Synthesis of laminarin oligosaccharide derivatives having D-arabinofuranosyl side-chains

Article abstract of DOI:10.1081/CAR-120023470

An efficient glycosylation strategy was applied in the synthesis of β-D-glucopyranosyl-(1→3)-[α-D-arabinopyranosyl-(1→4)] -β-D-glucopyranosyl-(1→3)-β-D-glucopyranosyl-(1→3) -[α-D-arabinopyranosyl-(1→6)]-D-glucopyranose to secure β-D-(1→3) glycosidic bond

Full text of DOI:10.1081/CAR-120023470

Journal of Carbohydrate Chemistry
ISSN: 0732-8303 (Print) 1532-2327 (Online) Journal homepage: http://www.tandfonline.com/loi/lcar20
Synthesis of Laminarin Oligosaccharide
Derivatives Having d‐Arabinofuranosyl Side‐Chains
Hongmei He M.Sc , Guofeng Gu M.Sc. Now Ph.D Candidate & Yuguo Du
To cite this article: Hongmei He M.Sc , Guofeng Gu M.Sc. Now Ph.D Candidate & Yuguo Du
(2003) Synthesis of Laminarin Oligosaccharide Derivatives Having d‐Arabinofuranosyl Side‐Chains,
Journal of Carbohydrate Chemistry, 22:5, 275-283, DOI: 10.1081/CAR-120023470
To link to this article: http://dx.doi.org/10.1081/CAR-120023470
Published online: 16 Aug 2006.
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Date: 07 August 2017, At: 04:08

JOURNAL OF CARBOHYDRATE CHEMISTRY
Vol. 22, No. 5, pp. 275–283, 2003
Synthesis of Laminarin Oligosaccharide Derivatives Having
D-Arabinofuranosyl Side-Chains
*
Hongmei He, Guofeng Gu, and Yuguo Du
Research Center for Eco-Environmental Sciences, Chinese Academy
of Sciences, Beijing, P.R. China
ABSTRACT
An efficient glycosylation strategy was applied in the synthesis of b-D-glucopyranosyl-
(1!3)-[a-D-arabinopyranosyl-(1!4)]-b-D-glucopyranosyl-(1!3)-b-D-glucopyrano-
syl-(1!3)-[a-D-arabinopyranosyl-(1!6)]-D-glucopyranose to secure b-D-(1!3)
glycosidic bond formation between glucopyranosyl residues. The new strategy using
a 4,6-O-benzylidenated acceptor avoided generation of the a major isomer in the
attempted b-D-(1!3) glycosylation under standard glycosylation conditions. The
hexasaccharide we prepared showed about 30% tumor growth inhibition towards S180
model study.
Key Words: Oligosaccharide; Laminarin; Glycosylation; Antitumor agent.
*
Correspondence: Yuguo Du, Research Center for Eco-Environmental Sciences, Chinese Academy
of Sciences, P.O. Box 2871, Beijing100085, P.R. China; E-mail: duyuguo@mail.rcees.ac.cn.
275
DOI: 10.1081/CAR-120023470
0732-8303 (Print); 1532-2327 (Online)
www.dekker.com
Copyright D 2003 by Marcel Dekker, Inc.

276
He, Gu, and Du
INTRODUCTION
Many natural polysaccharides, such as lentinan,[1,2] schizophyllan,[3] pestalosan[4]
and other fungal (1!6)-branched (1!3)-b-D-glucans,[5–7] exhibit high inhibition to the
growth of implanted tumors in mice. It is believed that the activity is closely related to
the organization of the (1!3)-b-D-linked backbone into a triple helix, the frequency
and complexity of the side-branching, and to the polymer molecular weight.[8,9]
To investigate the structure-activity relationship, we have synthesized a series of
b-D-glucosyl oligosaccharides to mimic the repeating units of natural b-glucan
chains.[10] The mice tumor tests revealed that our synthetic glucosyl oligosaccharides
showed weaker antitumor activities compared to their natural polysaccharides. How-
ever, a literature survey found that some synthetic branching-oligosaccharides with
arabinose side-chains exhibited antitumor activity as high as natural polysaccharides.[11]
We thus focused our attention on the synthesis of b-D-glucopyranosyl-(1!3)-[a-D-
arabinopyranosyl-(1!4)]-b-D-glucopyranosyl-(1!3)-b-D-glucopyranosyl-(1!3)-[a-D-
arabinopyranosyl-(1!6)]-D-glucopyranose to mimic the bioactive arabinosyl curdlan.
To prepare this hexasaccharide, one would think that a 3+3 strategy is more
efficient. However, the unexpected a glycosides were predominantly formed in this
case using fully acylated imidates or thioglycosides as glycosyl donors under standard
glycosylation conditions (see Scheme 1 for examples).[12] However, we found that a
4,6-O-benzylidenated acceptor was helpful in b-D-(1!3) bond formation. Here we
report the synthesis of b-D-glucopyranosyl-(1!3)-[a-D-arabinopyranosyl-(1!4)]-b-D-
Scheme 1. a) NIS, TMSOTf, CH2Cl2, 56%; b) TMSOTf, CH2Cl2, 77%.

Synthesis of Laminarin Oligosaccharide Derivatives
277
glucopyranosyl-(1!3)-b-D-glucopyranosyl-(1!3)-[a-D-arabinopyranosyl-(1!6)]-D-
glucopyranose based on a sequential glycosylation strategy, and antitumor activities of
the hexasaccharide.
RESULTS AND DISCUSSION
Glycosylation of 2,3,5-tri-O-benzoyl-a-D-arabinofuranosyl trichloroacetimidate (1),
Scheme 2, and allyl 2,6-di-O-benzoyl-3-O-tert-butyldimethylsilyl-a-D-glucopyranoside
(2)a in dry CH2Cl2 with TMSOTf as promoter afforded allyl 2,3,5-tri-O-benzoyl-a-D-
arabinofuranosyl-(1!4)-2,6-di-O-benzoyl-3-O-tert-butyldimethylsilyl-a-D-glycopyrano-
side (3, 78.4%). Removal of the tert-butyldimethylsilyl (TBS) group from 3 with
tetrabutylammonium fluoride (TBAF) was not straightforward. Thus, disaccharide 3
was treated with 90% aqueous trifluoroacetic acid (TFA) under reflux for 3 h to
generate 4 in 95% yield. The a-(1!4) glycosidic bond of 4 was very stable under these
acidic conditions. Condensation of 4 with 2,3,4,6-tetra-O-benzoyl-a-D-glucopyranosyl
trichloroacetimidate (5) under standard glycosylation conditions gave trisaccharide 6 in
good yield (80.4%). Treatment of 6 with PdCl2 in MeOH yielded 7, which was further
transformed into imidate 8 by reacting with trichloroacetonitrile and DBU in methylene
chloride; yield of 68.3% for two steps. Critical glycosylation of trisaccharide imidate 8
and disaccharide diol 9[10] using the method as described in the preparation of 3 gave
desired pentasaccharide 10 as the predominant product.b Acetylation of 10 with acetic
anhydride in pyridine followed by CeCl3ꢀ7H2O catalyzed regioselective removal of the
di-O-isopropylidene group[13] gave pentasaccharide diol 11 in 50% yield (from 9). H-
1
1III and H-2II of 11 in its H NMR spectrum appear at d 4.45 ppm (J 7.3 Hz) and 4.72
ppm, respectively, confirming the b-(1!3) linkage between sugar units II and III.
Primary hydroxyl group favored glycosylation of 11 and 1 in CH2Cl2 at ꢁ15°C
furnished the hexasaccharide derivative 12 in 65% yield. HMQC experiments showed
C-1III at 100.96 ppm (13C NMR), while the corresponding H-1III appeared at 4.47 ppm
(1H NMR), indicating a b linkage between sugar residue II and III in 12. Full
deprotection of 12 with 90% TFA, followed by deacetylation with NaOMe in MeOH,
afforded target hexasaccharide 13 in 43% isolated yield.
aTo a solution of allyl 2,6-di-O-benzoyl-3-O-a-D-glucopyranoside (1.0 g, 2.33 mmol) in dry DMF
(8 mL) was added imidazole (380 mg) and TBSCl (385 mg, 2.56 mmol) at rt. After 4 h, the mixture
was worked up as usual to give syrupy allyl 2,6-di-O-benzoyl-3-O-tert-butyldimethylsilyl-a-D-
glucopyranoside (872 mg, 69%). To prove the structure, a small amount of the above compound
was acetylated with acetic anhydride in pyridine to give the following 1H NMR (400 MHz, CDCl3):
ꢁ0.14, 0.17 (2 s, 6 H, 2 SiCH3), 0.73 (s, 9 H, C(CH3)3), 3.99 (dd, 1 H, J 7.3, 13.2 Hz, OCH2–
CH CH2), 4.16–4.20 (m, 2 H, H-5, OCH2–CH CH2), 4.31 (dd, 1 H, J 5.5, 12.5 Hz, H-6a), 4.36
(t, 1 H, J 9.1 Hz, H-3), 4.49 (dd, 1 H, J 2.6, 12.5 Hz, H-6b), 5.05 (dd, 1 H, OCH2–CH CH2), 5.09
(m, 2 H, H-1, H-4), 5.14 (dd, 1 H, J 3.7, 9.1 Hz, H-2), 5.25 (dd, 1 H, J 1.6, 12.7 Hz, OCH2–
CH CH2), 5.80–5.84 (m, 1 H, OCH2–CH CH2), 7.43–8.25 (m, 10 H, Ph). These spectra
assignments are consistent with the proposed structure for 2.
bCompound 10 was contaminated by an inseparable side product, presumably the decomposed
donor based on mass analysis. Thus it was hydrolyzed directly to give pure 11.

278
He, Gu, and Du
Scheme 2. a) TMSOTf, CH2Cl2, 78.4% for 3; 80.4% for 6; 65% for 12; b) 90% TFA, 95%.
c) Pd2Cl2, MeOH; d) CCl3CN, DBU, CH2Cl2, 68.3% for two steps; e) Ac2O, Pyr; CH3CN,
CeCl3ꢀ6H2O, H2O, 50% from 9; f) 90% TFA; NaOMe. MeOH, 43% for two steps.
Kun min mice weighing 20–22 g were used for the bioassay. Seven-day-old
S180 ascites (0.2 mL, about 2ꢂ106 cells) were transplanted into the right groins of
mice. The test samples, dissolved in distilled water, were injected daily for 7 days
starting 24 h after tumor implantation. At the end of the tenth day, the mice were
killed, and the tumors were extirpated and weighted. The results are summarized in
Table 1.
In conclusion, we have described the synthesis of the hexasaccharide 13 having a
(1!3)-b-D-glucan backbone and two arabinofuranosyl side chains. We showed here
that a predominant b product could be formed using a 4,6-O-benzylidenated

Synthesis of Laminarin Oligosaccharide Derivatives
279
Table 1. Preliminary studies on antitumor activity of hexasaccharide 13.
Body weight (g)
Dose
(mg/Kg)
Tumor growth
inhibition (%)
Tumor
weigth (g)
Sample
Day 1
Day 10
p
Control
CTX
13
0
20.0
21.3
20.1
20.0
20.0
29.6
27.4
29.7
26.9
29.6
1.68 0.63
0.19 0.11
1.09 0.63
1.11 0.60
0.15 0.41
<0.001
<0.01
<0.01
<0.01
<0.01
80ꢂ1
5.0ꢂ7
1.5ꢂ7
0.5ꢂ7
89.3
35.1
33.9
31.5
13
13
glucopyranosyl acceptor in complex oligosaccharide synthesis, while the a major was
generated using 4,6-diacylated acceptor under the same reaction conditions. The
hexasaccharide 13 showed a mild antitumor activity towards S180 model study.
EXPERIMENTAL
General methods. Optical rotations were determined at 20°C with a Perkin–
1
1
Elmer Model 241-Mc automatic polarimeter. H NMR, 13C NMR, H–1H COSY and
HMQC spectra were recorded with ARX 400 spectrometers for solutions in CDCl3 and
D2O. Chemical shifts are given in ppm downfield from internal Me4Si, or DSS in case
of D2O. Mass spectra were measured using MALDI-TOF-MS with (a-cyano-4-
hydroxycinnamic acid (CCA) as matrix. Thin-layer chromatography (TLC) was
performed on silica gel HF254 with detection by charring with 30% (v/v) H2SO4 in
MeOH or in some cases by a UV detector. Column chromatography was conducted by
elution of a column (16ꢂ240 mm, 18ꢂ300 mm, 35ꢂ400 mm) of silica gel (100–200
mesh) with EtOAc–petroleum ether (bp 60–90°C) as the eluent. Solutions were
concentrated at <60°C under diminished pressure.
Allyl 2,3,5-tri-O-benzoyl- -D-arabinofuranosyl-(1?4)-2,6-di-O-benzoyl-3-O-
tert-butyldimethylsilyl- -D-glucopyranoside (3). Compound 1 (1.33 g, 2.2 mmol)
and 2 (1.09 g, 2.0 mmol) were pre-dried in one flask under vacuum for 4 h. The
mixture was then dissolved in CH2Cl2 (15 mL). To the solution was added Me3SiOTf
(35 ꢀL, 0.19 mmol) under an N2 atmosphere at 0°C. The mixture was stirred at these
conditions for 1 h, then neutralized with triethylamine, concentrated under reduced
pressure, and purified on a silica gel column with petroleum ether–EtOAc (6:1) as the
1
eluent to give 3 (1.54 g, 78.4%) as a syrup; [aD]20 + 31° (c 1, CHCl3); H NMR
(CDCl3) d ꢁ0.01 (s, 3 H, SiCH3), 0.16 (s, 3 H, SiCH3), 0.68 (s, 9 H, C(CH3)3), 3.98–
4.40 (m, 2 H, H-3I, H-5I), 4.13 (dd, 1 H, J 5.1, 11.9 Hz, OCH2–CH CH2), 4.22 (dd, 1
H, J 5.1, 13.0 Hz, OCH2–CH CH2), 4.45–4.53 (m, 4 H, H-6aI, H-6bI, H-4II, H-4I),
4.69–4.75 (m, 2 H, H-5aII, H-5bII), 5.05 (d, 1 H, J 3.7 Hz, H-1I), 5.11–5.13 (m, 1 H,
OCH2–CH CH2), 5.15 (dd, 1 H, J 3.7, 9.5 Hz, H-2I), 5.26–5.28 (m, 1 H, OCH2–
CH CH2), 5.51 (d, 1 H, J 3.3 Hz, H-3II), 5.68 (s, 1 H, H-1II), 5.85 (m, 1 H, OCH2–
CH CH2), 5.87 (s, 1 H, H-2II), 7.37–8.29 (m, 25 H, Ph).
Anal. Calcd for C55H58O15Si: C, 66.92; H, 5.92. Found: C, 67.18; H, 5.85.

280
He, Gu, and Du
Allyl 2,3,4,5-tetra-O-benzoyl- -D-glucopyranosyl-(1?3)-[2,3,5-tri-O-benzoyl- -
D-arabinofuranosyl-(1?4)]-2,6-di-O-benzoyl- -D-glucopyranoside (6). A solution
of compound 3 (1.283 g, 1.3 mmol) in 90% aqueous trifluoroacetic acid (10 mL)
was stirred at 60°C for about 3 h, then co-evaporated with toluene under diminished
pressure to give a residue. Purification of the residue by column chromatography
(3:1 petroleum ether–EtOAc) gave 4 (1.079 g, 95.1%) as a syrup. To a solution of
compound 4 (1.05 g, 1.2 mmol) and 5 (1.00 g, 1.35 mmol) in anhydrous CH2Cl2
(12 mL) was added TMSOTf (35 mL, 0.19 mmol) under an N2 atmosphere at 0°C. The
mixture was stirred under this condition for 1.5 h, neutralized with Et3N and
concentrated under reduced pressure. The residue was purified on a silica gel column
with 3:1 petroleum ether–EtOAc as the eluent to give 6 (1.40 g, 80.4%) as a syrup;
1
[aD]20 + 30° (c 1, CHCl3); H NMR (CDCl3) d 3.90 (dd, 1 H, J 6.3, 14.3 Hz, OCH2),
3.96–3.98 (m, 2 H, H-5I, H-4I), 4.25 (dd, 1 H, J 5.2, 14.3 Hz, OCH2), 4.19–4.21
(m, 1 H, H-5II), 4.49–4.69 (m, 7 H, H-6aI, H-6bI, H-6aII, H-6bII, H-3I, H-4III, H-5aIII),
4.75 (dd, 1 H, J 3.9, 12.0 Hz, H-5bIII), 4.94 (dd, 1 H, J 3.7, 10.1 Hz, H-2I), 4.99 (dd, 1
H, J 1.3, 10.4 Hz, CH2), 5.09 (d, 1 H, J 3.7 Hz, H-1I), 5.11 (dd, 1 H, J 1.6, 10.4 Hz,
CH2), 5.13 (d, 1 H, J 8.0 Hz, H-1II), 5.42 (d, 1 H, J 4.4 Hz, H-3III), 5.45 (dd, 1 H, J
9.6, 8.0 Hz, H-2II), 5.54 (t, 1 H, J 9.6 Hz, H-4II), 5.63 (t, 1 H, J 9.6 Hz, H-3II), 5.64–
5.67 (m, 1 H, CH), 5.90–5.92 (m, 2 H, H-1III, H-2III), 7.07–8.26 (m, 45 H, Ph). 13C
NMR (100 MHz, CDCl3) d 63.05 (C-6II), 63.50 (C-6I), 63.97 (C-5III), 68.66 (OCH2),
69.05 (C-4I), 70.45 (C-4II), 71.84 (C-2II), 72.13 (C-5II), 73.24 (C-3II), 73.86 (C-2I),
74.45 (C-5I), 77.23 (C-3I), 78.27 (C-3III), 81.76 (C-2III), 82.70 (C-4III), 94.92 (C-1I),
101.12 (C-1II), 108.35 (C-1III) , 111.85 ( CH2), 164.89, 164.96, 165.23, 165.26,
165.55, 165.62, 166.13, 166.20, 166.30 (CO).
Anal. Calcd for C83H70O24: C, 68.68; H, 4.86. Found: C, 68.92; H, 4.73.
2,3,4,6-Tetra-O-benzoyl- -D-glucopyranosyl-(1?3)-[2,3,5-tri-O-benzoyl- -D-
arabinofuranosyl-(1?4)]-2,6-di-O-benzoyl- -D-glucopyranosyl trichloroacetimidate
(8). To a solution of compound 6 (1.435 g, 0.99 mmol) in methanol (20 mL) was
added PdCl2 (0.17 g, 0.50 mmol) at rt. The mixture was stirred under these conditions
for 3 h, then filtered, and the filtrate was concentrated. Purification of the residue by
column chromatography (3:1 petroleum ether–EtOAc) gave 7 (1.19 g, 85.3%) as a
syrup. This syrup was dissolved in anhydrous CH2Cl2 (6 mL), and trichloroacetonitrile
(0.3 mL, 3 mmol) and DBU (0.05 mL, 0.33 mmol) were added subsequently. The
mixture was stirred at rt for 2 h, and then concentrated. Purification of the residue by
column chromatography (3:1 petroleum ether–EtOAc) gave 8 (1.052 g, 80.1%) as an
amorphous solid; [a]D + 44° (c 1, CHCl3); H NMR (CDCl3) d 4.14 (m, 3 H, H-5I,
H-5II, H-4I), 4.55–4.80 (m, 8 H, H-6aI, H-6bI, H-6aII, H-6bII, H-5aIII, H-5bIII, H-4III,
H-3I), 5.09 (d, 1 H, J 7.9 Hz, H-1II), 5.21 (q, 1 H, J 3.5, 10.2 Hz, H-2I), 5.45–5.47 (m, 2
H, H-2II, H-3III), 5.51 (t, 1 H, J 9.5 Hz, H-4II), 5.64 (t, 1 H, J 9.5 Hz, H-3II), 5.95 (s, 1 H,
H-1III), 5.97 (s, 1 H, H-2III), 6.53 (d, 1 H, J 3.4 Hz, H-1I), 7.11–8.26 (m, 45 H, Ph), 8.27
(s,1 H, NH).
20
1
Anal. Calcd for C82H66Cl3NO24: C, 63.31; H, 4.28. Found: C, 63.03; H, 4.31.
2,3,4,6-Tetra-O-benzoyl- -D-glucopyranosyl-(1?3)-[2,3,5-tri-O-benzoyl- -D-
arabinofuranosyl-(1?4)]-2,6-di-O-benzoyl- -D-glucopyranosyl(1?3)-2-O-acetyl-
4,6-O-benzylidene- -D-glucopyranosyl-(1?3)-1,2-O-isopropylidene- -D-glucofura-
nose (10). To a solution of 8 (1.17 g, 0.75 mmol) and 9 (0.34 g, 0.67mmol) in dry

Synthesis of Laminarin Oligosaccharide Derivatives
281
CH2Cl2 was added TMSOTf (20 mL, 0.11 mmol) under an N2 atmosphere at 0°C. The
mixture was stirred under these conditions for 1.5 h, then neutralized with Et3N,
concentrated under reduced pressure, and purified on a silica gel column with 3:2
petroleum ether–EtOAc as the eluent to give crude 10 (1.02 g) as a syrup. This syrup
was treated with acetic anhydride (1 mL) in pyridine (2.0 mL) at rt for 4 h and
concentrated with the help of toluene. The above crude product was dissolved in
CH3CN, then CeCl3ꢀ6H2O (100 mg, 0.26 mmol) and H2O (0.1 mL) were added. The
mixture was stirred under reflux for 3 h, then diluted with water, extracted with
methylene chloride (3ꢂ15 mL). The organic phases were combined, dried over sodium
sulfate and concentrated. Purification of the residue by column chromatography (1:2
20
petroleum ether–EtOAc) gave 11 (653 mg, 50.1% from 9) as a solid; [a]D ꢁ 4° (c 1,
1
CHCl3); H NMR (CDCl3) d 1.26 (s, 3 H, CH3), 1.44 (s, 3 H, CH3), 1.78 (s, 3 H,
CH3CO), 2.99 (d, 1 H, J 4.1 Hz, OH), 3.36–3.38 (m, 1 H, H-5II), 3.51–3.53 (m, 1 H,
H-5), 3.59 (dd, 1 H, J 5.4, 8.7 Hz, H-4II), 3.67–3.71 (m, 2 H, H-6a, H-6b), 3.77–3.80
(m, 2 H, H-6a, H-6b), 3.88 (t, 1 H, J 8.5 Hz, H-4III), 3.98 (m, 1 H, H-5I), 4.04 (t, 1 H, J
8.7 Hz), 4.09–4.12 (m, 1 H), 4.19–4.25 (m, 3 H), 4.29 (t, 1 H, J 8.9 Hz, H-3II), 4.31
(q, 1 H, J 5.4, 14.6 Hz, H-5aV), 4.45 (d, 1 H, J 7.3 Hz, H-1III), 4.46–4.54 (m, 5 H),
4.68 (dd, 1 H, J 2.3, 14.6 Hz, H-5bV), 4.71–4.73 (m, 2 H, J 7.9, 8.9 Hz, H-1II, H-2II),
4.99 (d, 1 H, J 7.7 Hz, H-1IV), 5.18 (dd, 1 H, J 7.0, 8.2 Hz, H-2III), 5.34 (d, 1 H, J 3.7
Hz, H-3V), 5.45 (dd, 1 H, J 9.4, 11.0 Hz, H-2IV), 5.48 (s, 1 H, PhCH), 5.54 (t, 1 H, J
9.4 Hz, H-4IV), 5.61 (d, 1 H, J 3.7 Hz, H-1I), 5.66 (t, 1 H, J 9.4 Hz, H-3IV), 5.70 (d, 1
H, J 0.7 Hz, H-2V), 5.74 (s, 1 H, H-1V), 7.13–8.21 (m, 50 H, Ph); 13C NMR (100
MHz, CDCl3) d 26.79, 26.29, 29.30, 62.89, 63.23, 63.79, 64.19, 66.50, 68.05, 68.61,
70.08, 71.71, 72.04, 72.31, 72.63, 73.10, 73.78, 73.95, 77.19, 78.02, 78.47, 78.70,
79.51, 81.07, 81.55, 82.34, 82.70, 99.52, 99.68, 99.79, 101.364, 104.11 (C-1V), 107.65
(PhCH), 112.20 (CMe2), 164.30, 164.86, 164.88, 165.16, 165.49, 165.52, 165.90,
166.11, 166.25, 168.31 (CO).
Anal. Calcd for C104H96O35: C, 65.54; H, 5.08. Found: C, 65.27; H, 5.14.
2,3,4,6-Tetra-O-benzoyl- -D-glucopyranosyl-(1?3)-[2,3,5-tri-O-benzoyl- -D-
arabinofuranosyl-(1?4)]-2,6-di-O-benzoyl- -D-glucopyranosyl(1?3)-2-O-acetyl-
4,6-O-benzylidene- -D-glucopyranosyl-(1?3)-[2,3,5-tri-O-benzoyl- -D-arabinofura-
nosyl-(1?6)]-1,2-O-isopropylidene- -D-glucofuranose (12). To a solution of 1 (170
mg, 0.28 mmol) and 11 (533 mg, 0.28 mmol) in dry CH2Cl2 (5 mL) was added
TMSOTf (10 mL, 0.05 mmol) under an N2 atmosphere at ꢁ15°C. The mixture was
stirred under these conditions for 1.5 h, then neutralized with Et3N, concentrated
under reduced pressure, and purified on a silica gel column with 2:3 petroleum ether–
20
1
EtOAc as the eluent to give 12 (428 mg, 65%) as a solid; [a]D ꢁ6° (c 1, CHCl3); H
NMR (CDCl3) d 1.16 (s, 3 H, CH3), 1.65 (s, 3 H, CH3), 2.35 (s, 3 H, CH3CO), 3.09
(m, 1 H, H-5II), 3.14–3.17 (m, 1 H, H-5I), 3.52 (t, 1 H, J 9.1 Hz, H-4II), 3.38–3.40
(m, 1 H, H-5III), 3.77 (t, 1 H, J 9.1 Hz, H-3II), 3.91–4.10 (m, 6 H, H-6aI, H-6bI, H-3I,
H-4I, H-4III, H-5IV), 4.27–4.29 (m, 3 H, H-4IV, H-3III, H-2I), 4.37 (d, 1 H, J 7.9Hz,
H-1II), 4.47–4.76 (m, 13 H, H-6aII, H-6bII, H-6aIII, H-6bIII, H-6aIV, H-6bIV, H-5aI,
H-5bI, H-5aVI, H-5bVI, H-1III, H-2II, H-4VI), 4.96 (d, 1 H, J 7.5Hz, H-1IV), 5.17 (dd, 1
H, J 7.7, 8.2 Hz, H-2III), 5.31–5.34 (m, 2 H, H-3VI, H-1VI), 5.35 (d, 1 H, J 1.4 Hz,
H-3V), 5.44 (dd, 1 H, J 7.6, 9.4 Hz, H-2IV), 5.52–5.56 (m, 3 H, H-2VI, H-3VI, PhCH),
5.59 (d, 1 H, 3.7 Hz, H-3IV), 5.65 (t, 1 H, J 9.4 Hz, H-4IV), 5.69 (s, 1 H, H-2V), 5.75
(s, 1 H, H-1V), 7.16–8.02 (m, 65 H, Ph). 13C NMR (100 MHz, CDCl3) d 20.31,

282
He, Gu, and Du
21.46, 26.50, 62.97, 63.29, 63.52, 63.76, 63.90, 66.63, 67.06, 67.83, 70.12, 71.78,
72.10, 72.24, 72.65, 73.17, 73.88, 74.06, 74.24, 77.24, 77.65, 77.77, 78.16, 78.57,
78.83, 79.26, 80.20, 81.23, 81.61, 81.69, 82.12, 82.40, 82.78, 99.91 (C-1II), 100.21
(C-1IV), 100.96 (C-1III), 104.65 (C-5V), 105.22 (C-1I), 106.58 (C-1IV), 107.75 (PHCH),
111.82 (CMe2).
Anal. Calcd for C130H116O42: C, 66.43; H, 4.97. Found: C, 66.79; H, 4.83.
-D-Glucopyranosyl-(1?3)-[ -D-arabinopyranosyl-(1?4)]- -D-glucopyranosyl-
(1?3)- -D-glucopyranosyl-(1?3)-[ -D-arabinopyranosyl-(1?6)]-D-glucopyranose
(13). Compound 12 (310 mg, 0.132 mmol) was treated with 90% trifluoroacetic acid
(6 mL) for 60 min, concentrated and then co-evaporated with toluene. The syrup was
dissolved in methanol (15 mL), deacylated with sodium methoxide (0.5 M, kept pH at
9 to 10), neutralized with Amberlite 120 (H+), filtered and concentrated. The residue
was chromatographically purified on Sephadex LH-20 (EtOAc, then methanol) to yield
1
13 (53 mg, 43%) as a solid; [a]D + 19° (c 1, H2O); Selected H NMR (D2O) d 4.41–
4.72 (m, 3.3 H, H-1I,II,III,IV of b isomer), 5.20, 5.25 (2 s, 2 H, H-1V,VI), 5.30 (d, 0.7 H,
J 2.8 Hz, H-1I of a isomer). Selected 13C NMR (100 MHz, D2O) d 103.02, 103.70
(2C), 103.99, 110.23, 110.87 (C-1I–VI). MALDI-TOF-MS: Calcd for C34H58O29: 930.3
[M]; Found 953.8 [M+Na]+.
ACKNOWLEDGMENTS
This work was supported by NNSF of China (Projects 29972053, 39970179) and
RCEES of the Chinese Academy of Sciences. We thank Dr. Hongyan Hu of General
Hospital of Armed Police for mice experiments.
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Received December 22, 2002
Accepted April 14, 2003