Synthesis of the tetrasaccharide related to the repeating unit of the antigen from Shigella dysenteriae type 5

Article abstract of DOI:10.1016/S0008-6215(00)00011-2

Starting from L-rhamnose, D-mannose and 2-amino-2-deoxy-D-glucose hydrochloride, two disaccharide blocks, namely, ethyl 2,4-di-Ο-benzyl-3-Ο-[(R)-1-(methoxycarbonyl)ethyl]-α-L- rhamnopyranosyl-(1→3)-2-Ο-acetyl-4,6-di-Ο-benzyl-1-thio- α-D-mannopyranoside an

Full text of DOI:10.1016/S0008-6215(00)00011-2

www.elsevier.nl/locate/carres
Carbohydrate Research 325 (2000) 245–252
Synthesis of the tetrasaccharide related to the repeating
unit of the antigen from Shigella dysenteriae type 5ꢀ
Indrani Mukherjee, Saibal Kumar Das, Ali Mukherjee, Nirmolendu Roy *
Department of Biological Chemistry, Indian Association for the Culti6ation of Science, Jada6pur,
Calcutta 700 032, India
Received 28 July 1999; accepted 10 December 1999
Abstract
Starting from
namely, ethyl 2,4-di-O-benzyl-3-O-[(R)-1-(methoxycarbonyl)ethyl]-a-
O-benzyl-1-thio-a- -mannopyranoside and 2-(trimethylsilyl)ethyl 2-O-acetyl-3,6-di-O-benzyl-a-
(1“3)-4,6-di-O-benzyl-2-deoxy-2-phthalimido-b- -glucopyranoside, were synthesised and then allowed to react in
the presence of N-iodosuccinimide and trifluoromethane sulfonic acid to give a tetrasaccharide derivative. This
L
-rhamnose,
D
-mannose and 2-amino-2-deoxy-
D
-glucose hydrochloride, two disaccharide blocks,
-rhamnopyranosyl-(1“3)-2-O-acetyl-4,6-di-
-mannopyranosyl-
L
D
D
D
compound was converted into 2-(trimethylsilyl)ethyl 2,4-di-O-benzyl-3-O-[(R)-1-(methoxycarbonyl)ethyl]-a-
L
-
-
rhamno-pyranosyl-(1“3)-2-O-acetyl-4,6-di-O-benzyl-a- -mannopyranosyl-(1“4)-2-O-acetyl-3,6-di-O-benzyl-a-
D
D
mannopyranosyl-(1“3)-2-acetamido-4,6-di-O-benzyl-2-deoxy-b-D-glucopyranoside, which on hydrogenolysis, af-
forded the methyl ester 2-(trimethylsilyl)ethyl glycoside of the tetrasaccharide related to the repeating unit of the
O-antigen from Shigella dysenteriae type 5. © 2000 Elsevier Science Ltd. All rights reserved.
Keywords: Synthesis; Tetrasaccharide repeating unit; Shigella dysenteriae type 5
O-specific polysaccharide of Shigella may pro-
1. Introduction
tect the host against shigellosis, and that con-
jugate vaccines consisting of the O-specific
polysaccharide (O-SP) of Shigella covalently
attached to an immunogenic protein could,
indeed, confer protective immunity to humans
against shigellosis. Much work on the synthe-
sis of oligosaccharides related to Shigella
flexnery variant Y [6] and Shigella dysenteriae
types 1 [7] and 2 [8] has been reported. Pozs-
gay [9] prepared a glycogonjugate vaccine
against Shigella dysenteriae type 1 that
claimed to have better antigenicity than the
native O-SP. It is, therefore, probable that the
O-SP from Shigella dysenteriae type 5 may
also play a protective role against shigellosis
and bacillary dysentery in human. We report
herein the total synthesis of tetrasaccharide II
related to the repeating unit (I) of Shigella
Shigella dysenteriae is the most virulent
among the pathogenic bacilli of the genus
Shigella [1]. Enterobacteria from the Shigella
family are responsible for intestinal diseases
including dysentery, and have the potential for
causing catastrophic public health problems in
developing countries [2]. They are very resis-
tant to antimicrobial drugs. This resistance,
therefore, necessitates the exploration of other
medical approaches for control of diseases
caused by this pathogen [3]. It has been sug-
gested [4,5] that circulating antibodies to the
ꢀ Presented at the XIXth International Carbohydrate Sym-
posium, San Diego, CA, USA, 1998, Abstr. BP 006.
* Corresponding author. Fax: +91-33-4732805.
E-mail address: bcnr@mahendra.iacs.res.in (N. Roy)
0008-6215/00/$ - see front matter © 2000 Elsevier Science Ltd. All rights reserved.
PII: S0008-6215(00)00011-2

246
I. Mukherjee et al. / Carbohydrate Research 325 (2000) 245–252
2. Results and discussion
dysenteriae type 5 [10]. The synthesised
oligosaccharide can also be utilised as a
molecular probe for studying the immuno-
chemical behaviour of the antigen.
The known ethyl 2,4-di-O-benzyl-1-thio-a-
-rhamnopyranoside [11] (1), prepared from
-rhamnose, was allowed to react with (S)-2-
L
L
bromopropionic acid and sodium hydride to
give 2, which was esterified with diazomethane
[12] to afford the donor ethyl 2,4-di-O-benzyl-
3-O-[(R)-1-(methoxycarbonyl)ethyl]-1-thio-a-
L
-rhamnopyranoside (3) (Scheme 1). The
1
structure of 3 was confirmed by its H NMR
spectrum, which showed a broad singlet at l
5.29 for the anomeric proton, and peaks at l
4.10, 3.63 and 1.37 for CH(CH3)COOCH3,
CH(CH3)COOCH3 and CH(CH3)COOCH3,
respectively.
The position of the O-acetyl groups on the
mannose moiety in I was not unequivocally
established and was arbitrarily assigned to
either the C-2 or C-3 position. The possibility
that the importance of the R-lactic acid sub-
In another experiment, 2-(trimethylsilyl)-
ethyl 4,6-O-benzylidene-2-deoxy-2-phthalimi-
stituted -rhamnose component at the non-re-
L
ducing end might play a role in the immune
response is also a reason for our decision to
synthesise tetrasaccharide II related to
Shigella dysenteriae type 5.
do-b- -glucopyranoside [13] (4) was allylated
D
[14] with allyl bromide and sodium hydride to
afford 2-(trimethylsilyl)ethyl 3-O-allyl-4,6-O-
benzylidene - 2 - deoxy - 2 - phthalimido-b- -glu
D
copyranoside (5). Removal of the benzylidene
group from 5 followed by benzylation of
product 6 with benzyl bromide and sodium
hydride in N,N-dimethylformamide gave 2-
(trimethylsilyl)ethyl 3-O-allyl-4,6-di-O-benzyl-
2-deoxy-2-phthalimido-b- -glucopyranoside
D
(7). Removal of the allyl group from 7 with
palladium chloride [15] in methanol afforded
2-(trimethylsilyl)ethyl 4,6-di-O-benzyl-2-de-
oxy-2-phthalimido-b-
D
-glucopyranoside (8)
(Scheme 2).
Scheme 1. (i) NaH, (S)-2-bromopropionic acid, dioxane; (ii)
CH2N2, Et2O.
Ethyl 4,6-O-benzylidene-1-thio-a-
D
-manno-
pyranoside [16] (9) was converted into ethyl
3-O-benzyl-4,6-O-benzylidene-1-thio-a- -
D
mannopyranoside (10) via its stannylene
derivative [17]. Acetylation of 16 afforded
ethyl
2-O-acetyl-3-O-benzyl-4,6-O-benzyli-
-mannopyranoside (11)
dene-1-thio-a-
D
(Scheme 3). Compound 17 has signals for
CHPh (l 5.63), acetyl, benzyl and thioethyl
groups in the H NMR spectrum.
1
Donor 3 was then allowed to react with the
acceptor ethyl 2-O-acetyl-4,6-di-O-benzyl-1-
Scheme 2. (i) AllBr, DMF, NaH; (ii) 80% ACOH; (iii) BnBr,
NaH, DMF; (iv) PdCl2, MeOH.

I. Mukherjee et al. / Carbohydrate Research 325 (2000) 245–252
247
gave 2-(trimethylsilyl)ethyl 2-O-acetyl-3,6-di-
O-benzyl-a- -mannopyranosyl-(1“3)-4,6-di-
O-benzyl-2-deoxy-2-phthalimido-b- -glucopy-
D
D
ranoside (15) in 68% yield with a free OH
group at its C-4II position (Scheme 4). The
structure of 15 was confirmed from its signals
at l 5.44 (H-2II), 5.23 (H-1II), 5.17 (H-1I), 4.23
(H-2I), 3.63 (H-4II), 1.91 (CH3CO), 0.78
(OCH2CH2Si) and −0.13 (Si(CH3)3) in the 1H
NMR spectrum and at l 169.8 (COCH3), 99.6
(C-1I), 97.5 (C-1II), (C-2I), 20.7 (COCH3), 17.7
(CH2Si(CH3)3) and −1.5 (Si(CH3)3) in the
13C NMR spectrum. The presence of an OH
group at C-4II of 15 was confirmed by acetyla-
tion with acetic anhydride and pyridine as
Scheme 3. (i) Bu2SnO, C6H6, BnBr, Bu4NBr; (ii) Ac2O,
pyridine.
1
described above. In the H NMR spectrum of
the resulting acetate 16, the signal of H-4II had
shifted downfield to l 5.17 compared with its
position at l 3.63 in the spectrum of 15.
Reaction of donor 13 with acceptor 15 in
the presence of NIS and TfOH in di-
chloromethane afforded 2-(trimethylsilyl)ethyl
2,4-di-O-benzyl-3-O-[(R)-1-(methoxycarbon-
,
Scheme 4. (i) IDCP, CH2Cl2, 4 A MS; (ii) NIS, TfOH,
CH2Cl2; (iii) NaBH3CN, HCl–ether, THF; (iv) Ac2O,
pyridine.
yl)ethyl]-a-
acetyl-4,6-di-O-benzyl-a-
(1“4)-2-O-acetyl-3,6-di-O-benzyl-a-
nopyranosyl-(1“3)-4,6-di-O-benzyl-2-deoxy-
2-phthalimido-b- -glucopyranoside (17) in
L
-rhamnopyranosyl-(1“3)-2-O-
-mannopyranosyl-
-man-
D
D
thio-a- -mannopyranoside (12) [18] in the
D
D
presence of iodonium dicollidine perchlorate
(IDCP) [19] in dichloromethane to give the
disaccharide ethyl 2,4-di-O-benzyl-3-O-[(R)-1-
79% yield. Compound 17 was characterised by
its signals at l 5.43, 5.28 (2 bs, 2 H, H-2II,
H-2III), 5.25 (2 bs, 2 H, H-1II, H-1III), 5.16 (d,
2 H, J 8.4 Hz, H-1I, H-1IV), 3.41 (CH-
(CH3)COOCH3), 2.06, 1.94 (2 COCH3), 1.38
(CH(CH3)COOMe), 1.36 (H-6IV), 0.83
(OCH2CH2Si), −0.13 (Si(CH3)3) and at l
173.3, 169.8, 169.7 (3 CO), 99.2 (C-1I), 99.1,
97.6 (C-1II, C-1III), 93.4 (C-1IV), 55.6 (C-2I),
51.7 (COOCH3), 20.9, 20.7 (2 COCH3), 18.8
(CH(CH3)COOMe), 18.2 (C-6IV), 17.7 (CH2-
Si(CH3)3) and −1.5 (Si(CH3)3) in the 13C
NMR spectrum.
(methoxycarbonyl)ethyl] - a -
osyl-(1“3)-2-O-acetyl-4,6-di-O-benzyl-1-
thio-a- -mannopyranoside (13) in 71% yield.
L
- rhamnopyran -
D
The prevalence for the reaction [20,21] of the
ethyl thioglycoside 6 as donor, in the presence
of the ethyl thioglycoside 12 as acceptor, is
obviously ascribed to the activation of 6 by
the benzyl substituent at O-2 while 12 is deac-
tivated by the acetyl substituent at O-2
(Scheme 4).
In a separate experiment, donor 11 was
allowed to react with acceptor 8 in the pres-
ence of N-iodosuccinimide (NIS) and trifl-
uoromethanesulfonic acid (TfOH) [21] in
dichloromethane to afford the disaccharide 2-
(trimethylsilyl)ethyl 2-O-acetyl-3-O-benzyl-4,6
Dephthaloylation of 17 with ethylene di-
amine [22] in butanol followed by N-acetyla-
tion of the product with acetic anhydride and
triethylamine gave 2-(trimethylsilyl)ethyl 2,4-
di-O-benzyl-3-O-[(R)-1-(methoxycarbonyl)-
ethyl] - a -
acetyl-4,6-di-O-benzyl-a-
(1“4)-2-O-acetyl-3,6-di-O-benzyl-a-
nopyranosyl-(1“3)-2-acetamido-4,6-di-O-
benzyl-2-deoxy-b- -glucopyranoside (18) in
L
- rhamnopyranosyl- (1“3) - 2 - O -
-mannopyranosyl-
-man-
-O-benzylidene-a- -mannopyranosy-(1“3)-
D
D
4,6-di-O-benzyl-2-deoxy-2-phthalimido-b- -
D
D
glucopyranoside (14) in 90% yield. Treatment
of 14 with sodium cyanoborohydride and hy-
drogen chloride in ether and tetrahydrofuran
D

248
I. Mukherjee et al. / Carbohydrate Research 325 (2000) 245–252
,
Scheme 5. (i) NIS–TfOH, CH2Cl2, 4 A MS; (ii) ethylene diamine, butanol, Ac2O, triethyl amine; (iii) 10% Pd–C, H2, AcOH.
1
79% yield. The presence of the acetamido
241 MC polarimeter. The H and 13C NMR
spectra were recorded on a Varian A-60 or
Bruker DPX 300 spectrometer using CDCl3 as
solvent (internal standard TMS) unless other-
wise stated. Melting points were determined
on a paraffin oil bath and are uncorrected.
Ethyl 2,4-di-O-benzyl-3-O-[(R)-2-(methoxy-
group in 18 was confirmed by its signal at l
1
1.74 (NHCOCH3) in the H NMR spectrum
and at l 23.0 (NHCOCH3) in the 13C NMR
spectrum. Hydrogenolysis [23] of 18 gave 2-
(trimethylsilyl)ethyl 3-O-[(R)-1-(methoxycar-
bonyl)ethyl]-a-
O-acetyl-a- -mannopyranosyl-(1“4)-2-O-
acetyl-a- -mannopyranosyl-(1“3)-2-aceta-
mido-2-deoxy-b- -glucopyranoside (19) in
L
-rhamnopyranosyl-(1“3)-2-
D
carbonyl)ethyl] - 1 - thio - h -
ide (3).—To a solution of ethyl 2,4-di-O-ben-
zyl-1-thio-a- -rhamnopyranoside [11] (1, 1.6 g,
L
- rhamnopyranos-
D
D
L
73% yield (Scheme 5). Compound 19 had
signals at l 5.47–5.37 (H-2II, H-2III, H-1II,
H-1III), 5.15 (H-1IV), 5.14 (H-1I), 3.41
(CH(CH3)COOCH3), 2.03, 2.02 (2 OAc), 1.92
(NHCOCH3), 0.76 (OCH2CH2Si) and −0.13
4.09 mmol) in dioxane (42 mL) was added
NaH (60% oil coated, 883 mg, 22.09 mmol).
The solution was then stirred for 1 h at 95 °C.
The mixture was cooled to 65 °C and a solu-
tion of (S)-2-bromopropionic acid (2.2 mL,
24.1 mmol) in dioxane (10 mL) was added
with vigorous stirring. After 1.5 h, a suspen-
sion of NaH (3.5 g) in dioxane was added and
stirring was continued overnight at 65 °C. The
mixture was then cooled to room temperature
(rt) and MeOH (12 mL) was added to decom-
pose the excess of NaH. The reaction mixture
was then diluted with CH2Cl2, washed with
water, dried (Na2SO4) and concentrated to a
syrup. Column chromatography with 0.01%
AcOH in 3:1 toluene–EtOAc gave 2 (1.2 g,
64%). This acid (2) was dissolved in ether (10
mL) and an ethereal diazomethane solution
(20 mL) was added dropwise. The reaction
was completed within 1 min and the excess of
CH2N2 was decomposed by adding dilute
AcOH. The solvents were evaporated off and
traces of acid and water were removed by
co-evaporation with toluene. Chromatography
1
(Si(CH3)3) in the H NMR spectrum and at l
174.4, 174.1, 173.8, 173.8 (4 CO), 100.8 (C-1I),
100.3, 99.9 (C-1II, C-1III), 97.6 (C-1IV), 54.7
(C-2I), 51.9 (COOCH3), 23.7 (NCOCH3),
21.4, 21.1 (2 COCH3), 19.7 (CH(CH3)COO-
Me), 17.9 (C-6IV), 17.6 (CH2Si(CH3)3) and
−1.5 (Si(CH3)3) in the 13C NMR spectrum.
3. Experimental
General.—All reactions were monitored by
thin-layer chromatography (TLC) on Silica
Gel G (E. Merck). Column chromatography
was performed on 100–200 mesh Silica Gel
(SRL, India). All solvents were distilled and/
or dried before use and all evaporations were
conducted below 40 °C under reduced pres-
sure unless stated otherwise. Optical rotations
were measured with a Perkin–Elmer model

I. Mukherjee et al. / Carbohydrate Research 325 (2000) 245–252
249
pound 6 (1.2 g, 2.7 mmol) was benzylated
according to the conventional method [24].
Column chromatography of the product with
4:1 toluene–Et2O gave pure 7 (0.90 g, 55%);
with 3:1 toluene–EtOAc gave pure 3 (1.2 g,
97%); [h]2D5 −77.23° (c 0.3, CHCl3). 1H NMR:
l 7.43–7.19 (m, 10 H, aromatic protons), 5.29
(bs, 1 H, H-1), 5.04, 4.59 (2 d, 2 H, J 10.8,
CH2Ph), 4.75, 4.67 (2 d, 2 H, J 12.3 Hz,
CH2Ph), 4.10 (q, 1 H, J 6.6 Hz, CH(CH3)-
COOCH3), 4.00 (m, 1 H, H-5), 3.84 (bs, 1 H,
H-2), 3.76 (m, 1 H, H-3), 3.63 (s, 3 H,
COOCH3), 3.58 (t, 1 H, J 9.0 Hz, H-4), 2.58
(m, 2 H, SCH2CH3), 1.37 (d, 3 H, J 6.6 Hz,
CH(CH3)COOMe), 1.31 (d, 3 H, J 6.3 Hz,
H-6), 1.24 (t, 3 H, J 8.0 Hz, SCH2CH3). Anal.
Calcd for C26H34O6S: C, 65.79; H, 7.22.
Found: C, 65.68; H, 7.36.
1
[h]2D5 +10.67° (c 1.0, CHCl3). H NMR: l
8.02–7.23 (m, 14 H, aromatic protons), 5.28
(d, 1 H, J 8.4 Hz, H-1), 5.11 (m, 2 H,
CH2ꢀCHꢁCH2), 4.70 (m, 4 H, 2 CH2Ph), 4.50
(t, 1 H, J 9.6 Hz, H-3), 4.45 (dd, 1 H, J3,4 10.5,
J4,5 4.5 Hz, H-4), 4.20 (dd, 1 H, J1,2 9.0, J2,3
10.5 Hz, H-2), 4.17 (m, 2 H, CH2ꢀCHꢁCH2),
4.0 (m, 2 H, OCH2CH2Si), 3.80 (m, 1 H,
Heq-6), 3.70 (m, 1 H, Hax-6), 3.40 (m, 1 H,
H-5), 0.80 (m, 2 H, OCH2CH2Si), −0.13 (s, 9
H, Si(CH3)3). Anal. Calcd for C36H43O7NSi:
C, 68.65; H, 6.88. Found: C, 68.53; H, 7.10.
2-(Trimethylsilyl)ethyl 4,6-di-O-benzyl-2-de-
2-(Trimethylsilyl)ethyl3-O-allyl-4,6-O-benz-
ylidene- 2 -deoxy-2-phthalimido-i- -glucopyr-
D
anoside (5).—To a solution of 2-(trime-
oxy-2-phthalimido-i- -glucopyranoside (8).—
D
thylsilyl)ethyl
phthalimido-b-
4,6-O-benzylidene-2-deoxy-2-
-glucopyranoside [13] (4, 4.6
The allyl derivative 7 (0.8 g, 1.3 mmol) was
dissolved in dry MeOH (10 mL) and PdCl2
(114 mg, 0.6 mmol) was added. The mixture
was stirred at 25 °C for 4 h, then filtered
through a Celite bed and concentrated to dry-
ness. Column chromatography with 9:1
toluene–Et2O gave pure 8 (417 mg, 54%); [h]D25
D
g, 9.2 mmol) in DMF (37 mL) was added
NaH (60% oil coated, 552 mg, 13.8 mmol) at
0 °C with stirring. After 30 min, allyl bromide
(1.1 mL, 12.9 mmol) was added and stirring
was continued at rt for 7 h. Excess NaH was
decomposed by the addition of MeOH (2.3
mL). The reaction mixture was then diluted
with CH2Cl2. The organic layer was washed
with water, dried (Na2SO4) and concentrated.
Column chromatography of the syrupy
product with 3:1 toluene–Et2O gave 5 (1.44 g,
1
−6.85° (c 2.0, CHCl3). H NMR: l 8.02–7.20
(m, 14 H, aromatic protons), 5.22 (d, 1 H, J
8.4 Hz, H-1), 4.80–4.60 (m, 4 H, 2 CH2Ph),
4.40 (t, 1 H, J 9.6 Hz, H-3), 4.35 (dd, 1 H, J3,4
10.5, J4,5 4.5 Hz, H-4), 4.10 (dd, 1 H, J1,2 9.0,
J2,3 10.5 Hz, H-2), 3.90 (m, 2 H, OCH2CH2Si),
3.80 (m, 1 H, Heq-6), 3.60 (m, 1 H, Hax-6),
3.40 (m, 1 H, H-5), 0.80 (m, 2 H, OCH2-
CH2Si), −0.13 (s, 9 H, Si(CH3)3). Anal. Calcd
for C33H39O7NSi: C, 67.21; H, 6.66. Found: C,
67.33; H, 6.78.
1
29%); [h]2D5 −10.5° (c 1.2, CHCl3). H NMR:
l 8.05–7.23 (m, 9 H, aromatic protons), 5.56
(s, 1 H, CHPh), 5.38 (m, 1 H, CH2ꢀCHꢁCH2),
5.28 (d, 1 H, J 8.4 Hz, H-1), 5.14 (m, 2 H,
CH2ꢀCHꢁCH2), 4.70 (t, 1 H, J 9.6 Hz, H-3),
4.46 (dd, 1 H, J3,4 10.5, J4,5 4.5 Hz, H-4), 4.30
(dd, 1 H, J1,2 9.0, J2,3 10.5 Hz, H-2), 4.11 (m,
Ethyl 3-O-benzyl-4,6-O-benzylidene-1-thio-
h- -mannopyranoside (10).—To a solution of
D
2
H, CH2ꢀCHꢁCH2), 3.90 (m,
2
H,
9 (5.32 g, 17.0 mmol) in benzene (150 mL),
Bu2SnO (5.1 g, 20.4 mmol) was added and the
mixture was refluxed with azeotropic removal
of water for 6 h. The reaction mixture was
concentrated to dryness. Fresh benzene (60
mL), benzyl bromide (12 mL, 102.2 mmol)
and Bu4NBr (2.7 g, 8.5 mmol) were added and
stirred overnight at 65 °C. The solvent was
evaporated off, MeOH was added and the
mixture was cooled. Solids that separated
were filtered off and the filtrate was concen-
trated to a syrup. Column chromatography
with 3:1 toluene–EtOAc gave pure 10 (5.53 g,
81%); [h]2D5 +73.64° (c 0.7, CHCl3). 1H NMR:
OCH2CH2Si), 3.80 (m, 1 H, Heq-6), 3.65 (m, 1
H, Hax-6), 3.50 (m, 1 H, H-5), 0.80 (m, 2 H,
OCH2CH2Si), −0.13 (s, 9 H, Si(CH3)3). Anal.
Calcd for C29H35O7NSi: C, 64.78; H, 6.56.
Found: C, 64.64; H, 6.77.
2-(Trimethylsilyl)ethyl 3-O-allyl-4,6-di-O-
benzyl-2-deoxy-2-phthalimido-i- -glucopyran-
D
oside (7).—Compound 5 (1.4 g, 2.6 mmol)
was dissolved in AcOH (23.4 mL) and water
(5.9 mL) and stirred at 80 °C for 2 h. The
mixture was concentrated to dryness and co-
evaporated with toluene to remove traces of
acid and water to give 6 (1.2 g, 95%). Com-

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I. Mukherjee et al. / Carbohydrate Research 325 (2000) 245–252
3.37 (s, 3 H, COOCH3), 2.61 (m, 2 H,
SCH2CH3), 2.16 (s, 3 H, COCH3), 1.33 (d, 3
H, J 6.9 Hz, CH(CH3)COOMe), 1.26 (t, 3 H,
J 6.3 Hz, SCH2CH3), 1.25 (d, 3 H, J 6.3 Hz,
H-6II). 13C NMR: l 173.3, 170.1 (2 carbonyl
carbons), 139.3–127.2 (aromatic carbons),
93.0 (C-1II), 82.3 (C-1I), 79.7, 78.6, 75.8, 75.0,
73.9, 73.5, 73.4, 72.9, 72.6, 71.9, 71.7, 69.1,
68.6, 68.1, 51.7 (CH(CH3)COOCH3), 25.3
(CH(CH3)COOMe), 21.1 (COCH3), 18.8
(SCH2CH3), 18.0 (C-6II), 14.8 (SCH2CH3).
Anal. Calcd for C48H58O12S: C, 67.11; H, 6.81.
Found: C, 66.96; H, 7.00.
l 7.53–7.31 (m, 10 H, aromatic protons), 5.62
(s, 1 H, CHPh), 5.38 (s, 1 H, H-1), 486, 4.71
(2 d, 2 H, J 11.7 Hz, CH2Ph), 4.29–4.18 (m, 3
H, H-2, H-3, H-4), 4.13 (m, 1 H, Heq-6), 3.90
(m, 1 H, Hax-6), 3.70 (m, 1 H, H-5), 2.61 (m,
2 H, SCH2CH3), 1.30 (t, 3 H, J 7.5 Hz,
SCH2CH3). Anal. Calcd for C22H26O5S: C,
65.65; H, 6.51. Found: C, 65.76; H, 6.71.
Ethyl 2-O-acetyl-3-O-benzyl-4,6-O-benzyli-
dene-1-thio-h- -mannopyranoside (11).—To a
D
solution of 10 (5.5 g, 13.7 mmol), pyridine (30
mL) and Ac2O (15 mL) were added. After 3 h
at rt, the reaction mixture was evaporated and
then co-evaporated with toluene. Column
chromatography with 3:1 toluene–Et2O gave
pure 11 (6.0 g, 98.5%) as a syrup; [h]D25
2-(Trimethylsilyl)ethyl 2-O-acetyl-3-O-ben-
zyl-4,6-O-benzylidene-h- -mannopyranosyl-
D
(1“3) - 4,6 - di - O - benzyl - 2 - deoxy - 2 - phthal-
imido-i- -glucopyranoside (14).—A solution
1
+58.69° (c 0.2, CHCl3). H NMR: l 7.52–
D
7.26 (m, 10 H, aromatic protons), 5.63 (s, 1 H,
CHPh), 5.45 (dd, 1 H, H-2), 5.26 (s, 1 H,
H-1), 4.68 (m, 2 H, CH2Ph), 4.22 (m, 2 H,
H-3, H-5), 4.09 (t, 1 H, H-4), 3.96 (dd, 1 H,
Heq-6), 3.87 (t, 1 H, Hax-6), 2.63 (m, 2 H,
SCH2CH3), 2.17 (s, 3 H, COCH3), 1.29 (t, 3
H, J 7.5 Hz, SCH2CH3). Anal. Calcd for
C24H28O6S: C, 64.84; H, 6.35. Found: C,
64.96; H, 6.51.
of donor 11 (225.5 mg, 0.5 mmol) and accep-
tor 8 (250 mg, 0.4 mmol) in CH2Cl2 (2 mL)
,
containing 4 A MS (200 mg) was stirred at rt
for 14 h under N2. NIS (158 mg, 0.7 mmol)
and TfOH (6.2 mL, 0.07 mmol) were then
added at −20 °C. After 4 h, the reaction
mixture was diluted with CH2Cl2, filtered
through a Celite bed, washed with 5%
Na2S2O3, sat aq NaHCO3 and water, dried
(Na2SO4) and concentrated. Column chro-
matography with 15:1 toluene–Et2O gave
pure 14 (350 mg, 90%) as a white foam; [h]D25
Ethyl 2,4-di-O-benzyl-3-O-[(R)-1-(methoxy-
carbonyl)ethyl]-h-
L
-rhamnopyranosyl-(1“3)-
-man-
2-O-acetyl-4,6-di-O-benzyl-1-thio-h-
D
1
nopyranoside (13).—A solution of 3 (360 mg,
0.8 mmol) and ethyl 2-O-acetyl-4,6-di-O-ben-
+13.5° (c 0.3, CHCl3). H NMR: l 7.83–7.17
(m, 24 H, aromatic protons), 5.55 (s, 1 H,
CHC6H5), 5.38 (bs, 1 H, H-2II), 5.27 (bs, 1 H,
H-1II), 5.18 (d, 1 H, J 8.7 Hz, H-1I), 3.30 (m,
2 H, OCH2CH2Si), 1.95 (s, 3 H, COCH3), 0.78
(m, 2 H, OCH2CH2Si), −0.13 (s, 9 H,
Si(CH3)3). 13C NMR data (CDCl3): l 169.7
(COCH3), 138.8–126.2 (aromatic carbons),
101.1 (PhCH), 99.8 (C-1I), 97.7 (C-III), 79.8,
77.5, 76.8, 74.9, 74.3, 73.8, 73.5, 72.2, 69.5,
68.1, 66.9, 64.7, 55.4 (C-2I), 20.8 (COCH3),
17.8 (CH2SiMe3), −1.5 (Si(CH3)3). Anal.
Calcd for C55H61O13NSi: C, 67.95; H, 6.32.
Found: C, 67.82; H, 6.50.
zyl-1-thio-a- -mannopyranoside (12) [18] (395
D
mg, 0.9 mmol) in CH2Cl2 (15 mL) containing
,
MS 4 A (1 g) was stirred at rt for 12 h under
N2. Freshly prepared IDCP (750 mg, 1.6
mmol) was added at a time to the solution at
−10 °C. The mixture was stirred for 2 h at
24 °C. The mixture was then filtered and the
filtrate was washed with 10% aq Na2S2O3, sat
aq NaHCO3 and water in succession, dried
(Na2SO4) and concentrated to a syrup.
Column chromatography with 8:1 toluene–
Et2O gave pure 13 (550 mg, 71%); [h]D25
1
−38.97° (c 1.5, CHCl3). H NMR: l 7.48–
2-(Trimethylsilyl)ethyl 2-O-acetyl-3,6-di-O-
7.12 (m, 20 H, aromatic protons), 5.44 (bs, 1
H, H-2I), 5.30 (bs, 1 H, H-1II), 5.12 (bs, 1 H,
H-1I), 5.09–4.34 (m, 9 H, 4 CH2Ph, H-2II),
4.12 (dd, 1 H, J2,3 3.0, J3,4 9.6 Hz, H-3II), 3.97
(q, 1 H, J 6.6 Hz, CH(CH3)COOMe), 3.89
(dd, 1 H, H-4I), 3.86 (dd, 1 H, H-3I), 3.84 (dd,
1 H, H-4II%), 3.61 (m, 4 H, H-5I, H-5II, H-6I),
benzyl-h-
D
-mannopyranosyl-(1“3)-4,6-di-O-
-glucopyr-
benzyl-2-deoxy-2-phthalimido-i-
D
anoside (15).—To a solution of 14 (54.9 mg,
0.06 mmol) and NaBH3CN (32 mg, 0.5 mmol)
,
in THF (9 mL) containing MS 3 A (100 mg)
was added saturated HCl gas in ether at 0 °C
until the solution was acidic or the evolution

I. Mukherjee et al. / Carbohydrate Research 325 (2000) 245–252
251
pleted and then the reaction mixture was di-
luted with CH2Cl2, filtered through Celite and
washed with 5% aq Na2S2O3, sat aq NaHCO3
and water, respectively, dried (Na2SO4) and
concentrated. Column chromatography with
10:1 toluene–ether gave pure 17 (98 mg, 79%)
of H2 ceased. After 5 min, TLC indicated
complete reaction. The mixture was diluted
with CH2Cl2, washed in succession with water,
sat aq NaHCO3, water, then dried (Na2SO4)
and concentrated. Column chromatography
with 3:1 toluene–Et2O gave 15 (40 mg, 68%)
as white foam; [h]2D5 +19.5° (c 0.3, CHCl3).
1H NMR: l 7.76–7.16 (m, 24 H, aromatic
protons), 5.44 (dd, 1 H, J1,2 1.8, J2,3 3.0 Hz,
H-2II), 5.23 (d, 1 H, J 1.2 Hz, H-1II), 5.17 (d,
J 8.4 Hz, H-1I), 4.77–4.16 (m, 8 H, 4 CH2Ph),
4.23 (dd, 1 H, J1,2 10.5, J2,3 8.4 Hz, H-2I), 3.94
(m, 1 H, H-3I), 3.93 (m, 2 H, OCH2CH2Si),
3.84 (dd, 1 H, H-4I), 3.78 (m, 3 H, Hb-6I,
H-6%II), 3.63 (m, 2 H, Ha-6I, H-4II), 3.49 (m, 2
H, H-3II, H-5II), 3.20 (m, 1 H, H-5I), 1.91 (s, 3
H, CH3CO), 0.78 (m, 2 H, OCH2CH2Si),
−0.13 (s, 9 H, Si(CH3)3). 13C NMR: l 169.8
(COCH3), 137.9–127.1 (aromatic carbons),
99.6 (C-1I), 97.5 (C-1II), 79.6, 76.5, 73.4, 73.3,
71.9, 71.7, 67.9, 66.4, 55.5 (C-2I), 20.7
(COCH3), 17.7 (CH2Si(CH3)3), −1.5 (Si-
(CH3)3). Anal. Calcd for C55H63O13NSi: C,
67.81; H, 6.52. Found: C, 67.94; H, 6.65.
Compound 15 (10 mg) was acetylated in the
usual way with acetic anhydride and pyridine
1
as a syrup; [h]2D5 +31.4° (c 0.07, CHCl3). H
NMR: l 7.56–7.01 (m, 44 H, aromatic pro-
tons), 5.43, 5.28 (2 bs, 2 H, H-2II, H-2III), 5.25
(2 bs, 2 H, H-1II, H-1III), 5.16 (d, 2 H, J 8.4
Hz, H-1I, H-1IV), 3.91 (m, 2 H, OCH2CH2Si),
3.41 (s, 3 H, CH(CH3)COOCH3), 2.06, 1.94 (2
s, 6 H, 2 COCH3), 1.38 (d, 3 H, J 6 Hz,
CH(CH3)COOMe), 1.36 (d, 3 H, J 6.6 Hz,
H-6IV), 0.83 (m, 2 H, OCH2CH2Si), −0.13 (s,
9 H, Si(CH3)3). 13C NMR: l 173.3, 169.8,
169.7 (3 carbonyl carbons), 138.4–127.2 (aro-
matic carbons), 99.2 (C-1I), 99.1, 97.6 (C-1II,
C-1III), 93.4 (C-1IV), 79.8, 79.7, 78.7, 78.0,
75.6, 75.1, 74.9, 74.5, 73.9, 73.5, 73.3, 72.8,
72.6, 72.3, 72.0, 71.9, 71.6, 71.1, 68.8, 66.1,
55.6 (C-2I), 51.7 (COOCH3), 20.9, 20.7 (2
COCH3), 18.8 (CH(CH3)COOMe), 18.2 (C-
6IV), 17.7 (CH2Si(CH3)3), −1.5 (Si(CH3)3).
Anal. Calcd for C101H115O25NSi: C, 68.49; H,
6.54. Found: C, 68.60, H, 6.74.
1
to give the acetate 16 (9 mg), H NMR: l
2-(Trimethylsilyl)ethyl 2,4-di-O-benzyl-3-O-
7.73–7.19 (m, 24 H, aromatic protons), 5.39
(t, 1 H, J 2.7 Hz, H-2II), 5.24 (d, 1 H, J 1.5
Hz, H-1II), 5.18 (d, 1 H, J 8.1 Hz, H-1I), 5.17
(t, 1 H, J 9.3 Hz, H-4II), 4.76–4.26 (m, 8 H, 4
CH2PH), 4.22 (dd, 1 H, J1,2 10.8, J2,3 8.4 Hz,
H-2I), 3.92 (m, 2 H, OCH2CH2Si), 3.78 (m, 2
H, H-6II), 3.67 (m, 2 H, H-6I), 3.47 (m, 1 H,
H-5II), 3.24 (m, 1 H, H-5I), 1.94, 1.65 (2 S, 6
H, 2 COCH3), 0.78 (m, 2 H, OCH2CH2Si),
−0.14 (s, 9 H, Si(CH3)3).
[(R)-1-(methoxycarbonyl)ethyl]-h- -rhamno-
L
pyranosyl-(1“3)-2-O-acetyl-4,6-di-O-benzyl-
h- -mannopyranosyl-(1“4)-2-O-acetyl-3,6-
di-O-benzyl-h- -mannopyranosyl-(1“3)-2-
acetamido-4,6-di-O-benzyl-2-deoxy-i- -glu-
D
D
D
copyranoside (18).—Compound 17 (80 mg,
0.04 mmol) in butanol (10 mL) was added to
ethylenediamine (1.2 mL) under Ar. The solu-
tion was stirred for 20 h at 90 °C. The solvents
were then removed under reduced pressure by
evaporation twice with toluene and once with
ethanol to give a yellow syrup. The mixture
was then treated with Ac2O (1.3 mL) and
Et3N (125 mL). After stirring for 14 h at rt,
EtOH (25 mL) and water (1.3 mL) were
added, and the solution was concentrated to
dryness. The residue was purified by column
chromatography using 1:1 toluene–EtOAc to
give 18 (60 mg, 79%); [h]2D5+21.94° (c 2.4,
2-(Trimethylsilyl)ethyl 2,4-di-O-benzyl-3-O-
[(R)-1-(methoxycarbonyl)ethyl]-h- -rhamno-
L
pyranosyl-(1“3)-2-O-acetyl-4,6-di-O-benzyl-
h- -mannopyranosyl-(1“4)-2-O-acetyl-3,6-
di-O-benzyl-h- -mannopyranosyl-(1“3)-4,6-
di-O-benzyl-2-deoxy-2-phthalimido-i- -glu-
D
D
D
copyranoside (17).—A solution of donor 13
(80 mg, 0.09 mmol) and acceptor 15 (65.0 mg,
,
0.07 mmol) in CH2Cl2 (2 mL) containing 4 A
1
MS (200 mg) was stirred for 2 h under N2.
The temperature was then lowered to
−20 °C. N-Iodosuccinimide (28 mg, 0.12
mmol) and TfOH (3.5 mL, 0.04 mmol) were
then added. After 2 h, the reaction was com-
CHCl3). H NMR: l 7.23–7.01 (m, 40 H,
aromatic protons), 6.12, 5.32 (2 bs, 2 H, H-2II,
H-2III), 5.19, 5.11 (2 bs, 2 H, H-1II, H-1III),
5.17 (d, 1 H, J 10.2, H-1I), 4.99 (bs, 1 H,
H-1IV), 3.91 (m, 2 H, OCH2CH2Si), 3.52 (s, 3

252
I. Mukherjee et al. / Carbohydrate Research 325 (2000) 245–252
H, CH(CH3)COOCH3), 1.94, 1.90, 1.74 (3 s, 9
H, 2 OAc, 1 NHCOCH3), 0.83 (m, 2 H,
OCH2CH2Si), −0.13 (s, 9 H, Si(CH3)3). 13C
NMR data (CDCl3): l 175.6, 170.5, 169.8,
169.6 (4 carbonyl carbons), 137.0–123.3 (aro-
matic carbons), 99.9 (C-1I), 99.3, 98.6 (C-1II,
C-1III), 93.1 (C-1IV), 80.4, 78.3, 76.0, 75.4,
74.5, 73.8, 73.5, 73.3, 72.8, 72.2, 72.1, 71.3,
68.1, 66.7, 56.8 (C-2I), 51.7 (COOCH3), 23.0
(NCOCH3), 21.0, 20.6 (2 COCH3), 19.7
(CH(CH3)COOMe], 18.1 (C-6IV), 17.9 (CH2-
Si(CH3)3], −1.5 (Si(CH3)3) Anal. Calcd for
C95H115O24NSi: C, 67.79; H, 6.89. Found: C,
67.66; H, 7.09.
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2-O-acetyl-h-
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1
mg, 73%); [h]2D5 −30.57° (c 0.4, H2O). H
NMR: l 5.47–5.37 (m, 4 H, H-2II, H-2III,
H-1II, H-1III), 5.15 (bs, 1 H, H-1IV), 5.14 (d, 1
H, J 8.7 Hz, H-1I), 3.41 (s, 3 H, CH(CH3)-
COOCH3), 3.90 (m, 2 H, OCH2CH2Si), 2.03,
2.02, 1.92 (3 s, 9 H, 2 OAc, 1 NHCOCH3),
0.76 (m, 2 H, OCH2CH2Si), −0.13 (s, 9 H,
Si(CH3)3). 13C NMR: l 174.4, 174.1, 173.8,
173.8 (4 carbonyl carbons), 100.8 (C-1I),
100.3, 99.9 (C-1II, C-1III), 97.6 (C-1IV), 78.9,
76.5, 74.8, 74.1, 72.5, 71.8, 71.7, 69.8, 69.1,
68.1, 65.5, 61.4, 54.7 (C-2I), 51.9 (COOCH3),
23.7 (NCOCH3), 21.4, 21.1 (2 COCH3), 19.7
(CH(CH3)COOMe), 17.9 (C-6IV), 17.6 (CH2-
Si(CH3)3), −1.5 (Si(CH3)3). Anal. Calcd for
C39H67O24NSi: C, 48.69; H, 7.02. Found: C,
48.57; H, 7.19.
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Acknowledgements
One of the authors (I.M.) is indebted to
CSIR, New Delhi, for financial assistance.