Synthesis of the pentasaccharide related to the repeating unit of the antigen from Shigella dysenteriae type 4 in the form of its methyl ester 2-(trimethylsilyl)ethyl glycoside

Article abstract of DOI:10.1016/S0008-6215(02)00499-8

Starting from D-mannose, D-glucose and L-fucose, the pentasaccharide derivative methyl 2,3,4-tri-O-benzyl-α-L-fucopyranosyl-(1→3)-2-O-acetyl-4,6-O- benzylidene-α-D-mannopyranosyl-(1→3)-2-O-acetyl-6-O-benzyl-4-O- (2,3,4-tri-O-benzyl-α-L-fucopyranosyl)-α-D-

Full text of DOI:10.1016/S0008-6215(02)00499-8

Carbohydrate Research 338 (2003) 589–596
www.elsevier.com/locate/carres
Synthesis of the pentasaccharide related to the repeating unit of
the antigen from Shigella dysenteriae type 4 in the form of its
methyl ester 2-(trimethylsilyl)ethyl glycoside
Balaram Mukhopadhyay, Nirmolendu Roy*
Department of Biological Chemistry, Indian Association for the Culti6ation of Science, Jada6pur, Calcutta 700 032, India
Received 4 June 2002; accepted 23 November 2002
Abstract
Starting from
(1“3)-2-O-acetyl-4,6-O-benzylidene-a-
pyranosyl)-a- -mannopyranosyl-(1“4)-[2-(trimethylsilyl)ethyl 2,3-di-O-benzyl-b-
compound with two a-mannopyranosyl units was transformed, via Walden inversion and subsequent deprotection, into the
a- -glucosamine-type target compound, namely methyl a- -fucopyranosyl-(1“3)-2-acetamido-2-deoxy-a- -glucopyranosyl-(1“
3)-2-acetamido-2-deoxy-4-O-(a- -fucopyranosyl)-a- -glucopyranosyl-(1“4)-[2-(trimethylsilyl)ethyl b- -glucopyranosid]uronate
D
-mannose,
D
-glucose and
L
-fucose, the pentasaccharide derivative methyl 2,3,4-tri-O-benzyl-a-
-mannopyranosyl-(1“3)-2-O-acetyl-6-O-benzyl-4-O-(2,3,4-tri-O-benzyl-a-
-glucopyranosid]uronate was synthesized. This
L
-fucopyranosyl-
D
L
-fuco-
D
D
D
L
D
L
D
D
which is related to the repeating unit of the O-antigen from Shigella dysenteriae type 4. © 2003 Elsevier Science Ltd. All rights
reserved.
Keywords: Synthesis; Pentasaccharide repeating unit; Shigella dysenteriae type 4
1. Introduction
glycoconjugate vaccine against S. dysenteriae type 1
was synthesized12 which was shown to have better
antigenicity than the native antigen. It is, therefore,
probable that the O-SP from S. dysenteriae type 4 may
also play a protective role against bacillary dysentery
and shigellosis in human.
We report herein the total synthesis of the pentasac-
charide II related to the repeating unit I13 of S. dysente-
riae type 4. The reason for using the 2-(trimethylsilyl)-
Shigella dysenteriae is the most virulent among the
pathogenic bacilli of the genus Shigella.1 They are
responsible for many intestinal diseases including
dysentery and have the potential for causing
catastrophic public health problems in developing
countries.2 Their resistance to antimicrobial drugs ne-
cessitates the exploration of other medical approaches
for controlling the diseases caused by this pathogen.3 It
has been suggested4,5 that antibodies to the O-specific
polysaccharide of Shigella may have the potential to
protect the host from shigellosis, and that conjugate
vaccines consisting of the O-specific polysaccharide (O-
SP) of Shigella covalently attached to an immunogenic
protein could, indeed, confer protective immunity to
human against shigellosis. Much synthetic works on the
oligosaccharides related to Shigella flexneri variant Y,6
S. flexneri serotypes 5a7 and 2a8 and S. dysenteriae
types 1,9 210 and 511 have been reported. Recently, a
* Corresponding author
E-mail address: bcnr@mahendra.iacs.res.in (N. Roy).
0008-6215/03/$ - see front matter © 2003 Elsevier Science Ltd. All rights reserved.
PII: S0008-6215(02)00499-8

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B. Mukhopadhyay, N. Roy / Carbohydrate Research 338 (2003) 589–596
ethyl protecting group for the terminal sugar is the
possibility of its easy removal from the oligosaccharide
derivative and subsequent utilization of the product in
making glycoconjugates. The synthetic oligosaccharide
can also be utilized as a molecular probe for studying
the immunochemical behavior of the antigen.
2. Results and discussion
Our strategy was to synthesise the blocks CBA and ED
and attach the latter to the 3II position of CBA, and
finally convert the a-
NAc component.
D-Manp residue to the a-D-Glcp-
Starting from the known ethyl 4,6-O-benzylidene-1-
thio-a- -man-
-mannopyranoside (1)14, prepared from
nose, ethyl 3-O-allyl-4,6-O-benzylidene-1-thio-a-
Scheme 3. (i) NIS–TfOH, CH2Cl2; (ii) 80% AcOH; (iii) a.
CrO3, H2SO4, H2O, acetone; b. CH2N2, Et2O; (iv) PdCl2,
MeOH.
D
D
D-
mannopyranoside (2) was prepared in 83% yield by
treatment of 1 with dibutyltin oxide in methanol15
followed by reaction of the product with allyl bromide.
Acetylation16 of the monohydroxy compound (2) with
acetic anhydride and pyridine afforded the monoacetate
derivative 3. Regioselective opening17 of the benzyli-
dene ring of 3 using sodium cyanoborohydride and
hydrogen chloride-ether in tetrahydrofuran gave the
thioglycoside acceptor 4 with a hydroxyl group in its
4-position in 82% yield (Scheme 1). The structure of 4
characteristic NMR signals for allyl, acetyl and
thioethyl groups.
In another experiment, ethyl 2,3,4-tri-O-benzyl-1-
thio-b-
L
-fucopyranoside (5), was prepared from
L-fu-
cose as described by Lo¨nn.18 The thioglycoside acceptor
4 was allowed to react with the thioglycoside donor 5 in
the presence of N-iodosuccinimide (NIS) and trifl-
uoromethanesulfonic
dichloromethane at 0 °C19 to afford the disaccharide
ethyl 2,3,4-tri-O-benzyl-a- -fucopyranosyl-(1“4)-2-O-
acetyl-3-O-allyl-6-O-benzyl-1-thio-a- -mannopyran-
acid
(TfOH)
in
dry
1
was confirmed by its H NMR spectrum which showed
L
D
oside (6) in 74% yield (Scheme 1). The lack of reactivity
of 4 as a donor was ascribed to the deactivating effect
of the O-acetyl group at C-2 which contrast with the
activating benzyl group in the same position in 5. The
disaccharide 5 has the characteristic NMR signals for
allyl, acetyl, thioethyl, 6-deoxy-sugar, anomeric protons
and anomeric carbons.
In a separate experiment, 2-(trimethylsilyl)ethyl 4,6-
O-(4-methoxybenzylidene)-b-
D
-glucopyranoside
(7)20
was benzylated21 to give the di-O-benzyl derivative 8 in
89% yield. Regioselective opening of the 4-methoxyben-
zylidene ring of 8, using sodium cyanoborohydride and
trifluoroacetic acid in N,N-dimethylformamide,22 af-
forded the 6-O-(4-methoxybenzyl) derivative 9 in 79%
yield (Scheme 2). The structure of 9 was confirmed by
Scheme 1. (i) Bu2SnO, MeOH, AllBr; (ii) Ac2O, Py; (iii)
NaCNBH3, HCl–ether, THF; (iv) NIS–TfOH, CH2Cl2.
1
its H and 13C NMR spectra.
The disaccharide donor 6 was then allowed to react
with the acceptor 9 in the presence of NIS and TfOH in
dry dichloromethane at 0 °C19 to afford the trisaccha-
ride,
fucopyranosyl-(1“4)-2-O-acetyl-3-O-allyl-6-O-benzyl-
a- -mannopyranosyl-(1“4)-2,3-di -O-benzyl-6-O-(4-
methoxybenzyl)-b- -glucopyranoside (10) in 70% yield
2-(trimethylsilyl)ethyl
2,3,4-tri-O-benzyl-a-L-
D
D
(Scheme 3). Compound 10 was characterized by its
NMR signals for allyl, acetyl, one 6-deoxy sugar, one
methoxy, trimethylsilyl and anomeric protons and car-
Scheme 2. (i) BnBR, NaH, DMF; (ii) NaCNBH3, TFA, DMF
MP=4-methoxyphenyl, MBn=4-methoxybenzyl.

B. Mukhopadhyay, N. Roy / Carbohydrate Research 338 (2003) 589–596
591
presence of NIS and TfOH in dry dichloromethane to
afford the disaccharide 15 in 75% yield (Scheme 4). The
disaccharide 15 was characterized by its NMR signals
for benzylidene, acetyl, one 6-deoxy sugar, thioethyl
and anomeric protons and carbons.
The trisaccharide acceptor 13 was allowed to react
with the disaccharide donor 15 in the presence of NIS
and TfOH in dry dichloromethane at 0 °C to afford the
Scheme 4. (i) NIS–TfOH, CH2Cl2.
pentasaccharide methyl 2,3,4-tri-O-benzyl-a-
ranosyl-(1“3)-2-O-acetyl-4,6-O-benzylidene-a-
mannopyranosyl-(1“3)-2-O-acetyl-6-O-benzyl-4-O-
(2,3,4-tri-O-benzyl-a- -fucopyranosyl)-a- -mannopyra-
nosyl-(1“4)-[2-(trimethylsilyl)ethyl 2,3-di-O-benzyl-b-
-glucopyranosid]uronate (16) in 70% yield (Scheme 5).
The pentasaccharide 16 showed NMR signals for ben-
zylidene, methyl ester, two acetyl groups, two 6-deoxy
sugars, trimethylsilyl and anomeric protons and car-
bons. The two acetyl groups of 16 were removed in the
usual way to yield 17. Compound 17 was converted to
the di-O-triflyl derivative 18 with trifluoromethanesul-
fonic anhydride and pyridine and further treatment
with sodium azide in N,N-dimethylformamide9a gave
L-fucopy-
bons. The 6-O-(4-methoxybenzyl) group of 10 was re-
moved by treatment with 80% aqueous acetic acid at
80 °C23 to give 2-(trimethylsilyl)ethyl 2,3,4-tri-O-benzyl-
D-
L
D
a-
benzyl-a-
-glucopyranoside (11) in 80% yield. The primary car-
L
-fucopyranosyl-(1“4)-2-O-acetyl-3-O-allyl-6-O-
D
-mannopyranosyl-(1“4)-2,3-di-O-benzyl-b-
D
D
bon atom of 11 was then oxidized with chromium[VI]
oxide24 and the resulting carboxylic acid group was
esterified with diazomethane25 to afford the methyl
ester 12 in 63% overall yield. NMR spectral study of 12
revealed the disappearance of the 4-methoxybenzyl
group at C-5I position and the appearance of a
COOMe group. The allyl group of 12 was removed
with palladium chloride in methanol26 to afford the
trisaccharide acceptor (13). The structure of 13 was
confirmed by the disappearance of the signals of the
allyl group in the proton and carbon-13 NMR spectra.
In another experiment, ethyl 4,6-O-benzylidene-1-
the diazido compound, methyl 2,3,4-tri-O-benzyl-a-
fucopyranosyl-(1“3)-2-azido-4,6-O-benzylidene-2-de-
oxy-a- -glucopyranosyl-(1“3)-2-azido-6-O-benzyl-2-
deoxy-4-O-(2,3,4-tri-O-benzyl-a- -fucopyranosyl)-a-
glucopyranosyl-(1“4)-[2-(trimethylsilyl)ethyl-2,3-di-O-
-glucopyranosid]uronate (19), with inversion
L-
D
L
D-
thio-a- -mannopyranoside (1) was treated with
D
benzyl-b-
D
of configuration at the 2II and 2IV positions in 60%
overall yield. The structure of 19 was confirmed by its
characteristic IR signal at 2125 cm−1. The 13C NMR
spectrum of 19 showed signals for COOMe, CHPh,
anomeric carbons, peaks for C-2II, C-2IV at 63.8 and
63.5, COOCH3, CH2SiMe3 2 CHCH3 and Si(CH3)3.
trimethyl orthoacetate and p-toluenesulfonic acid in dry
acetonitrile27 at room temperature to afford the 2,3-or-
thoester derivative which on treatment with 80% acetic
acid at room temperature gave the 2-O-acetyl deriva-
tive 14 in 73% overall yield. The acceptor 14 was then
allowed to react with the thioglycoside donor 5 in the
Scheme 5. (i) NIS, TfOH; (ii) 0.05 M NaOMe, MeOH; (iii) Tf2O, Pyr; (iv) NaN3, DMF; (v) thioacetic acid, Pyr; (vi) PdꢀC, H2,
AcOH.

592
B. Mukhopadhyay, N. Roy / Carbohydrate Research 338 (2003) 589–596
Compound 19 was treated with thioacetic acid and
pyridine28 to afford methyl 2,3,4-tri-O-benzyl-a-
fucopyranosyl-(1“3)-2-acetamido-4,6-O-benzylidene-
2-deoxy-a- -glucopyranosyl-(1“3)-2-acetamido-6-O-
benzyl-2-deoxy-4-O-(2,3,4-tri-O-benzyl-a- -fucopyran-
osyl)-a- -glucopyranosyl-(1“4)-[2-(trimethylsilyl)ethyl
2,3-di-O-benzyl-b- -glucopyranosid]uronate (20) in
was stirred at rt for 2 h. The solvents were evaporated
and the residue was chromatographed using 6:1 ben-
zene–EtOAc to afford ethyl 2-O-acetyl-3-O-allyl-4,6-
L-
D
O-benzylidene-1-thio-a- -mannopyranoside (3) (3.4 g,
D
L
quantitative) as a syrup; [h]D +131.1° (c 1.2, CHCl3);
1H NMR: l 7.43–7.19 (m, 5 H, aromatic protons), 5.80
(m, 1 H, CH2ꢀCHꢁCH2), 5.54 (s, 1 H, CHPh), 5.33 (bs,
1 H, H-2), 5.25 (s, 1 H, H-1), 5.23–5.09 (m, 2 H,
CH2ꢀCHꢁCH2), 2.57 (m, 2 H, SꢀCH2CH3), 2.10 (s, 3
H, COCH3), 1.22 (t, 3 H, J 7.2 Hz, SꢀCH2CH3). Anal.
Calcd for C20H26O6S: C, 60.89; H, 6.64. Found: C,
60.72; H, 6.85.
D
D
60% overall yield (Scheme 5). The NMR spectra of 20
had signals for CHPh, anomeric carbons, COOMe, 2
NHCOCH3, COOCH3, C-2II and C-2IV (at 53.9, 53.3),
2 NHCOCH3 and 2 CHCH3. Hydrogenolysis of 20
with PdꢀC and H2 in AcOH29 afforded the target
pentasaccharide, methyl a-
acetamido-2-deoxy-a- -glucopyranosyl-(1“3)-2-ace-
tamido-2-deoxy-4-O-(a- -fucopyranosyl)-a- -gluco-
-glucopy-
L-fucopyranosyl-(1“3)-2-
D
3.3. Ethyl 2-O-acetyl-3-O-allyl-6-O-benzyl-1-thio-a-D-
mannopyranoside (4)
L
D
pyranosyl-(1“4)-[2-(trimethylsilyl)ethyl b-
D
ranosid]uronate (21) in 80% yield (Scheme 5). The
To a soln of 3 (3 g, 7.6 mmol) in THF (25 mL) at 0 °C,
NaCNBH3 (4.3 g, 68.4 mmol) was added and the soln
was stirred for 15 min. A saturated soln of HCl in ether
was then added dropwise to the soln until effervescence
was ceased. The soln was stirred for 10 min and was
poured into a cold satd NaHCO3 solution. The mixture
was extracted with diethyl ether (30 mL×3) and the
organic layer was successively washed with aq satd
NaHCO3 and water. The soln was collected, dried
(Na2SO4), filtered and evaporated to give a syrupy
product. Column chromatography using 5:1 benzene–
1
structure of 21 was confirmed by its H and 13C NMR
spectra. The peak for the azide was absent in the IR
spectrum.
3. Experimental
3.1. General
All the reactions were monitored by TLC on Silica Gel
G (E. Merck). Column chromatography were per-
formed on 100–200 mesh Silica Gel (SRL, India). The
organic extracts were dried over anhyd Na2SO4. All
solvents were distilled and/or dried before use and all
evaporations were conducted at or below 50 °C under
reduced pressure unless stated otherwise. Optical rota-
tions were measured at 25 °C with a Perkin–Elmer 241
EtOAc afforded 4 (2.4 g, 82%) as a syrup; [h]D
+
1
103.5° (c 1.2, CHCl3); H NMR: l 7.34–7.26 (m, 5 H,
aromatic protons), 5.88 (m, 1 H, CH2ꢀCHꢁCH2), 5.35
(d, 1 H, J 2.4 Hz, H-2), 5.32 (s, 1 H, H-1), 5.31–5.19
(m, 2 H, CH2ꢀCHꢁCH2), 4.68–4.54 (m, 2 H, CH2Ph),
4.55, 4.75 (2d, 2 H, J 11.5 Hz, SꢀCH2CH3), 2.11 (s, 3
H, COCH3), 1.28 (t, 3 H, J 7.5 Hz, SꢀCH2CH3). 13C
NMR: l 170.6 (COCH3), 134.4 (CH2ꢀCHꢁCH2), 118.5
(CH2ꢀCHꢁCH2), 82.9 (C-1), 77.5, 74.0, 71.1, 70.0, 67.5,
21.3 (COCH3), 15.2 (SCH2CH3). Anal. Calcd for
C20H28O6S: C, 60.58; H, 7.12. Found: C, 60.42; H, 7.38.
1
MC polarimeter. The H and 13C NMR spectra were
recorded with a Bruker DPX 300 spectrometer using
CDCl3 as solvent and Me4Si as internal standard unless
otherwise stated. Melting points were determined in a
paraffin oil bath and are uncorrected.
3.2. Ethyl 2-O-acetyl-3-O-allyl-4,6-O-benzylidene-1-
3.4. Ethyl 2,3,4-tri-O-benzyl-1-thio-a-L-fucopyranosyl-
(1“4)-2-O-acetyl-3-O-allyl-6-O-benzyl-1-thio-a-D-
thio-a-D-mannopyranoside (3)
mannopyranoside (6)
Ethyl 4,6-O-benzylidene-1-thio-a-
D
-mannopyranoside
(1)14 (3.5 g, 11.3 mmol) was dissolved in MeOH (30
mL) and Bu2SnO (2.8 g, 11.3 mmol) was added. The
soln was refluxed for 2 h until a clear soln was ob-
tained. The solvent was evaporated and the residue was
dried under diminished pressure for 2 h. The product
was dissolved in allyl bromide and the soln was stirred
at 63 °C for 10 h. Excess reagent was evaporated and
the residue was chromatographed using 5:1 benzene–
EtOAc as eluent to afford pure ethyl 3-O-allyl-4,6-O-
A soln of donor 5 (2.2 g, 4.6 mmol), acceptor 4 (1.4 g,
,
3.5 mmol) and 4 A MS (1.5 g) in dry CH2Cl2 (25 mL)
was stirred under nitrogen for 8 h. The soln was cooled
to −10 °C and NIS (1.3 g, 6 mmol) and TfOH (53 mL,
0.6 mmol) were added. The mixture was stirred for 45
min when TLC showed optimum reaction. The mixture
was then diluted with CH2Cl2 (25 mL) and filtered
through Celite. The filtrate was successively washed
with 10% aq Na2S2O7 and a saturated aq NaHCO3
soln. The organic layer was collected, dried (Na2SO4)
and evaporated to a syrup. Column chromatography
with 6:1 benzene–EtOAc gave 8 (2 g, 74%) as a syrup;
benzylidene-1-thio-a- -mannopyranoside (2) (3.3 g,
D
83%) as a syrup. To a soln of 2 (3 g, 8.5 mmol) in
pyridine (15 mL) was added Ac2O (10 mL) and the soln

B. Mukhopadhyay, N. Roy / Carbohydrate Research 338 (2003) 589–596
593
1
[h]D +21.3°; H NMR: 7.97–7.17 (m, 20 H, aromatic
OCH2CH2Si), −0.14 [s, 9 H, Si(CH3)3]. 13C NMR: l
140.08–129.04 (aromatic carbons), 103.1 (C-1), 84.2,
80.5, 75.7, 75.2, 70.4, 96.0, 66.5, 55.6 (C6H4OCH3), 18.1
(OCH2CH2Si), −1.5 [Si(CH3)3]. Anal. Calcd for
C33H44O7Si: C, 68.25; H, 7.63. Found: C, 67.96; H,
7.88.
protons), 5.96 (m, 1 H, CH2ꢀCHꢀCH2), 5.54 (m, 2 H,
CH2ꢀCHꢀCH2), 5.36 (bs, 1 H, H-2I), 5.32 (s, 1 H,
H-1I), 4.98 (d, 1 H, J 3.0 Hz, H-1II), 4.87–4.45 (m, 8 H,
4 CH2Ph), 2.66 (m, 2 H, SꢀCH2ꢀCH3), 2.11 (s, 3 H,
COCH3), 1.29 (t, 3 H, J 9.9 Hz, SꢀCH2ꢀCH3), 0.7 (d, 3
H, J 6.0 Hz, CꢀCH3). 13C NMR (CDCl3): 169.9
(COCH3), 133.1 (CH2ꢀCHꢁCH2), 117.2 (CH2ꢀCHꢁ
CH2), 99.6 (C-1II), 81.7 (C-1I), 77.9, 77.8, 74.5, 73.3,
72.8, 71.5, 71.0, 69.5, 69.4, 67.5, 66.4, 25.2
(SꢀCH2ꢀCH3), 20.9 (COCH3), 16.2 (SꢀCH2ꢀCH3), 14.7
(CꢀCH3). Anal. Calcd for C47H56O10S: C, 69.43; H,
6.94. Found: C, 69.22; H, 7.16.
3.7. 2-(Trimethylsilyl)ethyl 2,3,4-tri-O-benzyl-a-
fucopyranosyl-(1“4)-2-O-acetyl-3-O-allyl-6-O-benzyl-
a- -mannopyranosyl-(1“4)-2,3-di-O-benzyl-6-O-(4-
methoxybenzyl)-b- -glucopyranoside (10)
L-
D
D
A soln of the disaccharide donor 6 (1.2 g, 1.4 mmol),
,
acceptor 9 (830 mg, 1.4 mmol) and MS 4 A (1 g) in dry
3.5. 2-(Trimethylsilyl)ethyl 2,3-di-O-benzyl-4,6-O-(4-
methoxybenzylidene)-b-D-glucopyrano-side (8)
CH2Cl2 (10 mL) was stirred for 8 h. The mixture was
cooled to −10 °C and NIS (400 mg, 1.85 mmol) and
TfOH (16 mL, 0.18 mmol) were added. Stirring was
continued for 45 min when TLC showed a major spot
for the desired product in between the spots for the
trace amounts of donor and acceptor together with a
minor spot at the starting point. The mixture was then
diluted with CH2Cl2 (20 mL) and filtered through
Celite. The filtrate was washed successively with satu-
rated aq NaHCO3 and water. The organic layer was
dried (Na2SO4) and evaporated and the resulting
syrupy product was chromatographed using 10:1 ben-
zene–EtOAc yielding 10 as syrup (1.35 g, 70%); [h]D
2-(Trimethylsilyl)ethyl 4,6-O-(4-methoxybenzylidene)-
b-
-glucopyranoside (7)21 (5 g, 12.5 mmol) was dis-
D
solved in DMF (30 mL).The soln was cooled to 0 °C
and NaH (3 g, 62.5 mmol, 50% dispersion in mineral
oil) was introduced followed by the addition of BnBr
(3.6 mL, 30 mmol) and the mixture was allowed to stir
at rt for 6 h when TLC showed complete conversion.
Methanol (5 mL) was added to decompose the excess
NaH and the soln was diluted with ethyl ether and
washed with cold water (50 mL×3). The organic layer
was collected, dried (Na2SO4) and solvents were evapo-
rated. The residue was chromatographed with 2:1
petroleum ether (bp 40–60 °C)–ether to afford 8 as a
syrup (6.6 g, 90%); [h]D +9.8° (c 1.3, CHCl3); 1H
NMR: l 7.81–6.84 (m, 14 H, aromatic protons), 5.53
(s, 1 H, CHC6H4OCH3), 4.90 (m, 4 H, 2 CH2Ph), 4.52
(d, 1 H, J 9.3 Hz, H-1), 3.82 (s, 3 H, C6H4OCH3), 3.68
1
+3.9° (c 1.2, CHCl3); H NMR: l 7.41–6.75 (m, 34 H,
aromatic protons), 5.74 (m, 1 H, CH2ꢀCHꢁCH2), 5.32–
5.26 (m, 2 H, CH2ꢀCHꢁCH2), 5.18 (d, 1 H, J 3.9 Hz,
H-2II), 5.1 (s, 1 H, H-1II), 5.04 (d, 1 H, J 3.3 Hz,
H-1III), 4.62 (d, 1 H, J 11.4 Hz, H-1I), 3.73 (s, 3 H,
C6H4OCH3), 3.42 (m, 2 H, CH2CH2SiMe3), 1.99 (s, 3
H, COCH3), 1.02 (m, 2 H, CH2CH2SiMe3), 0.97 (d, 3
H, J 6.6 Hz, CꢀCH3), −0.14 [s, 9 H, Si(CH3)3], 13C
NMR: 170.2 (COCH3), 135.1 (CH2ꢀCHꢁCH2), 114.0
(CH2ꢀCHꢁCH2), 138.5–127.5 (aromatic carbons),
102.9 (C-1I), 99.4 (C-1II), 98.8 (C-1III), 84.3, 82.2, 79.3,
77.3, 77.2, 76.9, 74.8, 74.7, 74.4, 73.9, 73.2, 73.1, 73.0,
72.7, 72.1, 70.7, 69.8, 69.5, 68.7, 67.3, 66.9, 55.1
(C6H4OCH3), 20.6 (COCH3), 18.4 (CH2SiMe3), 16.5
(CꢀCH3), −1.5 [Si (CH3)3]. Anal. Calcd for
C78H94O17Si: C, 70.35; H, 7.11. Found: C, 70.64; H,
6.90.
(m,
2 H, OCH2CH2Si), 1.05 (t, 2 H, J 6.0,
OCH2CH2Si), −0.14 [s, 9 H, Si(CH3)3]. Anal. Calcd
for C33H42O7Si: C, 68.48; H, 7.31. Found: C, 68.73; H,
7.48.
3.6. 2-(Trimethylsilyl)ethyl 2,3-di-O-benzyl-6-O-(4-
methoxybenzyl)-b-D-glucopyranoside (9)
A soln of 8 (6 g, 10.3 mmol) in DMF (30 mL) was
cooled to 0 °C and NaCNBH3 (5.8 g, 93 mmol) was
added. A soln of TFA (7.9 mL) in DMF (20 mL) was
then added dropwise and the mixture was allowed to
stir at rt for 7 h. The reaction mixture was poured into
cold saturated aq NaHCO3 and extracted with di-
ethylether. The organic layer was collected, dried
(Na2SO4) and evaporated to give a syrupy liquid which
was chromatographed using 5:1 benzene–EtOAc to
3.8. Methyl 2,3,4-tri-O-benzyl-a-
4)-2-O-acetyl-3-O-allyl-6-O-benzyl-a-
L
-fucopyranosyl-(1“
D
-mannopyran-
osyl-(1“4)-[2-(trimethylsilyl)ethyl 2,3-di-O-benzyl-b-D-
glucopyranosid] uronate (12)
Compound 10 (2.35 g, 1.73 mmol) was dissolved in 80%
AcOH (15 mL) and the soln was stirred at 80 °C for 4
h. The soln was concentrated to dryness and the crude
material was chromatographed with 5:1 benzene–
EtOAc to give pure 11 (1.75 g, 80%). A soln of 11 (1.75
g, 1.4 mmol) in 3:2 acetone–CH2Cl2 (32 mL) was
1
give 9 (4.7 g, 79%); [h]D −14.1° (c 1.5, CHCl3); H
NMR: l 7.34, 6.81 (m, 14 H, aromatic protons), 4.91
(d, 1 H, J 10.8 Hz, H-3), 4.68 (dd, 1 H, J3,4 3.6 Hz, J4,5
7.5 Hz, H-4), 4.40 (d, 1 H, J 7.2 Hz, H-1), 3.77 (s, 3 H,
C6H4OCH3), 3.59 (m, 2 H, OCH2CH2Si), 1.01 (m, 2 H,

594
B. Mukhopadhyay, N. Roy / Carbohydrate Research 338 (2003) 589–596
cooled to 0 °C and a freshly prepared chromium(VI)
trioxide soln, prepared by dissolving 1.2 g of CrO3 in
3.5 M H2SO4 (6 mL), was added dropwise with stirring.
After 15 min, the reaction mixture was allowed to
attain rt and stirring was continued for another 9 h.
The reaction was quenched with EtOH and the solid
precipitates were filtered off. The filtrate was concen-
trated at 20 °C under diminished pressure to a small vol
and the remaining aq phase was extracted with CH2Cl2
(25 mL×3). The combined extract was washed with
water and a saturated NaCl solution, dried (Na2SO4)
and evaporated to a small vol (30 mL). To this soln, a
freshly prepared ethereal diazomethane soln was added
dropwise until persistence of the yellow colour. Excess
diazomethane was destroyed by adding ethereal AcOH
solution. The solution was concentrated to a syrupy
product which was chromatographed with 7:1 ben-
zene–EtOAc to afford pure 12 (1.13 g, 63%); [h]D
84.2, 81.5, 78.1, 77.0, 75.2, 74.7, 74.2, 73.4, 73.0, 72.5,
72.0, 70.7, 69.7, 68.5, 67.0, 57.3 (COOCH3), 20.3
(COCH3), 18.4 (CH2SiMe3), 15.7 (CꢀCH3), −1.5
[Si(CH3)3]. Anal. Calcd for C68H82O17Si: C, 68.09; H,
6.89. Found: C, 67.91; H, 7.12.
3.10. Ethyl 2-O-acetyl-4,6-O-benzylidene-1-thio-a-D-
mannopyranoside (14)
To a soln of 1 (2 g, 6.4 mmol) in CH3CN (15 mL),
trimethylorthoacetate (1.2 mL, 9.6 mmol) and p-TsOH
(200 mg) were added and the mixture was allowed to
stir at rt for 45 min after complete conversion (TLC),
the soln was neutralized with Et3N and the solvents
were evaporated. The residue was dissolved in 15 mL
80% AcOH and stirred for 30 min at rt when TLC
showed complete conversion. The solvents were evapo-
rated and the crude product was chromatographed
using 5:1 benzene–EtOAc to afford 14 (1.7 g, 74%);
1
+8.4° (c 1.2, CHCl3); H NMR: l 7.43–7.16 (m, 30 H,
aromatic protons), 5.75 (m, 1 H, CH2ꢀCHꢁCH2), 5.32–
5.25 (m, 2 H, CH2ꢀCHꢁCH2), 5.03 (s, 1 H, H-1II), 4.95
(d, 1 H, J 3.3 Hz, H-1III), 4.76 (d, 1 H, J 11.7 Hz, H-1I),
3.89 (s, 3 H, COOCH3), 3.50 (m, 2 H, CH2CH2SiMe3),
1.96 (s, 3 H, COCH3), 1.21 (m, 2 H, CH2CH2SiMe3),
1.08 (d, 3 H, J 6.3 Hz, CꢀCH3), −0.15 [s, 9 H,
Si(CH3)3]. 13C NMR: l 173.4 (COOCH3), 170.1
(COCH3), 134.3 (CH2ꢀCHꢁCH2), 140.4–128.9 (aro-
matic carbons), 117.1 (CH2ꢀCHꢁCH2), 103.0 (C-1I),
99.3 (C-1II), 99.0 (C-1III), 84.1, 82.3, 79.3, 77.3, 77.2,
76.7, 74.7, 74.6, 74.3, 73.8, 73.4, 73.2, 72.7, 72.1, 70.5,
69.7, 69.6, 68.6, 67.1, 56.3 (COOCH3), 20.5 (COCH3),
18.5 (CH2SiMe3), 16.2 (CꢀCH3), −1.5 [Si(CH3)3].
Anal. Calcd for C71H86O17Si: C, 68.80; H, 6.99. Found:
C, 70.01; H, 6.73.
1
[h]D +125.4°; H NMR: 7.55–7.25 (m, 4 H, aromatic
protons), 5.56 (s, 1 H, CHPh), 5.27 (d, 1 H, J 3.6 Hz,
H-2), 5.26 (s, 1 H, H-1), 2.65 (m, 2 H, SꢀCH2ꢀCH3),
2.12 (s, 3 H, COCH3), 1.26 (t, 3 H, J 7.5 Hz,
SꢀCH2ꢀCH3). 13C NMR: 170.9 (COCH3), 128.74–
126.6 (aromatic carbons), 102.6 (CHPh), 83.7 (C-1),
78.5, 74.0, 68.9, 68.1, 64.0, 26.0 (SꢀCH2ꢀCH3), 21.4
(COCH3), 15.3 (SꢀCH2ꢀCH3).
3.11. Ethyl 2,3,4-tri-O-benzyl-a-L-fucopyranosyl-(1“3)-
2-O-acetyl-4,6-O-benzylidene-1-thio-a-D-mannopyran-
oside (15)
A mixture of donor 7 (2.3 g, 4.74 mmol), acceptor 14
,
(1.3 g, 3.65 mmol) and 4 A MS (2 g) in CH2Cl2 (25 mL)
was stirred at rt for 12 h and then cooled to 0 °C. NIS
(1.3 g, 6.2 mmol) and TfOH (54 mL, 0.6 mmol) were
added and the soln was stirred for 45 min when TLC
showed complete conversion. The mixture was diluted
with CH2Cl2 (25 mL) and filtered through Celite. The
filtrate was washed successively with aq Na2S2O3, satu-
rated aq NaHCO3 and water. The organic layer was
dried (Na2SO4) and concentrated to a syrup. Column
chromatography of the material with 8:1 benzene–
EtOAc afforded 15 (2.3 g, 75%) also as syrup; [h]D
3.9. Methyl 2,3,4-tri-O-benzyl-a-
L-fucopyranosyl-(1“
4)-2-O-acetyl-6-O-benzyl-a- -mannopyranosyl-(1“4)-
D
[2-(trimethylsilyl)ethyl 2,3-di-O-benzyl-b-D-glucopyran-
osid]uronate (13)
To a mixture of 12 (1.3 g, 1 mmol) in MeOH (20 mL)
PdCl2 (90 mg, 0.5 mmol) was added and the solution
was stirred at rt for 3 h. The solvent was removed and
the crude product was immediately charged into a
column of silica gel and eluted with 7:1 benzene–
EtOAc to afford pure 13 (1.0 g, 80%); [h]D +10.2° (c
1
+59.1°. H NMR: 7.36–7.12 (m, 20 H, aromatic pro-
tons), 5.6 (s, 1 H, CHPh), 5.54 (bs, 1 H, H-2I), 5.38 (s,
1 H, H-1I), 5.01 (d, 1 H, J 3.5 Hz, H-1II), 2.65 (m, 2 H,
SꢀCH2ꢀCH3), 1.87 (s, 3 H, COCH3), 1.26 (t, 3 H, J 7.5
Hz, SꢀCH2ꢀCH3), 1.02 (d, 3 H, J 6.5 Hz, CꢀCH3). 13C
NMR: 169.9 (COCH3), 135.1–127.2 (aromatic car-
bons), 102.0 (CHC6H5), 94.6 (C-1II), 83.9 (C-1I), 24.7
(SꢀCH2ꢀCH3), 20.6 (COCH3), 16.7 (SꢀCH2ꢀCH3), 15.1
(CꢀCH3). Anal. Calcd for C44H50O10S: C, 68.55; H,
6.54. Found: C, 68.68; H, 6.66.
1
1.3, CHCl3); H NMR: l 7.41–7.25 (m, 30 H, aromatic
protons), 5.01 (s, 1 H, H-1II), 4.98 (d, 1 H, J 3.3 Hz,
H-1III), 4.75 (d, 1 H, J 11.7 Hz, H-1I), 3.87 (s, 3 H,
COOCH3), 3.46 (m, 2 H, CH2CH2SiMe3), 2.01 (s, 3 H,
COCH3), 1.14 (m, 2 H, CH2CH2SiMe3), 1.06 (d, 3 H, J
6.3 Hz, CCH3), −0.14 [s, 9 H, Si(CH3)3]. 13C NMR: l
172.4 (COOCH3), 169.1 (COCH3), 140.4–128.9 (aro-
matic carbons), 102.9 (C-1I), 99.2 (C-1II), 98.7 (C-1III),

B. Mukhopadhyay, N. Roy / Carbohydrate Research 338 (2003) 589–596
595
3.12. Methyl 2,3,4-tri-O-benzyl-a-
3)-2-O-acetyl-4,6-O-benzylidene-a-
osyl-(1“3)-2-acetyl-6-O-benzyl-4-O-(2,3,4-tri-O-ben-
zyl-a- -fucopyranosyl)-a- -mannopyranosyl-(1“4)-
[2-(trimethylsilyl)ethyl 2,3-di-O-benzyl-b-D-glucopyran-
osid]uronate (16)
L
-fucopyranosyl-(1“
-mannopyran-
dried under diminished pressure for 1 h, then dissolved
in DMF (5 mL) and NaN3 (100 mg, 0.54 mmol) was
added. The soln was stirred for 4 h at rt and then
diluted with CH2Cl2 and washed with cold water. The
organic layer was dried (Na2SO4) and evaporated to a
syrup. Column chromatography of the crude material
with 6:1 benzene–EtOAc afforded 19 (321 mg, 60%
overall); [h]D +31.4 (c 1.2, CHCl3). The IR spectrum
(CHCl3) of 19 showed a strong band at 2125 cm−1 for
D
L
D
A mixture of trisaccharide acceptor 13 (717 mg, 0.6
mmol), disaccharide donor 15 (714 mg, 0.9 mmol) and
1
,
4 A MS (1 g) in CH2Cl2 (15 mL) was allowed to stir at
the N3 stretching vibration; H NMR: l 7.65–7.20 (m,
rt for 12 h. The mixture was then cooled to 0 °C and
NIS (240 mg, 1.1 mmol) and TfOH (10 mL, 0.1 mmol)
were added. After stirring for 45 min (TLC optimum
conversion), the soln was diluted with CH2Cl2 (25 mL)
and filtered through Celite. The filtrate was washed
successively with aq Na2S2O3, saturated aq NaHCO3
and water. The organic layer was dried (Na2SO4) and
evaporated to a syrup. Column chromatography with
8:1 benzene–EtOAc gave 16 (850 mg, 70%) as glassy
50 H, aromatic protons), 5.54 (s, 1 H, CHPh), 5.04,
4.96 (m, 2 H, H-1II, H-1IV), 4.91 (d, 1 H, J 3.6 Hz,
H-1III), 4.80 (d, 1 H, J 3.2 Hz, H-1V), 4.72 (d, 1 H, J
10.8 Hz, H-1I), 3.72 (s, 3H, COOCH3), 1.02, 0.98 (2s,
6H, 2 CꢀCH3), −0.14 [Si(CH3)3]. 13C NMR: l 168.4
(COOMe), 126.3–138.8 (aromatic carbons), 103.2 (C-
1I), 102.2 (CHPh), 99.4, 99.2, 99.0, 97.1 (C-1II, C-1III,
C-1IV, C-1V), 83.4, 81.7, 79.8, 79.2, 79.1, 78.0, 77.6,
76.8, 76.1, 75.9, 75.2, 74.9, 74.8, 74.4, 73.4, 73.3, 73.2,
73.1, 73.0, 72.0, 71.8, 69.5, 68.5, 67.7, 67.4, 66.5, 64.3,
63.6, 63.1 (C-2II, C-2IV), 61.3 (CH2CH2SiMe3), 52.3
(COOCH3), 18.4 (CH2SiMe3), 16.7, 16.1 (2 CꢀCH3),
−1.5 [Si(CH3)3]. Anal. Calcd for C106H120O23N6Si: C,
67.93; H, 6.45; N, 4.48. Found: C, 67.70; H, 6.66; N,
4.69.
1
syrup; [h]D +37.5° (c 1.1, CHCl3); H NMR: l 7.39–
7.17 (m, 50 H, aromatic protons), 5.50 (s, 1 H, CHPh),
5.42, 5.26 (2 bs, 2 H, H-1II, H-1IV), 4.96 (d, 1 H, J 3.6
Hz, H-1III), 4.85 (d, 1 H, J 3.3 Hz, H-1V), 4.75 (d, 1 H,
J 11.4 Hz, H-1I), 3.95 (s, 3 H, COOCH3), 2.57 (m, 2 H,
CH2CH2SiMe3), 2.18, 2.05 (2 OCOCH3), 1.26 (m, 2 H,
CH2CH2SiMe3), 1.13 (d, 3 H, J 6.6 Hz, CꢀCH3), 1.09
(d, 3 H, J 6.3 Hz, CꢀCH3), −0.14 [s, 9 H, Si(CH3)3].
13C NMR: l 171.3 (COOMe), 168.4, 167.3 (2 COCH3),
103.3 (C-1I), 102.2 (CHPh), 100.2, 99.9 (C-1II, C-1IV),
98.5, 96.3 (C-1III, C-1V), 84.5, 81.8, 79.8, 78.0, 77.9,
77.7, 77.0, 76.8, 76.7, 75.8, 75.2, 74.8, 74.6, 74.2, 73.7,
73.5, 73.1, 73.0, 72.6, 72.2, 69.8, 69.5, 68.7, 68.6, 67.1,
66.5, 63.3 (CH2CH2SiMe3), 55.1 (COOMe), 20.9, 20.7
(2 COCH3), 18.7 (CH2SiMe3), 16.3, 16.1 (2 CꢀCH3),
−1.5 [Si(CH3)3]. Anal. Calcd for C110H126O27Si: C,
69.24; H, 6.66. Found: C, 68.96; H, 6.82.
3.14. Methyl 2,3,4-tri-O-benzyl-a-
3)-2-acetamido-4,6-O-benzylidene-2-deoxy-a-
glucopyranosyl-(1“3)-2-acetamido-6-O-benzyl-2-
deoxy-4-O-(2,3,4-tri-O-benzyl-a- -fucopyranosyl)-a-
glucopyranosyl-(1“4)-[2-(trimethylsilyl)ethyl 2,3-di-O-
benzyl-b- -glucopyranosid]uronate (20)
L-fucopyranosyl-(1“
D-
L
D-
D
A soln of compound 19 (400 mg, 0.21 mmol) in
thioacetic acid (5 mL) and pyridine (2.5 mL) was
allowed to stir at rt for 24 h. The solvents were care-
fully removed and the residue was chromatographed
with 5:1 benzene–EtOAc to afford 20 (240 mg, 60%);
3.13. Methyl 2,3,4-tri-O-benzyl-a-
3)-2-azido-4,6-O-benzylidene-2-deoxy-a-
pyranosyl-(1“3)-2-azido-6-O-benzyl-2-deoxy-4-O-
(2,3,4-tri-O-benzyl-a- -fucopyranosyl)-a- -gluco-
pyranosyl-(1“4)-[2-(trimethylsilyl)ethyl 2,3-di-O-ben-
zyl-b- -glucopyranosid] uronate (19)
L-fucopyranosyl-(1“
D-gluco-
1
[h]D +27.6° (c 1.2, CHCl3). H NMR: l 7.65–7.20 (m,
50 H, aromatic protons), 5.51 (s, 1 H, CHPh), 5.02 (d,
1 H, J 3.2 Hz, H-1II), 4.93, 4.90 (2 bs, 2 H, H-1III,
H-1IV), 4.80 (d, 1 H, J 3.4 Hz, H-1V), 4.70 (d, 1 H, J
11.0 Hz, H-1I), 3.71 (s, 3H, COOCH3), 1.04, 0.99 (2s,
6H, 2 CꢀCH3), −0.14 [Si(CH3)3]. 13C NMR: l 171.4
(COOMe), 168.6, 168.1 (2 NHCOCH3), 130.7–127.8
(aromatic carbons), 103.6 (C-1I), 102.2 (CHPh), 99.2,
98.9, 98.7, 96.9 (C-1II, C-1III, C-1IV, C-1V), 84.3, 81.4,
79.8, 78.2, 77.9, 77.5, 77.1, 76.8, 76.6, 75.4, 75.2, 74.6,
74.3, 74.2, 73.8, 73.3, 73.1, 72.8, 72.4, 72.2, 69.7, 69.1,
68.3, 68.2, 64.8, 63.9, 62.5, 54.4 (COOCH3), 53.9, 53.3
(C-2II, C-2IV), 22.4, 22.9 (2 NHCOCH3), 18.7
(CH2SiMe3), 16.9, 16.3 (2 CꢀCH3), −1.5 [Si(CH3)3].
Anal. Calcd for C110H128O25N2Si: C, 69.31; H, 6.77; N,
1.47. Found: C, 68.98; H, 6.92; N, 1.64.
L
D
D
To a soln of compound 16 (650 mg, 0.32 mmol) in
MeOH (15 mL), 0.05 M NaOMe (1 mL) was added
and the soln was stirred at rt for 3 h. Then the soln was
neutralized with a Dowex 50W H+ resin, filtered and
evaporated. Column chromatography of the material
with 5:1 benzene–EtOAc gave 17 (623 mg, quantita-
tive). Compound 17 (550 mg, 0.27 mmol) was dissolved
in CH2Cl2 (10 mL) and pyridine (500 mL) and the soln
was cooled to −35 °C. Triflic anhydride (135 mL, 0.8
mmol) was added and the soln was stirred for 3 h. The
reagents were then evaporated, the residue (18) was

596
B. Mukhopadhyay, N. Roy / Carbohydrate Research 338 (2003) 589–596
(b) Mulard, L. A.; Ughetto-Monfrin, J. J. Carbohydr.
3.15. Methyl a-L-fucopyranosyl-(1“3)-2-acetamido-2-
Chem. 2000, 19, 193–220;
deoxy-a-
4-O-(a-
[2-(trimethylsilyl) ethyl-b-
D
-glucopyranosyl-(1“3)-2-acetamido-2-deoxy-
-fucopyranosyl)-a- -glucopyranosyl-(1“4)-
-glucopyranosid]uronate (21)
(c) Mulard, L. A.; Ughetto-Monfrin, J. J. Carbohydr.
Chem. 2000, 19, 503–526;
(d) Mulard, L. A.; Ughetto-Monfrin, J. J. Carbohydr.
Chem. 1999, 18 (7), 721–753.
L
D
D
8. (a) Mulard, L. A.; Costachel, C.; Sansonetti, P. J. J.
Carbohydr. Chem. 2000, 19, 849–877;
Compound 20 (200 mg, 0.1 mmol) and 10% PdꢀC (300
mg) in AcOH (15 mL) were stirred under hydrogen for
48 h at rt. The mixture was filtered through a Celite bed
and and the filtrate was concentrated to dryness. The
crude product was chromatographed with 10:5:1
CHCl3–CH3OH–H2O and then filtered through a 0.45
mm Millipore membrane to afford pure 21 (81 mg,
(b) Costachel, C.; Sansonetti, P.; Mulard, L. A. J. Carbo-
hydr. Chem. 2000, 19, 1131–1150.
9. (a) Pozsgay, V.; Glaudemans, C. P. J.; Robbins, J. B.;
Schneerson, R. Tetrahedron 1992, 48, 10249–10264;
(b) Pozsgay, V.; Pannell, L. Carbohydr. Res. 1994, 258,
105–122;
(c) Pozsgay, V.; Coxon, B. Carbohydr. Res. 1994, 257,
189–215;
(d) Pozsgay, V. J. Am. Chem. Soc. 1995, 117, 6673–6681.
10. (a) Paulsen, H.; Bu¨nsch, H. Chem. Ber. 1981, 114, 3126–
3145;
(b) Paulsen, H.; Bu¨nsch, H. Tetrahedron Lett. 1988, 22,
47–50.
11. Mukherjee, I.; Das, S. K.; Mukherjee, A.; Roy, N. Car-
bohydr. Res. 2000, 325 (9), 245–252.
12. (a) Pozsgay, V. J. Org. Chem. 1998, 63, 5983–5999;
(b) Pozsgay, V.; Chu, C.; Pannell, L.; Wolfe, J.; Robbins,
J. B. Proc. Natl. Acad. Sci. USA 1999, 96, 5194–5197.
13. Dmitriev, B. A.; Backinowsky, L. V.; Knirel, Y. A.;
Kochetkov, N. K.; Hofman, I. L. Eur. J. Biochem. 1977,
78, 381–387.
14. Lemieux, R. U. Can. J. Chem. 1951, 29, 1070–1091.
15. David, S.; Thieffry, A.; Veyrieres, A. J. Chem. Soc.,
Perkin Trans. 1 1981, 1796–1801.
1
80%); [h]D +68.5° (c 0.5, CHCl3). H NMR (D2O): l
5.28 (bs, 2 H, H-1III, H-1V), 5.10, 5.03 (2 d, 2 H, J 3.8
Hz, H-1II, H-1IV), 4.81 (d, 1H, J 10.5 Hz, H-1I), 3.70 (s,
3H, COOCH3), 2.04, 1.90 (2s, 6H, 2 NHCOCH3), 3.29
(m, 2H, CH2CH2SiMe3), 1.16, 1.14 (2d, 6H, J 6.6 Hz, 2
CꢀCH3), 1.10 (t, 2H, CH2CH2SiMe3), −0.14
[Si(CH3)3]. 13C NMR (D2O):
l 175.4, 175.0 (2
NHCOCH3), 171.6 (COOMe), 102.7 (C-1I), 101.8,
100.4, 100.1, 97.3 (C-1II, C-1III, C-1IV, C-1V), 78.7, 76.9,
74.8, 73.9, 73.8, 73.7, 73.6, 72.9, 72.8, 70.6, 70.5, 69.7,
69.2, 69.0, 68.9, 68.1, 67.9, 61.4, 61.1 (CH2 CH2SiMe3),
54.5, 54.1 (C-2II, C-2IV), 49.5 (COOCH3), 23.2, 22.9 (2
NHCOCH3), 18.5 (CH2CH2SiMe3), 16.6, 16.3 (2
CꢀCH3), −1.5 [Si(CH3)3]. Anal. Calcd for C40H70O25-
N2Si: C, 47.71; H, 7.01; N, 2.79. Found: C, 47.56; H,
6.72; N, 2.95.
16. Hudson, C. S.; Da´le, J. K. J. Am. Chem. Soc. 1915, 37,
1264–1270.
17. (a) Garegg, P. A. J.; Hultberg, H.; Wallin, S. Carbohydr.
Res. 1992, 108, 97–101;
(b) Garegg, P. A. J.; Hultberg, H. Carbohydr. Res. 1981,
93, C10–C11.
Acknowledgements
18. Lo¨nn, H. Carbohydr. Res. 1985, 139, 105–113.
19. (a) Veeneman, G. H.; van Leeuwen, S. H.; van Boom, J.
H. Tetrahedron Lett. 1990, 31, 1331–1334;
(b) Zuurmond, H. M.; Veeneman, G. H.; van der Marel,
G. A.; van Boom, J. H. Carbohydr. Res. 1994, 241,
153–164.
Financial support from the Department of Science
and Technology, New Delhi, India (Project No. SP/S1/
G14/95) is thankfully acknowledged.
20. Zhang, Z.; Magnusson, G. J. Org. Chem. 1996, 61,
2383–2393.
21. Brimacombe, J. S. Methods. Carbohydr. Chem. 1972, 6,
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