Concise synthesis of a buffalo milk pentasaccharide derivative.

Article abstract of DOI:10.1016/S0008-6215(02)00131-3

An efficient synthesis of buffalo milk pentasaccharide derivative via a 3+2 strategy is described. The use of a trisaccharide isopropyl thioglycoside as a latent glycosyl donor and the application of two well-defined regioselective glycosylations significantly simplified the target preparation.

Full text of DOI:10.1016/S0008-6215(02)00131-3

Carbohydrate Research 337 (2002) 1313–1317
www.elsevier.com/locate/carres
Note
Concise synthesis of a buffalo milk pentasaccharide derivative
Guofeng Gu,a Yuguo Du,a,* Jingqi Panb
aResearch Center for Eco-En6ironmental Sciences, Academia Sinica, PO Box 2871, Beijing 100085, PR China
bCollege of Chemistry and Molecular Engineering, Peking Uni6ersity, Beijing 100871, PR China
Received 14 May 2002; accepted 5 June 2002
Abstract
An efficient synthesis of buffalo milk pentasaccharide derivative via a 3+2 strategy is described. The use of a trisaccharide
isopropyl thioglycoside as a latent glycosyl donor and the application of two well-defined regioselective glycosylations significantly
simplified the target preparation. © 2002 Elsevier Science Ltd. All rights reserved.
Keywords: Glycosylation; Antigens; Thioglycosides; Oligosaccharides; Regioselectivity
Milk, which contains numerous complex carbohy-
drate components, is known as a good source of
oligosaccharide antigens and bifidus factors for breast-
fed newborns.1 Monoclonal antibodies of several tu-
mour cell lines or carbohydrate antigens have provided
evidence that membrane glycoproteins or glycolipids,
which may function as differentiation antigens or tu-
mour-associate antigens, also occur as free oligosaccha-
rides in human milk.2 Different types of milk since then
have been analyzed for their oligosaccharides that have
immunological properties.3 Recently, Deepak and co-
workers4 isolated a novel pentasaccharide from im-
munostimulant oligosaccharide fraction of buffalo milk
well-designed glycosyl donors and acceptors are assem-
bled involving a minimum of steps of reactions. Ac-
cordingly, the target molecule was retrosynthetically
disconnected into a disaccharide acceptor 5 and a
trisaccharide donor 14 as shown in Scheme 1. Thus,
compound 15 was condensed with 36 in the presence of
N-iodosuccinimide (NIS) and catalytic amount of
trimethylsilyl triflate (TMSOTf) to afford disaccharide
4 in 89% yield. The stereochemical outcome is induced
by the neighbouring-group participation of donor 1 and
1
confirmed by the H NMR spectroscopy of 4 (H-1: l
4.49 ppm, J1,2 8.0 Hz). Hydrolysis of 4 in aqueous 90%
trifluoroacetic acid (TFA) furnished disaccharide accep-
tor 5 in good yield (84.5%). Convergently, 1 was re-
acted with p-methoxyphenol (MPOH) with the
promotion of NIS–TMSOTf in dry CH2Cl2 to give 2,
which was treated with 90% TFA to generate diol 6
(63.7% for two steps). Regioselective coupling of 6 with
glucosamine imidate 7 in anhydrous CH2Cl2 in the
presence of TMSOTf produced b-(1“3)-linked disac-
charide 8 in 72% yield. Acetylation of 8 with acetic
anhydride in pyridine gave 9 showing H-4 at l 5.63
ppm (J4,3 3.4 Hz), which confirmed the correct regiose-
lectivity. Ceric ammonium nitrate (CAN) promoted
cleavage of anomeric MP of 9 was carried out smoothly
in toluene–MeCN–H2O co-solvent system (“10), fol-
lowed by Schmidt activation using trichloroacetonitrile
and DBU, to afford imidate 11 in 72.3% yield (based
on 8).
with the following structure: b-
D
-GlcNAc-(1“3)-b-
D-
Gal-(1“4)-b- -GlcNAc-(1“3)-Gal-(1“4)-
D
D
-Glc. A
six-fold increase in haemagglutinating antibody (HA)
titre and a two-fold increase in plaque-forming cell
(PFC) count were reported in treated animals as com-
pared with untreated controls. To investigate struc-
ture–activity relationships, we planned to prepare a
monomer and a trimer of the above-mentioned pen-
tasaccharide. We present here the concise chemical
synthesis of this pentasaccharide derivative.
The efficient chemical synthesis of complex oligosac-
charides requires highly convergent strategies in which
* Corresponding author. Tel.: +86-10-62914475; fax: +
86-10-62923563
E-mail address: ygdu@mail.rcees.ac.cn (Y. Du).
0008-6215/02/$ - see front matter © 2002 Elsevier Science Ltd. All rights reserved.
PII: S0008-6215(02)00131-3

1314
G. Gu et al. / Carbohydrate Research 337 (2002) 1313–1317
To save steps in protection-group manipulation on
the bioactive buffalo milk pentasaccharide. Two well-
defined regioselective glycosylation steps and the use of
isopropyl thioglycoside as the latent donor simplified
the protecting-group manipulations in the synthesis and
the strategic principle described here is currently em-
ployed in the exploring of trimeric analogue prepara-
tion.
the anomeric centre, the isopropyl thioglycoside7 was
designed as a latent glycosyl donor for the glucosamine
residue. It was also reported8 that the 6-OH benzoyl-
ated glucosamine unit decreased the activity of the
group 4-OH while the ether-protected counterparts im-
proved the yields greatly. As we expected, coupling of
isopropyl thioglycoside 129 and 11 at 0 °C using TM-
SOTf as catalyst gave b-(1“4)-linked trisaccharide 13
(71%), which was further acetylated with acetic anhy-
dride in pyridine to furnish trisaccharide donor 14.
Neither a nor b product with 1“3 linkage10 was
detected in our experiments. 2D NMR experiments
showed that the chemical shift of H-3I moved downfield
from 4.39 ppm (in 13) to 5.64 ppm (in 14), together
with H-1II at l 4.74 ppm (J1,2 8.1 Hz), confirming the
formation of a b-(1“4) linkage. Glycosylation of iso-
propyl thioglycoside 14 and disaccharide diol 5 in the
presence of NIS–TMSOTf at −15 °C completed the
1. Experimental
General methods.—Optical rotations were deter-
mined at 20 °C with a Perkin–Elmer Model 241-Mc
automatic polarimeter. Melting points were determined
1
with a ‘‘Mel-Temp’’ apparatus. H NMR, 13C NMR
1
1
and H–1H, H–13C COSY spectra were recorded with
ARX 400 spectrometers for solutions in CDCl3. Chem-
ical shifts are given in ppm downfield from internal
Me4Si. Mass spectra were measured using MALDI-
TOF-MS with a-cyano-4-hydroxycinnamic acid (CCA)
as matrix. Thin-layer chromatography (TLC) was per-
formed on silica gel HF254 with detection by charring
with 30% (v/v) H2SO4 in MeOH, or in some cases by a
UV detector.
1
synthesis of pentasaccharide derivative 15 (66%). H–
1
1H and H–13C COSY analyses assigned the peak at l
81.25 ppm (13C NMR spectroscopy) as C-3II. This
downfield movement of C-3II, compared with signals of
C-3V (70.14 ppm), C-4II (67.67 ppm) and C-4IV (69.29
ppm), indicated the (1“3)-bond formation in the last
glycosylation step. H-1III appeared at l 5.31 ppm in the
1H NMR spectrum (J1,2 8.4 Hz), which confirmed the b
stereoselectivity.
Methyl 2,6-di-O-benzoyl-3,4-di-O-isopropylidene-i-
D
- galactopyranosyl - (1“4) - 2,3,4 - tri - O - benzyl - h - D-
glucopyranoside (4).—To a solution of 1 (290 mg, 0.558
mmol) and 3 (246 mg, 0.526 mmol) in anhyd CH2Cl2 (4
mL) was added NIS (310 mg, 1.38 mmol) and
Me3SiOTf (20 mL, 0.11 mmol) under an N2 atmosphere
at 0 °C. The mixture was stirred under these conditions
for 1 h, then at rt for another 30 min, at the end of
which time TLC (6:1 petroleum ether–EtOAc) indi-
cated that starting material 1 was completely con-
sumed. The reaction mixture was neutralized with Et3N
and concentrated. Column chromatography (5:1
petroleum ether–EtOAc) of the residue gave 4 (410 mg,
89.1%) as a syrup: [h]D +18° (c 0.75, CHCl3); 1H
NMR: 1.34, 1.60 (2 s, 2×3 H, 2 CH3), 3.27 (s, 3 H,
OCH3), 3.35–3.52 (m, 3 H, H-6a, H-6b, H-5), 3.67 (dd,
1 H, J2,1 2.5, J2,3 9.2 Hz, H-2), 3.80–3.92 (m, 3 H, H-3,
H-4, H-5%), 4.04 (dd, 1 H, J3%,4% 4.7, J3%,2% 7.5 Hz, H-3%),
4.16 (d, 1 H, H-4%), 4.29 (d, 1 H, J 12.2 Hz, one proton
of PhCH2), 4.36 (dd, 1 H, J6a%,6b% 11.3, J6a%,5% 7.0 Hz,
H-6a%), 4.49 (d, 1 H, J1%,2% 8.0 Hz, H-1%), 4.52–4.58 (m,
2 H, H-6b, H-1), 4.60, 4.68, 4.77, 4.78, 5.03 (5 d, 5 H,
J 12.2, 10.7 Hz, PhCH2), 5.21 (t, 1 H, J2%,3% 7.5, J2%,1% 8.0
Hz, H-2%), 7.25–8.04 (m, 30 H, Ph). MALDITOF-MS
Calcd for C51H54O13: 874 [M]; Found: 897.3 [M+Na]+.
In conclusion, we have described the concise synthe-
sis of the methyl glycoside derivative corresponding to
Methyl 2,6-di-O-benzoyl-i-
D
-galactopyranosyl-(1“
4)-2,3,4-tri-O-benzyl-h- -glucopyranoside (5).—A solu-
D
tion of compound 4 (400 mg, 0.458 mmol) in 90% TFA
(5 mL) was stirred at rt for 15 min, then neutralized
with aq NaHCO3 and extracted with CH2Cl2 (2×20
mL). The organic phases were combined and concen-
trated. The residue was purified on a silica gel column
Scheme 1. Reagents and conditions: (a) NIS, TMSOTf; 89.1%
for 4; 65.5% for 15; (b) 90% TFA; 84.5% for 5; 63.7% for 6
(from 1); (c) TMSOTf, CH2Cl2, 71.9% for 8; 71.2% for 13; (d)
Ac2O, Pyr; (e) CAN, 3:4:3 Toluene–MeCN–water; (f)
Cl3CCN, DBU, 78.7% from 9.

G. Gu et al. / Carbohydrate Research 337 (2002) 1313–1317
1315
using 2:1 petroleum ether–EtOAc as eluent to give
foamy 5 (323 mg, 84.5%): [h]D +6° (c 2.4, CHCl3); H
(m, 3 H, H-4, H-6a%, H-6b%), 4.38 (t, 1 H, J2%,3% 10.7, J2%,1%
8.2 Hz, H-2%), 4.68 (dd, 1 H, J6a,6b 11.4, J6a,5 7.9 Hz,
H-6a), 4.73 (dd, 1 H, J6b,5 4.3 Hz, H-6b), 4.83 (d, 1 H,
J1,2 8.0 Hz, H-1), 5.14 (t, 1 H, J4%,3%=J4%,5%=9.5 Hz,
H-4%), 5.54–5.72 (m, 3 H, H-2, H-1%, H-3%), 6.53 (d, 2 H,
Ph), 6.76 (d, 2 H, Ph), 7.17–8.09 (m, 14 H, Ph). Anal.
Calcd for C47H45NO18: C, 69.91; H, 4.97. Found: C,
70.12; H, 5.09.
1
NMR: 3.29 (s, 3 H, OCH3), 3.45–3.58 (m, 5 H, H-6a,
H-6b, H-5, H-3%, H-5%), 3.70 (dd, 1 H, J2,1 3.4, J2,3 10.8
Hz, H-2), 3.80–3.96 (m, 3 H, H-3, H-4, H-4%), 4.17 (dd,
1 H, J6a%,6b% 11.2, J6a%,5% 5.7 Hz, H-6a%), 4.31 (d, 1 H, J
12.8 Hz, one proton of PhCH2), 4.52 (dd, 1 H, J6b%,5% 7.8
Hz, H-6b%), 4.56 (d, 1 H, J1,2 3.4 Hz, H-1), 4.59 (d, 1 H,
J1%,2% 8.2 Hz, H-1%), 4.63, 4.76, 4.78, 4.84, 4.98 (5 d, 5 H,
J 12.3, 12.8, 10.7 Hz, PhCH2), 5.17 (t, 1 H, J2%,3% 9.2,
J2%,1% 8.2 Hz, H-2%), 7.25–8.04 (m, 30 H, Ph); 13C NMR
(100 MHz, CDCl3): 55.31 (OCH3), 62.03 (C-6%), 67.90
(C-6), 68.34 (C-4%), 69.56 (C-3%), 71.97 (C-2%), 72.68
(C-5%), 73.49 (PhCH2), 73.50 (PhCH2), 74.27 (C-5),
75.28 (PhCH2), 76.48 (C-3), 79.02 (C-2), 79.98 (C-4),
98.34 (C-1), 100.10 (C-1%), 166.50, 166.65 (2 C, PhCO);
MALDITOF-MS Calcd for C48H50O13: 834 [M]; Found
857.4 [M+Na]+, 873.4 [M+K]+. Anal. Calcd for
C48H50O13: C, 69.06; H, 6.04. Found: C, 68.84; H, 6.13.
p-Methoxyphenyl
thalimido-i- -glucopyranosyl-(1“3)-4-O-acetyl-2,6-
di-O-benzoyl-i- -galactopyranoside (9).—To a solu-
3,4,6-tri-O-acetyl-2-deoxy-2-ph-
D
D
tion of compound 8 (915 mg, 1.00 mmol) in pyridine (4
mL) was added Ac2O (2 mL). The mixture was stirred
at rt for about 12 h, then co-evaporated with toluene
under diminished pressure to remove pyridine. Column
chromatography (2:1 petroleum ether–EtOAc) of the
residue gave crystalline 9 (879 mg, 91.8%): mp 210–
212 °C; [h]D +53° (c 1.4, CHCl3); 1H NMR: 1.78, 2.03,
2.12, 2.23 (4 s, 4×3 H, 4 CH3CO), 3.64 (s, 3 H,
OCH3), 3.80–3.84 (m, 1 H, H-5%), 4.03–4.14 (m, 2 H,
H-3, H-5), 4.18 (dd, 1 H, J6a%,6b% 11.9, J6a%,5% 4.2 Hz,
H-6a%), 4.25 (dd, 1 H, J2%,3% 10.7, J2%,1% 8.2 Hz, H-2%), 4.33
(dd, 1 H, J6b%,5% 5.7 Hz, H-6b%), 4.41 (dd, 1 H, J6a,6b 11.4,
J6a,5 7.9 Hz, H-6a), 4.52 (dd, 1 H, J6b,5 4.3 Hz, H-6b),
p-Methoxyphenyl
2,6-di-O-benzoyl-i-D-galactopy-
ranoside (6).—To a solution of 1 (1.46 g, 2.81 mmol)
and p-methoxyphenol (418 mg, 3.37 mmol) in anhyd
CH2Cl2 (10 mL) was added NIS (948 mg, 4.22 mmol)
and Me3SiOTf (31 mL, 0.17 mmol) under N2 atmo-
sphere at −15 °C. The mixture was stirred under these
conditions for 1 h, at the end of which time TLC (5:1
petroleum ether–EtOAc) indicated that starting mate-
rial 1 was completely consumed. The reaction mixture
was neutralized with Et3N and concentrated. The above
residue was dissolved into 90% TFA (10 mL), stirred at
rt for 20 min, then co-evaporated with toluene under
diminished pressure to dryness. Purification of the
residue on a silica gel column using 1:1 petroleum
ether–EtOAc as eluent gave 6 (884 mg, 63.7%) as a
white solid: [h]D −9o (c 0.9, CHCl3); 1H NMR: 3.71 (s,
3 H, OCH3), 3.94 (dd, 1 H, J2,3 9.5, J3,4 3.5 Hz, H-3),
4.01 (dd, 1 H, J5,6a 7.6, J5,6b 5.4 Hz, H-5), 4.11 (d, 1 H,
H-4), 4.65 (dd, 1 H, J6a,6b 11.5 Hz, H-6a), 4.75 (dd, 1 H,
H-6b), 5.03 (d, 1 H, J1,2 8.0 Hz, H-1), 5.44 (dd, 1 H,
H-2), 6.65 (d, 2 H, Ph), 6.95 (d, 2 H, Ph), 7.40–8.08 (m,
10 H, Ph).
4.87 (d, 1 H, J1,2 8.0 Hz, H-1), 5.16 (t, 1 H, J4%,3%
=
J4%,5%=9.3 Hz, H-4%), 5.48–5.57 (m, 2 H, H-2, H-1%),
5.63 (d, 1 H, J4,3 3.4 Hz, H-4), 5.67 (t, 1 H, J3%,4% 9.3,
J3%,2% 10.7 Hz, H-3%), 6.50 (d, 2 H, Ph), 6.74 (d, 2 H, Ph),
7.26–8.08 (m, 14 H, Ph). Anal. Calcd for C49H47NO19:
C, 61.70; H, 4.97. Found: C, 61.64; H, 5.13.
3,4,6-Tri-O-acetyl-2-deoxy-2-phthalimido-i-
D-glu-
copyranosyl-(1“3)-4-O-acetyl-2,6-di-O-benzoyl-i-
D
-
galactopyranosyl trichloroacetimidate (11).—Ceric am-
monium nitrate (CAN; 1.22 g, 2.23 mmol) was added
to a solution of 9 (850 mg, 0.892 mmol) in 3:4:3
toluene–MeCN–H2O (30 mL), and the mixture was
stirred at rt for 2 h. An additional amount of CAN
(734 mg, 1.34 mmol) was added, and the stirring was
continued for another 2 h, at the end of which time
TLC (1:1 petroleum–EtOAc) indicated the completion
of the reaction. The resulting mixture was diluted with
EtOAc, washed successively with water, satd aq
NaHCO3, and brine. The organic phase was dried over
anhydrous Na2SO4 and concentrated, then subjected to
silica gel column chromatography (1:1 petroleum
ether–EtOAc). The product generated above was dis-
solved in anhydrous CH2Cl2 (5 mL). To the solution
was added trichloroacetonitrile (0.45 mL, 4.46 mmol)
and DBU (45 mL, 0.45 mmol) at rt. The mixture was
stirred for 2 h, then concentrated, and the residue was
subjected to a silica gel column (1.5:1 petroleum ether–
EtOAc) to afford syrupy 11 (696 mg, 78.7% for two
p-Methoxyphenyl
thalimido-i- -glucopyranosyl-(1“3)-2,6-di-O-benzo-
yl-i- -galactopyranoside (8).—Compound 6 (900 mg,
3,4,6-tri-O-acetyl-2-deoxy-2-ph-
D
D
1.82 mmol) and 7 (1.10 g, 1.90 mmol) were pre-dried in
one flask under vacuum at 60 °C for 2 h. The mixture
was then dissolved in CH2Cl2 (10 mL). To the solution
was added Me3SiOTf (36 mL, 0.20 mmol) at rt under an
N2 atmosphere. The mixture was stirred for 1.5 h, then
neutralized with Et3N, concentrated under reduced
pressure, and purified on a silica gel column with 1:1
petroleum ether–EtOAc as the eluents to give 8 (954
mg, 71.9%, based on recovered 5) as crystals: mp
203–205 °C; [h]D +50° (c 0.75, CHCl3); 1H NMR:
1.79, 2.05, 2.13 (3 s, 3×3 H, 3 CH3CO), 3.65 (s, 3 H,
OCH3), 3.85–4.08 (m, 3 H, H-3, H-5, H-5%), 4.16–4.34
1
steps): [h]D +96° (c 1.5, CHCl3); H NMR: 1.80, 2.02,
2.12, 2.20 (4 s, 4×3 H, 4 CH3CO), 3.85–3.92 (m, 1 H,
H-5%), 4.15–4.25 (m, 2 H, H-3, H-2%), 4.32–4.44 (m, 4
H, H-5, H-6a, H-6a%, H-6b%), 4.55 (dd, 1 H, J6b,6a 12.3,

1316
G. Gu et al. / Carbohydrate Research 337 (2002) 1313–1317
J6b,5 5.0 Hz, H-6b), 5.17 (t, 1 H, J4%,3% 9.2, J4%,5% 9.5 Hz,
H-4%), 5.46 (dd, 1 H, J2,3 10.5, J2,1 3.8 Hz, H-2), 5.52 (d,
1 H, J1%,2% 3.8 Hz, H-1%), 5.70–5.77 (m, 2 H, H-4, H-3%),
6.52 (d, 1 H, J1,2 3.8 Hz, H-1), 7.28–8.01 (m, 14 H, Ph),
8.34 (s, 1 H, NH). Anal. Calcd for C44H41Cl3N2O18: C,
53.25; H, 4.17. Found: C, 53.08; H, 4.22.
(t, 1 H, J2,3 9.8, J2,1 8.1 Hz, H-2II), 5.34 (d, 1 H, J1,2
10.6 Hz, H-1I), 5.44 (d, 1 H, J1,2 8.3 Hz, H-1III), 5.55 (d,
1 H, J4,3 3.6 Hz, H-4II), 5.64 (t, 2 H, J3,2 10.5, J3,4 9.4
Hz, H-3I, H-3III), 7.11–8.15 (m, 18 H, Ph); 13C NMR
(100 MHz, CDCl3): −5.47, 0.95 (2 C, SiCH3), 20.25,
20.44, 20.53, 20.65, 20.68 (5 C, CH3CO), 23.74, 24.14 (2
C, CH(CH3)2), 25.71 (4 C, C(CH3)3), 34.81 (CH(CH3)2),
54.27 (C-2III), 54.43 (C-2I), 60.88 (C-6I), 61.43 (C-6III),
62.45 (C-6II), 68.68 (C-4III), 69.24 (C-4II), 70.15 (C-3III),
71.01 (C-2II), 71.34 (C-3I), 71.36 (C-5III), 71.77 (C-5II),
74.57 (C-5I), 77.76 (C-3II), 78.83 (C-4I), 79.99 (C-1I),
98.39 (C-1III), 100.21 (C-1II), 163.83, 166.16 (2 C,
PhCO), 166.45, 167.26, 167.61 (4 C, CO of Phth, some
overlapped), 169.29, 169.91, 170.00, 170.65 (5 C,
CH3CO, some overlapped); MALDITOF-MS Calcd for
C67H76N2O24SSi: 1352 [M]. Found: 1375.6 [M+Na]+,
1391.6 [M+K]+.
Isopropyl 3,4,6-tri-O-acetyl-2-deoxy-2-phthalimido-
i-
yl-i-
ylsilyl-2-deoxy-2-phthalimido-1-thio-i-
D
-glucopyranosyl-(1“3)-4-O-acetyl-2,6-di-O-benzo-
-galactopyranosyl-(1“4)-6-O-tert-butyldimeth-
-glucopyran-
D
D
oside (13).—To a solution of compound 11 (660 mg,
0.666 mmol) and 12 (300 mg, 0.623 mmol) in anhyd
CH2Cl2 (5 mL) was added Me3SiOTf (12 mL, 0.067
mmol) under an N2 atmosphere at 0 °C. The mixture
was stirred under these conditions for 1 h, neutralized
with Et3N and concentrated under reduced pressure.
The residue was purified on a silica gel column with
1.3:1:0.1 petroleum ether–EtOAc–toluene as the eluent
to give 13 (582 mg, 71.2%) as a syrup: [h]D +47° (c 1,
CHCl3); 1H NMR: −0.17, −0.16 (2 s, 2×3 H, 2
SiCH3), 0.73 (s, 9 H, C(CH3)3), 1.10, 1.12 (2 d, 2×3 H,
J 6.6, 6.9 Hz, CH(CH3)2), 1.76, 2.00, 2.13, 2.18 (4 s,
4×3 H, 4 CH3CO), 3.00 (m, 1 H, CH(CH3)2), 3.24–
3.42 (m, 3 H, J6a,6b 10.4 Hz, H-6aI, H-6bI, H-5I), 3.57 (t,
1 H, J4,3=J4,5=8.7 Hz, H-4I), 3.82 (m, 1 H, H-5III),
3.88–4.25 (m, 6 H, H-5II, H-6aIII, H-6bIII, H-2I, H-2III,
H-3II), 4.34 (br d, 1 H, J6a,6b 11.6 Hz, H-6aII), 4.39 (t, 1
H, J3,4 8.7, J3,2 10.1 Hz, H-3I), 4.61–4.72 (m, 2 H,
H-1II, H-6bII), 5.14 (t, 1 H, J4,3=J4,5=9.3 Hz, H-4III),
5.26 (d, 1 H, J1,2 10.6 Hz, H-1I), 5.34 (br t, 1 H,
Methyl 3,4,6-tri-O-acetyl-2-deoxy-2-phthalimido-i-
-glucopyranosyl-(1“3)-4-O-acetyl-2,6-di-O-benzoyl-
i- -galactopyranosyl-(1“4)-3-O-acetyl-6-O-tert-but-
yldimethylsilyl-2-deoxy-2-phthalimido-i- -glucopyran-
osyl-(1“3)-2,6-di-O-benzoyl-i- -galactopyranosyl-
(1“4)-2,3,4-tri-O-benzyl-h- -glucopyranoside (15).—
D
D
D
D
D
To a solution of compound 14 (530 mg, 0.392 mmol)
and 5 (327 mg, 0.392 mmol) in anhyd CH2Cl2 (4 mL)
was added NIS (220 mg, 0.98 mmol) and Me3SiOTf (21
mL, 0.12 mmol) under an N2 atmosphere at −15 °C.
The mixture was stirred under these conditions for 1 h.
TLC (1:1 petroleum ether–EtOAc) indicated the com-
pletion of the reaction. The mixture was neutralized
with Et3N and concentrated. Purification of the residue
on a silica gel column with 1:1.3 petroleum ether–
EtOAc as eluent gave 15 (542 mg, 65.5%) as a syrup:
[h]D +34° (c 1, CHCl3); 1H NMR: −0.10, −0.03 (2 s,
2×3 H, 2 SiCH3), 0.80 (s, 9 H, C(CH3)3), 1.76, 1.79,
1.99, 2.10, 2.16 (5 s, 5×3 H, 5 CH3CO), 3.09–3.19 (m,
4 H, H-6aI, OCH3), 3.19–3.27 (m, 2 H, H-5I, H-5III),
3.28–3.39 (m, 3 H, H-2I, H-3II, H-6bI), 3.42 (dd, 1 H,
J6a,6b 11.4 Hz, H-6aIII), 3.48–3.57 (m, 2 H, H-5II,
H-6bIII), 3.67–3.80 (m, 6 H, H-3I, H-4I, H-4III, H-3IV,
H-5IV, H-5V), 3.94 (d, 1 H, J4,3 4.6 Hz, H-4II), 4.01–
4.26 (m, 6 H, H-2III, H-2V, H-6aII, H-6aIV, H-6aV, one
proton of PhCH2), 4.26–4.31 (m, 2 H, J1,2 8.1 Hz,
H-1II, H-6bV), 4.44 (d, 1 H, J1,2 3.6 Hz, H-1I), 4.46–
4.61 (m, 4 H, H-6bII, H-6bIV, two protons of PhCH2),
4.64 (d, 1 H, J 10.8 Hz, one proton of PhCH2), 4.72 (d,
1 H, J1,2 8.0 Hz, H-1IV), 4.73, 4.94 (2 d, 2 H, J 12.3,
10.8 Hz, PhCH2), 5.07–5.24 (m, 3 H, H-2II, H-2IV,
H-4V), 5.31 (d, 1 H, J1,2 8.4 Hz, H-1III), 5.43 (d, 1 H,
J1,2 8.3 Hz, H-1V), 5.51 (t, 1 H, J3,2 10.7, J3,4 9.1 Hz,
H-3III), 5.53 (d, 1 H, J4,3 4.5 Hz, H-4IV), 5.64 (t, 1 H,
J3,2 10.7, J3,4 9.1 Hz, H-3V), 7.09–8.10 (m, 43 H, Ph);
13C NMR (100 MHz, CDCl3): −5.45, −5.07 (2 C,
SiCH3), 20.27, 20.55, 20.67 (5 C, CH3CO, some over-
lapped), 25.63 (4 C, C(CH3)3), 54.43 (C-2V), 54.70
J
2,3=J2,1=8.7 Hz, H-2II), 5.47 (d, 1 H, J1,2 8.2 Hz,
H-1III), 5.57 (br s, 1 H, H-4II), 5.64 (t, 1 H, J3,2 10.6, J3,4
9.3 Hz, H-3III), 7.26–8.05 (m, 18 H, Ph). Anal. Calcd
for C65H74N2O23SSi: C, 59.54; H, 5.69. Found: C,
59.21; H, 5.50.
Isopropyl 3,4,6-tri-O-acetyl-2-deoxy-2-phthalimido-
i-
yl-i-
butyl-dimethylsilyl-2-deoxy-2-phthalimido-1-thio-i-
D
-glucopyranosyl-(1“3)-4-O-acetyl-2,6-di-O-benzo-
D
-galactopyranosyl-(1“4)-3-O-acetyl-6-O-tert-
D
-
glucopyranoside (14).—To a solution of compound 13
(560 mg, 0.427 mmol) in pyridine (2 mL) was added
Ac2O (1 mL). The mixture was stirred at 40 °C for
about 20 h, then co-evaporated with toluene under
diminished pressure to remove pyridine. The residue
was purified by silica-gel column chromatography (2:1
petroleum ether–EtOAc) to give syrupy 14 (550 mg,
1
95.2%): [h]D +41° (c 1.3, CHCl3); H NMR: −0.06,
0.13 (2 s, 2×3 H, 2 SiCH3), 0.81 (s, 9 H, C(CH3)3),
1.10, 1.11 (2 d, 6 H, J 6.1, 6.5 Hz, CH(CH3)2), 1.76,
1.88, 2.00, 2.10, 2.18 (5 s, 5×3 H, 5 CH3CO), 2.97 (m,
1 H, CH(CH3)2), 3.20 (m, 1 H, H-5I), 3.47–3.55 (m, 2
H, H-6aI, H-6bI), 3.79–3.90 (m, 4 H, H-4I, H-3II, H-5II,
H-5III), 4.08–4.22 (m, 4 H, H-2I, H-2III, H-6aIII, H-
6bIII), 4.30 (dd, 1 H, J6a,6b 11.4, J6a,5 2.1 Hz, H-6aII),
4.55 (t, 1 H, J6b,5 4.5 Hz, H-6bII), 4.74 (d, 1 H, J1,2 8.1
Hz, H-1II), 5.13 (t, 1 H, J4,3 9.4, J4,5 9.8 Hz, H-4III), 5.19

G. Gu et al. / Carbohydrate Research 337 (2002) 1313–1317
1317
(C-2III), 55.12 (OCH3), 60.45 (C-6III), 60.47 (C-6V),
References
61.41 (C-6IV), 63.19 (C-6II), 67.38 (C-6I), 67.67 (C-4II),
68.62 (C-4V), 69.17 (C-5III), 69.29 (C-4IV), 69.99 (C-3III),
70.14 (C-3V), 70.85 (C-2II), 70.98 (C-2IV), 71.45 (C-5II),
71.55 (C-5V), 71.80 (C-5IV), 73.29 (PhCH2), 73.42
(PhCH2), 74.00 (C-4III), 75.01 (C-5I), 75.38 (PhCH2),
76.04 (C-3I), 77.76 (C-3IV), 78.65 (C-2I), 79.76 (C-4I),
81.25 (C-3II), 98.37 (2 C, C-1I, C-1V), 98.57 (C-1III),
99.81 (C-1II), 100.11 (C-1IV), 163.80, 164.09, 166.13,
166.17 (4 C, PhCH2), 166.60, 167.68, 167.72 (4 C, CO
of Phth, some overlapped), 169.29, 169.91, 170.01,
170.65 (5 C, CH3CO, some overlapped); MALDITOF-
MS Calcd for C112H118N2O37Si: 2110 [M]. Found:
[M+Na]+ 2133.98; [M+K]+ 2148.96. Anal. Calcd for
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Acknowledgements
This work was supported by NNSF of China
(Projects 29972053 and 39970179) and RCEES of
CAS.