCl (1.36 mL, 5.3 mmol) was then added in a drop-wise manner and the reaction mixture was allowed to attain room temperature and was stirred, overnight. The resulting suspension was again cooled using an ice-bath and benzoyl chloride (1.12 mL, 9.7 mmol) was added slowly and the mixture was allowed to warm to room temperature and was stirred, overnight. Methanol (5 mL) was then added and the resulting slurry was diluted with EtOAc (50 mL), washed twice with 1 m HCl (50 mL), satd aqueous NaHCO3 (50 mL), brine (50 mL), dried over Na2SO4, filtered and the solvent was removed under diminished pressure. Flash chromatography of the residue (petroleum ether/EtOAc, 7:3) gave 7 (2.53 g, 76%) as a foam; [a]D = -19.5 (c 0.1, CH2Cl2); 1H NMR (500 MHz, CDCl3): d = 8.15-7.13 (ms, 25H; Ar-H), 6.26 (aptt,

3/(H,H) = 10.0 Hz, 1H; H-4), 5.96 (dd, 3J(H,H) = 3.2, 1.3 Hz, 1H; H-2), 5.56 (dd, 3J(H,H) = 10.3, 3.2 Hz, 1H; H-3), 5.00 (d, 3J(H,H) = 1.3 Hz, 1H; H-1), 3.99-3.88 (m, 3H; H-6a, H-6b, H-5, overlapping peaks), 1.12 ppm (s, 9H; C(CH3)3); 13CNMR (126MHz, CDCl3): d = 165.7, 165.4, 164.9 (each COPh), 135.7, 135.5 (5 x Ar-CH, overlapping peaks), 133.5 133.3 (2s), 132.6 (5xAr-C), 130.2, 129.8, 129.7 (2s), 129.6, 129.3, 129.0, 128.8, 128.6, 128.5, 128.3, 127.8, 127.6 (20 x Ar-CH, overlapping peaks), 85.4 (C-1), 77.4 (C-5), 72.4 (C-3), 70.3 (C-2), 65.4 (C-4), 61.8 (C-6), 26.5 (C-(CH3)3, overlapping peaks), 19.2ppm (C(CH3)3); IR (film): n = 2931, 2119, 1729, 1452, 1259, 1092, 1025 cm"1; ESI-HRMS calcd for C43H41N3O8SiNa 778.2561, found m/z (%) 778.2553 [M+Na]+. 2-Acetamido-6-O-ferf-butyldiphenylsilyl-3,4-di-O-benzoyl-2-deoxy-ß-D-glucopyranosyl azide (11): Pentaacetyl-D-glucosamine (3 g, 7.7 mmol) was suspended in CH2Cl2 (30 mL) and cooled to 0 "C. A 33% solution of HBr in AcOH (30 mL) was added and the reaction mixture was stirred for 5 h, keeping the reaction on ice. The reaction was then diluted with CH2Cl2 (50 mL) and poured onto ice (100 mL). The layers were separated and the aqueous layer was washed with a further portion of CH2Cl2 (30 mL). The combined organic extracts were washed with ice (100 mL), satd. aq. NaHCO3 (100 mL), brine (100 mL), dried over Na2SO4, filtered and the solvent was removed under diminished pressure to give 9. Freshly prepared 9 was dissolved in CH2Cl2 (30 mL) and tetrabutylammonium azide (4.38 g, 15.4 mmol) was added. The reaction mixture was stirred, overnight, and the solvent was removed under diminished pressure. Flash chromatography of the residue (EtOAc) gave the intermediate azide (1.55 g, 54%) as a white solid; [a]D = -49.8 (c 0.15, CH2Cl2); 1H NMR (500 MHz, CDCl3): d = 5.66 (d, 3J(H,H) = 8.9 Hz, 1H; NHCOCH3), 5.24 (dd, 3J(H,H) = 10.6, 9.4 Hz, 1H; H-3), 5.10 (dd, 3J(H,H) = 10.1, 9.4 Hz, 1H; H-4), 4.76 (d, 3J(H,H) = 9.2 Hz, 1H; H-1), 4.27 (dd, 2J(H,H) = 12.4 Hz, 3J(H,H) = 4.9 Hz, 1H; H-6a), 4.16 (dd, 2J(H,H) = 12.4 Hz, 3J-(H,H) = 2.3 Hz, 1H; H-6b), 3.91 (aptdt, 3J(H,H) = 10.6, 9.2 Hz, 1H; H-2), 3.79 (ddd, 3/(H,H) = 10.1, 4.9, 2.3 Hz, 1H; H-5), 2.10 (s, 3H; COCH3), 2.04 (s, 3H; COCH3), 2.03 (s, 3H; NHCOCH3), 1.98ppm (s, 3H; COCH3); 13C NMR (126 MHz, CDCl3): d = 171.0, 170.6, 170.3 (each COCH3), 169.2 (NHCOCH3), 88.4 (C-1), 74.0 (C-5), 72.1 (C-3), 68.0 (C-4), 61.8 (C-6), 54.2 (C-2), 23.2 (NHCOCH3), 20.7, 20.6 ppm (2s) (3x COCH3); IR (film): n = 3334, 2959, 2141, 2105, 1740, 1659, 1371, 1224, 1034 cm-1; ESI-HRMS calcd for C14H20N4O8Na 395.1179, found m/z (%) 395.1187 [M+Na]+. This intermediate (1.5 g, 4.0 mmol) was dissolved in MeOH (20 mL) and NaOMe (0.04 g, 0.8 mmol) was added. The reaction was quenched after 1 h by the addition of Dowex 50WX8 H+-resin (50 mg). The reaction was filtered and the solvent was removed to give the unprotected GlcNAc derivative (0.89 g, 91 %) as a white solid; [a]D = -21.9 (c 0.07, CH3OH); 1H NMR (500 MHz, D2O): d = 4.78 (d, 3J-(H,H) = 9.4 Hz, 1H; H-1), 3.95 (dd, 2J(H, H) = 12.5 Hz, 3J(H,H) = 2.2 Hz, 1H; H-6a), 3.79 (dd, 2J(H,H) = 12.5 Hz, 3J(H,H) = 5.5 Hz, 1H; H-6b), 3.73 (dd, 3J(H,H) = 10.2, 9.4 Hz, 1H; H-2), 3.62-3.57 (m, 1H; H-3), 3.573.34 (m, 1H; H-5), 3.50 (dd, 3J(H,H) = 9.8, 8.7 Hz, 1H; H-4), 2.08 ppm (s, 3H; NHCOCH3); 13CNMR (126MHz, D2O): d = 174.7 (NHCOCH3), 88.6 (C-1), 77.8 (C-5), 73.6 (C-3), 69.4 (C-4), 60.5 (C-6), 55.0 (C-2), 22.0 ppm (NHCOCH3); IR (film): n = 3266, 2920, 2112, 1737, 1544, 1373, 1235, 1034 cm-1; ESI-HRMS calcd for C8H15N4O5 233.1012, found m/z (%) 233.1019[M+H]+. This polyhydroxylated intermediate (0.84 g, 3.4 mmol) was taken up in pyridine (15 mL) and the resulting solution was cooled and treated with TBDPSCl (1.1 mL, 4.1 mmol) followed by benzoyl chloride (0.87 mL, 7.5 mmol) as described above in formation of 7. Flash chromatography (petroleum ether/EtOAc 6:4) gave 11 (1.8 g, 76%) as a white foam; [a]D = -51.2 (c 0.13, CH2Cl2); 1HNMR (500 MHz, CDCl3): d = 7.98-7.91 (m, 2H; Ar-H), 7.90-7.83 (m, 2H; Ar-H), 7.75-7.68 (m, 2H; Ar-H), 7.61-7.45 (m, 4H; Ar-H), 7.42-7.32 (m, 6H; Ar-H), 7.18 (dd, 3J(H,H) = 8.1, 7.0 Hz, 2H; Ar-H), 5.82-5.70 (m, 2H; H-4, NHCOCH3, overlapping peaks), 5.59 (dd, 3J(H,H) = 10.7, 9.6 Hz, 1H; H-3), 4.76 (d, 3J(H,H) = 9.2 Hz, 1H; H-1), 4.25 (aptdt, 3J-(H,H) = 10.7, 9.2 Hz, 1H; H-2), 3.91-3.78 (m, 3H; H-6a, H-6b, H-5, overlapping peaks), 1.91 (s, 3H; NHCOCH3), 1.04ppm (s, 9H; C(CH3)3); 13C NMR (126 MHz, CDCl3): d = 170.5 (NHCOCH3), 167.1, 164.8 (2x COPh), 135.6, 135.5, 133.6, 133.5, 133.3 (6x Ar-CH, overlapping peaks), 132.9, 132.8 (2xAr-C), 130.0, 129.7 (2s), 129.6, 128.5 (2s) (6xAr-CH, overlapping peaks) (Ar-C, 2x Ar-CH, overlapping peaks), 128.4 (2s) (Ar-

C, 2 x Ar-CH, overlapping peaks), 127.7, 127.6 (4 x Ar-CH, overlapping peaks), 88.6 (C-1), 77.1 (C-5), 73.2 (C-3), 68.3 (C-4), 62.2 (C-6), 54.6 (C-

2), 26.6 (C(CH3)3, overlapping peaks), 23.3 (NHCOCH3), 19.2 ppm (c-(CH3)3); IR (film): n = 3268, 2931, 2113, 1725, 1657, 1548, 1240, 1061 cm-1; ESI-HRMS calcd for C38H40N4O7SiNa 701.2533, found m/z (%) 701.2540 [M+Na]+.

2-Acetamido-6-O-ferf-butyldiphenylsilyl-3,4-di-O-benzoyl-2-deoxy-ß-D-

galactopyranosyl azide (12): Treatment of pentaacetyl-D-galactosamine (3 g, 7.7 mmol) as described above for the glucosamine gave, via bromide 10, the intermediate azide (1.7 g, 59%) as a white solid; [a]D = -30.5 (c 0.04, CH2Cl2); 1H NMR (500 MHz, CDCl3): d = 5.56 (d, 3J(H,H) = 8.8 Hz, 1H; NHCOCH3), 5.38 (dd, 3J(H,H) = 3.3, 1.1 Hz, 1H; H-4), 5.24 (dd, 3J-(H,H) = 11.1, 3.3Hz, 1H; H-3), 4.79 (d, 3J(H,H) = 9.2Hz, 1H; H-1), 4.19-4.13 (m, 2H; H-6a, H-6b, overlapping peaks), 4.07-3.97 (m, 2H; H-5, H-2, overlapping peaks), 2.16 (s, 3H; NHCOCH3), 2.06 (s, 3H; COCH3), 2.01 (s, 3H; COCH3), 1.99 ppm (s, 3H; COCH3); 13CNMR (126 MHz, CDCl3): d = 170.5, 170.4 (3x COCH3), 170.1 (NHCOCH3), 88.7 (C-1), 72.8 (C-5), 69.7 (C-3), 66.5 (C-4), 61.4 (C-6), 50.8 (C-2), 23.4 (NHCOCH3), 20.7, 20.6 ppm (2s) (3x COCH3); IR (film): n = 3267, 2932, 2113, 1723, 1549, 1315, 1240, 1061 cm-1; ESI-HRMS calcd for C14H20N4O8Na 395.1179, found m/z (%) 395.1184 [M+Na]+. Treatment of this azide (1.65 g, 4.4 mmol) as described above for the corresponding GlcNAc derivative with MeOH (20 mL) and NaOMe (0.05 g, 0.9 mmol) gave the unprotected GalNAc azide (0.93 g, 86%) as a white solid; [a]D = -145.2 (c 0.04, CH3OH); 1HNMR (500 MHz, D2O): d = 4.68 (d, 3J(H,H) = 9.3 Hz, 1H; H-1), 3.99 (dd, 3J(H,H) = 3.1, 0.8 Hz, 1H; H-4), 3.94 (dd, 3J(H,H) = 10.7, 9.3 Hz, 1H; H-2), 3.85-3.75 (m, 4H; H-6a, H-6b, H-5, H-3, overlapping peaks), 2.07 ppm (s, 3H; NHCOCH3); 13C NMR (126 MHz, D2O): d = 174.9 (NHCOCH3), 89.0 (C-1), 77.2 (C-5), 70.7 (C-

3), 67.6 (C-4), 60.9 (C-6), 51.7 (C-2), 22.1 ppm (NHCOCH3); IR (film): n = 3329, 2907, 2095, 1639, 1553, 1429, 1326, 1226, 1018 cm-1; ESI-HRMS calcd for C8H14N4O5Na 269.0862, found m/z (%) 269.0851 [M+Na]+. This intermediate (0.9 g, 3.7 mmol) when treated with pyridine (15 mL) and TBDPSCl (1.14 mL, 4.4 mmol) and then benzoyl chloride (0.93 mL, 8.0 mmol) as described above in preparation of 7 gave after chromatogra-phy (petroleum ether/EtOAc, 6:4) the title compound 12 (1.79 g, 70%) as a white foam; [a]D = + 32.7 (c 0.1, CH2Cl2); 1H NMR (500 MHz, CDCl3): d = 8.07-8.02 (m, 2H; Ar-H), 7.87-7.83 (m, 2H; Ar-H), 7.667.60 (m, 3H; Ar-H), 7.54-7.47 (m, 5H; Ar-H), 7.42-7.28 (m, 5H; Ar-H), 7.11 (t, 3J(H,H) = 7.6 Hz, 2H; Ar-H), 6.00-5.94 (m, 1H; H-3), 5.64-5.57 (m, 2H; H-4, NHCOCH3, overlapping peaks), 4.80 (d, 3J(H,H) = 9.2 Hz, 1H; H-1), 4.33 (aptdt, 3J(H,H) = 11.1, 9.0 Hz, 1H; H-2), 4.06 (ddd, 3J-(H,H) = 7.4, 6.1, 1.2 Hz, 1H; H-5), 3.86-3.75 (m, 2H; H-6a, H-6b, overlapping peaks), 1.89 (s, 3H; NHCOCH3), 0.99ppm (s, 9H; C(CH3)3); 13C NMR (126 MHz, CDCl3): d = 170.5 (NHCOCH3), 166.4, 165.3 (2x COPh), 135.5, 135.4, 133.5 (2s), 133.4 (6xAr-CH, overlapping peaks), 132.7, 132.5 (2xAr-C), 129.9 (2s), 129.8, 129.7 (6xAr-CH, overlapping peaks), 129.4, 128.8 (2 x Ar-C), 128.6, 128.4, 127.8, 127.6 (8 x Ar-CH, overlapping peaks), 89.0 (C-1), 75.7 (C-5), 71.0 (C-4), 67.1 (C-3), 61.1 (C-6), 51.4 (C-2), 26.6 (C(CH3)3, overlapping peaks), 23.3 (NHCOCH3), 19.0 ppm (C(CH3)3); IR (film): n=3994, 2860, 2115, 1722, 1657, 1272, 1106, 1068 cm-1; ESI-HRMS calcd for C38H40N4O7SiNa 701.2533, found m/z (%) 701.2525[M+Na]+.

4,6-O-(1,1,3,3-Tetraisopropyl-1,3-disiloxanediyl)-ß-D-glucopyranosyl azide (16): Sodium methoxide (0.2 g, 4.0 mmol) was added to the azide 15 (7.5 g, 20.1 mmol) in MeOH (50 mL) and the mixture was stirred for 1 h and then Dowex 50WX8 H+-resin (500 mg) was added and the resulting suspension was stirred until the pH was 7. This mixture was then filtered and the solvent was removed under diminished pressure to give ß-D-glu-copyranosyl azide (3.92g, 95%) as a white solid; [a]D = -31.0 (c 0.3, CH3OH); 1H NMR (500 MHz, D2O): d = 4.75 (d, 3J(H,H) = 8.8 Hz, 1H; H-1), 3.93 (dd, 2J(H,H) = 12.4 Hz, 3J(H,H) = 2.2 Hz, 1H; H-6a), 3.75 (dd, 2J(H,H) = 12.4Hz, 3J(H,H) = 5.7Hz, 1H; H-6b), 3.57-3.49 (m, 2H; H-5, H-3, overlapping peaks), 3.41 (aptt, 3J(H,H) = 9.0 Hz, 1H; H-4), 3.27 ppm (aptt, 3J(H,H) = 9.0 Hz, 1H; H-2); 13C NMR (126 MHz, D2O): d = 90.9 (C-1), 79.0 (C-5), 76.9 (C-3), 73.6 (C-2), 69.9 (C-4), 61.4 ppm (C-6); IR (film): n = 3303, 2881, 2125, 1472, 1377, 1263, 1064cm-1; ESI-HRMS calcd for C6H12N3O5 206.0777, found m/z (%) 206.0772 [M +H]+. To this intermediate (3.5 g, 17.1 mmol) in pyridine (50 mL) at 0"C was

CHEMISTRY

A EUROPEAN JOURNAL

P. V. Murphy et al.

added 1,3-dichloro-1,1,3,3-tetraisopropyldisiloxane (0.99 mL, 20.5 mmol) and the mixture was allowed to warm to room temperature and was then stirred for 5 h at which point MeOH (1 mL) was added and the solvent removed under diminished pressure. The resulting residue was taken up in EtOAc (50 mL) and washed with 1 м HCl (50 mL), NaHCO3 (50 mL), brine (50 mL), then dried over Na2SO4, filtered and the solvent removed under diminished pressure. Flash chromatography of the residue (petroleum ether/EtOAc, 7:3) gave 16 (4.7 g, 61%) as a white solid; [a]D = -80.7 (c 0.20, CH2Cl2); 1HNMR (500 MHz, CDCl3): d = 4.58 (d, 3J-(H,H) = 8.6 Hz, 1H; H-1), 4.09 (dd, 2J(H,H) = 12.7 Hz, 3J(H,H) = 2.1 Hz, 1H; H-6a), 4.00 (dd, 2J(H,H) = 12.7 Hz, 3J(H,H) = 1.5 Hz, 1H; H-6b), 3.83 (aptt, 3J(H,H) = 9.1 Hz, 1H; H-4), 3.60 (aptt, 3J(H,H) = 9.1 Hz, 1H; H-3), 3.34-3.26 (m, 2H; H-5, H-2, overlapping peaks), 2.56 (s, 2H; 2x OH), 1.25-0.89 ppm (m, 28H; 4xCH(CH3)2, overlapping peaks); 13C NMR (126 MHz, CDCl3): d = 90.8 (C-1), 78.7 (C-5), 76.5 (C-3), 73.5 (C-2), 68.8 (C-4), 60.6 (C-6), 17.4, 17.3, 17.2 (3s), 17.1 (2s) (8xCH(CH3)2, overlapping peaks), 13.6, 13.2, 12.5 ppm (2s) (4x CH(CH3)2, overlapping peaks); IR (film): n = 3420, 2868, 2115, 1465, 1248, 1025cm-1; ESI-HRMS calcd for C18H37N3O6Si2Na 442.2349, found m/z (%) 442.2352 [M+Na]+.

Methyl 1-azido-1-deoxy-3,4-O-(1,1,3,3-tetraisopropyl-1,3-disiloxanediyl)-ß-D-glucopyranuronate (17): p-TsOH.H2O (0.17 g, 0.9 mmol) was added to diol 16 (2 g, 4.45 mmol), in DMF (25 mL) and the mixture was stirred at room temperature for 5 h and it was then diluted with EtOAc (50 mL), washed with H2O (2x25 mL), satd. aq. NaHCO3 (50 mL), brine (50 mL), dried over Na2SO4, filtered and the solvent was removed under diminished pressure. Flash chromatography of the residue (petroleum ether/EtOAc 8:2) gave the 3,4-protected intermediate (1.87 g, 94%) as a clear oil; [a]D = -4.8 (c 0.17, CH2Cl2); 1HNMR (500 MHz, CDCl3): d = 4.60 (d, 3J(H,H) = 8.6 Hz, 1H; H-1), 3.93 (ddd, 2J(H,H) = 12.0 Hz, 3J-(H,H) = 6.3, 2.2 Hz, 1H; H-6a), 3.77 (ddd, 2J(H,H) = 12.0 Hz, 3J(H,H) = 7.2, 4.9 Hz, 1H; H-6b), 3.73-3.64 (m, 2H; H-4, H-3, overlapping peaks), 3.45 (ddd, 3J(H,H) = 8.9, 4.9, 2.8 Hz, 1H; H-5), 3.38 (apttd, 3J(H,H) = 8.6, 2.2 Hz, 1H; H-2), 2.44 (d, 3J(H,H) = 2.3 Hz, 1H; OH), 1.93 (aptt, 3J-(H,H) = 6.8 Hz, 1H; OH), 1.16-0.86 ppm (m, 28H; 4xCH(CH3)2, overlapping peaks); 13CNMR (126 MHz, CDCl3): d = 89.5 (C-1), 79.8 (C-3), 78.4 (C-5), 73.9 (C-2), 72.1 (C-4), 61.9 (C-6), 17.3 (3s), 17.2 (2s), 17.1 (8 x CH(CH3)2, overlapping peaks), 12.9, 12.8, 12.1 ppm (2s) (4x CH(CH3)2, overlapping peaks); IR (film): n = 3349, 2868, 2114, 1464, 1248, 1052, 987 cm-1; ESI-HRMS calcd for C18H37N3O6Si2Na 442.2349, found m/z (%) 442.2356 [M+Na]+. This intermediate (1.8 g, 4.0 mmol) was dissolved in MeCN/H2O (60 mL, 3:1) and treated with BAIB (3.24 g, 10.1 mmol) and TEMPO (0.06 g, 0.4 mmol) as described above to give the carboxylic acid, which when treated in DMF (25 mL) with NaHCO3 (0.5 g, 6.0 mmol) and methyl iodide (0.37 mL, 6.0 mmol) gave 17 (0.97 g, 51%) as a clear oil after chromatography (petroleum ether/EtOAc 9:1); [a]D:-3.6° (c 0.06, CH2Cl2); 1HNMR (500 MHz, CDCl3): d = 4.61 (d, 3J-(H,H) = 8.7 Hz, 1H; H-1), 3.96-3.90 (m, 2H; H-5, H-4, overlapping peaks), 3.78 (s, 3H; OCH3), 3.68 (ddd, 3J(H,H) = 8.5, 6.4, 1.9 Hz, 1H; H-3), 3.45 (td, 3J(H,H) = 8.7, 1.9Hz, 1H; H-2), 2.43 (d, 3J(H,H) = 2.4Hz, 1H; OH), 1.29-0.46ppm (m, 28H; 4xC#(CH3)2, overlapping peaks); 13C NMR (126 MHz, CDCl3): d = 168.2 (CO2CH3), 89.9 (C-1), 79.3 (C-3), 77.4 (C-5), 73.7 (C-4), 73.4 (C-2), 52.4 (CO2CH3), 17.3, 17.2 (4s), 17.1, 17.0 (2s) (8xCH(CH3)2, overlapping peaks), 12.9, 12.8, 12.2, 12.1 ppm (4xCH(CH3)2, overlapping peaks); IR (film): n = 3441, 2867, 2125, 1785, 1736, 1464, 1251, 1081, 987 cm-1; ESI-HRMS calcd for C19H37N3O7Si2Na 498.2068, found m/z (%) 498.2074 [M+Na]+.

Methyl 2-O-(2,3,4,6-tetra-O-benzoyl-ß-D-glucopyranosyl)-1-azido-1-deoxy-3,4-O-(1,1,3,3-tetraisopropyM,3-disüoxanediyl)-ß-D-glucopyranur-onate (19): Compound 17 (0.25 g, 0.5 mmol), 18[13] (0.58 g, 0.8 mmol) and CH2Cl2 (6 L) were added to a flame-dried flask containing freshly activated 4 A molecular sieves (0.6 g). The resulting suspension was stirred at room temperature for 30 min before being cooled to 0 °C using an ice-bath. TMSOTf (0.029 mL, 0.16 mmol) was then added and the reaction mixture was allowed to attain room temperature over 1 h. Triethylamine (0.25 mL) was added, the mixture filtered and the solvent was removed under diminished pressure. Flash chromatography of the residue (petroleum ether/EtOAc 8:2) gave 19 (0.35 g, 67%) as a white foam; [a]D = -22.6 (c 0.07, CH2Cl2); 1H NMR (500 MHz, CDCl3): d = 8.06-8.01 (m,

2H; Ar-H), 7.91 (ddd, 3J(H,H) = 8.5, 4.0, 1.3 Hz, 4H; Ar-H), 7.82-7.71 (m, 2H; Ar-H), 7.57-7.52 (m, 1H; Ar-H), 7.50 (dd, 3/(H,H) = 8.3, 6.7 Hz, 2H; Ar-H), 7.41 (aptq, 3J(H,H) = 7.8 Hz, 3H; Ar-H), 7.35 (td, 3J(H,H) = 7.7, 4.2 Hz, 4H; Ar-H), 7.28-7.22 (m, 1H; Ar-H), 5.85 (aptt, 3j(h,h) = 9.5 Hz, 1H; H-3), 5.73 (aptt, 3J(H,H) = 9.6 Hz, 1H; H-4), 5.58 (dd, 3J-(H,H) = 9.6, 7.7 Hz, 1H; H-2), 5.35 (d, 3J(H,H) = 7.7 Hz, 1H; H-1), 4.71 (dd, 2J(H,H) = 12.1Hz, 3J(H,H) = 3.2 Hz, 1H; H-6a), 4.57-4.47 (m, 2H; H-1', H6-b, overlapping peaks), 4.11 (ddd, 3/(H,H) = 10.0, 5.2, 3.2 Hz, 1H; H-5), 3.93 (aptt, 3J(H,H) = 8.5 Hz, 1H; H-2'), 3.89-3.79 (m, 3H; H-3', H-4', H-5', overlapping peaks), 3.75 (s, 3H; OCH3), 1.06-0.68 ppm (m, 28 H ; 4xCH(CH3)2, overlapping peaks); 13CNMR (126 MHz, CDCl3): d = 168.1 (CO2CH3), 166.1, 165.8, 165.1 (2s) (4x COPh), 133.4, 133.2 (2s),

133.1, 129.9, 129.8, 129.7 (12xAr-CH, overlapping peaks), 129.6, 129.2, 128.8, 128.0 (4x Ar-C), 128.4 (2s), 128.3, 128.2 (8 x Ar-CH, overlapping peaks), 100.0 (C-1), 88.4 (C-1'), 79.7 (C-3'), 77.2 (C-5'), 76.4 (C-2'), 74.0 (C-4'), 73.1 (C-3), 72.5 (C-2), 72.3 (C-5), 69.6 (C-4), 62.9 (C-6), 52.4 (C02CH3), 17.5, 17.4, 17.2 (2s), 17.1, 17.0 (2s) (8 x CH(CH3)2, overlapping peaks), 12.8, 12.7, 12.3, 12.2ppm (4xCH(CH3)2, overlapping peaks); IR (film): n = 2946, 2119, 1728, 1452, 1249, 1089, 986 cm-1; ESI-HRMS calcd for C53H63N3O16Si2Na 1076.3645, found m/z (%) 1076.3652 [M+Na]+. Allyl 6-O-ferf-butyldiphenylsilyl-2,3,4-tri-O-benzoyl-ß-D-glucopyranoside (22): Deacetylation of 21 (9 g, 23.2 mmol) as described for 15 gave the intermediate (4.4g, 87%) as a white solid; [a]D = -35.0 (c 0.24, CH3OH); 1H NMR (500 MHz, D2O): d = 5.99 (dddd, J = 17.0, 10.5, 6.3, 5.5 Hz, 1H; CH2CH=CH2), 5.40 (dq, 3/(H,H) = 17.0Hz, 2/(H,H) 1.5Hz, 1H; CH2CH=CH2), 5.30 (dq, 3J(H,h) = 10.5 Hz, 2J(H,h) = 1.5 Hz, 1H; CH2CH=CH2), 4.51 (d, J=8.0 Hz, 1H; H-1), 4.40 (ddt, 2J(H,H) = 12.7, 1.4 Hz, 3J(H,H) = 5.5 Hz, 1H; CH2CH=CH2), 4.24 (ddt, 2j(h,h) = 12.7, 1.4 Hz, 3J(H,H) = 6.3 Hz, 1H; CH2CHCH2), 3.93 (dd, 2J(H,H) = 12.3 Hz, 3J(H,H) = 2.2 Hz, 1H; H-6a), 3.73 (dd, 2J(H,H) = 12.3 Hz, 3J(H,H) = 6.0 Hz, 1H; H-6b), 3.50 (aptt, 3J(H,H) = 9.2 Hz, 1H; H-3), 3.47-3.44 (m, 1H; H-5), 3.39 (dd, 3J(H,H) = 9.9, 8.9Hz, 1H; H-4), 3.30ppm (dd, 3J-(H,H) = 9.3, 8.0Hz, 1H; H-2); 13CNMR (126MHz, D2O): d = 133.2 (CH2CHCH2), 118.7 (CH2CHCH2), 101.1 (C-1), 75.8 (C-5), 75.7 (C-3), 73.0 (C-2), 70.5 (CH2CHCH2), 69.6 (C-4), 60.7 ppm (C-6); IR (film): n= 3295, 2915, 1664, 1458, 1365, 1109, 1073, 1022 cm-1; ESI-HRMS calcd for C9H16O6Na 243.0845, found m/z (%) 243.0852 [M+Na]+. This intermediate (10 g, 45.4 mmol) was treated with pyridine (100 mL), TBDPSCl (14.1 mL, 54.5 mmol) and benzoyl chloride (34.82 mL, 299.7 mmol) as described previously to give 22 (27.3 g, 78 %) as a foam; [a]D = -21.1 (c 0.1, CH2Cl2); 1HNMR (500 MHz, CDCl3): d = 7.99-7.94 (m, 1H), 7.88-7.81 (m, 2H; Ar-H), 7.71-7.67 (m, 4H; Ar-H), 7.62-7.58 (m, 2H; Ar-H), 7.57.48 (m, 2H; Ar-H), 7.44-7.27 (m, 9H; Ar-H), 7.25-7.21 (m, 2H; Ar-H), 5.88-5.78 (m, 2H; CH2CHCH2, C-3, overlapping peaks ), 5.62 (aptt, 3J-(H,H) = 9.2 Hz, 1H; H-4), 5.53 (dd, 3J(H,H) = 9.7, 7.9 Hz, 1H; H-2), 5.25 (dq, 3J(H,H) = 17.3 Hz, 2J(H,H) 1.7 Hz, 1H; CH2CHCH2), 5.15 (dq, 3J-(Н,Н) = 10.5Hz, 2J(H,H) 1.4Hz, 1H; CH2CH=CH2), 4.85 (d, 3J(H,H) = 7.9 Hz, 1H; H-1), 4.38 (ddt, 2J(H,H) = 13.3 Hz, 3J(H,H) = 4.8, 1.7 Hz, 1H; CH2CH=CH2), 4.17 (ddt, 2J(H,H) = 13.3 Hz, 3J(H,H) = 6.3, 1.4 Hz, 1H; CH2CH=CH2), 3.90-3.82 (m, 2H; C-5, C-6a, C-6b, overlapping peaks), 1.04 ppm (s, 9H; C(CH3)3); 13CNMR (126 MHz, CDCl3): d = 165.9, 165.0 (3x COPh, overlapping peaks), 135.6, 135.5 (4 x Ar-CH, overlapping peaks), 133.6 (CH2CH=CH2), 133.2 (2 x Ar-CH), 133.1 (2s) (Ar-C, 2 x ArCH, overlapping peaks), 133.0 (Ar-C), 129.8 (2s), 129.7, 129.6 (2s) (6x Ar-CH, overlapping peaks), 129.5, 129.2, 129.0 (3x Ar-C),128.3 (2s),

128.2, 127.6 (2s) (11 x Ar-CH, overlapping peaks), 117.6 (CH2CHCH2), 99.7 (C-1), 75.2 (C-5), 73.4 (C-3), 72.0 (C-2), 69.6 (CH2CH=CH2), 69.3 (C-4), 62.8 (C-6), 26.6 (C(CH3)3, overlapping peaks), 19.2 ppm (C-(CH3)3) ; IR (film): n = 3071, 2857, 1729, 1451, 1259, 1091, 1026 cm-1; ESI-HRMS calcd for C46H46O9SiNa 793.2809, found m/z (%) 793.2798 [M+Na]+.

1-O-Allyl-2,3,4-tri-O-benzoyl-ß-D-glucopyranosiduronic acid, methyl

ester (23): The TBDPS derivative 22 (27.0 g, 35.0 mmol) was dissolved in THF (250 mL) and the resulting solution was cooled using an ice-bath. AcOH (4 mL, 70.0 mmol) and 1 м TBAF in THF (70 mL, 70.0 mmol) were added to this. The mixture was allowed to attain room temperature and was stirred for 16 h and the product was adsorbed on silica gel. Flash chromatography (petroleum ether/EtOAc 3:2) gave the intermediate alcohol (14.4g, 77%) as a white solid; [a]D = -23.0 (c 0.2, CH2Cl2);

1HNMR (500 MHz, CDCl3): d = 7.95 (apttt, 3J(H,H) = 7.3, 1.4 Hz, 4H; Ar-H), 7.89-7.81 (m, 2H; Ar-H), 7.59-7.47 (m, 2H; Ar-H), 7.46-7.35 (m, 5H; Ar-H), 7.31-7.26 (m, 2H; Ar-H), 5.93 (aptt, 3J(H,H) = 9.7 Hz, 1H; H-3), 5.81 (dddd, 3J(H,H) = 17.0, 10.7, 6.1, 5.0 Hz, 1H; CH2CHCH2), 5.60-5.39 (m, 2H; H-2, H-4, overlapping peaks), 5.26 (dq, 3J(H,H) = 17.0 Hz, 2j(h,H) = 1.4 Hz, 1H; CH2CHCH2), 5.15 (dq, 3J(H,H) = 10.7 Hz, 2/(H,H) = 1.4 Hz, 1H; CH2CHCH2), 4.89 (d, 3J(H,H) = 7.9 Hz, 1H; H-1), 4.39 (ddt, 2J(H,H) = 13.3 Hz, 3J(H,H) = 5.0, 1.6 Hz, 1H; CH2CHCH2), 4.19 (ddt, 2j(h,h) = 13.3 Hz, 3j(h,h) = 6.1, 1.4 Hz, 1H; CH2CHCH2), 3.86 (ddd, 2J(H,H) = 12.4 Hz, 3J(H,H) = 8.8, 1.9 Hz, 1H; H-6a), 3.83-3.68 (m, 2H; H-6b, H-5), 2.55 ppm (dd, 3J(H,H) = 8.8, 5.3 Hz, 1H; OH); 13C NMR (126 MHz, CDCl3): d = 166.0, 165.8, 165.0 (3x COPh), 133.7 (Ar-CH, overlapping peaks), 133.4 (CH2CHCH2), 133.2 (2s) (2 x Ar-CH), 129.9, 129.8, 129.7 (6x Ar-CH, overlapping peaks), 129.3, 128.8, 128.6 (3x Ar-C), 128.5, 128.3 (2s) (6xAr-CH), 117.7 (CH2CHCH2), 100.0 (C-1), 74.6 (C-5), 72.8 (C-3), 71.8 (C-4), 70.2 (CH2CHCH2), 69.6 (c-2), 61.4ppm (C-6); IR (film): n=3380, 2955, 1722, 1451, 1252, 1066, 1026 cm-1; ESI-HRMS calcd for C30H28O9Na 555.1631, found m/z (%) 555.1637 [M+Na]+. This intermediate (14 g, 26.3 mmol) in MeC/H2O (100 mL, 3:1) was oxidised, using BAIB (21.17 g, 65.7 mmol) and TEMPO (0.4 g, 2.6 mmol), and the resulting acid was esterified in DMF (80 mL) using NaHCO3 (3.3 g, 39.5 mmol) and methyl iodide (2.5 mL, 39.5 mmol) as described above to give 23 (8.7 g, 59%) as a foam; [a]D = -40.0 (c 0.07, CH2Cl2); 1H NMR (500 MHz, CDCl3): d = 7.98-7.92 (m, 4H; Ar-H), 7.90-7.83 (m, 2H; Ar-H), 7.52 (dddd, 3J(H,H) = 7.6, 4.9, 2.4, 1.3 Hz, 2H; Ar-H), 7.47-7.43 (m, 1H; Ar-H), 7.38 (dddd, 3/(H,H) = 8.2, 6.2, 3.5, 1.7 Hz, 4H; Ar-H), 7.33-7.28 (m, 2H; Ar-H), 5.90 (aptt, 3J-(H,H) = 9.3 Hz, 1H; H-3), 5.80 (dddd, 3J(H,H) = 17.0, 10.5, 6.4, 4.7 Hz, 1H; CH2CHCH2), 5.71 (aptt, 3j(h,H) = 9.4 Hz, 1H; H-4), 5.57 (dd, 3J-(H,H) = 9.3, 7.3 Hz, 1H; H-2), 5.26 (dq, 3J(H,H) = 17.0 Hz, 2J(H,H) = 1.6 Hz, 1H; CH2CHCH2), 5.16 (dq, 3J(H,H) = 10.5 Hz, 3J(H,H) = 1.4 Hz, 1H; CH2CHCH2), 4.92 (d, 3J(H,H) = 7.3 Hz, 1H; H-1), 4.42 (ddt, 2J-(H,H) = 13.2 Hz, 3J(H,H) = 4.8, 1.6 Hz, 1H; CH2CH=CH2), 4.35 (d, 3J-(h,h) = 9.4Hz, 1H), 4.17 (ddt, 2J(H,H) = 13.2Hz, 3J(H,H) = 6.4, 1.4Hz, 1H; CH2CH=CH2), 3.70ppm (s, 3H; CO2CH3); 13CNMR (126 MHz, CDCl3): d = 167.4 (CO2CH3), 165.6, 165.2, 165.0 (3 x COPh), 133.4, 133.3, 133.2 (3x Ar-CH), 133.1 (CH2CH=CH2), 129.8 (3s) (6 x Ar-CH, overlapping peaks), 129.2, 128.7, 128.5 (3xAr-C), 128.4 (2s), 128.3 (6 x Ar-CH, overlapping peaks), 118.0 (CH2CH=CH2), 99.6 (C-1), 72.9 (C-5), 72.0 (C-3), 71.5 (C-2), 70.2 (CH2CHCH2), 70.1 (C-4), 52.9 ppm (CO2CH3); IR (film): n = 3068, 1761, 1726, 1451, 1250, 1088 cm-1; ESI-HRMS calcd for C31H32NO10 578.2026, found m/z (%) 578.2031 [M+NH4]+. 2,3,4-Tri-O-benzoyl-1-deoxy-1-(2,2,2-lrichloro-1-immoelhoxy)-D-glucopyr-anuronale, methyl ester (24): The allyl glycoside 23 (8.5 g, 15.1 mmol) was dissolved in MeOH/CH2Cl2 (60 mL, 3:1) and PdCl2 (0.54 g, 3.0 mmol) was added and the mixture was stirred for 16 h at room temperature. The resulting suspension was filtered through Celite and the solvent was removed to give a foam. Flash chromatography (petroleum ether/EtOAc 6:4) gave the hemiacetal (5.6 g, 10.8 mmol). This intermediate was dissolved in CH2Cl2 (50 mL) and cooled on an ice-bath and tri-chloroacetonitrile (10.8 mL, 107.6 mmol) and DBU (0.5 mL) were added. The mixture was stirred for 5 h and was directly subjected to flash chro-matography (petroleum ether/EtOAc 7:3, 0.1 % Et3N) to give 24 (6.95 g, 69%) as a white foam; [a]D = + 44.4 (c 0.18, CH2Cl2); 1H NMR (500 MHz, CDCl3): d = 8.68 (s, 1H; NH), 8.00-7.93 (m, 4H; Ar-H), 7.927.85 (m, 2H; Ar-H), 7.58-7.49 (m, 2H; Ar-H), 7.46 (ddt, 3/(H,H) = 8.7, 7.2, 1.3Hz, 1H; Ar-H), 7.42-7.30 (m, 5H; Ar-H), 6.91 (d, 3J(H,H) = 3.6 Hz, 1H; H-1), 6.29 (aptt, 3J(H,H) = 9.9 Hz, 1H; H-3), 5.76 (aptt, 3J-(H,H) = 9.9Hz, 1H; H-4), 5.63 (dd, 3J(H,H) = 10.1, 3.6Hz, 1H; H-2), 4.77 (d, 3J(H,H) = 10.5 Hz, 1H; H-5), 3.69 ppm (s, 3H; CO2CH3); 13C NMR (126 MHz, CDCl3): d = 167.2 (CO2CH3), 165.5, 165.2 (3x COPh, overlapping peaks), 160.3 (OC(NH)CCl3), 133.6 (2s), 133.4, 129.9 (2s), 129.7 (9 x Ar-CH, overlapping peaks), 128.7, 128.6 (2 x Ar-C), 128.5 (2 x Ar-CH, overlapping peaks), 128.4 (2s) (4 x Ar-CH, Ar-C, overlapping peaks), 92.9 (C-1), 70.9 (C-5), 70.2 (C-2), 69.6 (C-4), 69.3 (C-3), 53.0 ppm (CO2CH3); IR (film): n = 3068, 1728, 1451, 1278, 1092, 1025 cm-1. 6-O-Acetyl-3,4-O-(1,1,3,3-lelraisopropyl-1,3-disiloxanediyl)-ß-D-glucopyr-anosyl azide (26): A solution of 25 (0.75 g, 1.7 mmol) in collidine (5 mL), prepared from 16 as described above was cooled to -35 °C. Freshly dis-

tilled AcCl (0.13 mL, 1.84 mmol) was added to this and the reaction mixture was allowed to attain room temperature. Methanol was added and the solvent was removed under diminished pressure. Flash chromatogra-phy of the residue (petroleum ether/EtOAc 9:1) gave 26 (0.58 g, 70%) as a white solid; [a]D = -23.0 (c 0.18, CH2Cl2); 1H NMR (500 MHz, CDCl3): d = 4.56 (d, 3J(H,H) = 8.7 Hz, 1H; H-1), 4.44 (dd, 2J(H,H) = 12.0 Hz, 3J-(H,H) = 2.1 Hz, 1H; H-6a), 4.20 (dd, 2j(h,H) = 12.0 Hz, 3J(H,H) = 5.2 Hz, 1H; H-6b), 3.74-3.67 (m, 1H; H-4), 3.67-3.62 (m, 1H; H-3), 3.56 (ddd, 3J(H,H) = 9.3, 5.3, 2.1 Hz, 1H; H-5), 3.40 (aptt, 3J(H,H) = 8.7 Hz, 1H; H-2), 2.44 (d, 3J(H,H) = 2.6Hz, 1H; OH), 2.09 (s, 3H; COCH3), 1.120.93 ppm (m, 28 H ; 4xCH(CH3)2, overlapping peaks); 13CNMR (126 MHz, CDCl3): d = 170.7 (OCOCH3), 89.6 (C-1), 79.7 (C-3), 76.1 (C-

5), 73.7 (C-2), 72.2 (C-4), 62.9 (C-6), 20.9, 17.3 (3s), 17.2 (3s), 17.1 (8x CH(CH3)2, overlapping peaks), 12.8, 12.7, 12.1 ppm (2s) (4x CH(CH3)2, overlapping peaks); IR (film): n = 3504, 2947, 2868, 2114, 1725, 1463, 1250, 1028, 980 cm-1; ESI-HRMS calcd for C20H39N3O7Si2Na 512.224, found m/z (%) 512.2229 [M+Na]+.

2-O-(2,3,4-Tri-O-benzoyl-5-S-(melhoxycarbonyl)-ß-D-xylopyranosyl)-3,4-O-(1,1,3,3-lelraisopropyl-1,3-disiloxanediyl)-6-O-acetyl-ß-D-glucopyrano-syl azide (27): Glycosidation with acceptor 26 (0.5 g, 1.0 mmol) and donor 24 (0.91 g, 1.2 mmol) as described above gave 27 (0.88 g, 89%) as a foam; [a]D = -4.0 (c 1.0, CHCl3); 1H NMR (500 MHz, CDCl3): d = 7.91 (ddt, 3J(H,H) = 17.1, 7.0, 1.4 Hz, 4H; Ar-H), 7.81 (dd, 3J(H,H) = 8.4, 1.4 Hz, 2H; Ar-H), 7.54-7.48 (m, 2H; Ar-H), 7.44-7.33 (m, 5H; Ar-H), 7.28 (d, 3J(H,H) = 7.8 Hz, 2H; Ar-H), 5.84 (aptt, 3J(H,H) = 9.2 Hz, 1H; H-3'), 5.78 (aptt, 3J(H,H) = 9.5 Hz, 1H; H-4'), 5.58 (dd, 3J(H,H) = 9.0, 7.6Hz, 1H; H-2'), 5.34 (d, 3J(H,H) = 7.5Hz, 1H; H-1'), 4.54 (d, 3J-(H,H) = 8.1 Hz, 1H; H-1), 4.44 (dd, 2J(H,H) = 12.0 Hz, 3J(H,H) = 2.2 Hz, 1H; H-6a), 4.33 (d, 3J(H,H) = 9.6 Hz, 1H; H-5'), 4.14 (dd, 3J(H,H) = 12.0 Hz, 3J(H,H) = 5.1 Hz, 1H; H-6b), 3.87-3.82 (m, 1H; H-2), 3.79 (aptt, 3J(H,H) = 8.5 Hz, 1H; H-3), 3.73 (s, 3H; CO2CH3), 3.71-3.63 (m, 1H; H-4), 3.49 (ddd, 3J(H,H) = 9.5, 5.1, 2.1 H-z, 1H; H-5), 2.08 (s, 3H; COCH3), 1.08-0.72ppm (m, 28H; 4xCH(CH3)2, overlapping peaks); 13CNMR (126 MHz, CDCl3): d = 170.7 (COCH3), 167.0 (CO2CH3), 165.7, 165.0 (2s), (3 x COPh), 133.4, 133.3 (2s)129.9, 129.8, 129.7 (9 x Ar-CH, overlapping peaks), 129.2, 128.8, 128.6 (3x Ar-C), 128.4, 128.3, 128.2 (6 x Ar-CH, overlapping peaks), 100.2 (C-1'), 88.4 (C-1), 79.8 (C-3), 78.0 (C-2), 75.6 (C-5), 73.1 (C-5'), 72.6 (C-3'), 72.5 (C-4), 72.1 (C-2'), 70.1 (C-4'), 62.8 (C-

6), 53.0 (CO2CH3), 20.9 (COCH3), 17.5 (2s) 17.4, 17.3, 17.2 (3s)17.1 (8 x CH(CH3)2, overlapping peaks), 12.8, 12.7, 12.3 ppm (2s) (4x CH(CH3)2, overlapping peaks); IR (film): n = 3073, 2952, 2120, 1727, 1686, 1452, 1248, 1091, 1067, 1026 cm-1; ESI-HRMS calcd for C48H61O16N3Si2Na 1014.3488, found m/z (%) 1014.3491 [M+Na]+.

2,3,4-Tri-O-benzoyl-ß-D-glucopyranosyl azide (29): Azide 28 (1 g, 4.87 mmol) prepared from 15 as described, was treated with TBDPSCl (1.5 mL, 5.85 mmol) in pyridine and then benzoyl chloride (3.73 mL, 32.14 mmol) as described above, to give the silylated intermediate (1.99 g, 54%) as a foam; [a]D = -25.9 (c 0.41, CH2Cl2); 1H NMR (500 MHz, CDCl3): d = 7.99-7.94 (m, 2H; Ar-H), 7.91-7.86 (m, 2H; Ar-H), 7.86-7.81 (m, 2H; Ar-H), 7.74-7.69 (m, 2H; Ar-H), 7.61-7.56 (m, 2H; Ar-H), 7.56-7.50 (m, 2H; Ar-H), 7.45-7.34 (m, 7H; Ar-H), 7.34-7.27 (m, 3H; Ar-H), 7.23-7.18 (m, 2H; Ar-H), 5.86 (aptt, 3J(H,H) = 9.7 Hz, 1H; H-3), 5.75 (aptt, 3J(H,H) = 9.7 Hz, 1H; H-4), 5.47 (dd, 3J(H,H) = 9.7, 8.8 Hz, 1H; H-2), 4.87 (d, 3J(H,H) = 8.8 Hz, 1H; H-1), 3.96-3.84 (m, 3H; H-6a, H-6b, H-5, overlapping peaks), 1.06 ppm (s, 9H; C(CH3)3); 13C NMR (126 MHz, CDCl3): d = 165.8, 165.1, 164.8 (3x COPh), 135.6, 135.5, 133.4, 133.3, 133.2 (7 x Ar-CH, overlapping peaks), 132.9, 132.8 (2x Ar-C), 129.9, 129.8, 129.8, 129.7, 129.6 (8 x Ar-CH, overlapping peaks), 129.0, 128.8, 128.7 (3xAr-C), 128.4, 128.4, 128.3, 127.7, 127.6 (10xAr-CH, overlapping peaks), 88.1 (C-1), 77.3 (C-5), 73.1 (C-3), 71.5 (C-2), 68.5 (C-4), 62.3 (C-6), 26.6 (C(CH3)3), 19.2 ppm (C(CH3)3); IR (film): n = 3071, 2858, 2116, 1731, 1451, 1245, 1088, 1068 cm-1; ESI-HRMS calcd for C43H42N3O8Si 756.2736, found m/z (%) 756.2742 [M+H]+. This intermediate in THF (50 mL) was cooled over ice and AcOH (0.29 mL, 5.03 mmol) and 1 м TBAF in THF (5.03 mL, 5.03 mmol) added and the mixture stirred for 16 h. The product was adsorbed onto silica gel and flash chromatography (petroleum ether/EtOAc 3:2) gave 29 (1.02 g, 79%) as a white solid; [a]D = + 88.1 (c 0.2, CH2Cl2); 1HNMR (500MHz, CDCl3): d = 7.95 (td, 3J(H,H) = 8.2, 1.4 Hz, 4H; Ar-H), 7.83 (dd, 3J-

CHEMISTRY

A EUROPEAN JOURNAL

(H,H) = 8.3, 1.4 Hz, 2H; Ar-H), 7.54 (tdd, 3J(H,H) = 6.7, 4.8, 1.3 Hz, 2H; Ar-H), 7.45-7.35 (m, 5H; Ar-H), 7.28 (t, 3J(H,H) = 7.8 Hz, 2H; Ar-H), 5.96 (aptt, 3J(H,H) = 9.8 Hz, 1H; H-3), 5.54 (aptt, 3J(H,H) = 9.8 Hz, 1H; H-4), 5.47 (dd, 3J(H,H) = 9.8, 8.8 Hz, 1H; H-2), 4.96 (d, 3J(H,H) = 8.8 Hz, 1 H; H-1), 3.96-3.86 (m, 2H; H-5, H-6a, overlapping peaks), 3.77 (dt, 2J-(H,H) = 13.2 Hz, 3J(H,H) = 4.8 Hz, 1H; H-6b), 2.60 ppm (dd, 3J(H,H) = 8.8, 5.6Hz, 1H; OH); 13CNMR (126MHz, CDCl3): d = 166.0, 165.7, 165.0 (3x COPh), 133.8, 133.5, 133.4, 130.0, 129.9, 129.7 (9 x Ar-CH, overlapping peaks), 128.7, 128.6 (2 x Ar-C), 128.5, 128.4 (4 x Ar-CH, overlapping peaks), 128.3 (2s) (Ar-C, 2x Ar-CH, overlapping peaks), 88.4 (C-1),

77.0 (c-5), 72.6 (C-3), 71.2 (C-2), 69.0 (C-4), 61.1 ppm (C-6); IR (film): n = 3491, 2122, 1723, 1450, 1244, 1088 cm-1; ESI-HRMS calcd for C27H27NO8Na 399.0903, found m/z (%) 399.0887 [M+Na]+. 2,3,4-Tri-O-benzoyl-6-O-(2,3,4-tri-O-benzoyl-5-S-(methoxycarbonyl)-ß-D-xylopyranosyl)-ß-D-glucopyranosyl azide (30): The glycosidation of acceptor 29 (0.2 g, 0.39 mmol) and donor 24 (0.43 g, 0.58 mmol) was carried out as previously described to give 30 (0.33 g, 84 %) as a white solid; [a]D = -10.1 (c 0.75, CH2Cl2); 1H NMR (500 MHz, CDCl3): d = 8.06-7.97 (m, 2H), 7.98-7.90 (m, 4H), 7.90-7.85 (m, 4H), 7.79-7.74 (m, 2H), 7.52 (t, 3J(H,H) = 7.5 Hz, 4H), 7.48-7.34 (m, 10H), 7.31 (t, 3J(H,H) = 7.7 Hz, 2H), 7.29-7.24 (m, 3H), 5.91 (aptt, 3J(H,H) = 9.2Hz, 1H; H-3'), 5.79 (aptt, 3J(H,H) = 9.6 Hz, 1H; H-3), 5.68 (aptt, 3/(H,H) = 9.3 Hz, 1H; H-4'), 5.54 (dd, 3J(H,H) = 9.3, 7.1Hz, 1H; H-2'), 5.38 (aptt, 3J(H,H) =

9.8 Hz, 1H; H-4), 5.35 (aptt, 3J(H,H) = 9.3 Hz, 1H; H-2), 5.04 (d, 3J-(H,H) = 7.3 Hz, 1H; H-1), 4.65 (d, 3/(H,H) = 8.8 Hz, 1H; H-1'), 4.35 (d, 3/(H,H) = 9.4 Hz, 1H; H-5'), 4.13 (dd, 2J(H,H) = 12.0 Hz, 3J(H,H) =

1.9 Hz, 1H; H-6a), 4.06 (ddd, 3/(H,H) = 9.8, 7.4, 1.9 Hz, 1H; H-5), 3.90 (dd, 2J(H,H) = 12.0 Hz, 3J(H,H) = 7.4 Hz, 1H; H-6b), 3.66ppm (s, 3H; CO2CH3); 13C NMR (126 MHz, CDCl3): d = 167.4 (CO2CH3), 165.7, 165.7, 165.4, 165.3, 165.2, 165.1 (6x COPh), 133.8, 133.6, 133.6, 133.5, 130.0, 130.0, 130.0, 129.9 (18 x Ar-CH, overlapping peaks), 129.3, 128.9, 128.9, 128.9, 128.7 (5 x Ar-C), 128.6, 128.6 (8 x Ar-CH, Ar-C, overlapping peaks), 128.5, 128.4 (4 x Ar-CH, overlapping peaks), 101.6 (C-1), 88.0 (C-1'), 76.6 (C-5), 73.0 (C-5'), 72.8 (C-3), 72.0 (C-3'), 71.6 (C-2'), 71.4 (C-2),

70.1 (C-4'), 69.2 (C-4), 68.8 (C-6), 53.0ppm (CO2CH3); IR (film): n = 2956, 2120, 1727, 1452, 1245, 1087, 1067, 1026 cm-1; ESI-HRMS calcd for C55H45O17N3Na 1042.2647, found m/z (%) 1042.2656 [M+Na]+. 2-O-Acetyl-3-O-(2,3,4-tri-O-benzoyl-5-S-(methoxycarbonyl)-ß-D-xylopyr-anosyl)-4,6-O-(1,1,3,3-tetraisopropyl-1,3-disiloxanediyl)-ß-D-glucopyrano-syl azide (31): A solution of 16 (0.5 g, 1.1 mmol) in collidine (2.5 mL) was cooled to -35°C. Freshly distilled AcCl (0.087 mL, 1.23 mmol) was added to this and the reaction mixture was allowed to attain room temperature and stirred for 16 h. MeOH was added and the solvent was removed and flash chromatography of the residue (petroleum ether/EtOAc 9:1) gave the 2-O-acetylated intermediate (0.42 g, 78%); [a]D = -1.8 (c 0.1, CH2Cl2); 1H NMR (500 MHz, CDCl3): d = 4.92-4.84 (m, 1H; H-2), 4.53 (d, 3J(H,H) = 9.0 Hz, 1H; H-1), 3.99-3.91 (m, 1H; H-6a), 3.82-3.71 (m, 3H; H-6b, H-4, H-3, overlapping peaks), 3.45 (dddd, 3J(H,H) = 7.9, 5.2, 2.8, 1.3 Hz, 1H; H-5), 2.09 (s, 3H; COCH3), 1.98-1.91 (m, 1H; OH), 1.13-0.89 (m, 28 H; 4xCH(CH3)2, overlapping peaks); 13CNMR (126 MHz, CDCl3): d = 169.2 (COCH3), 87.9 (C-1), 78.4 (C-5), 77.3 (C-4), 72.7 (C-3), 72.5 (C-2), 61.9 (C-6), 20.6 (COCH3), 17.2 (2s), 17.1 (4s) (8x CH(CH3)2, overlapping peaks), 12.8 (2s), 12.1, 12.0 ppm (4x CH(CH3)2, overlapping peaks); IR (film): n = 3533, 2943, 2866, 2121, 1729, 1462, 1243, 980 cm-1; ESI-HRMS calcd for C20H39N3O7Si2Na 512.224, found m/z (%) 512.2232 [M+Na]+. Glycosidation of this intermediate (0.4 g, 0.8 mmol) with 24 (0.91 g, 1.2 mmol) gave 31 (0.65 g, 82%) after chromatography (petroleum ether/EtOAc 8:2) as a foam; [a]D = -24.1 (c 0.1, CH2Cl2); 1HNMR (500 MHz, CDCl3): d = 7.98 (dd, 3J(H,H) = 8.3, 1.4 Hz, 2H; Ar-H), 7.93 (dd, 3J(H,H) = 8.4, 1.4Hz, 2H; Ar-H), 7.86 (dd, 3J-(H,H) = 8.3, 1.4 Hz, 2H; Ar-H), 7.51 (dd, 3J(H,H) = 7.5, 3.6 Hz, 2H; Ar-H), 7.47-7.42 (m, 1H), 7.38 (q, 3J(H,H) = 7.9 Hz, 4H; Ar-H), 7.30 (t, 3J-(H,H) = 7.8 Hz, 2H; Ar-H), 5.89 (aptt, 3J(H,H) = 9.3 Hz, 1H; H-3'), 5.71 (aptt, 3J(H,H) = 9.4Hz, 1H; H-4'), 5.53 (dd, 3J(H,H) = 9.3, 7.4Hz, 1H; H-2'), 5.09 (d, 3J(H,H) = 7.4 Hz, 1H; H-1'), 4.83 (t, 3J(H,H) = 9.0 Hz, 1H; H-2), 4.36 (d, 3J(H,H) = 9.5 Hz, 1H; H-5), 4.28-4.19 (m, 2H; H-6a, H-1, overlapping peaks), 3.85 (dd, 2J(H,H) = 12.2 Hz, 3/(H,H) = 7.3 Hz, 1H; H-6b), 3.70 (s, 3H; CO2CH3), 3.63 (dd, 3J(H,H) = 9.1, 7.7 Hz, 1H; H-3), 3.59-3.49 (m, 2H; H-5, H-4, overlapping peaks), 2.06 (s, 3H; COCH3),

1.09-0.94 ppm (m, 28 H ; 4xCH(CH3)2, overlapping peaks); 13CNMR (126 MHz, CDCl3): d = 169.3 (COCH3), 167.5 (CO2CH3), 165.7, 165.3, 165.2 (3x COPh), 133.6, 133.4, 130.0, 129.9 (9 x Ar-CH, overlapping peaks), 129.4, 129.0, 128.9 (3xAr-C), 128.6 (2s), 128.5 (6x Ar-CH, overlapping peaks), 101.7 (C-1'), 87.6 (C-1), 79.0 (C-5), 77.4 (C-3), 73.3 (C-4), 73.0 (C-5'), 72.6 (C-2), 72.3 (C-3'), 71.8 (C-2'), 70.3 (C-4'), 69.0 (C-6), 53.0 (CO2CH3), 20.8 (C0CH3), 17.6, 17.5, 17.3 (4s), 17.2 (8 x CH(CH3)2, overlapping peaks), 12.9, 12.8, 12.3, 12.2 ppm (4x CH(CH3)2, overlapping peaks); IR (film): n = 2948, 2868, 2118, 1732, 1452, 1248, 1223, 1092, 1068, 1041, 1027, 984 cm-1; ESI-HRMS calcd for C48H61O16N3Si2Na 1014.3488, found m/z (%) 1014.3533 [M+Na]+.

2,4,6-Tri-O-benzoyl-3-O-(2,3,4-tri-O-benzoyl-5-S-(methoxycarbonyl)-ß-D-xylopyranosyl)-ß-D-glucopyranosyl azide (32): Disaccharide 31 (0.25 g, 0.252 mmol) was added to 1.25 м HCl in methanol (10 mL) at 0 °C and the resulting solution was allowed to attain room temperature and stirred for 16 h. The reaction mixture was cooled over an ice-bath, diluted with MeOH (20 mL) and NaHCO 3 was added. The resulting slurry was concentrated to dryness and the residue suspended was in pyridine and cooled over an ice-bath. BzCl (0.18 mL, 1.5 mmol) was then added and the reaction mixture was allowed to warm to room temperature and was stirred, overnight. Methanol (0.5 mL) was added and the mixture was diluted with EtOAc (10 mL). This layer was washed with 1 м HCl (2x5 mL), satd. aq. NaHCO3 (10 mL), brine (10 mL), dried over Na2SO4, filtered and the solvent was removed under diminished pressure. Flash chromatography of the residue (petroleum ether/EtOAc 6:4) gave 32 (0.15 g, 63%) as a glass; [a]D = -15.6 (c 1.25, CH2Cl2); 1HNMR (500 MHz, CDCl3): d = 8.00 (dd, 3J(H,H) = 8.4, 1.4 Hz, 2H; Ar-H), 7.957.90 (m, 4H; Ar-H), 7.88 (ddd, 3J(H,H) = 8.4, 3.0, 1.4 Hz, 4H; Ar-H), 7.79-7.75 (m, 2H; Ar-H), 7.55-7.50 (m, 4H; Ar-H), 7.48-7.27 (m, 14H; Ar-H), 5.91 (aptt, 3J(H,H) = 9.3 Hz, 1H; H-3'), 5.79 (aptt, 3J(H,H) = 9.6 Hz, 1H; H-3), 5.68 (aptt, 3J(H,H) = 9.3 Hz, 1H; H-4'), 5.54 (dd, 3J-(H,H) = 9.2, 7.3 Hz, 1H; H-2'), 5.38 (aptt, 3J(H,H) = 9.8 Hz, 1H; H-2), 5.35 (dd, 3J(H,H) = 9.7, 8.7 Hz, 1H; H-4), 5.04 (d, 3J(H,H) = 7.3 Hz, 1H; H-1'), 4.65 (d, 3j(H,H) = 8.8 Hz, 1H; H-1), 4.35 (d, 3j(H,H) = 9.4 Hz, 1H; H-5'), 4.13 (dd, 2J(H,H) = 12.0 Hz, 3J(H,H) = 1.9 Hz, 1H; H-6a), 4.06 (ddd, 3J(H,H) = 9.7, 7.6, 1.9 Hz, 1H; H-5), 3.90 (dd, 2J(H,H) = 12.0 Hz, 3J-(Н,Н) = 7.6Hz, 1H; H-6b), 3.66ppm (s, 3H; CO2CH3); 13CNMR (126 MHz, CDCl3): d = 167.2 (CO2CH3), 165.6, 165.5, 165.3, 165.2, 165.0, 164.9 (6x COPh), 133.6, 133.5, 133.4, 133.3, 129.9 (2s), 129.8 (2s), 129.7 (18 x Ar-CH, overlapping peaks), 129.1, 128.8, 128.7 (2s), 128.6 (5 x Ar-C, overlapping peaks), 128.5, 128.4 (2s) (8 x Ar-CH, Ar-C, overlapping peaks), 128.3 (2s) (4 x Ar-CH, overlapping peaks), 101.5 (C-1'), 87.8 (C-1), 76.5 (C-5), 72.8 (C-5'), 72.6 (C-3), 71.8 (C-3'), 71.5 (C-2'), 71.2 (C-2), 70.0 (C-4'), 69.1 (C-4), 68.6 (C-6), 52.9ppm (CO2CH3); IR (film): n= 2956, 2120, 1714, 1451, 1247, 1088, 1068, 1026 cm-1; ESI-HRMS calcd for C55H45O17N3Na 1042.2647, found m/z (%) 1042.2646 [M+Na]+. 2,3-O-(1,1,3,3-Tetraisopropyl-1,3-disiloxanediyl)-6-O-acetyl-ß-D-glucopyr-anosyl azide (33): Azide 28 (1.5 g, 7.3 mmol) was dissolved in DMF (15 mL) and 2,2-dimethoxypropane (1.78 mL, 14.6 mmol) and p-toluene-sulfonic acid (0.14 g, 0.73 mmol) were added and the reaction mixture was stirred at room temperature for 3 h. Triethylamine (1 mL) was added and the solvent was removed and the residue was dissolved in pyridine (15 mL) and the mixture was cooled over ice. 1,3-Dichloro-1,1,3,3-tetra-isopropyldisiloxane (2.88 g, 9.13 mmol) was added and the mixture stirred for 16 h at room temperature. Methanol (1 mL) was added followed by EtOAc (50 mL) and this layer was washed with 1 м HCl (2x50 mL), satd. aq. NaHCO3 (50 mL), brine (50 mL), dried over Na2SO4, filtered and the solvent was removed under diminished pressure. Flash chroma-tography of the residue (petroleum ether/EtOAc 95:5) gave the protected intermediate (2.53 g, 71%) as a clear oil; [a]D =+78.8 (c 0.25, CH2Cl2); 1H NMR (500 MHz, CDCl3): d = 4.57 (d, 3J(H,H) = 8.2 Hz, 1H; H-1), 3.95 (dd, 2J(H,H) = 10.8 Hz, 3J(H,H) = 5.3 Hz, 1H; H-6a), 3.75 (aptt, 2J-(H,H) = 10.5 Hz, 1H; H-6b), 3.68 (dd, 3J(H,H) = 8.9, 7.9 Hz, 1H; H-3), 3.55-3.49 (m, 2H; H-2, H-4, overlapping peaks), 3.32 (td, 3J(H,H) = 10.0, 5.3Hz, 1H; H-5), 1.47 (s, 3H; C(CH3)2), 1.38 (s, 3H; C(CH3)2), 1.130.99 ppm (m, 28 H ; 4xCH(CH3)2, overlapping peaks); 13CNMR (126 MHz, CDCl3): d = 99.5 (c(cH3)2), 91.3 (C-1), 78.1 (C-2), 76.6 (C-3), 72.7 (C-4), 69.5 (C-5), 62.0 (C-6), 28.9, 19.0 (c(ch3)2), 17.3, 17.2, 17.1 (2s), 17.0, 16.8 (8 x CH(CH3)2, overlapping peaks), 12.9, 12.8, 12.2,

12.0ppm (4xCH(CH3)2, overlapping peaks); IR (film): n = 2945, 2867, 2115, 1738, 1465, 1064, 983 cm-1; ESI-HRMS calcd for C21H42N3O6Si2 488.7451, found m/z (%) 488.7458 [M+H]+. This intermediate (2.5 g, 5.1 mmol) was dissolved in MeOH and Amberlyst 15 H+ (3.0 g) was added and the mixture was stirred for 5 h. The resin was filtered off and the solvent was removed and flash chromatography of the residue (petroleum ether/EtOAc, 8:2) gave the required 2,3-O-silylated intermediate (1.88 g, 82%) as a wax; [a]D = -18.0 (c 0.11, CH2Cl2); 1H NMR (500 MHz, CDCl3): d = 4.61 (d, 3J(H,H) = 8.1 Hz, 1H; H-1), 3.95 (dd, 2J-(Н,Н) = 12.1Hz, 3J(H,H) = 3.1Hz, 1H; H-6a), 3.81 (dd, 2J(H,H) = 12.1Hz, 3J(H,H) = 4.7 Hz, 1H; H-6b), 3.66 (aptt, 3J(H,H) = 8.5 Hz, 1H; H-3), 3.55 (apttd, 3J(H,H) = 9.2, 8.6, 1.4 Hz, 1H; H-4), 3.51-3.45 (m, 2H; H-5, H-2, overlapping peaks), 2.45 (d, 3J(H,H) = 2.2 Hz, 1H; OH), 2.04 (s, 1H; OH), 1.12-0.99ppm (m, 28H; 4xCH(CH3)2, overlapping peaks); 13C NMR (126 MHz, CDCl3): d = 90.8 (C-1), 80.1 (C-3), 76.9 (C-5) 76.5 (C-2), 70.6 (C-4), 62.3 (C-6), 17.4, 17.2 (3s) 17.1, 17.0 (8xCH(CH3)2, overlapping peaks), 12.8 (2s), 12.1, 12.4 ppm (4x CH(CH3)2, overlapping peaks); IR (film): n = 3372, 2945, 2868, 2117, 1738, 1464, 1143, 1036, 986 cm-1; ESI-HRMS calcd for C18H37N3O6Si2Na 442.2349, found m/z (%) 442.2354 [M+Na]+. This intermediate (1.5 g, 3.35 mmol) was treated with freshly distilled AcCl (0.26 mL, 3.69 mmol) in collidine (7.5 mL) as previously described and gave 33 (0.97 g, 59 %) after flash chromatogra-phy (petroleum ether/EtOAc 9:1); [a]D = -25.6 (c 0.25, CH2Cl2); 1HNMR (500 MHz, CDCl3): d = 4.57 (d, 3J(H,H) = 8.2 Hz, 1H; H-1), 4.42 (dd, 2J(H,H) = 12.2 Hz, 3J(H,H) = 2.2 Hz, 1H; H-6a), 4.30 (dd, 2J-(Н,Н) = 12.2 Hz, 3J(H,H) = 5.4 Hz, 1H; H-6b), 3.64 (aptt, 3J(H,H) = 8.6 Hz, 1H; H-3), 3.59 (ddd, 3J(H,H) = 9.7, 5.4, 2.2 Hz, 1H; H-5), 3.49 (aptt, 3J(H,H) = 8.4Hz, 1H; H-2), 3.44 (ddd, 3J(H,H) = 9.7, 8.6, 2.2Hz, 1H; H-4), 2.48 (d, 3J(H,H) = 2.2 Hz, 1H; OH), 2.11 (s, 3H; COCH3), 1.11-1.03 ppm (m, 28 H ; 4xCH(CH3)2, overlapping peaks); 13CNMR (126 MHz, CDCl3): d = 171.1 (COCH3), 90.8 (C-1), 80.0 (C-3), 76.4 (C-2),

75.1 (C-5), 70.2 (C-4), 63.1 (C-6), 20.9 (COCH3), 17.3, 17.2 (3s), 17.1, 17.0 (8x CH(CH3)2, overlapping peaks), 12.8 (2s), 12.1 (2s), 12.1 ppm (4x CH-(CH3)2, overlapping peaks); IR (film): n = 3484, 2946, 2869, 2116, 1736, 1464, 1245, 1149, 1039, 985 cm-1; ESI-HRMS calcd for C20H39N3O7Si2Na 512.224, found m/z (%) 512.2219[M+Na]+.

2,3-O-(1,1,3,3-Telraisopropyl-1,3-disiloxanediyl)-4-O-(2,3,4-lri-O-benzoyl-5-S-(melhoxycarbonyl)-ß-D-xylopyranosyl)-6-O-acelyl-ß-D-glucopyranosyl azide (34): Glycosidation of 33 (0.5 g, 1.02 mmol) with donor 24 (1.13 g,

I.53 mmol) as previously described gave 34 (0.67 g, 66%) after chromatography (petroleum ether/EtOAc 8:2) as a glass; [a]D = -75.3 (c 0.3, CH2Cl2); 1H NMR (500 MHz, CHCl3): d = 7.98-7.90 (m, 4H; Ar-H), 7.86-7.81 (m, 2H; Ar-H), 7.58-7.51 (m, 2H; Ar-H), 7.48-7.36 (m, 6H; Ar-H), 7.30 (t, 3J(H,H) = 7.8 Hz, 2H; Ar-H), 5.84 (aptt, 3J(H,H) = 9.5 Hz, 1H; H-3'), 5.69 (aptt, 3J(H,H) = 9.6 Hz, 1H; H-4'), 5.50 (dd, 3J(H,H) = 9.6, 7.8 Hz, 1H; H-2'), 4.92 (d, 3J(H,H) = 7.8 Hz, 1H; H-1'), 4.47 (d, 3J-(H,H) = 8.3 Hz, 1H; H-1), 4.35 (dd, 2J(H,H) = 12.2 Hz, 3J(H,H) = 2.0 Hz, 1H; H-6a), 4.28 (d, 3J(H,H) = 9.7 Hz, 1H; H-5'), 4.14 (dd, 3J(H,H) =

12.2 Hz, 3J(H,H) = 4.9 Hz, 1H; H-6b), 3.80 (aptt, 3J(H,H) = 8.4 Hz, 1H; H-3), 3.76-3.69 (m, 4H; CO2CH3, H-4, overlapping peaks), 3.49 (aptt, 3J-(H,H) = 8.3 Hz, 1H; H-2), 3.42 (ddd, 3J(H,H) = 10.0, 4.9, 2.0 Hz, 1H; H-5), 2.03 (s, 3H; COCH3), 1.23-1.04 ppm (m, 28 H ; 4xCH(CH3)2, overlapping peaks); 13CNMR (126 MHz, CDCl3): d = 170.3 (COCH3), 166.5 (COCH3), 165.5, 164.9, 164.6 (3x COPh), 133.5, 133.4, 133.3, 129.8 (2s) (9 x Ar-CH, overlapping peaks), 128.7, 128.6 (3xAr-C, overlapping peaks), 128.5, 128.4, 128.3 (6 x Ar-CH, overlapping peaks), 100.9 (C-1'), 90.5 (C-1), 77.8 (C-3), 77.1 (C-4), 74.6 (C-5), 73.7 (C-5'), 72.3 (C-3'), 71.8 (C-2'), 70.2 (C-4'), 61.9 (C-6), 52.8 (CO2CH3), 29.7, 20.8, 17.4, 17.3, 17.2 (2s), 17.1 (2s), 17.0 (8xCH(CH3)2, overlapping peaks), 12.8 (2s), 12.1,

II.6ppm (4xCH(CH3)2, overlapping peaks); IR (film): n = 3072, 2955, 2118, 1728, 1691, 1451, 1248, 1090, 1067, 1025 cm-1; ESI-HRMS calcd for C48H61O16N3Si2Na 1014.3488, found m/z (%) 1014.3469 [M+Na]+. 2,3,6-Tri-O-benzoyl-4-O-(2,3,4-tri-O-benzoyl-5-S-(methoxycarbonyl)-ß-D-xylopyranosyl)-ß-D-glucopyranosyl azide (35): Removal of the acetyl group and silyl protecting group from 34 (0.3 g, 0.3 mmol) as described above gave 35 (0.17 g, 54%) as a glass after chromatography (petroleum ether/EtOAc 6:4); [a]D = -56.6 (c 1.15, CH2Cl2); 1HNMR (500 MHz, CDCl3): d = 8.02-7.98 (m, 2H; Ar-H), 7.89 (dd, 3J(H,H) = 8.3, 1.4Hz, 2H; Ar-H), 7.76-7.72 (m, 4H; Ar-H), 7.62 (dd, 3/(н,Н) = 8.4, 1.4Hz,

2H; Ar-H), 7.58 (dd, 3J(H,H) = 8.3, 1.4Hz, 2H; Ar-H), 7.55-7.45 (m, 3H; Ar-H), 7.45-7.33 (m, 7H; Ar-H), 7.29-7.17 (m, 8H; Ar-H), 5.78-5.67 (m, 3H,H-3, H-4', H-3', overlapping peaks), 5.54-5.48 (m, 2H; H-2', H4', overlapping peaks), 5.07 (d, 3J(H,H) = 7.6 Hz, 1H; H-1'), 4.87 (d, 3J-(H,H) = 8.0 Hz, 1H; H-1), 4.57 (dd, 2J(H,H) = 12.4 Hz, 3J(H,H) = 3.0 Hz, 1H; H-6a), 4.41 (dd, 2J(H,H) = 12.4 Hz, 3J(H,H) = 5.1Hz, 1H; H-6b), 4.35 (d, 3/(H,H) = 9.1 Hz, 1H; H-5'), 4.12-4.07 (m, 2H; H-5, H-2, overlapping peaks), 3.73 ppm (s, 3H; CO2CH3); 13C NMR (126 MHz, CDCl3): d = 166.7 (CO2CH3), 166.0, 165.5, 165.1, 165.0, 164.9, 164.7 (6x COPh), 133.4 (2s), 133.3, 133.1, 132.9, 129.8 (2s), 129.7 (3s), 129.6 (18 x Ar-CH, overlapping peaks), 129.5, 128.8, 128.7, 128.5 (3s) (6 x Ar-C), 128.4 (2s), 128.3 (2s), 128.2, 128.1 (12xAr-CH, overlapping peaks), 100.8 (C-1'), 88.8 (C-1), 77.7 (C-2), 73.9 (C-5 and C-3, overlapping peaks), 73.0 (C-5'), 72.2 (C-3'), 71.6 (C-2'), 70.0 (C-4'), 69.0 (C-4), 62.8 C-6), 53.0 ppm (CO2CH3); IR (film): n = 2945, 2867, 2120, 1724, 1452, 1248, 1092, 1066, 1027, 986, 702 cm-1; ESI-HRMS calcd for C55H45O17N3Na 1042.2647, found m/z (%) 1042.2631 [M+Na]+.

2,3,4-Tri-O-benzoyl-1-deoxy-1-(2,2,2-trichloro-1-iminoethoxy)-D-galacto-pyranuronate, methyl ester (37): The compound 36[33] (10 g, 0.017 mol) in CH2Cl2 (100 mL) and H2O (40 mL) was treated with TEMPO (0.5 g) and BAIB (16.2 g, 0.05 mol) as described above to give the galacturonic acid (9.5 g, 91%). Some of this acid (3 g, 4.9 mmol) was dissolved in DMF (40 mL) and treated with NaHCO3 (0.8 g, 9.5 mmol) and MeI (0.50 mL, 7.2 mmol) as described above and gave after chromatography (petroleum ether/EtOAc 3:1) the methyl ester as a white solid (2.58 g, 86%, mixture of anomers, a/ß = 3:1). Analytical data for the a anomer: 1HNMR (500MHz, CDCl3): d = 8.10-8.03 (m, 4H; Ar-H), 7.89 (d, 3J(H,H) = 7.8 Hz, 2H; Ar-H), 7.83 (d, 3J(H,H) = 6.9 Hz, 2H; Ar-H), 7.61 (t, 3J-(H,H) = 7.3 Hz, 1H; Ar-H), 7.59-7.51 (m, 1H; Ar-H), 7.51-7.40 (m, 6H; Ar-H), 7.30 (m, 4H; Ar-H), 6.27 (m, 2H; H4 and H1), 6.15-6.08 (m, 1H; H2), 5.78 (dd, 3J(H,H) = 10.3, 3.3 Hz, 1H; H3), 4.84 (s, 1H; H5), 3.71 ppm (s, 3H; CH3); 13CNMR (125 MHz, CDCl3): d = 165.9, 165.4, 165.2, 164.70 (each C=O), 133.9, 133.6, 133.5, 133.4 (each CH), 130.3, 130.1, 129.8, 129.7 (each CH), 128. 8, 128.7, (each C), 128.6, 128.5, 128.4, 128.3 (each CH), 92.6 (C-1), 73.7 (C-5), 71.2 (C-3), 69.0 (C-4), 68.2 (C-2), 52.9 ppm (CH3); ESI-HRMS calcd for C35H28O11Na 647.1529, found m/z (%) 647.1533 [M+Na]+. This intermediate (2g, 3.2 mmol) was dissolved in CH2Cl2 (5 mL) and cooled to 0 "C and 33% HBr in AcOH (8 mL) was then added and the mixture was stirred at room temperature for 6 h. The mixture was then diluted with EtOAc, washed with water, satd. aq. NaHCO3, water, brine, dried over Na2SO4, and the solvent was removed under diminished pressure to give the glycosyl bromide as a colourless oil. This was taken up in acetone (90 mL) and water (10 mL) and Ag2CO3 (530 mg, 1.9 mmol) were added and the mixture was stirred for 16 h at room temperature. The mixture was filtered through Celite, which was subsequently rinsed with CH2Cl2. The combined filtrate were dried over Na2SO4, and the solvent was removed under diminished pressure. Flash chromatography (petroleum ether/EtOAc 2:1) gave the hemiacetal as a white solid (1.21 g, 73% over 2 steps) and as mixture of anomers (a/ß = 3:1). Analytical data for the a anomer: 1H NMR (500 MHz, CDCl3): d = 8.00 (dd, 3J(H,H) = 17.5, 7.8 Hz, 4H; Ar-H), 7.81 (d, 3J-(H,H) = 7.7 Hz, 2H; Ar-H), 7.59 (t, 3J(H,H) = 7.2 Hz, 1H; Ar-H), 7.51 (t, 3J(H,H) = 7.3 Hz, 1H; Ar-H), 7.45 (t, 3J(H,H) = 7.7 Hz, 3H; Ar-H Ar-H), 7.37 (t, 3J(H,H) = 7.5 Hz, 2H; Ar-H), 7.30-7.24 (m, 3H; Ar-H), 6.27 (s, 1H; H1), 6.06 (dd, 3J(H,H) = 10.7, 3.2 Hz, 1H; H3), 5.96 (s, 1H; H4), 5.69 (dd, 3J(H,H) = 10.8, 3.0 Hz, 1H; H2), 5.16 (s, 1H; H5), 3.71 (s, 3H; CH3), 3.55 ppm (s, 1H; OH); 13CNMR (125 MHz, CDCl3): a = 167.8, 165.9, 165.5, 165.2 (each C=O), 133.5 (2s), 133.2 (each CH), 129.9, 129.8, 129.7 (each C), 129.1, 129.0 (2s), 128.6, 128.5, 128.3 (each CH), 91.2 (C-1), 69.9 (c-4), 68.8 (2s) (C-5 and C-2), 67.6 (C-3), 52.8 ppm (CH3); ESI-HRMS calcd for C34H28O10Na 619.1580, found m/z (%) 619.1591 [M+Na]+. This hemiacetal (540 mg, 1.0 mmol) was dissolved in CH2Cl2 (20 mL) and cooled to 0"C And Cl3CCN (1.0 mL, 10.3 mmol) was added followed by DBU (6 drops). The mixture was stirred at 0"C for 5 h, concentrated to 5 mL and subsequent chromatography of the residue (petroleum ether/ EtOAc 2:1) gave the title compound 37 (425 mg, 61 %) as a white solid; 1H NMR (500 MHz, CDCl3): d = 8.69 (s, 1H; NH), 8.03 (d, 3J(H,H) = 7.7 Hz, 2H; Ar-H), 7.94 (d, 3J(H,H) = 7.8 Hz, 2H; Ar-H), 7.82 (d, 3J-(H,H) = 7.8 Hz, 2H; Ar-H), 7.61 (t, 3J(H,H) = 7.4 Hz, 1H; Ar-H), 7.54-

CHEMISTRY

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7.43 (m, 4H; Ar-H), 7.35 (t, 3J(H,H) = 7.7 Hz, 2H; Ar-H), 7.28 (t, 3J-(H,H) = 7.8 Hz, 2H; Ar-H), 7.03 (d, 3J(H,H) = 2.8 Hz, 1H; H-1), 6.34 (d, 3/(H,H) = 1.4 Hz, 1H; H-4), 6.08 (dd, 3J(H,H) = 10.7, 3.1Hz, 1H; H-3), 5.96 (dd, 3J(H,H) = 10.7, 3.2 Hz, 1H; H-2), 5.09 (s, 1H; H-5), 3.72 ppm (s, 3H; CH3); 13C (125 MHz, CDCl3): d = 166.4, 165.5, 165.4, 165.1, 160.2 (each C=O), 133.7, 133.6, 133.4 (each CH), 130.0, 129.8, 129.7 (each CH), 128.8, 128.7 (each C), 128.6 (CH), 128.6(C), 128.4, 128.3 (each CH), 93.6 (C-1), 90.6 (C=NH), 71.2 (C-5), 69.4 (C-4), 67.8 (C-3), 67.3 (C-2), 52.9 ppm (CH3); HRMS calcd for C28H25O10 521.1448, found m/z (%) 521.1446 [M+H]+.

Methyl 6-O-(2,3,4-tri-O-benzoyl-5-S-(methoxycarbonyl)-a-L-arabinopyra-nosyl)-2,3,4-tri-O-benzoyl-a-D-galactopyranose (39): Regioselective gly-cosidation of 3S[34'35] (150 mg, 0.22 mmol) and 37 (100 mg, 0.22 mmol) as described above gave the intermediate alcohol (165 mg, 77 %) as a colorless foam; 1H NMR (500 MHz, CDCl3): d = 8.02-7.92 (m, 8H; Ar-H), 7.80 (d, 3J(H,H) = 7.3 Hz, 2H; Ar-H), 7.56 (t, 3J(H,H) = 7.5 Hz, 1H; Ar-H), 7.52-7.41 (m, 6H; Ar-H), 7.39-7.32 (m, 6H; Ar-H), 7.26 (dd, 3J-(H,H) = 9.1, 6.5 Hz, 2H; Ar-H), 6.17 (d, 3J(H,H) = 3.3 Hz, 1H; H-4'), 5.78 (dd, 3J(H,H) = 10.4, 7.9 Hz, 1H; H-2'), 5.69 (dd, 3J(H,H) = 10.7, 3.5 Hz, 1H; H-2), 5.62 (ddd, 3J(H,H) = 10.5, 7.3, 3.5 Hz, 2H; H-3 and H-3'), 5.01 (d, 3J(H,H) = 3.5 Hz, 1H; H-1), 4.97 (d, 3J(H,H) = 7.9 Hz, 1H; H-1'), 4.61 (s, 1H; H-5'), 4.54 (s, 1H; H-4), 4.26 (dd, 2J(H,H) = 10.2 Hz, 3/(H,H) = 6.4 Hz, 1H; H-6a), 4.18 (t, 3J(H,H) = 6.3 Hz, 1H; H-5), 4.00 (dd, 2J(H,H) = 10.2Hz, 3J(H,H) = 6.4Hz, 1H; H-6b), 3.61 (s, 3H; CH3), 3.42(d, 3J(H,H) = 5.0Hz, 1H; OH), 3.17ppm (s, 3H; CH3); 13CNMR (125 MHz, CDCl3): d = 166.8, 166.1, 165.8, 165.6, 165.2, 165.1 (each C= O), 133.6, 133.4 (x 2), 133.2, 133.1 (each CH), 130.0, 129.8 (x2), 129.7 (each CH), 129.5, 129.2, 128.8, 128.7 (each C), 128.6, 128.4 (2s), 128.3 (each CH), 101.4 (C-1',), 97.3 (C-1), 72.6 (C-5'), 71.3 (C-3'), 70.9 (C-2), 69.3 (C-3 and C-2'), 68.9 (C-4'), 68.7 (C-6), 68.5 (C-5), 67.3 (C-4), 55.1 (CH3), 52.9 ppm (CH3) ; ESI-HRMS calcd for C49H45O17 905.2657, found m/z (%) 905.2655 [M+H]+. This intermediate (125 mg, 0.132 mmol) was benzoylated using pyridine (4 mL) and benzoyl chloride (30 mL, 0.263 mmol) as described above to give 39 (118 mg, 90%) as a white solid after chromatography (petroleum ether/EtOAc 2:1); 1HNMR (500 MHz, CDCl3): d = 8.11-8.05 (m, 2H; Ar-H), 8.05- 8.00(m, 2H; Ar-H), 7.93 (m, 4H; Ar-H), 7.81-7.78 (m, 2H; Ar-H), 7.76-7.72 (m, 2H; Ar-H), 7.60 (m, 2H; Ar-H), 7.53-7.30 (m, 12H; Ar-H), 7.29-7.17 (m, 4H; Ar-H), 6.21-6.12 (m, 1H; H-4'), 5.90 (m, 2H; H-4, H-3), 5.83 (dd, 3J-(H,H) = 10.4, 7.9 Hz, 1H; H-2'), 5.61 (dd, 3J(H,H) = 10.4, 3.5 Hz, 1H; H-3'), 5.56 (dd, 3J(H,H) = 10.2, 3.6 Hz, 1H; H-2), 4.99 (d, 3J(H,H) = 3.6 Hz, 1H; H-1), 4.89 (d, 3J(H,H) = 7.9 Hz, 1H; H-1'), 4.58 (m, 1H; H-5'), 4.49 (m, 1H; H-5), 4.21 (dd, 2J(H,H) = 11.0 Hz, 3J(H,H) = 2.3 Hz, 1H; H-6a), 3.82 (dd, 2J(H,H) = 11.0 Hz, 3J(H,H) = 8.6 Hz, 1H; H-6b), 3.69 (s, 3H; CH3), 3.10ppm (s, 3H; CH3); 13CNMR (125MHz, CDCl3): d = 166.3, 166.1, 165.5 (2s) 165.3, 165.2 (2s) (each C=O), 133. (2s), 133.3 (2s), 133.0 (each CH), 130.0, 129.9, 129.8 (2s), 129.7, 129.6 (each CH), 129.3, 129.2 (2s), 128.9, 128.7 (each C), 128.6 (2s), 128.4 (2s), 128.4, 128.3, 128.2 (each CH), 101.9 (C-1'), 97.0 (C-1), 72.9 (C-5'), 71.2 (C-3'), 70.2 (C-6), 70.0 (C-4), 69.4 (C-2), 69.2 (C-2'), 69.1 (C-4'), 68.4 (C-5), 68.9 (C-3), 55.0 (CH3), 52.8 ppm (CH3) ; ESI-HRMS calcd for C56H49O18 1009.2919, found m/z (%) 1009.2924 [M+H]+.

Methyl 4-O-(6-O-ferf-butyldiphenylsilyl-2,3,4-tri-O-benzoyl-p-D-galacto-pyranosyl)-2,3,6-tri-O-benzyl-a-D-galactopyranose (43): Tf2O (0.080 mL, 0.48 mmol) was added to a stirred solution of the thioglycoside 41[36'37] (370 mg, 0.44 mmol), benzene sulfonyl pyridine (92 mg, 0.44 mmol), 2,4,6-tri-tert-butylpyrimidine (220 mg, 0.89 mmol), and activated 3 A powdered sieves in CH2Cl2 (5 mL), at —60 °C, under argon. After 5 min, a solution of the glycosyl acceptor 42 (286 mg, 0.60 mmol) in dichlorome-thane (4 mL) was added. The mixture was allowed to attain room temperature, filtered, washed with satd. aq. NaHCO3, brine, dried (Na2SO4), and the solvent was then removed under diminished pressure. Chroma-tography of the residue (petroleum ether/EtOAc, 3:1) gave the title compound 43 (466 mg, 90%) as a white foam; 1HNMR (500 Hz, CDCl3): d = 8.04 (d, J=7.4 Hz, 2H; Ar-H), 7.91 (d, J=7.5 Hz, 2H; Ar-H), 7.82 (d, J=7.4 Hz, 2H; Ar-H), 7.64 (dd, 3J(H,H) = 13.1, 7.0 Hz, 3H; Ar-H), 7.49 (t, 3J(H,H) = 7.7 Hz, 2H; Ar-H), 7.46-7.31 (m, 12H; Ar-H), 7.29-7.00 (m, 15H; Ar-H), 6.95 (d, 3J(H,H) = 3.8Hz, 2H; Ar-H), 6.07 (d, 3J(H,H) = 2.2 Hz, 1H; Ar-H), 5.74-5.63 (m, 1H; Ar-H), 5.54 (dd, 2J(H,H) = 10.4,

3.2Hz, 1H; Ar-H), 5.12 (d, 2J(H,H) = 7.9Hz, 1H; Ar-H), 4.69 (d, 2J-(H,H) = 11.7Hz, 1H; 1 xPhCHH), 4.62 (d, 2J(H,H) = 11.7Hz, 1H; 1x PhCHH), 4.47-4.38 (m, 2H; 1 xPhCHH and H-1), 4.34 (d, 2J(H,H) = 11.9 Hz, 1H; 1 xPhCHH), 4.12-4.04 (m, 2H; 1 xPhCHH and H-4), 3.92 (t, 3J(H,H) = 7.2 Hz, 1H; H-5'), 3.81 (m, 3H; 1 xPhCHH and H-5 and H-3), 3.71 (m, 2H; H-6a' and H-6b'), 3.67-3.50 (m, 3H; H-6a and H-6b and H-2), 3.28 (s, 3H; CH3), 0.99 (s, 9H; C(CH3)3); 13CNMR (125MHz, CDCl3): d = 171.2, 165.6, 165.3, 165.1 (each C=O), 138.8, 138.4, 138.1 (each C), 135.5, 135.4 (each CH), 133.3, 133.0, 132.9 (each CH), 132.8,

132.4 (each C), 130.0, 129.9, 129.8, 129.7 (2s), (each CH), 129.6, 129.1 (each C), 128.6, 128.5, 128.2 (2s), 128.1, 127.8 (2s) 127.8, 127.7, 127.6 (2s),

127.5 (2s) (each CH), 101.6 (C-1'), 98.5 (C-1), 78.1 (C-3), 77.4 (C-2), 75.1 (C-4), 73.8 (PhCH2), 73.5 (PhCH2), 73.4 (PhCH2), 73.2 (C-5'), 72.2 (C-3'), 70.3 (C-2'), 69.7 (C-6), 69.1 (C-5), 67.6 (C-4'), 60.8 (C-6), 55.3 (OCH3),

26.6 (C(CH3)3), 18.9 ppm (C(CH3)3); ESI-HRMS calcd for C71H73O14Si 1177.4770, found m/z (%) 1177.4762 [M+H] + .

Methyl 4-O-(2,3,4-tri-O-benzoyl-5-S-(methoxycarbonyl)-a-L-arabinopyra-nosyl)-2,3,6-tri-O-benzoyl-a-D-galactopyranoside (44): Acetic acid (13 mL, 1 equiv) was added to a solution of 43 (263 mg, 0.22 mmol) in THF (6 mL), and the mixture was cooled to 0°C. After addition of TBAF (1 m in THF, 0.25 mL, 0.25 mmol), the mixture was stirred at 0°C for 2 h, then diluted with diethyl ether and washed with brine (x 2). The aqueous phase was reextracted with diethyl ether, and the combined organic phases were dried with Na2SO4, filtered, and the solvent was removed under diminished pressure. Flash chromatography furnished the desilylated intermediate (172 mg, 82%) as a white foam; 1HNMR (500 MHz, CDCl3): d = 8.10 (d, 3J(H,H) = 7.3 Hz, 2H; Ar-H), 7.93 (d, 3J-(H,H) = 7.4 Hz, 2H; Ar-H), 7.82 (d, 3J(H,H) = 7.3 Hz, 2H; Ar-H), 7.64 (t, 3J(H,H) = 7.4 Hz, 1H; Ar-H), 7.51 (t, 3J(H,H) = 7.7 Hz, 2H; Ar-H), 7.487.33 (m, 7H; Ar-H), 7.33-7.20 (m, 10H; Ar-H), 7.17 (t, 3J(H,H) = 7.8 Hz, 2H; Ar-H), 6.97 (dd, 3J(H,H) = 6.5, 2.7 Hz, 2H; Ar-H), 5.84 (dd, 3J-(H,H) = 10.3, 8.0 Hz, 1H; H-2'), 5.79 (d, 3/(H,H) = 3.4 Hz, 1H; H-4'), 5.52 (dd, 3J(H,H) = 10.3, 3.4 Hz, 1H; H-3'), 5.04 (d, 3J(H,H) = 8.0 Hz, 1H; H-1'), 4.70-4.59 (ABq, 2J(H,H) = 16.8, 11.7 Hz, 2H; PhCH2), 4.584.49 (ABq, 2J(H,H) = 15.9, 12.2 Hz, 2H; PhCH2), 4.44 (d, 3J(H,H) = 3.6 Hz, 1H; H-1), 4.18 (d, 2J(H,H) = 11.8 Hz, 1H; 1 x PhCH2), 4.14 (d, 3J-(H,H) = 2.4 Hz, 1H; H-4), 4.05 (dd, 2J(H,H) = 10.6 Hz, 3J(H,H) = 8.1 Hz, 1H; H-6a), 3.95 (dd, 3J(H,H) = 7.9, 5.2 Hz, 1H; H-5), 3.89 (d, 2J(H,H) = 11.8 Hz, 1H; 1xPhCH2), 3.75 (m, 2H; H-5 and H-3), 3.72-3.65 (m, 1H; H-6a), 3.65-3.54 (m, 2H; H-6b and H-2), 3.45 (dd, 3J(H,H) = 10.6, 5.0 Hz, 1H; H-6b), 3.32-3.27 (m, 1H; OH), 3.26 (s, 3H; CH3); 13CNMR (125 MHz, CDCl3): d = 166.3, 165.6, 165.3 (each C=O), 138.7, 138.4, 137.8 (each C), 133.7, 133.3, 133.0 (each CH), 130.0 (2s), 129.8 (each CH), 129.5, 128.9, 128.8 (each C), 128.7, 128.6, 128.5, 128.3, 128.2, 128.1, 128.0, 127.9 (2 s), 127.8 (3s) (each CH), 102.3 (C-1'), 98.8 (C-1), 77.9 (C-3), 77.1 (C-2), 76.0 (C-4), 74.0 (C-5'), 73.7 (2 x PhCH2), 73.5 (PhCH2), 72.2 (c-3'), 70.1 (C-2'), 68.8 (C-4'), 68.3 (C-6), 67.6 (C-5), 61.0 (C-6'), 55.3 ppm (CH3); ESI-HRMS calcd for C55H54NaO14 961.3411, found m/z (%) 961.3407 [M+Na]+. This intermediate (326 mg, 0.35 mmol) was added to CH2Cl2 (10 mL) and H2O (5 mL) and treated with TEMPO (10 mg, 0.065 mmol) and BAIB (336 mg, 1.043 mmol) to give the acid. This was esterified in DMF (10 mL) using NaHCO3 (220 mg, 2.6 mmol) and MeI (0.055 mL, 0.87 mmol) to give the ester (290 mg, 87 %) after chromatography (petroleum ether/EtOAc 2:1) as a white foam; 1HNMR (500 MHz, CDCl3): d = 8.02 (dd, 3J(H,H) = 8.2, 1.1Hz, 2H; Ar-H), 7.96 (dd, 3J(H,H) = 8.3, 1.1Hz, 2H; Ar-H), 7.83 (dd, 3J(H,H) = 8.3, 1.2 Hz, 2H; Ar-H), 7.63-7.57 (m, 1H; Ar-H), 7.51-7.16 (m, 21H; Ar-H), 7.01 (dd, 3J(H,H) = 6.8, 2.6Hz, 2H; Ar-H), 6.14 (dd, 3J(H,H) = 3.4, 1.1Hz, 1H; H-4'), 5.80 (dd, 3J(H,H) = 10.4, 7.9 Hz, 1H; H-2'), 5.53 (dd, 3J-(H,H) = 10.4, 3.4 Hz, 1H; H-3'), 5.18 (d, 3/(H,H) = 7.9 Hz, 1H; H-1'), 4.71 (dd, 2J(H,H) = 11.8, 8.0 Hz, 2H; PhCH2), 4.64 (dd, 2J(H,H) = 11.8, 4.3 Hz, 2H; PhCH2), 4.50 (d, 3J(H,H) = 3.6 Hz, 1H; H-1), 4.43 (d, 3J-(H,H) = 1.2Hz, 1H; H-5'), 4.26 (d, 3J(H,H) = 2.4Hz, 1H; H-4), 4.15 (d, 2J(H,H) = 11.7 Hz, 1H; PhCHH), 4.01 (dd, 2J(H,H) = 9.9 Hz, 3J(H,H) = 6.0 Hz, 1H; H-6a), 3.96 (t, 3J(H,H) = 6.0 Hz, 1H; H-5), 3.91 (d, 2j(h,h) =

11.7 Hz, 1H; PhCHH), 3.86 (dd, 3J(H,H) = 10.0, 2.4 Hz, 1H; H-3), 3.79 (dd, 2J(H,H) = 9.9 Hz, 3J(H,H) = 6.0 Hz, 1H; H-6b), 3.65-3.59 (m, 4H; CH3 and H-2), 3.32 ppm (s, 3H; CH3); 13CNMR (125 MHz, CDCl3): d = 166.2, 165.6, 165.2, 165.1 (each C=O), 138.8 (2s), 138.4 (each C), 133.5,

133.3, 133.1 (each CH), 130.0, 129.9, 129.8 (each CH), 129.5, 129.1, 128.8 (each C), 128.6 (2s), 128.3 (3s), 128.2, 127.9, 127.7 (3s), 127.6, 127.5, 127.4 (each CH), 101.6 (C-1'), 98.5 (C-1), 78.2 (C-3), 77.4 (C-2), 76.1 (C-4), 73.9 (PhCH2), 73.5 (PhCH2), 73.4 (PhCH2), 72.5 (C-5'), 71.6 (C-3'), 70.0 (C-6), 69.5 (C-2'), 69.3 (C-5), 69.1 (C-4'), 55.3 (CH3), 52.5 ppm (CH3); ESI-HRMS calcd for C56H54NaO15 989.3360, found m/z (%) 989.3355 [M+Na]+. To this intermediate (155 mg, 0.160 mmol) in MeOH (5 mL), Pd/C (30 mg) was added and the mixture was stirred under hydrogen for 24 h. The mixture was filtered through Celite and the filtrate concentrated to dryness. The residue was taken up in pyridine (4 mL) and cooled to 0 °C and benzoyl chloride (100 mL, 0.80 mmol) was added and the reaction allowed to attain room temperature for 24 h. Work up as described previously and chromatography (petroleum ether/EtOAc 1:1) gave 44 (138 mg, 86%) as a white solid; 1H NMR (500 MHz, CDCl3): d = 8.12 (d, 3/(H,H) = 7.2 Hz, 2H; Ar-H), 8.05 (d, 3J(H,H) = 7.2 Hz, 2H; Ar-H), 7.95 (d, 3J(H,H) = 7.3 Hz, 2H; Ar-H), 7.91 (d, 3J(H,H) = 7.3 Hz, 2H; Ar-H), 7.83 (m, 4H; Ar-H), 7.63-7.53 (m, 3H, Ar-H), 7.53-7.42 (m, 6H; Ar-H), 7.39-7.24 (m, 7H; Ar-H), 7.16 (t, 3J(H,H) = 7.8 Hz, 2H; Ar-H), 6.12 (d, 3/(H,H) = 2.5 Hz, 1H; H4), 5.89-5.82 (m, 2H; H-2' and H-3), 5.57 (dd, 3J-(H,H) = 10.5, 2.5 Hz, 1H; H-3'), 5.37 (dd, 3J(H,H) = 10.8, 3.5 Hz, 1H; H-2), 5.24 (d, 3J(H,H) = 3.5 Hz, 1H; H-1), 5.02 (d, 3J(H,H) = 7.9 Hz, 1H; H-1'), 4.96 (dd, 2J(H,H) = 12.1 Hz, 3J(H,H), 3.9 Hz, 1H; H-6a), 4.80 (dd, 2J-(H,H) = 12.1Hz, 3J(H,H) = 7.9 Hz, 1H; H-6b), 4.72 (d, 3J(H,H) = 1.9 Hz, 1H; H-4), 4.48-4.39 (m, 2H; H-5 and H-5'), 3.61 (s, 3H; CH3), 3.39 ppm (s, 3H; CH3); 13CNMR (125 MHz, CDCl3): d = 166.2, 166.0, 165.9, 165.6,

165.4, 165.2 (s), (each C=O), 133.6 (2s), 133.4, 133.1, 132.9 (2s), 132.9 (each CH), 130.3 (C), 130.1, 129.8 (2s), 129.8, 129.7 (2s) (each CH), 129.4, 129.3, 129.0, 128.9 (each C), 128.7 (2s, CH), 128.7 (C), 128.4, 128.3, 128.2 (2s) (each CH), 101.0 (C-1), 97.3 (C-1), 74.7 (C-4), 72.7 (C-5), 71.2 (C-3'), 70.6 (C-3), 69.7 (C-2'), 69.4 (C-2), 69.0 (C-4), 68.1 (C-5), 64.5 (C-6), 55.3 (CH3), 52.7 ppm (CH3). ESI-HRMS calcd for C56H49O18 1009.2919, found m/z (%) 1009.2922 [M+H]+.

General procedure for the anomerisation reaction (conditions B; see Tables 1 and 2): The ß-anomer (1 equiv) was added to a flame-dried round bottomed flask and anhydrous CH2Cl2 (10 mL per g of substrate) was added. The flask was then cooled on an ice-bath and 2.5 equiv TiCl4 (1 м in CH2Cl2) was added dropwise. The flask was then left to stand in a freezer (-15 to -18 °C) for 48-72 h. The mixture was diluted with CH2Cl2 and washed with NH4Cl (1.0M, 10 mL). The aqeous layer was extracted with CH2Cl2 and the combined organic layers were washed with satd. aq. NaHCO3 and brine. The organic layer was dried over Na2SO4, filtered through silica gel and the solvent removed to give the products. 2-O-(2,3,4-Tri-O-benzoyl-5-S-(methoxycarbonyl)-a-D-xylopyranosyl)-3,4-O-(1,1,3,3-tetraisopropyl-1,3-disiloxanediyl)-6-O-acetyl-ß-D-glucopyrano-syl azide (52): [a]D = 48.0 (c 0.35, CH2Cl2); 1H NMR (500 MHz, CDCl3): d = 8.00 (dd, 3J(H,H) = 8.3, 1.5 Hz, 2H; Ar-H), 7.96-7.91 (m, 2H; Ar-H), 7.88 (dd, 3J(H,H) = 8.3, 1.5 Hz, 2H; Ar-H), 7.57-7.49 (m, 1H; Ar-H), 7.46-7.37 (m, 5H; Ar-H), 7.30 (t, 3J(H,H) = 7.7 Hz, 2H; Ar-H), 6.21 (aptt, 3J(H,H) = 10.1 Hz, 1H; H-3'), 6.08 (d, 3J(H,H) = 3.7 Hz, 1H; H-1'), 5.65 (aptt, 3J(H,H) = 10.0 Hz, 1H; H-4'), 5.35 (dd, 3J(H,H) = 10.4, 3.7 Hz, 1H; H-2'), 4.94 (d, 3J(H,H) = 10.3 Hz, 1H; H-5'), 4.49 (d, 3J(H,H) = 8.7Hz, 1H; H-1), 4.40 (dd, 2J(H,H) = 12.0Hz, 3J(H,H) = 2.2Hz, 1H; H-6a), 4.15 (dd, 2J(H,H) = 12.0 Hz, 3J(H,H) = 5.0 Hz, 1H; H-6b), 3.87 (aptt, 3/(H,H) = 8.7 Hz, 1H; H-3), 3.73 (aptt, 3J(H,H) = 8.9 Hz, 1H; H-4), 3.64 (s, 3H; CO2CH3), 3.56 (aptt, 3J(H,H) = 8.8 Hz, 1H; H-2), 3.51 (dq, 3J-(H,H) = 7.3, 3.0, 2.5 Hz, 1H; H-5), 2.05 (s, 3H; COCH3), 1.45-0.75 ppm (m, 28 H ; 4хСЯ(СЯ3)2, overlapping peaks); 13CNMR (126 MHz, CDCl3): d = 170.7 (COCH3), 168.2 (CO2CH3), 165.6, 165.4, 165.3 (3х COPh), 133.4 (2s), 133.2, 129.8, 129.7 (9 х Ar-CH, overlapping peaks),129.1, 129.0, 128.9 (3xAr-C) 128.5, 128.4, 128.3 (6 х Ar-CH, overlapping peaks), 94.9 (C-1'), 89.7 (C-1), 78.0 (C-3), 76.9 (C-2), 75.7 (C-5), 72.7 (C-4), 71.0 (C-2'), 70.0 (C-4'), 69.0 (C-3'), 68.6 (C-5'), 62.7 (C-6), 52.7 (CO2CH3), 29.7 (COCH3), 20.8, 17.5 (2s), 17.4, 17.3, 17.2 (2s), 17.1 (2s) (8xCH(CH3)2, overlapping peaks), 12.9, 12.7, 12.2, 11.4ppm (4хCH-(CH3)2, overlapping peaks); IR (film): n = 3072, 2953, 2120, 1727, 1452, 1248, 1091, 1067, 1026 cm-1; ESI-HRMS calcd for C48H61O16N3Si2Na 1014.3488, found m/z (%) 1014.3494 [M+Na]+.

2,3,4-Tri-O-benzoyl-6-O-(2,3,4-tri-O-benzoyl-5-S-(methoxycarbonyl)-a-D-xylopyranosyl)-ß-D-glucopyranosyl azide (53): [a]D = 44.9 (c 1.1, CH2Cl2); 1H NMR (500 MHz, CDCl3): d = 8.13-8.02 (m, 2H; Ar-H), 8.00 (dd, 3J-(H,H) = 8.5, 1.5 Hz, 2H; Ar-H), 7.96 (d, 3J(H,H) = 6.9 Hz, 2H; Ar-H), 7.91 (ddd, 3J(H,H) = 8.2, 3.7, 1.4 Hz, 4H; Ar-H), 7.81 (dd, 3J(H,H) = 8.3, 1.5 Hz, 2H; Ar-H), 7.55-7.27 (m, 17H; Ar-H), 6.29 (aptt, 3J(H,H) = 9.8 Hz, 1H; H-3'), 5.88 (aptt, 3J(H,H) = 9.7 Hz, 1H; H-3), 5.68 (aptt, 3J-(H,H) = 9.8 Hz, 1H; H-4'), 5.60 (aptt, 3J(H,H) = 9.8 Hz, 1H; H-4), 5.51 (d, 3J(H,H) = 3.6 Hz, 1H; H-1'), 5.40-5.31 (m, 2H; H-2, H-2', overlapping peaks), 4.90 (d, 3J(H,H) = 8.8 Hz, 1H; H-1), 4.74 (d, 3J(H,H) = 10.1Hz, 1 H; H-5'), 4.16-4.02 (m, 2H; H-5, H-6a, overlapping peaks), 3.80 (dd, 2J-(H,H) = 11.5Hz, 3J(H,H) = 1.9Hz, 1H; H-6b), 3.60 (s, 3H; CO2CH3); 13C NMR (126 MHz, CDCl3): d = 168.3 (CO2CH3), 165.9, 165.8, 165.7, 165.5, 165.2, 165.0 (6x COPh), 133.7 (2s), 133.6, 133.5, 133.3, 130.1 (2s), 130.0, 129.9 (2s) (18 х Ar-CH, overlapping peaks), 129.2, 129.1, 129.0, 128.9 (4 х Ar-C), 128.7 (2s) (2 х Ar-CH, Ar-C, overlapping peaks), 128.6 (2s) (4 х Ar-CH, Ar-C, overlapping peaks), 128.5 (2s), 128.4 (6 х Ar-CH, overlapping peaks), 96.4 (C-1'), 88.2 (C-1), 75.5 (C-5), 72.9 (C-3), 71.5 (C-2), 71.3 (C-2'), 70.2 (C-4') 69.9 (C-3'), 68.9 (C-4), 68.6 (C-5'), 67.0 (C-6), 52.9 ppm (CO2CH3); IR (film): n = 2955, 2924, 2118, 1726, 1451, 1248, 1090, 1067, 1025 cm-1; ESI-HRMS calcd for C55H45O17N3Na 1042.2647, found m/z (%) 1042.2649 [M+Na]+.

2-O-Acetyl-3-O-(2,3,4-tri-O-benzoyl-5-S-(methoxycarbonyl)-a-D-xylopyr-anosyl)-4,6-O-(1,1,3,3-tetraisopropyl-1,3-disiloxanediyl)-ß-D-glucopyrano-syl azide (54): [a]D = -9.7 (c 0.35, CH2Cl2); 1H NMR (500 MHz, CDCl3): d = 8.00 (dd, 3J(H,H) = 8.2, 1.4Hz, 2H; Ar-H), 7.95 (dd, 3J(H,H) = 8.3, 1.4 Hz, 2H; Ar-H), 7.90 (dd, 3J(H,H) = 8.3, 1.4 Hz, 2H; Ar-H), 7.54-7.49 (m, 2H; Ar-H), 7.46-7.36 (m, 5H; Ar-H), 7.31 (t, 3J(H,H) = 7.7 Hz, 2H; Ar-H), 6.19 (aptt, 3J(H,H) = 9.9 Hz, 1H; H-3'), 5.68-5.62 (m, 2H; H-1', H-4', overlapping peaks), 5.32 (dd, 3J(H,H) = 10.1, 3.7 Hz, 1H; H-2), 4.68 (d, 3J(H,H) = 10.1Hz, 1H; H-5'), 4.56 (aptt, 3J(H,H) = 8.8 Hz, 1H; H-2), 4.43 (d, 3J(H,H) = 9.0 Hz, 1H; H-1), 4.01-3.98 (m, 2H; H-6a, H-6b, overlapping peaks), 3.71-3.63 (m, 5H; CO2CH3, H-3, H-4, overlapping peaks), 3.53-3.46 (m, 1H; H-5) 2.05 (s, 3H; COCH3), 1.22-0.94 (m, 28H; 4xCH(CH3)2, overlapping peaks); 13CNMR (126MHz, CDCl3): d = 168.9 (COCH3), 168.4 (CO2CH3), 165.7 (2s), 165.5 (3х COPh), 133.6, 133.5, 133.3, 130.0, 129.9 (9 х Ar-CH, overlapping peaks), 129.2, 129.0, 128.9 (3х Ar-C), 128.7, 128.5 (2s) (6 х Ar-CH, overlapping peaks), 96.6 (C-1'), 87.9 (C-1), 77.9 (C-5), 77.6 (C-4), 72.5 (C-2), 72.4 (C-3), 71.6 (C-2'), 70.3 (C-4), 69.8 (C-3'), 68.7 (C-5), 65.9 (C-6), 53.0 (CO2CH3), 20.8 (COCH3), 17.4 (4s), 17.3 (2s) (8х CH(CH3)2, overlapping peaks), 12.9, 12.8, 12.3, 12.2ppm (4хCH(CH3)2, overlapping peaks); IR (film): n = 2925, 2867, 2117, 1731, 1452, 1260, 1095, 1067, 1041, 983 cm-1; ESI-HRMS calcd for C48H61O16N3Si2Na 1014.3488, found m/z (%) 1014.3492 [M+Na]+.

2,4,6-Tri-O-benzoyl-3-O-(2,3,4-tri-O-benzoyl-5-S-(methoxycarbonyl)-a-D-xylopyranosyl)-ß-D-glucopyranosyl azide (55): [a]D = 40.2 (c 0.95, CH2Cl2); 1H NMR (500 MHz, CDCl3): d = 8.15-8.10 (m, 2H; Ar-H), 8.08-8.03 (m, 2H; Ar-H), 8.02-7.98 (m, 2H; Ar-H), 7.97-7.94 (m, 2H; Ar-H), 7.94-7.89 (m, 3H Ar-H), 7.83-7.77 (m, 2H; Ar-H), 7.64-7.60 (m, 1H; Ar-H), 7.56-7.27 (m, 19H; Ar-H), 6.29 (aptt, 3J(H,H) = 9.8 Hz, 1H; H-3'), 5.88 (aptt, 3J(H,H) = 9.7 Hz, 1H; H-3), 5.68 (aptt, 3J(H,H) = 9.8 Hz, 1H; H-4'), 5.59 (aptt, 3J(H,H) = 9.8 Hz, 1H; H-4), 5.51 (d, 3J-(H,H) = 3.7 Hz, 1H; H-1'), 5.40-5.30 (m, 2H; H-2, H-2', overlapping peaks), 4.90 (d, 3J(H,H) = 8.8 Hz, 1H; H-1), 4.74 (d, 3J(H,H) = 10.1Hz, 1H; H-5'), 4.11 (ddd, 3J(H,H) = 9.6, 6.4, 1.7 Hz, 1H; H-5), 4.05 (dd, 2J-(H,H) = 11.3 Hz, 3J(H,H) = 6.4 Hz, 1H; H-6a), 3.79 (d, 2J(H,H) = 11.3 Hz, 3J(H,H) = 1.7Hz, 1H; H-6b), 3.60ppm (s, 3H; CO2CH3); 13CNMR (126 MHz, CDCl3): d = 168.1 (CO2CH3), 165.7 (2s), 165.6, 165.4, 165.0, 164.8 (6x COPh), 133.7, 133.6, 133.5 (2s), 133.3, 133.2, 130.2, 130.0 (2s), 129.9, 129.8 (2s) (18 х Ar-CH, overlapping peaks), 129.1, 128.9, 128.8 (2s), 128.6 (5 х Ar-C), 128.5 (3s) (4 х Ar-CH, Ar-C, overlapping peaks), 128.4 (2s), 128.3 (2s) (8 х Ar-CH, overlapping peaks), 96.3 (C-1'), 88.1 (C-1), 75.4 (C-5), 72.8 (C-3), 71.3 (C-3'), 71.2 (C-4'), 70.0 (C-2'), 69.8 (C-2), 68.8 (C-4), 68.4 (C-5'), 66.8 (C-6), 52.8 ppm (CO2CH3); IR (film): n = 2957, 2924, 2119, 1724, 1452, 1248, 1090, 1067, 1025 cm-1; ESI-HRMS calcd for C55H45O17N3Na 1042.2647, found m/z (%) 1042.2653 [M+Na]+.

CHEMISTRY

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2,3-O-(1,1,3,3-Tetraisopropyl-1,3-disiloxanediyl)-4-O-(2,3,4-tri-O-benzoyl-5-S-(methoxycarbonyl)-a-D-xylopyranosyl)-6-O-acetyl-p-D-glucopyrano-syl azide (56): [a]D = + 29.0 (c 0.2, CH2Cl2); 1H NMR (500 MHz, CDCl3): d = 8.05 (dd, 3J(H,H) = 8.2, 1.4 Hz, 2H; Ar-H), 7.94-7.89 (m, 4H; Ar-H), 7.58-7.53 (m, 2H; Ar-H), 7.51-7.46 (m, 1H; Ar-H), 7.43-7.36 (m, 4H; Ar-H), 7.26 (m, 2H; Ar-H), 5.99 (d, 3J(H,H) = 2.4 Hz, 1H; H-1'), 5.81 (aptt, 3J(H,H) = 5.5 Hz, 1H; H-3'), 5.65 (aptt, 3J(H,H) = 4.9 Hz, 1H; H-4'), 5.46 (dd, 3J(H,H) = 5.9, 2.4 Hz, 1H; H-2'), 4.77 (d, 3J(H,H) = 4.7 Hz, 1H; H-5'), 4.60 (dd, 2J(H,H) = 12.2 Hz, 3J(H,H) = 2.3 Hz, 1H; H-6a), 4.53 (d, 3J(H,H) = 8.2 Hz, 1H; H-1), 4.40 (dd, 2J(H,H) = 12.2 Hz, 3J(H,H) = 5.0 Hz, 1H; H-6b), 4.04 (dd, 3J(H,H) = 9.9, 8.6 Hz, 1H; H-4), 3.87 (aptt, 3/(H,H) = 8.6 Hz, 1H; H-3), 3.65-3.59 (m, 4H; CO2CH3, H-5, overlapping peaks), 3.53 (aptt, 3/(H,H) = 8.4Hz, 1H; H-2), 2.06 (s, 3H; COCH3), 1.17-0.83ppm (m, 28H; 4xCH(CH3)2, overlapping peaks); 13CNMR (126 MHz, CDCl3): d = 170.7 (COCH3), 168.4 (COCH3), 165.4, 165.2 (3 x COPh, overlapping peaks), 133.7, 133.4, 130.1, 130.0, 129.8 (9 x Ar-CH, overlapping peaks), 199.3 128.8, 128.6 (3xAr-C) 128.4, 128.4, 128.3 (6x Ar-CH, overlapping peaks), 94.6 (C-1'), 90.5 (C-1), 80.3 (C-3), 76.7 (C-2), 74.4 (C-5), 74.2 (C-4) 72.3 (C-5'), 68.6 (H-3'), 68.2 (H-4'), 67.4 (H-2') 63.0 (C-6), 52.6 (CO2CH3), 20.8 (COCH3), 17.3 (2s), 17.2 (2s), 17.1, 16.9 (8x CH(CH3)2, overlapping peaks), 12.9, 12.7, 12.1, 12.0ppm (4x CH(CH3)2, overlapping peaks); IR (film): n = 2927, 2868, 2118, 1729, 1452, 1246, 1091, 1068, 1026, 988 cm-1; ESI-HRMS calcd for C48H61O16N3Si2Na 1014.3488, found m/z (%) 1014.3467 [M+Na]+.

2,3,6-Tri-O-benzoyl-4-O-(2,3,4-tri-O-benzoyl-5-S-(methoxycarbonyl)-a-D-xylopyranosyl)-p-D-glucopyranosyl azide (57): [a]D =+ 65.3 (c 0.15, CH2Cl2); 1H NMR (500 MHz, CDCl3): d = 8.07-8.02 (m, 2H; Ar-H), 8.01-7.98 (m, 2H; Ar-H), 7.97-7.94 (m, 2H; Ar-H), 7.91 (ddd, 3J(H,H) = 8.5, 3.9, 1.4 Hz, 4H; Ar-H), 7.83-7.79 (m, 2H; Ar-H), 7.55-7.27 (m, 17H; Ar-H), 6.28 (aptt, 3J(H,H) = 9.8 Hz, 1H; H-3'), 5.87 (aptt, 3J(H,H) = 9.7 Hz, 1H; H-3), 5.67 (aptt, 3J(H,H) = 9.8 Hz, 1H; H-4'), 5.59 (aptt, 3J-(H,H) = 9.7 Hz, 1H; H-4), 5.50 (d, 3J(H,H) = 3.7 Hz, 1H; H-1'), 5.38-5.32 (m, 2H; H-2, H-2', overlapping peaks), 4.89 (d, 3J(H,H) = 8.8 Hz, 1H; H-1), 4.73 (d, 3J(H,H) = 10.1Hz, 1H; H-5'), 4.10 (ddd, 3J(H,H) = 9.8, 6.3, 1.7 Hz, 1H; H-5), 4.05 (dd, 2J(H,H) = 11.3 Hz, 3J(H,H) = 6.4 Hz, 1H; H-6a), 3.79 (dd, 2J(H,H) = 11.3 Hz, 3J(H,H) = 1.7 Hz, 1H; H-6b), 3.60 ppm (s, 3H; CO2CH3); 13CNMR (126 MHz, CDCl3): d = 168.1 (CO2CH3), 165.7 (2s), 165.6, 165.4, 165.0, 164.8 (6x COPh), 133.6, 133.5 (2s), 133.3,

133.2, 130.0, 129.9 (2s), 129.8 (2s) (18 x Ar-CH, overlapping peaks), 129.1, 128.9, 128.8 (2s), 128.6 (5 x Ar-C), 128.5 (2s) (2 x Ar-CH, Ar-C, overlapping peaks), 128.4(2s), 128.3 (2s) (10 x Ar-CH, overlapping peaks), 96.3 (C-1'), 88.1 (C-1), 75.4 (C-5), 72.8 (C-3), 71.3 (C-2), 71.2 (C-2'), 70.0 (c4'), 69.8 (C-3'), 68.8 (C-4), 68.4 (C-5'), 66.8 (C-6), 52.8 ppm (CO2CH3); IR (film): n = 2952, 2119, 1725, 1452, 1247, 1091, 1067, 1026, 704 cm-1; ESI-HRMS calcd for C55H45O17N3Na 1042.2647, found m/z (%) 1042.2665 [M+Na]+.

Methyl 6-O-(2,3,4-tri-O-benzoyl-5-S-(methoxycarbonyl)-p-L-arabinopyra-nosyl)-2,3,4-tri-O-benzoyl-a-D-galactopyranose (58): 1H NMR (500 MHz, CDCl3): d = 8.08-7.93 (m, 8H; Ar-H), 7.83-7.78 (m, 2H; Ar-H), 7.767.73 (m, 2H; Ar-H), 7.64-7.56 (m, 2H; Ar-H), 7.55-7.32 (m, 12H; Ar-H), 7.24 (m, 4H; Ar-H), 6.23 (dd, 3J(H,H) = 3.4, 1.5 Hz, 1H; H-4'), 5.995.93 (m, 2H; H-3' and H-3), 5.87 (d, 3J(H,H) = 3.2 Hz, 1H; H-4), 5.72 (dd, 3J(H,H) = 10.7, 3.5 Hz, 1H; H-2), 5.66 (dd, 3J(H,H) = 10.7, 3.5 Hz, 1H; H-2'), 5.48 (d, 3J(H,H) = 3.5 Hz, 1H; H-1'), 5.30 (d, 3J(H,H) = 3.5 Hz, 1H; H-1), 5.08 (d, 3J(H,H) = 1.5 Hz, 1H; H-5'), 4.51 (dd, 3/(H,H) = 7.9, 3.6 Hz, 1H; H-5), 4.00 (dd, 2J(H,H) = 10.5 Hz, 3J(H,H) = 7.9 Hz, 1H; H-6a), 3.77 (dd, 2J(H,H) = 10.5 Hz, 3J(H,H) = 3.6 Hz, 1H; H-6b), 3.72 (s, 3H; CH3), 3.54ppm (s, 3H; CH3); 13CNMR (125 MHz, CDCl3): d =

167.3, 166.1, 165.8, 165.5 (2s), 165.4, 165.2 (each C=O), 133.6, 133.5,

133.4, 133.2, 133.1 (each CH), 129.9 (3s), 129.8, 129.7, 129.6 (each CH), 129.2, 129.1, 129.0 (4s) (each C), 128.6 (2s), 128.4, 128.3, 128.2 (each CH), 97.6 (C-1), 96.9 (C-1'), 70.0 (C-4), 69.6 (C-4), 69.4 (C-2'), 69.2 (C-5'), 68.3 (C-3'), 68.3 (C2), 68.0 (C-5), 67.9 (C-3'), 67.7 (C-6), 55.7 (CH3), 52.8 ppm (CH3); ESI-HRMS calcd for C56H48NaO18 1031.2738, found m/z (%) 1031.2745 [M+Na]+.

Methyl 4-O-(2,3,4-tri-O-benzoyl-5-S-(methoxycarbonyl)-p-L-arabinopyra-nosyl)-2,3,6-tri-O-benzoyl-a-D-galactopyranose (59): 1H NMR (500 MHz, CDCl3): d = 8.06-8.03 (m, 2H; Ar-H), 7.97-7.90 (m, 8H; Ar-H), 7.83-

7.79 (m, 2H; Ar-H), 7.64-7.23 (m, 18H; Ar-H), 6.27 (dd, 3J(H,H) = 3.4, 1.9 Hz, 1H; H-4'), 6.18 (dd, 3J(H,H) = 11.0, 3.4 Hz, 1H; H-3'), 5.89-5.80 (m, 2H; H-2' and H-2), 5.63 (d, 3J(H,H) = 3.6 Hz, 1H; H-1'), 5.59 (dd, 3J-(H,H) = 11.0, 2.6 Hz, 1H; H-3), 5.30 (d, 3J(H,H) = 1.5 Hz, 1H; H-5'), 5.26 (d, 3J(H,H) = 3.6 Hz, 1H; H-1), 4.67 (d, 3J(H,H) = 2.6 Hz, 1H; H-4), 4.50 (dd, 2J(H,H) = 10.3 Hz, 3J(H,H) = 5.9 Hz, 1H; H-6a), 4.38-4.32 (m, 1H; H-5), 4.28 (dd, 2J(H,H) = 10.3 Hz, 3J(H,H) = 8.3 Hz, 1H; H-6b), 3.45 (s, 3H; OCH3), 3.08 ppm (s, 3H; COOCH3); 13CNMR (125 MHz, CDCl3): d = 166.6, 166.3, 166.0, 165.8, 165.6, 165.5, 165.0 (each C=O), 133.5, 133.4, 133.3, 133.2 (2s), 129.8 (2s), 129.7 (2s) (each CH), 129.3 (2s) 129.1, 129.0, 128.9, 128.6 (each C), 128.5 (2s) 128.4 (2s), 128.3, 128.2 (each CH), 99.5 (C-1'), 97.7 (C-1), 77.1 (C-4), 71.0 (C-3), 70.2 (C-4'), 70.0 (C-5'), 68.5 (C-2' and C-2), 67.5 (C-3'), 67.2 (C-5), 60.8 (C-6), 55.7 (CH3), 52.1 ppm (CH3). ESI-HRMS calcd for C56H48NaO18 1031.2738, found m/z (%) 1031.2742 [M+Na]+.

Supporting information: Additional experimental prodedures and NMR spectra can be found in the Supporting Information.

Acknowledgements

Material presented herein was supported by Science Foundation Ireland (Grant No. 12/IA/1398) and the Irish Research Council through an Enterprise Partnership funded by Roche Ireland, Ltd. (M.F.).

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Received: July 21, 2013 Published online: September 20, 2013