A facile synthesis of the tetrasaccharide repeating unit of mannoglucan from Microellobosporia grisea

Article abstract of DOI:10.1016/S0008-6215(00)00160-9

A facile synthesis of the tetrasaccharide repeating unit of mannoglucan from Microellobosporia grisea was achieved through coupling of 4,6-O-benzylidene-1,2-O-ethylidene-α-D-glucopyranose with per-O-benzoylated mannopyranosyl trichloroacetimidate, followed by debenzylidenation, selective 6-O-mannopyranosylation, then hydrolysis of the 1,2-O-ethylidene group, 1,2-O-acetylation and conversion to the 1-trichloroacetimidate, and subsequent condensation of the activated trisaccharide with allyl 2,3,6-tri-O-benzoyl-α-D-glucopyranoside. (C) 2000 Elsevier Science Ltd.

Full text of DOI:10.1016/S0008-6215(00)00160-9

www.elsevier.nl/locate/carres
Carbohydrate Research 329 (2000) 199–205
Note
A facile synthesis of the tetrasaccharide repeating unit of
mannoglucan from Microellobosporia grisea
Yuliang Zhu, Fanzuo Kong *
Research Center for Eco-En6ironmental Sciences, Academia Sinica, PO Box 2871, Beijing 100085, PR China
Received 13 April 2000; accepted 17 May 2000
Abstract
A facile synthesis of the tetrasaccharide repeating unit of mannoglucan from Microellobosporia grisea was achieved
through coupling of 4,6-O-benzylidene-1,2-O-ethylidene-a-D-glucopyranose with per-O-benzoylated mannopyranosyl
trichloroacetimidate, followed by debenzylidenation, selective 6-O-mannopyranosylation, then hydrolysis of the
1,2-O-ethylidene group, 1,2-O-acetylation and conversion to the 1-trichloroacetimidate, and subsequent condensation
of the activated trisaccharide with allyl 2,3,6-tri-O-benzoyl-a-D-glucopyranoside. © 2000 Elsevier Science Ltd. All
rights reserved.
Keywords: Mannoglucan; Oligosaccharides; Regio- and stereoselective synthesis
A
D
-manno-
D
-glucan from Microellobospo-
deemed to be helpful to synthesize the repeat-
ing unit of the mannoglucan.
ria grisea, an actinomycete, has a high degree
of antitumor activity and consists of tetra-
saccharide repeating units having the structure
shown in Fig. 1 [1]. For study on the relation-
ship of structure and antitumor activity, it was
Although the repeating unit only contains
four sugar residues, its heterogeneity of com-
position and its nonlinear structure make the
synthesis troublesome. However, using appro-
priate starting materials in combination with a
selective glycosylation technique, the target
compound can be synthesized in a facile and
effective way. Herein we report the synthesis
of the repeating tetrasaccharide unit.
As outlined in Scheme 1, 1,2-O-ethylidene-
a-
compound [2], was converted into 4,6-O-ben-
-glucopyranose
D
-glucopyranose (1), a readily prepared
zylidene-1,2-O-ethylidene-a-
D
Fig. 1. The
grisea.
D-manno-D-galactan from Microellobosporia
(2) [3] with diethoxytoluene in the presence of
zinc chloride. Coupling of 2 with the donor
2,3,4,6-tetra-O-benzoyl-a-
trichloroacetimidate afforded 2,3,4,6-tetra-O-
benzoyl-a- -mannopyranosyl-(1“3)-4,6-O-
benzylidene-1,2-O-ethylidene-a- -glucopyran-
D-mannopyranosyl
* Corresponding author. Tel.: +86-10-62563167; fax: +
86-10-62923563.
E-mail address: fzkong@mail.rcees.ac.cn (F. Kong).
D
D
0008-6215/00/$ - see front matter © 2000 Elsevier Science Ltd. All rights reserved.
PII: S0008-6215(00)00160-9

200
Y. Zhu, F. Kong / Carbohydrate Research 329 (2000) 199–205
Scheme 1. Reagents and conditions: (a) PhCH(OEt)2, ZnCl2, rt, 4 h, 88%. (b) CH2Cl2, Me3SiOTf, −42 °C to rt, 90%. (c) AcOH,
4:1 Cl2CHCOOH–water (v/v), rt, 6 h, 91%. (d) CH2Cl2, Me3SiOTf, −42 °C to rt, 85%. (e) Ac2O/Pyr, 98%. (f) F3CCOOH (90%),
rt, 1 h, then Ac2O/Pyr, rt, 3 h, 70%. (g) K2CO3, DMF, rt, 12 h, 95%, then CH2Cl2, CCl3CN, DBU, rt, 2 h, 90%. (h) CH2Cl2,
Me3SiOTf, −42 °C to rt, 90%. (I). MeONa/MeOH, rt, 85%.
ose
Cl2CHCOOH–water at room temperature
smoothly yielded 2,3,4,6-tetra-O-benzoyl-a-
mannopyranosyl-(1“3)-1,2-O-ethylidene-a-
-glucopyranose (4). In our preceding papers
(3).
Debenzylidenation
with
4:1
osyl - (1“3) - [2,3,4,6 - tetra - O - benzoyl - a -
D
-
mannopyranosyl-(1“6)]-1,2-O-ethylidene-a-
D
-
D
-glucopyranose (5) in satisfactory yield
(85%). Acetylation of 5 then gave 6.
D
Removal of the 1,2-O-ethylidene group
from 6 with 90% trifluoroacetic acid, followed
by acetylation with acetic anhydride in pyri-
dine, furnished 3,6 - di - O - (2,3,4,6 - tetra - O-
[3,4], selective 6-O-glycosylation using per-O-
acetyl glycosyl bromides as the donors and
unprotected or partially protected glycosides
as the acceptors was successfully achieved via
orthoester formation–rearrangement. It was
reported that with sugar trichloroacetimidates
as the glycosyl donors under kinetic control
conditions, orthoesters were the intermediates
that were converted into the corresponding
glycosidic linkage in situ by simple elongation
of the reaction time [5,6]. Thus, in the present
research, selective 6-O-glycosylation of 4 was
carried out at −40 °C using 2,3,4,6-tetra-O-
benzoyl-a-
D
-mannopyranosyl)-1,2,4-tri-O-
acetyl- -glucopyranose (7) in 70% yield. Selec-
D
tive 1-O-deacetylation with potassium carbon-
ate in DMF [7], followed by treatment with
trichloroacetonitrile and DBU [8], gave the
trisaccharide trichloroacetimidate 8 in high
yield (90%). Condensation of the trisaccharide
donor 8 with the monosaccharide acceptor
allyl 2,3,6-tri-O-benzoyl-a-
(9) afforded the tetrasaccharide allyl 2,3,4,6-
tetra-O-benzoyl-a- -mannopyranosyl-(1“3)-
[2,3,4,6-tetra-O-benzoyl-a- -mannopyranosyl-
(1“6)]-2,4-di-O-acetyl-b- -glucopyranosyl-
D-glucopyranoside
benzoyl-a-
idate as the donor to give the trisaccharide,
2,3,4,6 - tetra - O - benzoyl - a - - mannopyran-
D-mannopyranosyl trichloroacetim-
D
D
D
D

Y. Zhu, F. Kong / Carbohydrate Research 329 (2000) 199–205
201
(1“4)-2,3,6-tri-O-benzoyl-a-
D
-glucopyrano-
tures usually gave one isomer (R or S), which
was subjected to NMR spectroscopic analysis,
but isomerization of the pure isomer occurred
upon a long-term standing and during NMR
determination.
side (10) in high yield (90%). Deacylation at
room temperature with saturated ammonia in
methanol afforded the unprotected tetra-
saccharide allyl glycoside 11.
In summary, herein we present a facile and
effective synthesis of the targeted tetra-
saccharide. Most of the reactions involved in
the synthesis were readily carried out with
satisfactory yields, whereas the use of acyl
protective groups substantially simplified the
reaction routes.
2,3,4,6-Tetra-O-benzoyl-h-
osyl-(1“3)-4,6-O-benzylidene-1,2-O-(R,S)-
ethylidene-h- -glucopyranose (3).—2,3,4,6-Te-
tra-O-benzoyl-a- -glucopyranosyl trichloro-
acetimidate (741 mg, 1 mmol) and 4,6-O-ben-
zylidene-1,2-O-(R,S)-ethylidene-a- -gluco-
D
-mannopyran-
D
D
D
pyranose (2) (293 mg, 1 mmol) were dried
together under high vacuum for 2 h, then
dissolved in anhyd CH2Cl2 (60 mL).
Trimethylsilyltriflate (20 mL, 0.10 equiv) was
added dropwise at −42 °C with N2 protec-
tion. The reaction mixture was stirred for 3 h,
at the end of which time thin-layer chro-
matography (TLC) (3:1 petroleum ether–
EtOAc) indicated that the reaction was
complete. Then the mixture was neutralized
with triethylamine and concentrated under re-
duced pressure to dryness. Further purifica-
tion by column chromatography (3:1
petroleum ether–EtOAc) gave 3 (785 mg,
90%) as a colorless solid: mp 140–145 °C; [h]D
1. Experimental
General methods.—Melting points were de-
termined with a ‘Mel–Temp’ apparatus. Opti-
cal rotations were determined with
a
Perkin–Elmer model 241-MC automatic po-
larimeter for solutions in a 1 dm jacketed cell.
1H NMR spectra were recorded with Varian
XL-400 and XL-200 spectrometers, for solu-
tions in CDCl3 with tetramethylsilane (Me4Si)
as the internal standard. Chemical shifts are
expressed in ppm downfield from the internal
Me4Si absorption. Mass spectra were recorded
with a VG PLATFORM mass spectrometer
using the ESI technique to introduce the sam-
ple. Thin-layer chromatography (TLC) was
performed on silica gel HF, detection being
affected by charring with 30% (v/v) H2SO4 in
MeOH or sometimes by UV detection.
Column chromatography was conducted by
elution of a column (8/100 mm, 16/240 mm,
18/300 mm, 35/400 mm) of silica gel (100–200
mesh) and EtOAc–petroleum ether (bp 60–
90 °C) as the eluent. Analytical LC was per-
formed with a Gilson HPLC consisting of a
pump (model 306), stainless steel packed with
silica gel (Spherisorb SiO2, 10×300 or 4.6×
250 mm), differential refractometer (132-RI
Detector), UV–vis detector (model 118), and
EtOAc–petroleum ether (bp 60–90 °C) was
used as the eluent at a flow rate of 1–4
mL/min. Solutions were concentrated at a
temperature B60 °C under diminished pres-
sure. Compounds 3, 4, 5, and 6 containing
1,2-O-ethylidenated sugar residues were ob-
tained as R, S mixtures that were used directly
in the next reaction. Purification of the mix-
1
+13.0° (c 1.1, CHCl3); H NMR: l 8.12–7.25
(m, 20 H, Bz-H), 6.23 (t, 1 H, J3%,4% 10.2 Hz,
H-4%), 5.95 (dd, 1 H, J2%,3% 3.2 Hz, H-3%), 5.84
(dd, 1 H, J1%,2% 1.6 Hz, H-2%), 5.62 (s, 1 H,
PhꢀCꢀH), 5.56 (d, 1 H, J1.2 4.5 Hz, H-1), 5.52
(d, 1 H, H-1%), 5.21 (dd, 1 H, CH3CH), 4.72–
4.67 (m, 2 H), 4.50–4.40 (m, 2 H), 4.20–4.16
(m, 2 H), 4.00–3.97 (m, 1 H), 3.83–3.74 (m, 2
H), 1.49 (d, 3 H, CH3CH). Anal. Calcd for
C49H44O15: C, 67.43; H, 5.05. Found: C, 67.45;
H, 5.03.
2,3,4,6-Tetra-O-benzoyl-h-
osyl - (1“3) - 1,2 - O - (R,S) - ethylidene - h -
glucopyranose (4).—2,3,4,6-Tetra-O-benzoyl-
a- -mannopyranosyl-(1“3)-4,6-O-benzyli-
dene-1,2-O-(R,S)-ethylidene-a- -glucopyran-
D
-mannopyran-
D
-
D
D
ose (3) (872 mg, 1 mmol) was dissolved in
AcOH (10 mL) and treated with 4:1
Cl2CHCOOH–water (v/v) (0.8 mL) at rt for 6
h, at the end of which time TLC (1:1
petroleum ether–EtOAc) indicated that the
reaction was complete. The reaction mixture
was diluted with water, extracted with CH2Cl2
(3×30 mL), and the organic phase was
washed with satd aq Na2CO3 (3×50 mL) and

202
Y. Zhu, F. Kong / Carbohydrate Research 329 (2000) 199–205
mannopyranosyl-(1“3)-[2,3,4,6-tetra-O-ben-
zoyl - a - - mannopyranosyl - (1“6)] - 1,2 - O-
(R,S)-ethylidene-a- -glucopyranose (5) (1362
water (2×50 mL), dried, and concentrated to
yield crude 4 (R, S mixture) (713 mg, 91%) as
crystals. Further purification by column chro-
matography (1:1 petroleum ether–EtOAc)
D
D
mg, 1 mmol) in pyridine (25 mL) was added
Ac2O (0.5 mL, 5 mmol), and the mixture was
stirred overnight at rt. TLC (3:1 petroleum
ether–EtOAc) indicated that the reaction was
complete. Ice water was added, and the mix-
ture was diluted with CH2Cl2, washed with 1
N HCl, water, and satd aq sodium bicarbon-
ate. The organic layer was combined, dried,
and concentrated. Further purification by
column chromatography (3:1 petroleum
ether–EtOAc) gave 6 (1376 mg, 98%) as col-
orless crystals: mp 137–140 °C; [h]D −2.5° (c
gave fine needles: mp 150–152 °C; [h]D
−
1
24.0° (c 1.3, CHCl3); H NMR: l 8.12–7.25
(m, 20 H, Bz-H), 6.22 (t, 1 H, J3%,4% 10.0 Hz,
H-4%), 5.93 (dd, 1 H, J2%,3% 3.3 Hz, H-3%), 5.81
(dd, 1 H, J1%,2% 1.4 Hz, H-2%), 5.56–5.54 (m, 2
H, H-1%, H-1), 5.52 (dd, 1 H, CH3CH), 4.71–
4.68 (m, 2 H), 4.50–4.46 (m, 1 H), 4.37–4.15
(m, 1 H), 3.99–3.90 (m, 4 H), 3.70–3.68 (m, 1
H), 1.35 (d, 3 H, CH3CH). Anal. Calcd for
C42H40O15: C, 64.29; H, 5.10. Found: C, 64.26;
H, 5.12.
1
2,3,4,6-Tetra-O-benzoyl-h-
osyl - (1“3) - [2,3,4,6 - tetra - O - benzoyl - h -
mannopyranosyl-(1“6)]-1,2-O-(R,S)-ethyli-
dene-h- -glucopyranose (5).—2,3,4,6-Tetra-
O-benzoyl-a- -mannopyranosyl trichloroace-
timidate (741 mg, 1 mmol) and 2,3,4,6-
tetra-O-benzoyl-a- -mannopyranosyl-(1“3)-
1,2-O-(R,S)-ethylidene-a- -glucopyranose (4)
D
-mannopyran-
1.1, CHCl3); H NMR: l 8.12–7.26 (m, 40 H,
D-
Bz-H), 6.26 (t, 1 H, J 10.0 Hz), 6.15 (t, 1 H, J
10.2 Hz), 5.99–5.95 (m, 2 H), 5.89 (dd, 1 H, J
1.4, J 3.2 Hz), 5.86 (dd, 1 H, J 1.5, J 3.2 Hz),
5.82–5.75 (m, 4 H), 5.28 (dd, 1 H, CH3CH),
4.77–4.64 (m, 4 H), 4.60–4.40 (m, 3 H), 4.22–
4.15 (m, 2 H), 3.99–3.95 (m, 1 H), 3.90–3.85
(m, 1 H), 2.04 (s, 3 H, CH3CO), 1.38 (d, 3 H,
CH3CH). Anal. Calcd for C78H68O25: C, 66.67;
H, 4.84. Found: C, 66.69; H, 4.82.
D
D
D
D
(784 mg, 1 mmol) were dried together under
high vacuum for 2 h, then dissolved in anhyd
CH2Cl2 (60 mL). Trimethylsilyltriflate (20 mL,
0.10 equiv) was added dropwise at −42 °C
with N2 protection. The reaction mixture was
stirred for 3 h, at the end of which time TLC
(3:1 petroleum ether–EtOAc) indicated that
the reaction was complete. The mixture was
then neutralized with triethylamine and con-
centrated under reduced pressure to dryness.
Further purification by column chromatogra-
phy (3:1 petroleum ether–EtOAc) gave 5
(1158 mg, 85%) as a colorless solid: mp 131–
2,3,4,6-Tetra-O-benzoyl-h-
D
-mannopyran-
osyl - (1“3) - [2,3,4,6 - tetra - O - benzoyl - h -
D
-
mannopyranosyl-(1“6)] – 1,2,4-tri-O-acetyl-
h,i-
D
-glucopyranose
(7).—2,3,4,6-Tetra-O-
benzoyl-a-
D
-mannopyranosyl-(1“3)-[2,3,4,6-
tetra-O-benzoyl-a-
D
-mannopyranosyl-(1“6)]-
-gluco-
4-O-acetyl-1,2-O-(R,S)-ethylidene-a-
D
pyranose (6) (1404 mg, 1 mmol) was treated
with 90% F3CCOOH (5 mL) at rt for 1 h, and
the solution was concentrated and co-concen-
trated with toluene. The residue was dissolved
in pyridine (5 mL) and treated with Ac2O (3
mL) for 2 h. After conventional workup, the
residue was subjected to column chromatogra-
phy (3:1 petroleum ether–EtOAc) to yield the
title compound 7 as a solid consisting predom-
inantly of the a anomer (1023 mg, 70%): mp
1
134 °C; [h]D −1.5° (c 1.0, CHCl3); H NMR:
l 8.12–7.25 (m, 40 H, Bz-H), 6.27 (t, 1 H, J
10.2 Hz), 6.13 (t, 1 H, J 10.1 Hz), 5.97–5.93
(m, 2 H), 5.87 (dd, 1 H, J 1.5, J 3.3 Hz), 5.85
(dd, 1 H, J 1.4, J 3.2 Hz), 5.80–5.76 (m, 3 H),
5.25 (dd, 1 H, CH3CH), 4.74–4.67 (m, 3 H),
4.55–4.43 (m, 3 H), 4.25–4.20 (m, 3 H), 4.03–
4.00 (m, 1 H). 3.96–3.89 (m, 2 H), 1.42 (d, 3
H, CH3CH). Anal. Calcd for C76H66O24: C,
66.96; H, 4.85. Found: C, 66.99; H, 4.82.
1
135–138 °C; [h]D −5.1° (c 1.1, CHCl3); H
NMR: l 8.12–7.26 (m, 40 H, Bz-H), 6.37 (d,
1 H, J1,2 3.8 Hz, H-1), 6.27 (t, 1 H, J 10.2 Hz),
6.11 (t, 1 H, J 10.1 Hz), 5.86 (dd, 1 H, J 10.1,
J 3.1 Hz), 5.76 (dd, 1 H, J 10.2, J 3.4 Hz),
5.73 (dd, 1 H, J 1.7, J 3.4 Hz), 5.57 (dd, 1 H,
J 1.5, J 3.1 Hz), 5.30 (d, 1 H, J 1.7 Hz),
5.23–5.19 (m, 2 H), 5.09 (s, 1 H), 4.80–4.72
(m, 2 H), 4.52–4.32 (m, 5 H), 4.14–4.11 (m, 1
2,3,4,6-Tetra-O-benzoyl-h-
osyl - (1“3) - [2,3,4,6 - tetra - O - benzoyl - h -
mannopyranosyl - (1“6)] - 4 - O - acetyl - 1,2 - O-
(R,S)-ethylidene-h- -glucopyranose (6).—To
the solution of 2,3,4,6-tetra-O-benzoyl-a-
D
-mannopyran-
D-
D
D
-

Y. Zhu, F. Kong / Carbohydrate Research 329 (2000) 199–205
203
H), 4.56–4.52 (m, 1 H), 4.44–4.37 (m, 3 H),
4.29–4.22 (m, 1 H), 3.98–3.95 (m, 1 H), 3.73–
3.70 (m, 1 H), 2.34 (s, 3 H, CH3CO), 2.16 (s,
H), 3.94–3.92 (m, 1 H), 3.70–3.68 (m, 1 H),
2.34 (s, 3 H, CH3CO), 2.23 (s, 3 H, CH3CO),
2.15 (s, 3 H, CH3CO). 13C NMR: l 170.06,
169.81, 168.87 (3 CH3CO), 166.09, 165.97,
165.53, 165.45, 165.43, 165.36, 165.33, 165.17
(8 C6H5CO), 100.02, 99.22, 97.38 (C-1I–III),
89.12 (C-3), 70.73, 70.53, 70.47, 70.19, 70.19,
69.77, 69.63, 69.62, 68.87, 66.83, 66.46, 66.00,
62.70, 61.93 (C-2,3,4,5,6I–III). Anal. Calcd for
C80H70O27: C, 65.66; H, 4.79. Found: C, 65.63;
H, 4.81.
3
H,
CH3CO).
Anal.
Calcd
for
C80H68Cl3O26N: C, 61.34; H, 4.35. Found: C,
61.32; H, 4.36.
Allyl 2,3,6-tri-O-benzoyl-h-
oside (9).—Allyl 4,6-O-benzylidene-a-
D
-glucopyran-
-glu-
D
copyranoside [9] (616 mg, 2 mmol) was dis-
solved in pyridine (15 mL), and BzCl (0.69
mL, 6 mmol) was added dropwise under stir-
ring. The reaction was monitored by TLC (2:1
petroleum ether–EtOAc). After 3 h at rt, the
reaction was complete, and the reaction mix-
ture was worked up in the conventional way.
The crude product was dissolved in tetrahy-
drofuran (20 mL), and H2SO4 (1 M, 5 mL)
was added under stirring. The reaction was
monitored by TLC (1:1 petroleum ether–
EtOAc). After 2 h at 70 °C, the reaction was
shown to be complete, and the reaction mix-
ture was washed with water, then satd aq
sodium bicarbonate. The organic layer was
combined, dried, and concentrated. Further
purification by column chromatography (1:1
petroleum ether–EtOAc) gave allyl 2,3-di-O-
2,3,4,6-Tetra-O-benzoyl-h- -mannopyran-
D
osyl - (1“3) - [2,3,4,6 - tetra - O - benzoyl - h -
mannopyranosyl-(1“6)]–2,4-di-O-acetyl-h-
D
-
-
D
glucopyranosyl trichloroacetimidate (8).—A
solution of 3,6-di-O-(2,3,4,6-tetra-O-benzoyl-
a-
D
-mannopyranosyl)-1,2,4-tri-O-acetyl- -
D
glucopyranose (7) (731 mg, 0.5 mmol) and
K2CO3 (69 mg, 0.5 mmol) in DMF was stirred
for 12 h at rt, at the end of which time TLC
(2:1 petroleum ether–EtOAc) showed that the
reaction to be complete. Water was added,
and the mixture was diluted with CH2Cl2,
washed with 1 N HCl, water, and satd aq
sodium bicarbonate. The organic layer was
combined, dried, and concentrated. The
residue thus obtained was passed through a
short silica gel column with 2:1 petroleum
ether–EtOAc as the eluent to give crude 3,6-
benzoyl-a- -glucopyranoside (762 mg, 89%)
D
as a colorless solid. The solid was dissolved in
pyridine (15 mL), and BzCl (0.25 mL, 2.1
mmol) was added dropwise under stirring.
The reaction was monitored by TLC (2:1
petroleum ether–EtOAc). After 3 h at rt, the
reaction was complete, and the reaction mix-
ture was worked up in the conventional way.
Further purification by column chromatogra-
phy (2:1 petroleum ether–EtOAc) gave allyl
di-O-(2,3,4,6-tetra-O-benzoyl-a-
D
-mannopy-
ranosyl)-2,4-di-O-acetyl- -glucopyranose (675
D
mg, 95%), which was dissolved in CH2Cl2 (20
mL) to which CCl3CN (0.1 mL, 1 mmol) and
DBU (14 mL, 0.1 mmol) were added. The
reaction mixture was stirred for 2 h, at the end
of which time TLC (2:1 petroleum ether–
EtOAc) indicated that the reaction was com-
plete. Concentration of the reaction mixture,
followed by purification on a silica gel column
with 2:1 petroleum ether–EtOAc as the eluent
furnished the trisaccharide donor 8 as crystals
in a good yield (669 mg, 90%): mp 123–
2,3,6-tri-O-benzoyl-a- -glucopyranoside (928
D
mg, 98%) as a colorless solid: mp 148–151 °C;
1
[h]D +4.5° (c 1.2, CHCl3); H NMR: l 8.12–
7.26 (m, 15 H, Bz-H), 5.91–5.79 (m, 1 H,
CH2ꢁCHꢀCH2), 5.80 (t, 1 H, J3,4 9.3 Hz, H-3),
5.32–5.30 (dd, 1 H, J1,2 1.6, J2,3 9.3 Hz, H-2),
5.28 (s, 1 H, H-1), 5.29–5.26 (dd, 1 H,
1
126 °C; [h]D +1.5° (c 1.1, CHCl3); H NMR:
l 8.92 (s, 1 H, CꢁNH), 8.15–7.25 (m, 40 H,
Bz-H), 6.55 (d, 1 H, J1,2 3.8 Hz, H-1), 6.29 (t,
1 H, J 10.2 Hz), 6.09 (t, 1 H, J 10.1 Hz), 5.88
(dd, 1 H, J 10.2, J 3.3 Hz), 5.78 (dd, 1 H, J
10.1, J 3.1 Hz), 5.68 (dd, 1 H, J 1.8, J 3.3 Hz),
5.60 (dd, 1 H, J 1.4, J 3.1 Hz), 5.32 (d, 1 H, J
1.8 Hz), 5.24–5.20 (m, 2 H), 5.10 (d, 1 H, J
1.4 Hz), 4.78–4.74 (m, 2 H), 4.64–4.58 (m, 1
CH2ꢁCHꢀCH2), 5.17–5.14 (dd,
1
H,
CH2ꢁCHꢀCH2), 4.81 (dd, 1 H, H-6e), 4.62–
4.59 (dd, 1 H, H-6a), 4.29–4.24 (m, 1 H,
CH2ꢁCHꢀCH2), 4.19–4.16 (m,
1
H,
CH2ꢁCHꢀCH2), 4.11–4.06 (m, 1 H, H-5), 3.88
(t, 1 H, H-4). Anal. Calcd for C30H28O9: C,
67.67; H, 5.26. Found: C, 67.63; H, 5.29.

204
Y. Zhu, F. Kong / Carbohydrate Research 329 (2000) 199–205
(1“4)-h-
4,6 - tetra - O - benzoyl - a -
(1“3)-[2,3,4,6-tetra-O-benzoyl-a-
pyranosyl-(1“6)]–2,4-di-O-acetyl-b-
pyranosyl-(1“4)-2,3,6-tri-O-benzoyl-a-
D
-glucopyranoside (11).—Allyl 2,3,-
- mannopyranosyl-
-manno-
-gluco-
Allyl
2,3,4,6-tetra-O-benzoyl-h- -manno-
D
D
pyranosyl-(1“3)-[2,3,4,6-tetra-O-benzoyl-h-
mannopyranosyl-(1“6)]–2,4-di-O-acetyl-i-
D-
D
D-
D
glucopyranosyl-(1“4)-2,3,6-tri-O-benzoyl-h-
-glucopyranoside (10).—2,3,4,6-Tetra-O-ben-
zoyl - a - - mannopyranosyl - (1“3) - [2,3,4,6-
tetra-O-benzoyl-a- -mannopyranosyl-(1“6)]–
2,4 - di - O - acetyl - a,b - - glucopyranosyl tri-
chloroacetimidate (8) (782 mg, 0.5 mmol) and
allyl 2,3,6-tri-O-benzoyl-a- -glucopyranoside
D
-
D
glucopyranoside (10) (77 mg, 0.04 mmol) was
suspended in freshly distilled MeOH (5 mL), a
solution of CH3ONa (2 M, 0.1 mL) was
added, and the mixture was stirred overnight
at rt. TLC showed that the reaction to be
complete, and the resulting solution was
deionized with Amberlite IR-120 (H+) anion-
exchange resin, filtered, and concentrated. The
tetrasaccharide 11 was finally obtained after
chromatography on a Sephadex G-25 column
(water) as an amorphous powder (24 mg,
85%) after freeze-drying; mp 154–160 °C; [h]D
D
D
D
D
(9) (266 mg, 0.5 mmol) were dried together
under high vacuum for 2 h, then dissolved in
anhyd CH2Cl2 (20 mL). Trimethylsilyltriflate
(10 mL, 0.10 equiv) was added dropwise at
−42 °C with N2 protection. The reaction mix-
ture was stirred for 3 h, at the end of which
time TLC (2:1 petroleum ether–EtOAc) indi-
cated that the reaction was complete. Then the
mixture was neutralized with triethylamine
and concentrated under reduced pressure to
dryness. Further purification by column chro-
matography (2:1 petroleum ether–EtOAc)
gave 10 (870 mg, 90%) as a colorless solid: mp
1
−6.9° (c 0.8, water); H NMR: l 6.02–5.97
(m, 1 H, CH2ꢁCHꢀCH2), 5.39–5.28 (m, 2 H,
CH2ꢁCHꢀCH2), 4.90 (d, J 7.8 Hz, 1 H), 4.86
(s, 1 H), 4.79 (s, 1 H), 4.50 (d, J 7.9 Hz, 1 H),
4.21–3.66 (m, 26 H). MS Calcd for C27H45O21:
705.2 [M]. Found: 705.4. Anal. Calcd for
C27H46O21: C, 45.89; H, 6.51. Found: C, 45.80;
H, 6.55.
1
133–136 °C; [h]D +38.5° (c 1.2, CHCl3); H
NMR: l 8.09–7.26 (m, 55 H, Bz-H), 6.26 (t, 1
H, J 10.1 Hz), 6.12 (t, 1 H, J 10.2 Hz), 6.08 (t,
1 H, J 9.80 Hz), 5.89 (dd, 1 H, J 10.1, J 3.30
Hz) 5.86–5.75 (m, 1 H, CH2ꢁCHꢀCH2), 5.68
(dd, 1 H, J 10.2, J 2.60 Hz), 5.65 (dd, 1 H, J
2.60, J 1.60 Hz), 5.53 (dd, 1 H, J 2.60, J 1.60
Hz), 5.30 (d, 1 H, J 1.6 Hz), 5.28 (d, 1 H, J 1.6
Hz),5.27–5.22 (dd, 1 H, CH2ꢁCHꢀCH2),
5.16–5.06 (m, 4 H), 5.05 (d, 1 H, J 3.5 Hz),
4.89–4.86 (m, 2 H), 4.77–4.68 (m, 2 H), 4.65
(d, 1 H, J 7.8 Hz), 4.57 (dd, 1 H), 4.50 (dd, 1
H), 4.43 (dd, 1 H), 4.39–4.25 (m, 3 H), 4.10 (t,
1 H, J 10.0 Hz), 4.05 (dd, 1 H), 3.80 (t, 1 H,
J 10.0 Hz), 3.40–3.30 (m, 2 H), 2.26 (s, 3 H,
Acknowledgements
This work was supported by The Chinese
Academy of Sciences (Projects KJ952J1510
and RCEES9904) and by The National Natu-
ral Science Foundation of China (Projects
29802009 and 39970864).
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h-
D
-mannopyranosyl-(1“3)-[h-
D
-
mannopyranosyl-(1“6)]–i-
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