Synthesis of a tetrasaccharide fragment of cobra venom factor oligosaccharide

Article abstract of DOI:10.1016/S0008-6215(99)00107-X

Synthesis of a tetrasaccharide fragment, α-L-Fuc-(1→3)-β-D-GlcNAc-(1→2)-α-D-Man-(1→6)-α-D-Man-OMe of the cobra venom factor (CVF) oligosaccharide is described. Copyright (C) 1999 Elsevier Science Ltd.

Full text of DOI:10.1016/S0008-6215(99)00107-X

www.elsevier.nl/locate/carres
Carbohydrate Research 320 (1999) 1–7
Synthesis of a tetrasaccharide fragment of cobra venom
factor oligosaccharide
Zhong-Jun Li *, Hui Li, Meng-Shen Cai
Department of Bioorganic Chemistry, School of Pharmaceutical Sciences, Beijing Medical Uni6ersity,
Beijing 100083, Peoples’s Republic of China
Received 22 December 1998; accepted 30 March 1999
Abstract
Synthesis of a tetrasaccharide fragment, a-
L
-Fuc-(1“3)-b-
D
-GlcNAc-(1“2)-a-
D
-Man-(1“6)-a-D-Man-OMe of
the cobra venom factor (CVF) oligosaccharide is described. © 1999 Elsevier Science Ltd. All rights reserved.
Keywords: Cobra venom factor; Tetrasaccharide; Synthesis
This carbohydrate fragment, which contains
the Lex antigen, a well-known tumor antigen,
is related to the immunogencity of the CVF
[7]. Accordingly, we chose the outer bianten-
nal structure as a synthesis target and used
block-building strategy to accomplish the syn-
thesis of a tetrasaccharide fragment, namely
1. Introduction
Cobra venom factor (CVF) is a non-toxic
glycoprotein present in cobra venom with
strong complement-activating activity through
the alternative pathway [1,2]. When conju-
gated to a tumor monoclonal antibody or its
fragment F(ab)%2, CVF selectively generates
cytotoxicity, killing cells of melanonoma,
leukemia, and neuroblastoma [3–5]. Accord-
ing to Gowda et al. [6], the CVF molecule
contains three chains a, b, and g, among
which the a and b chains have two or three
oligosaccharides with the same biantennal
structure.
a -
L
- Fuc - (1“3) - b -
D
- GlcNAc-(1“2)-
a-
D
-Man-(1“6)-a- -Man-OMe. The terminal
D
methyl group was introduced as a signal to
confirm the structure in NMR.
2. Results and discussion
The tetrasaccharide fragment was synthe-
sized via a 2+2 model (see Scheme 1). Build-
ing block A was prepared according to Lo¨nn’s
method [8], in which ethyl 2,3,4-tri-O-benzyl-
1-thio-a- -fucopyranoside was converted into
L
the corresponding glycosyl bromide and then
immediately coupled to the glycosyl acceptor.
The ethylthio group at C-1 of the disaccharide
was introduced as both a protective and a
leaving group.
* Corresponding author. Tel.: +86-10-6209-1504; fax: +
86-10-6201-5584.
E-mail address: zjli@mail.bjmu.edu.cn (Z.-J. Li)
0008-6215/99/$ - see front matter © 1999 Elsevier Science Ltd. All rights reserved.
PII: S0008-6215(99)00107-X

2
Z.-J. Li et al. / Carbohydrate Research 320 (1999) 1–7
in three steps from the starting material
methyl a- -mannopyranoside; the trityl group
was introduced selectively at O-6 of the start-
The other disaccharide building block was
obtained from the coupling of glycosyl donor
5 and acceptor 1. Compound 1 was prepared
D
Scheme 1. (a) Ph3CCl–C5H5N; (b) BnBr–NaH–DMF; (c) HBr–HOAc; (d) MeOH–C5H5N; (e) NH3–MeOH; (f) BnBr–NaH–
,
DMF; (g) 80% HOAc–H2O; (h) CNCCl3, DBU–CH2Cl2; (i) Me3SiOTf, 4 A molecular sieves–CH2Cl2, −12 °C; (j) NaOMe–
,
MeOH; (k) NaBH3CN–HCl–Et2O; (l) Ac2O–C5H5N; (m) MeOTf, 4 A molecular sieves–ether; (n) NH2–NH2·H2O–EtOH,
reflux; (o) Ac2O–C5H5N; (p) H2, Pd–C.

Z.-J. Li et al. / Carbohydrate Research 320 (1999) 1–7
3
ing material with chlorotriphenylmethane in
3. Experimental
pyridine. Conventional benzylation at O-2,3,4
followed by detritylation with HBr–HOAc so-
lution gave 1 in total yield over three steps of
38.9%. The mannosyl trichloroacetimidate 5
was prepared in five steps. The starting mate-
General.—Melting points (uncorrected)
were determined with an X4 model micromelt-
ing apparatus. Thin-layer chromatography
was performed on glass plates coated with
Silica Gel GF254 (Qingdao) with detection by
quenching of fluorescence and/or charring
with 5% H2SO4–EtOH. Column chromatog-
raphy was performed on Silica Gel H (Qing-
dao). Optical rotations were recorded with a
Perkin–Elmer model 243B polarimeter. IR
spectra were recorded with a Perkin–Elmer
model 240C spectrophotometer, using KBr
pellets for crystalline samples and films for
rial 2,3,4,6-tetra-O-acetyl-a- -mannopyran-
D
osyl bromide [9] was stirred in dry MeOH–
pyridine to give the methyl 1,2-O-orthoacetate
2. The conventional deacetylation with
NaOMe–MeOH unexpectedly gave no com-
pound 3, but 3 was obtained in good yield
(64% in two steps) by using NH3–MeOH
instead of NaOMe–MeOH for deacetylation
(and then benzylation). Compound 3 was
stirred in 80% acetic acid solution at room
temperature (rt) to give compound 4 in satis-
factory yield (92.5%). The imidate 5 was then
prepared from compound 4 with trichloroace-
tonitrile and 1,8-diazabicyclo[5.4.0]undec-7-
ene (DBU). The yield was also satisfactory
(90.2%).
1
13
syrupy samples. H NMR and C NMR were
recorded on a Bruker ARX-400 spectrometer.
High-resolution mass spectra were recorded
with a VG-ZAB-2F mass spectrometer.
Methyl 2,3,4-tri-O-benzyl-h-
noside (1).—Powdered methyl
D
-mannopyra-
O-a-
D
-
mannopyranoside (2.0 g) was dissolved in dry
pyridine (30 mL). To the solution was added
Ph3CCl (3.5 g) and the mixture was stirred
overnight at rt. The mixture was then poured
into ice–water (150 mL) and stirred vigor-
ously. The waxy solid obtained through filtra-
tion and washing successively with water and
light petroleum was dissolved in dry DMF (40
mL). Sodium hydride (80%, Serva, 2.5 g) was
added carefully to the solution and the mix-
ture was stirred vigorously for 30 min. Benzyl
bromide (7.0 mL) was then added dropwise.
After stirring overnight at rt, MeOH (5 mL)
was added to the mixture to decompose unre-
acted NaH and the mixture was poured into
ice–water (100 mL). Toluene (3×60 mL) was
used to extract the mixture and the dried
(Na2SO4) extract was evaporated in vacuo.
The crude syrup was dissolved in a mixture of
80% AcOH (40 mL) and 20% HBr–HOAc
solution (20 mL). The mixture was stirred in a
60 °C water bath for 1 h. After cooling to rt,
the mixture was poured into ice–water (200
mL) and the solution was extracted with
CHCl3 (50 mL). The organic layer was washed
successively with water, saturated NaHCO3
solution, and water to pH 7, and then dried
(Na2SO4). The solvent was evaporated off in
vacuo and the residue purified by column
chromatography [1:5 to 1:4 EtOAc–light
The blocked disaccharide 6 was prepared in
excellent yield (93.2%) by coupling com-
pounds 1 and 5 according to the Schmidt
method [10], in which trimethylsilyl triflate
(Me3SiOTf) was used as promoter in the pres-
,
ence of 4 A molecular sieves and dry CH2Cl2.
Deacetylation of compound 6 gave the disac-
charide glycosyl acceptor 7 in quantitative
yield.
The coupling of disaccharide A and disac-
charide 7 in the presence of methyl triflate as
a promoter gave the blocked tetrasaccharide
10 (53%), which was not very stable, even
when stored below −10 °C. We therefore
converted compound A into compound 8 by
selective reduction of the benzylidene group in
the presence of NaBH3CN and HCl–ether.
Compound 9 resulting from the acetylation of
compound 8 was coupled to the glycosyl
donor to give another blocked tetrasaccharide
11 (38%), which was more stable and could be
stored for a long time. Another advantage of
compound 11 is that the acetyl group could
then be readily removed, allowing further
glycosylation.
The deblocking of compound 10 involved
three steps: dephthaloylation with hydrazine
hydrate, acetylation of the amino group, and
hydrogenolysis. The resultant tetrasaccharide
12 was affirmed by 1D and 2D NMR spectra.

4
Z.-J. Li et al. / Carbohydrate Research 320 (1999) 1–7
mL) and the aq layer was removed. The or-
ganic layer was washed successively with wa-
ter, saturated NaHCO3, and water, to pH 7,
and then dried (Na2SO4). After removal of the
solvent in vacuo, the residue was purified by
column chromatography [3:1 to 2:1 petroleum
ether (60–90 °C)–EtOAc] to give compound
4, 1.35 g (92.5%), as a colorless syrup, [h]D
+6.2° (c 1.0, CHCl3); IR (cm−1): 3400 (OH),
1738 (CꢀO). Anal. Calcd for C29H32O7: C,
70.73; H, 6.50. Found: C, 70.59; H, 6.68.
petroleum (60–90 °C)] to give compound 1,
1.86 g (total yield 38.9%), as a colorless syrup,
[h]D +34.8° (c 0.28, CHCl3); IR (cm−1): 3456
(OH). Anal. Calcd for C28H33O6: C, 72.41; H,
6.90. Found: C, 72.10; H, 6.97.
3,4,6-Tri-O-acetyl-1,2-O-(methoxyethyli-
dene)-i-D-mannopyranoside
(2).—Absolute
MeOH (10 mL) was added to a solution of
2,3,4,6-O-tetra-O-acetyl-a- -mannopyranosyl
D
bromide (10.2 g) in dry pyridine (20 mL). The
mixture was stirred at rt for 24 h, when TLC
showed that most of the material had been
converted, and then poured into ice–water
(200 mL). Dichloromethane (3×50 mL) was
used for extraction. The separated organic
layer was washed with water, dried (Na2SO4),
and concentrated. Toluene (50 mL) was added
to the residue to remove traces of pyridine and
water by azeotropic distillation in vacuo. The
resultant residue was purified by column chro-
matography [3:1 to 2:1 light petroleum (60–
90 °C)–EtOAc] to give compound 2, yield 5.8
g (70%) as a white powder, mp 110–112 °C
(lit. [11] 109–110 °C, 111–113 °C [12]).
2-O-Acetyl-3,4,6-tri-O-benzyl-h,i- -man-
D
nopyranosyl trichloroacetimidate (5).—To a
solution of compound 4 (1.02 g) in dry
CH2Cl2 (15 mL), trichloroacetonitrile (1 mL)
was added. The mixture was cooled and
stirred in an ice–water bath, and then five
drops of DBU was added. After stirring for 1
h, TLC showed complete conversion and the
mixture was concentrated in vacuo. Column
chromatography of the resulting residue (5:1
light petroleum (60–90 °C)–EtOAc) gave
compound 5, 1.19 g (90.2%) as a colorless
syrup.
3,4,6-Tri-O-benzyl-1,2-O-(methoxyethyli-
Methyl 2,3,4-tri-O-benzyl-6-O-(2-O-acetyl-
dene)-i-D-mannopyranoside (3).—To a solu-
3,4,6-tri-O-benzyl-h-
D
-mannopyranosyl)-h- -
D
tion of compound 2 (2.0 g) in abs. MeOH (20
mL), saturated NH3–MeOH (10 mL) was
added and the mixture was stirred overnight
at rt. After removing the solvent in vacuo, the
residue was benzylated according to the gen-
eral method used in the preparation of com-
pound 1. Column chromatography [10:1 to
8:1 light petroleum (60–90 °C)–EtOAc] gave
compound 3, 1.80 g (yield over two steps,
64%), as colorless needles, mp 74–76 °C (lit.
[11] 76–78 °C); [h]D +32.8° (c 0.37, CHCl3).
1H NMR (400 MHz): lH (ppm) 1.57 (s, 3
H, CH3), 3.28 (s, 3 H, OCH3), 3.44–5.35 (m,
13 H, H-1, 2, 3, 4, 5, 6, 3×PhCH2), 7.24–7.89
mannopyranoside (6).—To a stirred solution
of compound 5 (1.04 g) and compound 1 (0.75
,
g) in dry CH2Cl2 (10 mL), powdered 4 A
molecular sieves (1.0 g) were added. The mix-
ture was kept at rt for 30 min and then in an
ice–salt bath (−12 °C) for 20 min, and ten
drops of Me3SiOTf were added to the mixture.
The mixture was stirred for 3 h, when TLC
showed that the material had been converted
into a new compound. The mixture was
filtered through a layer of Celite and washed
with CH2Cl2. The combined filtrate was
washed with water, saturated NaHCO3 and
water, and dried (Na2SO4). The solvent was
concentrated in vacuo to a syrup which was
then chromatographed [6:1 light petroleum
(60–90 °C)–EtOAc] to give compound 6, 1.10
g (93.2%) as a colorless syrup; [h]D +39.2° (c
13
(m, 15 H, aromatic H); C NMR (100 MHz):
lC (ppm) 24.42 (CH3), 49.77 (OCH3), 68.99–
79.02 (8C, C-2, 3, 4, 5, 6, 3×PhCH2), 97.55
(C-1), 124.0–138.2 (aromatic C). Anal. Calcd
for C30H34O7: C, 71.18; H, 6.71. Found: C,
71.25; H, 6.56.
1
0.14, CHCl3); IR (cm−1): 1739 (CꢀO); H
NMR (400 MHz): lH (ppm) 2.16 (s, 3 H,
CH3CO), 3.25 (s, 3 H, OCH3), 3.67–5.50 (m,
36 H, H-1, 2, 3, 4, 5, 6, H-1%,2%,3%,4%,5%,6%,6×
PhCH2), 7.30 (m, 30 H, aromatic H); 13C
NMR (100 MHz): lC (ppm) 21.17 (CH3CO),
54.70 (OCH3), 68.57–80.25 (16C, C-2, 3, 4, 5,
2-O-Acetyl-3,4,6-tri-O-benzyl-h,i- -man-
D
nopyranose (4).—Compound 3 (1.50 g) was
suspended in 80% HOAc (30 mL) and stirred
at rt for 24 h. The mixture was poured into a
mixture of toluene (100 mL) and water (100

Z.-J. Li et al. / Carbohydrate Research 320 (1999) 1–7
5
6, C-2%, 3%, 4%, 5%, 6%, 6×PhCH2), 97.97, 98.71
(C-1, C-1%), 127.40–138.60 (36 C, aromatic C),
170.37 (CH3CO). Anal. Calcd for C52H62O12:
C, 72.92; H, 6.61. Found: C, 72.65; H, 6.50.
Methyl 2,3,4-tri-O-benzyl-6-O-(3,4,6-tri-O-
Ethyl 4-O-acetyl-6-O-benzyl-2-deoxy-2-ph-
thalimido-3-O-(2,3,4-tri-O-benzyl-h-
L
–fuco-
(9).—
pyranosyl)-1-thio-i-glucopyranoside
Compound 8 (0.31 g) was dissolved in 1:1
Ac2O–pyridine (8 mL) and stirred overnight.
The mixture was poured into ice–water (50
mL), and CHCl3 (3×10 mL) was used to
extracted the solution. The extract was
washed successively with water, saturated
NaHCO3 solution, and water, and then dried
(Na2SO4). The resultant residue was purified
by PTLC [5:1 light petroleum (60–90 °C)–
EtOAc] to give compound 9, 0.27 g, as a
colorless syrup; IR (cm−1): 1766, 1740, 1707
benzyl - h -
D
- mannopyranosyl) - h -
D
- manno-
pyranoside (7).—Sodium (20 mg) was added
to a solution of compound 6 (950 mg) in abs
MeOH (20 mL). The mixture was stirred for
12 h at rt and then neutralized with AcOH.
After removal of the solvent in vacuo, the
residue was purified by column chromatogra-
phy [3:1 light petroleum (60–90 °C)–acetone]
to give compound 7 in quantitative yield, as a
colorless syrup; [h]D +60.0° (c 0.24, CHCl3);
1
(phth and acetyl CꢀO); H NMR (400 MHz):
1
IR (cm−1): 3457 (OH); H NMR (400 MHz)
lH (ppm) 0.95 (d, 3 H, J5,6 =6.5 Hz, H-6%),
1.23 (t, 3 H, SCH2CH3), 1.88 (s, 3 H,
CH3CO), 2.71 (m, 2 H, SCH2CH3), 4.55 (d, 1
H, J1,2 =3.6 Hz, H-1%), 5.53 (d, 1 H, J1,2 =
10.0 Hz, H-1), 3.41–4.80 (18H, H-2, 3, 4, 5, 6,
H-2%, 3%, 4%, 5%, 4×PhCH2), 7.02–7.80 (m, 24
H, aromatic H); 13C NMR (100 MHz): lC
(ppm) 14.85 (s, SCH2CH3), 15.71 (C-6%), 21.05
(CH3CO), 23.81 (SCH2CH3), 54.02 (C-2),
60.12, 67.90, 69.64, 72.72, 73.23, 73.28, 74.56,
74.88, 77.33, 78.25, 79.16, 80.05, 80.67 (13C,
C-1, 3, 4, 5, 6, C-2%, 3%, 4%, 5%, 4×PhCH2),
101.55 (C-1%), 122.83–138.65 (30C, aromatic
C), 167.68, 168.41 (phth, 2×CꢀO), 169.95
(CH3CO); FABMS: (m/z) 908 [M+Li]+, 924
[M+Na]+.
lH (ppm) 2.46 (s, 1 H, OH), 3.26 (s, 3 H,
CH3), 3.60–5.08 (m, 26 H, H-1, 2, 3, 4, 5, 6,
H-1%, 2%, 3%, 4%, 5%, 6%, 6×PhCH2), 7.31 (m, 30
H, aromatic H); 13C NMR (100 MHz): lC
(ppm) 54.59 (OCH3), 66.17, 67.92, 68.67,
70.93, 71.19, 71.30, 71.91, 73.24, 74.08 74.43,
74.64, 74.88, 79.32, 80.08 (16C, C-2, 3, 4, 5, 6,
C-2%, 3%, 4%, 5%, 6%, 6×PhCH2), 98.64, 99.51
(C-1, C-1%), 127.40–138.39 (36C, aromatic C).
Anal. Calcd for C55H60O11: C, 73.66; H, 6.70.
Found: C, 73.59; H, 6.70.
Ethyl 6-O-benzyl-2-deoxy-2-phthalimido-3-
O-(2,3,4-tri-O-benzyl-h-
thio-i-
benzylidene - 2 - deoxy - 2 - phthalimido - 3 - O-
(2,3,4-O-tribenzyl-a- -fucopyransyl)-1-thio-b-
-glucopyranoside (0.42 g) [8] was dissolved in
L
-fucopyranosyl)-1-
D-glucopyranoside (8).—Ethyl 4,6-O-
L
Methyl 2,3,4-tri-O-benzyl-6-O-{3,4,6-tri-O-
benzyl-2-O-[4,6-O-benzylidene-2-deoxy-2-ph-
D
,
dry THF (15 mL), and then powdered 4 A
molecular sieves (1.0 g) and NaBH3CN (0.2 g)
were added slowly. After stirring at rt for 20
min, the mixture was added to saturated
HCl–dry ether solution until the bubbles dis-
appeared and pH 3 was reached. The mixture
was stirred for another 2 h, when TLC
showed that the reactant had been converted.
The mixture was then filtered through a layer
of Celite and washed with ether. The com-
bined filtrate was washed with water, satu-
rated NaHCO3 solution, and the solution was
concentrated to a syrup, which was then
purified by column chromatography [6:1 light
petroleum (60–90 °C)–acetone] to give com-
pound 8, 0.38 g (90%) as a colorless syrup;
[h]D +27.6° (c 0.6, CHCl3); IR (cm−1): 3416
(OH), 1770, 1707 (phth CꢀO); FABMS: (m/z)
860 [M+1]+.
thalimido-3-O-(2,3,4-tri-O-benzyl-h-
anosyl)-i- -glucopyranosyl]-h- -mannopyr-
anosyl}-h- -mannopyranoside (10).—Com-
L-fucopyr-
D
D
D
pound A (0.55 g) and compound 7 (0.62 g)
were dissolved in dry ether (20 mL), the solu-
tion was stirred for 1 h at rt with powdered 4
,
A molecular sieves (1.0 g), and then methyl
triflate (MeOTf, 100 mL) was added to the
mixture. After 48 h, Et3N (0.5 mL) was added
to the mixture to quench the reaction. The
mixture was filtered through a layer of Celite
and washed with CH2Cl2. The combined
filtrate was washed with water, saturated
NaHCO3 solution and water, and then dried
(Na2SO4). The product was purified by
column chromatography [5:5:2 benzene–light
petroleum (60–90 °C)–EtOAc) to give com-
pound 10, 0.58 g (53.0%) as a colorless syrup;

6
Z.-J. Li et al. / Carbohydrate Research 320 (1999) 1–7
[h]D +9.4° (c 0.3, CHCl3); IR (cm−1): 1772,
residue was dissolved in 1:2 Ac2O–pyridine
(12 mL) and stirred for 24 h at rt. Conven-
tional processing gave a white waxy solid, 76
mg (71.6%); FABMS: (m/z) 1611 [M+Li+
1]+, 1627 [M+Na+1]+. The foregoing
waxy solid (63 mg) was dissolved in MeOH
(40 mL) and hydrogenolyzed with 10% Pd–C
(100 mg) and 330 kPa of hydrogen pressure
for 24 h. The mixture was filtered and washed
with MeOH and distilled water. The com-
bined filtrate was concentrated and purified by
PTLC (8:1 to 5:1 CHCl3–MeOH), and the
resulting syrup was lyophilized to give com-
pound 12, 17 mg (61.4%), as a yellowish foam.
1
1708 (phth, CꢀO). H NMR (400 MHz): lH
(ppm) 0.88 (d, 3 H, J3,6 =6.5 Hz), H-6%%%), 3.30
(s, 3 H, OCH3), 5.55 (s, 1 H, phCH), 5.47 (d,
1 H, J1,2=8.5 Hz, H-1%%), 3.21–4.83 (43 H,
H-1, 2, 3, 4, 5, 6, H-1%, 2%, 3%, 4%, 5%, 6%, H-2%%,
3%%, 4%%, 5%%, 6%%, H-1%%%, 2%%%, 3%%%, 4%%%, 5%%%, 9×
PhCH2), 7.17–7.61 (m, 54 H, aromatic H); 13C
NMR (100 MHz): lC (ppm) 16.41 (C-6%%%),
54.72 (OCH3), 55.60 (C-2%%), 66.20–82.20
(27C, C-2, 3, 4, 5, 6, C-2%, 3%, 4%, 5%, 6%, C-3%%,
4%%, 5%%, 6%%, C-2%%%, 3%%%, 4%%%, 5%%%, 9×PhCH2),
97.61 (C-1%), 98.93 (C-1), 99.45 (C-1%%%), 101.15
(phCH), 102.25 (C-1%%), 167.90, 168.83 (phth,
2×CꢀO); FABMS: (m/z) 1714 [M+Na]+.
Anal. Calcd for C103H105NO21: C, 73.09; H,
6.21; N, 0.83. Found: C, 73.24; H, 6.31; N,
0.76.
1
[h]D −19.5° (c 0.4, H2O); H NMR (400
MHz, D2O): lH (ppm) 1.19 (d, 3 H, J5,6 =6.6
Hz, H-6%%%), 2.11 (s, 3 H, CH3CꢀO), 3.44 (s, 3
H, OCH3), 3.43–4.39 (22H, H-2, 3, 4, 5, 6,
H-2%, 3%, 4%, 5%, 6%, H-2%%, 3%%, 4%%, 5%%, 6%%, H-2%%%,
3%%%, 4%%, 5%%), 4.62 (d, 1 H J1,2 =8.56 Hz, H-1%%),
4.78 (d, 1 H, J1,2=2.2 Hz, H-1%), 4.96 (s, 1 H,
H-1), 5.02 (d, 1 H, J1,2 =4.08 Hz, H-1%%%); 13C
NMR (100 MHz), D2O): lC (ppm) 17.77 (C-
6%%%), 22.23 (CH3CꢀO), 57.35 (OCH3), 57.74
(C-2%%), 63.24–82.43 (18C, C-2, 3, 4, 5, 6, C-2%,
3%, 4%, 5%, 6%, C-3%%, 4%%, 5%%, 6%%, C-2%%%, 3%%%, 4%%%,
5%%%), 99.37 (C-1%%%), 101.84 (C-1%%), 102.37,
103.64 (C-1, C-1%), 170.20 (CH3CꢀO).
Methyl 2,3,4-tri-O-benzyl-6-O-{3,4,6-tri-O-
benzyl-2-O-[4-O-acetyl-6-O-benzyl-2-deoxy-2-
phthalimido-3-O-(2,3,4-tri-O-benzyl-h-
pyranosyl)-i- -glucopyranosyl]-h- -manno-
pyranosyl}-h- -mannopyranoside (11).—Com-
L
-fuco-
D
D
D
pound 9 (0.21 g) and compound 7 (0.26 g)
were coupled as in the procedure for the
preparation of the tetrasaccharide 10. The re-
sult of chromatography (10:1 benzene–
EtOAc) gave compound 11, 0.15 g (38%), as a
colorless syrup; IR (cm−1): 1769, 1744, 1706
1
(phth and acetyl, CꢀO); H NMR (400 MHz):
lH (ppm) 0.94 (d, 3 H, J5,6 =6.4 Hz, H-6%%%),
1.87 (s, 3 H, CH3CꢀO), 3.27 (s, 3 H, OCH3),
3.42–5.59 (m, 46 H, H-1, 2, 3, 4, 5, 6, H-1%, 2%,
3%, 4%, 5%, 6%, H-1%%, 2%%, 3%%, 4%%, 5%%, 6%%, H-1%%%, 2%%%,
3%%%, 4%%%, 5%%%, 10×PhCH2), 7.17–7.30 (m, 54 H,
Acknowledgements
This project was supported by the National
Natural Science Foundation of the People’s
Republic of China and a grant from the Min-
istry of Science and Technology of the Peo-
ple’s Republic of China.
13
aromatic H); C NMR (100 MHz): lC (ppm)
15.85 (C-6%%%), 21.19 (CH3CꢀO), 54.57 (OCH3),
54.89 (C-2%%), 67.96–80.37 (28C, C-2, 3, 4, 5, 6,
C-2%, 3%, 4%, 5%, 6%, C-3%%, 4%%, 5%%, 6%%, C-2%%%, 3%%%,
4%%%, 5%%%, 10×PhCH2), 96.79, 97.46 (C-1, C-1%),
98.87 (C-1%%%), 101.73 (C-1%%), 167.70, 168.99,
170.14 (phth 2×CꢀO, CH3CꢀO).
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