Synthesis of galactose-containing analogues of (1→6)-branched (1→3)-glucohexaose and its lauryl glycoside

Article abstract of DOI:10.1016/j.carres.2005.01.011

Coupling of the trisaccharide acceptor either 2,4,6-tri-O-acetyl-β-D- glucopyranosyl-(1→3)-[2,3,4,6-tetra-O-benzoyl-β-D-glucopyranosyl- (1→6)]-5-O-acetyl-1,2-O-isopropylidene-α-D-glucofuranose (13) or lauryl 2,4,6-tri-O-acetyl-β-D-glucopyranosyl-(1→3)-[2,

Full text of DOI:10.1016/j.carres.2005.01.011

Carbohydrate
RESEARCH
Carbohydrate Research 340 (2005) 597–602
Synthesis of galactose-containing analogues of
(1!6)-branched (1!3)-glucohexaose and its lauryl glycoside
Guohua Zhang, Mingkun Fu and Jun Ning*
Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, PO Box 2871, Beijing 100085, China
Received 7 January 2005; accepted 12 January 2005
Available online 2 February 2005
Abstract—Coupling of the trisaccharide acceptor either 2,4,6-tri-O-acetyl-b-D-glucopyranosyl-(1!3)-[2,3,4,6-tetra-O-benzoyl-b-D-
glucopyranosyl-(1!6)]-5-O-acetyl-1,2-O-isopropylidene-a-D-glucofuranose (13) or lauryl 2,4,6-tri-O-acetyl-b-D-glucopyranosyl-
(1!3)-[2,3,4,6-tetra-O-benzoyl-b-D-glucopyranosyl-(1!6)]-2,5-di-O-acetyl-a-D-glucopyranoside (15) with the trisaccharide donor
2,3,4,6-tetra-O-benzoyl-b-D-glucopyranosyl-(1!3)-[2,3,4,6-tetra-O-benzoyl-b-D-glucopyranosyl-(1!6)]-2,4-di-O-acetyl-a-D-galac-
topyranosyl trichloroacetimidate (12) gave a-linked hexasaccharides 14 and 16, respectively, while coupling of either 13 or 15 with
trisaccharide donor 2,3,4,6-tetra-O-benzoyl-b-D-galactopyranosyl-(1!3)-[2,3,4,6-tetra-O-benzoyl-b-D-galactopyranosyl-(1!6)]-
2,4-di-O-acetyl-a-D-galactopyranosyl trichloroacetimidate 17 did not afford any hexasaccarides. The analogues of the immuno-
modulator b-D-Glcp-(1!3)-[b-D-Glcp-(1!6)]-a-D-Glcp-(1!3)-b-D-Glcp-b-(1!3)-[b-D-Glcp-(1!6)]-b-D-Glcp (1) was obtained by
deprotection of 14 and 16.
ꢀ 2005 Elsevier Ltd. All rights reserved.
Keywords: Glucohexaose; Galactoglucan; Oligosaccharide; Synthesis
1. Introduction
its macroscopic morphology, and this hypothesis
was proved by our research results.6 During our study,
an interesting and surprising result was found in that
a b-(1!6)-branched, a-D-(1!3)-linked glucohexaose,
b-D-Glcp-(1!3)-[b-D-Glcp-(1!6)]-a-D-Glcp-(1!3)-b-D-
Glcp-(1!3)-[b-D-Glcp-(1!6)]-D-Glcp (1), had similar or
even better activity compared to that of lentinan.7
Moreover, compound 1 was more easily obtained than
Unlike most of chemotherapeutic antitumor agents that
have severe side effects due to their cytotoxicity against
healthy cells, some glucans coming from fungi such as
Ganoderma lucidum, Schizophyllum commune, and Lenti-
nus edodes1 exert their antitumor function through stim-
ulating the host immunopotentiation, which is
associated with macrophage activation, the promotion
of T cell differentiation, and the augmentation of NK-
activity,2 rather than the direct inhibition of tumor cell
growth.3 Early, some physicochemical and immuno-
pharmacological investigations showed that the antitu-
mor activity of these glucans may be closely related to
their triple-helix4 structures with certain molecular
weights (MW > 16,000).5 However, we hypothesized
that the activity of lentinan might be dependent upon
its basic structure—the oligosacharide unit—rather than
Glcp
Glcp
1,6
Glcp
Manp
1,6
Glcp
β
β
β
1,6
1,3
α
1
1,3
1,3
1,3
β
1,3
β
1,3
α
4
Glcp
Glcp
Glcp
Glcp
Glcp
Glcp
Manp
β
β
Glcp
Glcp
Glcp
β
β
β
1,6
1,6
1,6
1,3
1,3
1,3
α
1,3
β
1,3
1,3
β
Glcp
Glcp
Manp
Glcp
Glcp
Glcp
β
β
β
5
2
Manp
Glcp
Glcp
β
β
β
1,6
1,6
1,6
1,3
1,3
α
1,3
1,3
β
1,3
β
1,3
α
Glcp
Glcp
Glcp
Manp
Glcp
Glcp
OLauryl
β
β
*
Corresponding author. Tel.: +86 10 62849157; fax: +86 10 62923563;
e-mail: jning@mail.rcees.ac.cn
6
3
0008-6215/$ - see front matter ꢀ 2005 Elsevier Ltd. All rights reserved.
doi:10.1016/j.carres.2005.01.011

598
G. Zhang et al. / Carbohydrate Research 340 (2005) 597–602
its corresponding b-(1!6)-branched b-D-(1!3)-linked
glucohexaose isomer by a synthetic route.6 Encouraged
by this discovery, many analogues of 1, such as a-D-
Manp-(1!3)-[b-D-Glcp-(1!6)]-a-D-Glcp-(1!3)-b-D-Glcp-
(1!3)-[b-D-Glcp-(1!6)]-b-D-Glcp (2), a-D-Manp-(1!3)-
[a-D-Manp-(1!6)]-a-D-Glcp-(1!3)-b-D-Glcp-(1!3)-[b-
D-Glcp-(1!6)]-b-D-Glcp (3), and a-D-Manp-(1!3)-
[a-D-Glcp-(1!6)]-a-D-Glcp-(1!3)-b-D-Glcp-(1!3)-[b-D-
Manp-(1!6)]-b-D-Glcp (4) were synthesized in our lab
to develop new immunopotentiating reagents.8,9 For
furthering the study of structure–activity relationships
of this kind of antitumor oligosaccharide, we present
herein the synthesis of a galactose-containing hexasac-
charide 5 and its lauryl glycoside 6.
2. Results and discussion
As shown in Scheme 1, coupling of acceptor 710 with
donor 811 in the presence of TMSOTf as the catalyst,
O
BzO
O
BzO
O
OH
O
O
a
BzO
BzO
O
BzO
O
O
+
O
BzO
O
O
OBz
OR1
OR2
OBz
OCNHCCl3
9 R1=R2=C(CH3)2
10 R1=R2=H
7
8
b
8
a
BzO
BzO
BzO
O
BzO
O
O
BzO
BzO
O
OAc
O
BzO
O
O
OBz
O
O
OBz
O
c
BzO
OH
O
BzO
BzO
O
BzO
BzO
OAc
OCNHCCl3
OBz
OBz
11
12
BzO
O
BzO
BzO
O
AcO
OBz
O
a
O
12
+
O
AcO
O
O
AcO
HO
OAc
13
BzO
BzO
O
BzO
O
BzO
BzO
O
AcO
BzO
O
OAc
O
O
OBz
AcO
OBz
O
BzO
O
O
d
O
5
O
O
BzO
BzO
AcO
OAc
O
OBz
OAc
14
Scheme 1. Reagents and conditions: (a) TMSOTf, CH2Cl2, rt, 3 h, 90% for 11, 30% for 14, 25% for 16; (b) 90% HOAc, 40 ꢁC, 24 h, 81% for 10 (for
two steps); (c) (i) 80% HOAc, reflux, 5 h; (ii) Ac2O–pyridine, rt, 3 h; (iii) THF–CH3OH–1.5 N NH3, rt, 3 h; (iv) CH2Cl2, CCl3CN, K2CO3, rt, 12 h,
71% (for four steps); (d) (i) 80% HOAC, reflux, 4 h; (ii) CH2Cl2–CH3OH satd with NH3, rt, 24 h, 85% (for two steps); (e) CH2Cl2–CH3OH sat. with
NH3, rt, 24 h, 90%.

G. Zhang et al. / Carbohydrate Research 340 (2005) 597–602
599
BzO
O
BzO
BzO
O
OBz
O
OAc
+
12
AcO
O
a
OC12H25
O
AcO
HO
OAc
OAc
15
BzO
BzO
BzO
O
BzO
BzO
O
BzO
BzO
O
O
AcO
O
AcO
OBz
OBz
OC12H25
AcO
O
O
e
O
AcO
OAc
6
O
O
OAc
O
BzO
BzO
OAc
OBz
16
BzO
BzO
O
BzO
BzO
O
OAc
OBz
O
O
13 or 15
No coupling product
a
O
BzO
BzO
OAc
OCNHCCl3
OBz
17
Scheme 1 (continued)
followed by selective 5,6-O-deacetonation, afforded 2,3,4,6-
tetra-O-benzoyl-b-D-glucopyranosyl-(1!3)-1,2-O-isoprop-
ylidene-a-D-galactofuranose (10) in a high yield (81%
over two steps). Condensation of b-(1!3)-linked disac-
charide 10 with 8 catalyzed by TMSOTf regio- and
stereoselectively gave 2,3,4,6-tetra-O-benzoyl-b-D-gluco-
pyranosyl-(1!3)-[2,3,4,6-tetra-O-benzoyl-b-D-glucopyr-
anosyl-(1!6)]-1,2-O-isopropylidene-a-D-galactofuranose
(11) in excellent yield (90%). Removal of the 1,2-O-iso-
propylidene group of 11 in 80% HOAc, followed by
acetylation with acetic anhydride in pyridine, selective
1-O-deacetylation with PhCH2NH2 in THF, and subse-
quent treatment with trichloroacetonitrile in the pres-
ence of K2CO3, afforded the 2,3,4,6-tetra-O-benzoyl-b-
D-glucopyranosyl-(1!3)-[2,3,4,6-tetra-O-benzoyl-b-D-
glucopyranosyl-(1!6)]-2,4-di-O-acetyl-a-D-galactopyr-
anosyl trichloroacetimidate (12) in good yield (71% over
four steps).
a-linked hexasaccharides, 2,3,4,6-tetra-O-benzoyl-b-D-
glucopyranosyl-(1!3)-[2,3,4,6-tetra-O-benzoyl-b-D-gluco-
pyranosyl-(1!6)]-2,4-di-O-acetyl-a-D-galactopyranosyl-
(1!3)-2,4,6-tri-O-acetyl-b-D-glucopyranosyl-(1!3)-[2,3,
4,6-tetra-O-benzoyl-b-D-glucopyranosyl-(1!6)]-5-O-acet-
yl-1,2-O-isopropylidene-a-D-glucofuranose (14) and lau-
ryl 2,3,4,6-tetra-O-benzoyl-b-D-glucopyranosyl-(1!3)-[2,3,
4,6-tetra-O-benzoyl-b-D-glucopyranosyl-(1!6)]-2,4-di-
O-acetyl-a-D-galactopyranosyl-(1!3)-2,4,6-tri-O-acet-
yl-b-D-glucopyranosyl-(1!3)-[2,3,4,6-tetra-O-benzoyl-b-
D-glucopyranosyl-(1!6)]-2,5-di-O-acetyl-a-D-glucopyr-
anoside (16) in low yields. The structures of 14 and
16 were unambiguously confirmed by 13C NMR data.
The 13C NMR spectra of 14 showed that characteristic
signals at d 95.56 with JC-1–H-1 175 Hz for a-C-1 of Galp,
and correspondingly the 13C NMR spectrum of 16
showed a signal (d 93.93 ppm) in the anomeric region,
which was in accordance with the a-configuration at
C-1. Deprotection of a-linked hexasaccharides 14 and
16 gave the target compounds 5 and 6, respectively.
In order to obtain more analogues, coupling of trisac-
charide glycosyl donor 1712 with 13 or 15 was carried
Coupling of the trisaccharide glycosyl donor 12 with
either trisaccharide glycosyl acceptor 136 or 15,6 cata-
lyzed by TMSOTf in CH2Cl2, didnÕt afford the expected
b-linked hexasaccharides, but stereoselectively gave the

600
G. Zhang et al. / Carbohydrate Research 340 (2005) 597–602
out. But we found that no expected coupling product
was obtained, and only the decomposed byproducts of
the donor were detected. A similar result also occurred
in our previous work.13 These results indicate that glyco-
sidic bond formation is strongly dependent on the prop-
erties of both the glycosyl donor and acceptor.14 Now in
our laboratory, a number of derivatives of (1!6)
branched (1!3)-linked glucohexaoses are in prepara-
tion, and interesting results about the structure–activity
relationship of the newly discovered biologically active
oligosaccharides will be reported in the due course.
4.19–4.16 (m, 1H, H-5), 4.08 (dd, 1H, J 4.9 Hz, H-40),
3.88 (m, 1H, H-5), 3.68 (m, 2H, 2H-60), 1.47 (s, 3H,
C(CH3)), 1.25 (s, 3H, C(CH3)). Anal. Calcd for
C43H42O15: C, 64.66; H, 5.30. Found: C, 64.79; H, 5.25.
3.3. 2,3,4,6-Tetra-O-benzoyl-b-D-glucopyranosyl-(1!3)-
[2,3,4,6-tetra-O-benzoyl-b-D-glucopyranosyl-(1!6)]-1,2-
O-isopropylidene-a-D-galactofuranose (11)
To a stirred solution of 10 (8.0 g, 0.010 mol) and 8
(8.0 g, 0.011 mol) in dry CH2Cl2 (400 mL) was added
TMSOTf (40 lL) at room temperature. After 3 h,
Et3N was added to the solution to quench the reaction.
The solution was concentrated, and the residue was sub-
jected to column chromatography with 2:1 petroleum
ether–EtOAc as the eluent to give the trisaccharide 11
(12.4 g, 90%): [a]D +13.3 (c 1.0, CHCl3); 1H NMR
(400 MHz, CDCl3): d 8.15–7.18 (m, 40H, 8BzH), 5.86
(t, 1H, J 9.7 Hz, H-4), 5.81 (t, 1H, J 9.7 Hz, H-4), 5.63
(t, 1H, J 9.7 Hz, H-3), 5.56 (t, 1H, J 9.7 Hz, H-3), 5.62
(dd, 1H, J 9.7 Hz, H-2), 5.53–5.45 (m, 2H, H-10, H-2),
5.35 (dd, 1H, J 7.9 Hz, J 9.7 Hz, H-2), 4.90 (d, 1H, J
7.9 Hz, H-1), 4.89 (d, 1H, J 7.9 Hz, H-1), 4.66 (dd,
1H, J 3.4 Hz, J 12.3 Hz, H-6), 4.58 (dd, 1H, J 4.9 Hz,
J 12.2 Hz, H-6), 4.40 (dd, 1H, J 3.4 Hz, J 12.2 Hz, H-
6), 4.34–4.30 (m, 2H, H-6, H-30), 4.22 (d, 1H, J
4.2 Hz, H-20), 4.11–4.07 (m, 2H, 2H-5), 3.91–3.88 (m,
2H, H-50, H-6a0), 3.65 (dd, 1H, J 6.0, 11.7 Hz, H-6b0),
3. Experimental
3.1. General methods
Optical rotations were determined at 25 ꢁC with a digital
polarimeter. The NMR spectra were recorded with a
Bruker ARX 400 spectrometer (400 MHz for 1H,
100 MHz for 13C) for solutions in CDCl3 or D2O as
indicated. Mass spectra were recorded on an Autospec
mass spectrometer using the ESI technique to introduce
the sample. Elemental analyses were done on an elemen-
tal analyzer, model 1108 EA. Thin-layer chromatogra-
phy (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 chromato-
graphy was conducted on a column (10 · 240 mm, or
18 · 300 mm, or 35 · 400 mm) of silica gel (100–200
mesh) with EtOAc–petroleum ether bp 60–90 ꢁC as
eluent. Solutions were concentrated at <60 ꢁC under
reduced pressure. Dry solvents were distilled over
CaH2 and stored over molecular sieves.
1.36, 1.30 (2s, 6H, 2 CCH3). Anal. Calcd for
C77H68O24: C, 67.15; H, 4.98. Found: C, 67.29; H, 5.02.
3.4. 2,3,4,6-Tetra-O-benzoyl-b-D-glucopyranosyl-(1!3)-
[2,3,4,6-tetra-O-benzoyl-b-D-glucopyranosyl-(1!6)]-2,4-
di-O-acetyl-a-D-galactopyranosyl trichloroacetimidate
(12)
3.2. 2,3,4,6-Tetra-O-benzoyl-b-D-glucopyranosyl-(1!3)-
1,2-O-isopropylidene-a-D-galactofuranose (10)
Compound 11 (10 g, 7.3 mmol) was added to 80% aq
HOAc (50 mL), and the mixture was heated under reflux
for 5 h. Then the mixture was concentrated, and the resi-
due was acetylated with AC2O (50 mL) in pyridine
(56 mL) for 3 h at rt. The resultant trisaccharide was dis-
solved in a 1.5 N NH3 solution of 3:1 THF–CH3OH
(200 mL), and the solution was stirred at rt for 3 h.
The solution was concentrated, and the residue was dis-
solved in CH2Cl2 (400 mL). To the solution were added
K2CO3 (20 g), CCl3CN (3.2 mL), and the mixture was
stirred at rt for 12 h. Filtering the mixture, the filtration
and washings were concentrated, and the residue was
subjected to column chromatography (2:1 petroleum
ether–EtOAc) giving the trisaccharide donor 12 (8.1 g,
71% for four steps): [a]D +23.6 (c 1.0, CHCl3); 1H
NMR (400 MHz, CDCl3): d 8.22 (s, 1H, NH), 7.90–
7.26 (m, 40H, 8BzH), 6.29 (d, 1H, J 3.6 Hz, H-10),
5.88–5.80 (m, 2H, 2H-4), 5.67–5.60 (m, 3H, 2H-3, H-
40), 5.49–5.43 (m, 2H, 2H-2), 5.11 (dd, 1H, J 3.6,
10.4 Hz, H-20), 4.94 (dd, 1H, J 7.9 Hz, H-1), 4.93 (dd,
To a stirred solution of 1,2:5,6-di-O-isopropylidene-a-D-
galactofuranose (7) (10 g, 0.038 mol) and 2,3,4,6-tetra-
O-benzoyl-a-D-glucopyranosyl trichloroacetimidate (8)
(26 g, 0.035 mol) in dry CH2Cl2 (600 mL) was added
TMSOTf (70 lL) at room temperature. After 3 h,
Et3N was added to the solution to quench the reaction.
The solution was concentrated, and the resulting residue
was directly dissolved in 90% aq HOAc (500 mL). The
mixture was kept at 40 ꢁC for 24 h, and then concen-
trated to a residue under reduced pressure. The resulting
residue was subjected to a short silica-gel column (3:1
petroleum ether–EtOAc) to give compound 10 (22.6 g,
81% for two steps): [a]D +18.5 (c 2.5, CHCl3). 1H
NMR (400 MHz, CDCl3): d 8.07–7.26 (m, 20H,
4BzH), 5.90 (t, 1H, J 9.7 Hz, H-3), 5.71–5.66 (m, 2H,
H-10, H-4), 5.49 (dd, 1H, J 7.9 Hz, 9.7 Hz, H-2), 5.03
(d, 1H, J 7.9 Hz, H-1), 4.81 (dd, 1H, J 3.7 Hz, J
11.9 Hz, H-6a), 4.45–4.40 (m, 3H, H-20, H-30, H-6b),

G. Zhang et al. / Carbohydrate Research 340 (2005) 597–602
601
1H, J 7.9 Hz, H-1), 4.66–4.58 (m, 2H, 2H-6), 4.50–4.44
(m, 2H, H-6, H-50), 4.15–4.13 (m, 4H, H-30, 2H-5, H-
6a0), 3.92 (dd, 1H, J 2.8 Hz, J 11.3 Hz, H-6), 3.64 (dd,
1H, J 6.0, 11.7 Hz, H-6b0), 2.05 (s, 3H, CH3CO), 1.58
(s, 3H, CH3CO). Anal. Calcd for C80H68Cl3NO26: C,
61.37; H, 4.38. Found: C, 61.53; H, 4.41.
165.03, 165.02, 164.72 (12 PhCO), 101.67, 101.42,
101.21, 100.49, 100.37 (5 b-C-1), 93.93 (a-C-1). Anal.
Calcd for C146H148O50: C, 64.88; H, 5.52. Found: C,
64.56; H, 5.67.
3.7. b-D-Glucopyranosyl-(1!3)-[b-D-glucopyranosyl-(1!
6)]-a-D-galactopyranosyl-(1!3)-b-D-glucopyranosyl-(1!3)-
[b-D-glucopyranosyl-(1!3)-[b-D-glucopyranosyl-(1!6)]-
b-D-glucopyranose (5)
3.5. 2,3,4,6-Tetra-O-benzoyl-b-D-glucopyranosyl-(1!3)-
[2,3,4,6-tetra-O-benzoyl-b-D-glucopyranosyl-(1!6)]-2,4-
di-O-acetyl-a-D-galactopyranosyl-(1!3)-2,4,6-tri-O-acet-
yl-b-D-glucopyranosyl-(1!3)-[2,3,4,6-tetra-O-benzoyl-b-D-
glucopyranosyl-(1!3)-[2,3,4,6-tetra-O-benzoyl-b-D-gluco-
pyranosyl-(1!6)]-5-O-acetyl-1,2-O-isopropylidene-a-D-
glucofuranose (14)
Compound 14 (1.0 g, 0.40 mmol) was dissolved in 80%
aq HOAc (60 mL), and the mixture was heated under
reflux for 4 h. Concentration of the mixture, followed
by deacylation in a solution of CH2Cl2 (10 mL) and
CH3OH (90 mL) saturated with ammonia at rt for
24 h, gave 5 (333 mg, 85%): [a]D +5.7 (c 1.0, D2O);
1H NMR (400 MHz, CDCl3): d 4.65 (m, 2H, 2H-1),
4.52–4.45 (m, 4H, 4H-1). 13C NMR (100 MHz, D2O):
d 103.86, 102.92, 102.81, 102.74, 102.67 (5 b-C-1),
99.28 (1 a-C-1). Anal. Calcd for C36H62O31: C, 43.64;
H, 6.30. Found: C, 43.56; H, 6.65. MALDI-TOFMS:
Calcd for C36H62O31, 990.86 [M]. Found: 1013.92
(M+Na)+.
To a stirred solution of 12 (6.7 g, 4.3 mmol) and 13
(4.5 g, 4.0 mmol) in dry CH2Cl2 (80 mL) was added
TMSOTf (40 lL) at rt. After 3 h, Et3N was added to
the solution to quench the reaction, and the solution
was concentrated to dryness. The residue was purified
by column chromatography (1.5:1 petroleum ether–
EtOAc) to afford the hexasaccharide 14 (3.0 g, 30%):
[a]D +23.6 (c 1.0, CHCl3); 1H NMR (400 MHz, CDCl3):
d 4.99 (d,1H, a-H-1, J 3.9 Hz), 4.96 (d, 1H, b-H-1, J
8.0 Hz), 4.92 (b-H-1, J 8.0 Hz), 4.82 (d, 1H, a-H-1, J
3.7 Hz). 13C NMR (100 MHz, CDCl3) d 171.45,
171.36, 170.20, 170.03, 170.03, 170.02 (6 COCH3),
167.01, 167.01, 166.87, 166.67, 166.65, 166.40, 166.15,
165.99, 165.97, 165.94, 165.78, 165.78 (12 COPh),
112.9 (C(CH3)2, 105.78 (JC-1-H-1 181 Hz, a-C-1), 101.85
(JC-1-H-1 164 Hz, b-C-1), 100.60 (JC-1-H-1 165 Hz, b-C-
1), 100.59 (JC-1-H-1 165 Hz, b-C-1), 98.75 (JC-1-H-1
158 Hz, b-C-1), 95.56 (JC-1-H-1 175 Hz, a-C-1). Anal.
Calcd for C135H126O49: C, 64.03; H, 5.01. Found: C,
64.43; H, 4.97.
3.8. Lauryl b-D-glucopyranosyl-(1!3)-[b-D-glucopyrano-
syl-(1!6)]-a-D-galactopyranosyl-(1!3)-b-D-glucopyrano-
syl-(1!3)-[b-D-glucopyranosyl-(1!6)]-b-D-glucopyran-
ose (6)
Compound 16 (1.0 g, 0.37 mmol) was dissolved in an
ammonia-saturated solution of 1:9 CH2Cl2–MeOH
(100 mL) at rt. After 24 h, the mixture was concentrated
to about 10 mL, and then CH2Cl2 (100 mL) was added.
The mixture was filtered and washed with CH2Cl2
(4 · 50 mL) to afford 6 (386 mg, 90%) as a white solid:
1
[a]D ꢀ18.6 (c 1.0, D2O); H NMR (400 MHz, CDCl3):
3.6. Lauryl 2,3,4,6-tetra-O-benzoyl-b-D-glucopyranosyl-(1!
3)-[2,3,4,6-tetra-O-benzoyl-b-D-glucopyranosyl-(1!6)]-2,
4-di-O-acetyl-a-D-galactopyranosyl-(1!3)-2,4,6-tri-O-
acetyl-b-D-glucopyranosyl-(1!3)-[2,3,4,6-tetra-O-benzo-
yl-b-D-glucopyranosyl-(1!6)]-2,5-di-O-acetyl-a-D-gluco-
pyranoside (16)
d 4.56 (d, 1H, J 4.1 Hz, a-H-1), 4.39–4.20 (m, 5H, 5H-
1), 1.53–1.19 (m, 23H, CH2C11H23). 13C NMR
(100 MHz, D2O): d 103.91, 103.11, 102.80, 102.69,
102.26 (5 b-C-1), 99.28 (1 a-C-1). Anal. Calcd for
C48H86O31: C, 49.74; H, 7.48. Found: C, 49.65; H,
7.60. MALDI-TOFMS: Calcd for C48H86O31, 1159.18
[M]. Found: 1182.30 (M+Na)+.
To a stirred solution of 12 (4.5 g, 2.9 mmol) and 15
(3.5 g, 2.7 mmol) in dry CH2Cl2 (80 mL) was added
TMSOTf (40 lL) at rt. After 3 h, Et3N was added to
the solution to quench the reaction, and the solution
was concentrated to dryness. The residue was purified
by column chromatography (1.5:1 petroleum ether–
EtOAc) to afford the hexasaccharide 16 (1.8 g, 25%):
[a]D +23.6 (c 1.0, CHCl3); 1H NMR (400 MHz, CDCl3):
d 4.97 (d, 1H, J 9.7 Hz, b-H-1), 4.92 (d, 1 H, J 9.5 Hz, b-
H-1), 4.86 (d, 1H, J 3.6 Hz, a-H-1). 13C NMR
(100 MHz, CDCl3): d 170.73, 170.43, 169.98, 169.87,
169.48, 169.28, 168.72 (7 CH3CO), 166.05, 165.94,
165.66, 165.60, 165.51, 165.47, 165.14, 165.13, 165.06,
Acknowledgements
This work was supported by the National Key Project
for Basic Research (2003CB114400), the Beijing Natural
Science Foundation (6021004) and The Ministry of
Science and Technology (2001AA246014).
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