Synthesis of a tetrasaccharide representing a minimal epitope of an arabinogalactan

Article abstract of DOI:10.1016/S0008-6215(99)00252-9

The hydrophobic alkyl chain-containing tetrasaccharide, dodecyl β-D- galactopyranosyl-(1→6)-β-D-galactopyranosyl-(1→6)-[α-L-arabinofuranosyl- (1→2)]-β-D-galactopyranoside, was synthesized efficiently using a convergent strategy. In coupling reactions, protected trichloroacetimidates proved to be better donors than their corresponding bromides in the preparation of the dodecyl disaccharide and trisaccharide. Zemplen deacylation provided the target tetramer in good overall yield. (C) 2000 Elsevier Science Ltd.

Full text of DOI:10.1016/S0008-6215(99)00252-9

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Carbohydrate Research 323 (2000) 28–35
Synthesis of a tetrasaccharide representing a minimal
epitope of an arabinogalactan
Yuguo Du, Qingfeng Pan, Fanzuo Kong *
Research Center for Eco-En6ironmental Sciences, Academia Sinica, PO Box 2871, Beijing 100085, PR China
Received 6 July 1999; accepted 6 September 1999
Abstract
The hydrophobic alkyl chain-containing tetrasaccharide, dodecyl b-
D
-galactopyranosyl-(1“6)-b-
D-galactopyra-
nosyl-(1“6)-[a- -arabinofuranosyl-(1“2)]-b- -galactopyranoside, was synthesized efficiently using a convergent
L
D
strategy. In coupling reactions, protected trichloroacetimidates proved to be better donors than their corresponding
bromides in the preparation of the dodecyl disaccharide and trisaccharide. Zemple´n deacylation provided the target
tetramer in good overall yield. © 2000 Elsevier Science Ltd. All rights reserved.
Keywords: Carbohydrate; Arabinogalactan; Regioselective reaction; Antigen
1. Introduction
type of cell-wall polysaccharide consists of a
b-(1“6)-linked galactan containing at least
Arabinogalactan-proteins (AGPs) are an
important class of proteoglycans/glycopro-
teins widely distributed in plant tissues and
exudates. Their precise biological functions in
plants remain unknown, but using a panel of
monoclonal antibodies, it has been demon-
strated that the presence of certain AGP epi-
topes is closely related to cell development in
plant morphogenetic processes [1,2]. Arabino-
galactan AG-II, extracted from Chinese herbs,
the roots of Angelica acutiloba and Bupleurum
falcatum, is a well-known component of Chi-
nese herbal medicine for the treatment of gy-
necological diseases and arthritis [3].
three
D
-galactopyranosyl residues functional-
ized at one hydroxyl group with an a-linked
L-arabinofuranosyl unit. Although the struc-
ture and activity studies of AGIIb-1 show the
importance of arabinofuranose side-chains in
potential pharmacological activities [3], we do
not yet have complete structural knowledge of
these AGPs. Besides, it is very difficult to
obtain arabinose-containing oligosaccharides
of known structure for biological studies from
natural sources. We present here the synthesis
of a well-defined dodecylated arabinogalactan
tetrasaccharide for use in antibody screening,
immunogen development and inhibitor con-
struction [6].
There is no unambiguous report concerning
the detailed composition of the arabinogalac-
tan [4]. Albersheim and co-workers [5] demon-
strated that the immunogenic region in this
2. Results and discussion
* Corresponding author. Tel.: +86-10-6293-6613(0); fax:
+86-10-6292-3563.
E-mail address: fzkong@mail.rcees.ac.cn (F. Kong)
2,3,4,6-Tetra-O-acetyl-b-
D
-galactopyran-
osyl-(1“6)-1,2:3,4-di-O-isopropylidene-a-
D
-
0008-6215/00/$ - see front matter © 2000 Elsevier Science Ltd. All rights reserved.
PII: S0008-6215(99)00252-9

Y. Du et al. / Carbohydrate Research 323 (2000) 28–35
29
galactopyranose (3) was prepared from 2,3,-
4,6-tetra-O-acetyl-a- -galactopyranosyl bro-
mide (1) and 1,2:3,4-di-O-isopropylidene-a-
-galactopyranose (2) using modified
Koenigs–Knorr reaction [7] (see Scheme 1).
Compound 3 was deacetalated with 90% tri-
fluroacetic acid (TFA), followed by acetyla-
tion with acetic anhydride in pyridine (“4a).
Regioselective deacetylation at the anomeric
carbon with benzylamine (“4b) [8], and acti-
vation with trichloroacetonitrile using 1,8-di-
azabicyclo[5.4.0]undec-7-ene(1,5-5) (DBU) as
a catalyst, furnished the disaccharide donor
D
D
a
2,3,4,6-tetra-O-acetyl-b-
(1“6)-2,3,4-tri-O-acetyl-a-
osyl 2,2,2-trichloroacetimidate (4c). At the
D
-galactopyranosyl-
D
-galactopyran-
Scheme 1.

30
Y. Du et al. / Carbohydrate Research 323 (2000) 28–35
trasaccharide dodecyl 2,3,4,6-tetra-O-acetyl-
b - - galactopyranosyl - (1“6) - 2,3,4 - tri - O-
acetyl - b - - galactopyranosyl(1“6) - [2,3,5-
- arabinofuranosyl(1“2)]-
same time, dodecyl 2,3,4,6-tetra-O-acetyl-b- -
D
D
galactopyranoside (5) was prepared by the
classic Koenigs–Knorr reaction of 1 and do-
decyl alcohol with promotion by silver oxide
[9]. Zemple´n deacetylation of 5 (“6), fol-
lowed by regioselective O-isopropylidenation
with 2,2-dimethoxypropane and p-toluenesul-
fonic acid, gave dodecyl 3,4-O-isopropylidene-
D
tri-O-benzoyl - a -
3,4-O-iso-propylidene-b-
L
D
-galactopyranoside
(13) in 74% yield.
In order to improve the efficiency of the
synthesis, a convergent strategy was used.
Thus, acceptor 8 was first glycosylated with 9b
in the presence of Me3SiOTf, affording dode-
b- -galactopyranoside (7) in good yield (80%
D
from 5). Selective protection of the primary
alcohol of 7 with tert-butylchlorodiphenylsi-
lane in triethylamine gave dodecyl 6-O-tert-
cyl 2,3,5-tri-O-benzoyl-a-
(1“2) - 6 - O - tert - butyldiphenylsilyl - 3,4 - O-
- galactopyranoside (10),
L
-arabinofuranosyl-
butyldiphenylsilyl-3,4-O-isopropylidene-b-
D
-
isopropylidene - b -
D
galactopyranoside (8). It is worth noting that
the glycosylation between acceptor 8 and
which was desilylated with tetrabutylammo-
nium fluoride (TBAF) in THF furnishing do-
2,3,5-tri-O-benzoyl-a-
L
-arabinofuranosyl bro-
decyl 2,3,5-tri-O-benzoyl-a-
L
-arabinofuran-
-galacto-
mide (9a) [10] with silver trifluoromethanesul-
fonate as the promotor was not satisfactory
due to migration of dodecyl group from ac-
ceptor 8 to donor 9a. Dodecyl 2,3,5-tri-O-ben-
osyl-(1“2)-3,4-O-isopropylidene-b-
D
pyranoside (11). Coupling of the disaccharide
donor 4c with the acceptor 11 in the presence
of Me3SiOTf in anhydrous CH2Cl2 generated
tetrasaccharide 13 in high yield (89%). Com-
pound 13 was treated with 90% TFA, then
acetylated with acetic anhydride in pyridine
(“14) and fully deprotected by Zemple´n dea-
cylation, giving the target compound dodecyl
zoyl- -arabinofuranoside was produced as a
L
mixture in about 40% yield with the a isomer
predominant. Alkyl migration did not appear
to occur when octyl glucopyranoside was gly-
cosylated with tetra-O-acetyl-a- -glucopyr-
D
anosyl bromide under the same reaction
conditions [11]. Since 9a did not work well in
its coupling with 8, it was converted to 2,3,5-
b-
D
-galactopyranosyl-(1“6)-b-
D
-galactopyr-
anosyl-(1“6)-[a-
L
-arabinofuranosyl-(1“2)]-
b- -galactopyranoside (15) in a total yield of
D
tri-O-benzoyl-a- -arabinofuranosyl 2,2,2-tri-
L
70% (from 13).
chloroacetimidate (9b) by debromination with
silver carbonate in 5:1 acetone–water, fol-
lowed by Schmidt activation [12] in a total
yield of 79% (two steps).
3. Experimental
General methods.—Optical rotations were
determined at 25 °C with a Perkin–Elmer
model 241MC automatic polarimeter. Melting
points were determined with a ‘Mel-Temp’
An attempt at regioselective glycosylation
of 7 with 4d as the donor using the orthoester
formation–rearrangement method [13] was
also disappointing due to dodecyl migration
and the poor regioselectivity between 6-OH
and 2-OH of the galactose moiety. While re-
gioselective glycosylation of 7 with 4c as the
donor in CH2Cl2 at −42 °C using Me3SiOTf
as the catalyst gave predominantly dodecyl
apparatus. H NMR, 13C NMR and H–1H,
1H–13C COSY spectra were recorded with
Bruker ARX 400 spectrometers for solutions
in CDCl3, MeOD and D2O. Chemical shifts
are given in ppm downfield from internal
Me4Si. Mass spectra were recorded with a VG
PLATFORM mass spectrometer using the
ESI technique to introduce the sample. 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 chromatogra-
phy was conducted by elution of a column
(16×240 mm, 18×300 mm, 35×400 mm) of
1
1
2,3,4,6-tetra-O-acetyl-b-
D
-galactopyranosyl-
-galactopyran-
-galacto-
(1“6)-2,3,4-tri-O-acetyl-b-
D
osyl-(1“6)-3,4-O-isopropylidene-b-
pyranoside (12, 59%), together with its 2-
linked regioisomer, dodecyl 2,3,4,6 - tetra - O -
D
acetyl-b-
O-acetyl-b-
isopropylidene-b-
Further coupling of 12 with 9b furnished te-
D
-galactopyranosyl-(1“6)-2,3,4-tri-
-galactopyranosyl-(1“2)-3,4-O-
-galactopyranoside (31%).
D
D

=Y. Du et al. / Carbohydrate Research 323 (2000) 28–35
31
mL, 31 mmol) under cooling with an ice-water
bath. The soln was stirred at rt for 10 h, then
poured into cold water and extracted with
CH2Cl2. The organic phase was washed with
5% HCl (2×100 mL) and water (100 mL),
then dried over Na2SO4 and concd. Column
chromatography (1:1 petroleum ether–
EtOAc) of the residue gave 4b as a syrup (1.6
g, 85%). To a soln of 4b (2.1 g, 3.3 mmol) in
anhyd CH2Cl2 (40 mL) was added
trichloroacetonitrile (3.0 mL, 30 mmol) and
DBU (0.45 mL, 3.0 mmol), and the mixture
was stirred at rt for 2 h. TLC (2:1 petroleum
ether–EtOAc) indicated that the reaction was
complete. The mixture was concd and purified
on a silica gel column using 2:1 petroleum
ether–EtOAc as eluent to give 4c as a syrup
silica gel (100–200 mesh) with EtOAc–
petroleum ether (bp 60–90 °C) as the eluent.
Solutions were concd at B60 °C under dimin-
ished pressure.
Preparation of 2,3,4,6-tetra-O-acetyl-i-
galactopyranosyl-(1“6)-1,2:3,4-di-O-isopro-
pylidene-h-
D
-
D
-galactopyranose (3).—To a soln
of 1 (4.5 g, 11 mmol) and 2 (2.4 g, 10 mmol)
in anhyd CH2Cl2 (80 mL) was added silver
,
triflate (2.9 g, 11 mmol) in the presence of 4 A
molecular sieves under a N2 atmosphere at
−15 °C. The mixture was stirred in a dark
room at room temperature (rt) for 2 h, neu-
tralized with Et3N and filtered, and then the
filtrate was concd. Purification of the product
by column chromatography (3:1 petroleum
ether–EtOAc) gave crystalline 3 (4.86 g, 81%);
mp 97–99 °C. [lit. [14]: 101–102 °C]; [h]2D5−
1
(2.06 g, 80%); [h]2D5−34° (c 1.0, CHCl3); H
1
45° (c 1.0, CHCl3); H NMR (CDCl3): l 1.32
NMR (CDCl3): l 1.97, 2.01, 2.03, 2.03, 2.06,
2.15, 2.17 (7 s, 21 H, 7 CH3CO), 3.71 (dd, 1
H, J5,6a 6.9, J6a,6b 10.9 Hz, H-6a), 3.80 (dd, 1
H, J5,6b 5.2 Hz, H-6b), 3.87–3.90 (m, 1 H,
H-5). 4.08–4.17 (m, 2 H, H-6%a, H-6%b), 4.37–
4.40 (m, 1 H, H-5%), 4.50 (d, 1 H, J1%,2% 7.9 Hz,
H-1%), 4.97 (dd, 1 H, J1,2 3.4, J2,3 10.4 Hz,
H-2), 5.13 (dd, 1 H, J2%,3% 10.4 Hz, H-2%), 5.34
(dd, 1 H, J3,4 3.5 Hz, H-4), 5.37 (dd, 1 H, J4,5
0.8 Hz, H-4), 5.41 (dd, 1 H, J3%,4% 3.1 Hz, H-3%),
5.54 (dd, 1 H, J4%,5% 1.1 Hz, H-4%), 6.58 (d, 1 H,
H-1), 8.65 (s,1 H, NH). Anal. Calcd for
C28H36Cl3NO18: C, 43.05; H, 4.61. Found: C,
43.11; H, 4.66.
(s, 6 H, 2 CH3), 1.45, 1.51 (2 s, 6 H, 2 CH3),
1.98, 2.05, 2.09, 2.14 (4 s, 12 H, 4 CH3CO),
3.68 (dd, 1 H, J5,6a 7.6, J6a,6b 11.4 Hz, H-6a),
3.90–3.95 (m, 2 H, H-5, H-6%a), 4.04 (dd, 1 H,
J5,6b 3.2 Hz, H-6b), 4.11–4.19 (m, 3 H, H-3,
H-5%, H-6%b), 4.29 (dd, 1 H, J1,2 5.0, J2,3 2.4
Hz, H-2), 4.58 (d, 1 H, J1%,2% 8.0 Hz, H-1%), 4.59
(dd, 1 H, J3,4 8.0, J4,5 2.1 Hz, H-4), 5.02 (dd,
J2%,3% 10.5, J3%,4% 3.4 Hz, H-3%), 5.22 (dd, 1 H,
H-2%), 5.39 (dd, 1 H, J4%,5% 0.7 Hz, H-4%), 5.00
(d, 1 H, H-1). 13C NMR (CDCl3, 100 MHz): l
20.0, 20.1, 20.1, 20.3, (4 CH3), 24.0, 24.7, 25.6,
25.7 (4 CH3CO), 60.9, 66.9, 67.5, 68.5, 69.1,
70.3, 70.4, 70.5, 70.6, 71.0 (C-2,3,4,5,6/C-
2%,3%,4%,5%.6%), 95.9 (C-1), 101.7 (C-1%), 108.3
((CH3)2C(OR)2), 109.1 ((CH3)2C(OR)2), 169.5,
169.7, 169.7, 169.8(4 CO).
Dodecyl 2,3,4,6-tetra-O-acetyl-i- -galac-
D
topyranoside (5).—To a soln of compound 1
(9.4 g, 22.9 mmol) and dodecyl alcohol (6 g,
32.3 mmol) in anhyd ether was added silver
,
2,3,4,6-Tetra-O-acetyl-i-
D
-galactopyran-
-galacto-
oxide (9 g, 38.8 mmol) and 4 A molecular
osyl-(1“6)-2,3,4-tri-O-acetyl-h-
D
sieves. The mixture was stirred in a dark room
at rt for 16 h, then filtered, and the filtrate was
concd to a syrup which was purified by
column chromatography using 3:1 petroleum
ether–EtOAc as the eluent, to give syrupy 5
pyranosyl 2,2,2-trichloroacetimidate (4c).—
Compound 3 (2.2 g, 3.7 mmol) was dissolved
in aq 90% trifluoroacetic acid (10 mL). The
soln was stirred at rt for 3 h and then co-evap-
orated with toluene to dryness under dimin-
ished pressure. The syrup thus generated was
fully acetylated with Ac2O (5 mL) in pyridine
(8 mL) for 4 h at rt, then co-evaporated with
toluene (2×20 mL) to dryness. Column chro-
matography using 2:1 petroleum ether–
EtOAc as the eluent gave syrupy 4a (2.0 g,
79%). To a soln of 4a (2.10 g, 3.1 mmol) in
THF (20 mL) was added benzylamine (3.4
1
(8.26 g, 70%); [h]2D5−14° (c 0.8, CHCl3); H
NMR (CDCl3): l 0.88 (t, 3 H, J 6.7 Hz, CH3),
1.26 (bs, 18 H, 9 CH2), 1.56–1.57 (m, 2 H,
CH2), 1.99, 2.04, 2.05, 2.15 (4 s, 12 H,
CH3CO), 3.44–3.50 (m, 1 H, one proton of
ꢀOCH2(CH2)10CH3), 3.86–3.92 (m, 2 H, H-5
and one proton of ꢀOCH2(CH2)10CH3), 4.10–
4.21 (m, 2 H, J5,6a 7.9, J5,6b 7.0, J6a,6b 11.2 Hz,
H-6a, H-6b), 4.45 (d, 1 H, J1,2 7.9 Hz, H-1),

32
Y. Du et al. / Carbohydrate Research 323 (2000) 28–35
(m, 2 H, CH2), 2.22–2.41 (bs, 1 H, OH),
3.43–3.49 (m, 1 H, one proton of OCH2R),
3.54 (t, 1 H, J1,2 =J2,3=7.8 Hz, H-2), 3.84–
3.90 (m, 2 H, H-5 and one proton of OCH2R),
3.93 (dd, 1 H, J5,6a 6.1, J6a,6b 9.8 Hz, H-6a),
3.99 (dd, 1 H, J5,6b 7.3 Hz, H-6b), 4.07 (dd, 1
H, J3,4 5.48 Hz, H-3), 4.14 (d, 1 H, H-1), 4.27
(dd, 1 H, J4,5 2.1 Hz, H-4), 7.37–7.72 (m, 10
H, 2 Ph). Anal. Calcd for C37H58O6Si: C,
70.93; H, 9.26. Found: C, 70.95; H, 9.27.
5.02 (dd, 1 H, J2,3 10.4, J3,4 3.4 Hz, H-3), 5.21
(dd, 1 H, H-2), 5.39 (d, 1 H, H-4). Anal.
Calcd for C26H44O10: C, 60.46; H, 8.53.
Found: C, 60.50; H, 8.51.
Dodecyl
3,4-O-isopropylidene-i- -galac-
D
topyranoside (7).—A soln of 5 (3.2 g, 6.2
mmol) in MeOH (25 mL) was treated with
NaOMe (3.0 mL, 0.5 M in MeOH) at rt for 6
h. The soln was neutralized with Dowex-50W
(H+) resin, then filtered, and the filtrate was
evaporated to give 6 as a syrup. Compound 6
(1.7 g, 4.9 mmol) was dissolved in acetone (10
mL), and 2,2-dimethoxypropane (3.0 mL, 25
mmol) and p-toluenesulfonic acid monohy-
drate (25 mg) was added. The mixture was
stirred at rt for 16 h, then neutralized with
Et3N (2.0 mL) and concd. Column chro-
matography (3:2 petroleum ether–EtOAc) of
the residue gave 7 as a syrup (3.4 g, 80%).
Compound 7 was converted into its acetylated
derivative, dodecyl 2,6-di-O-acetyl-3,4-O-iso-
2,3,5-Tri-O-benzoyl-h- -arabinofuranosyl
L
2,2,2-trichloroacetimidate (9b).—To a soln of
9a (800 mg, 1.64 mmol) in 1:1 acetone–water
(10 mL) was added silver carbonate (905 mg,
3.28 mmol). The reaction mixture was stirred
in a dark room at rt for 16 h, at the end of
which time TLC (3:1 petroleum ether–EtOAc)
indicated that the reaction was complete. The
reaction mixture was filtered, and the filtrate
was concd to dryness. The syrup thus ob-
tained was subjected to Schmidt activation
with trichloroacetonitrile (0.3 mL, 3.0 mmol)
and anhyd K2CO3 (1.09 g) in CH2Cl2 (5 mL)
for 8 h at rt. The mixture was filtered, and the
filtrate was concd. Purification of the residue
on column chromatography (3:1 petroleum
ether–EtOAc) gave 9b as a glassy solid (785
mg, 79%); [h]2D5 −24° (c 1.0, CHCl3); 1H NMR
(CDCl3): l 4.73–4.86 (m, 3 H, H-4,5a,5b),
5.68 (d, 1 H, J3,4 3.3 Hz, H-3), 5.81 (s, 1 H,
H-2), 6.67 (s, 1 H, H-1), 7.24–8.13 (m, 15 H,
3 PhCO), 8.73 (s, 1 H, NH). Anal. Calcd for
C28H22Cl3NO8: C, 55.42; H, 3.66. Found: C,
55.13; H, 3.99.
propylidene-b- -galactopyranoside showing
D
the following physical data: [h]2D5 +110° (c 0.2,
1
CHCl3); H NMR (CDCl3): l 0.88 (t, 3 H, J
6.7 Hz, CH3), 1.25 (bs, 18 H, 9 CH2), 1.34 (s,
3 H, CH3), 1.55 (bs, 5 H, CH3 and CH2), 2.09,
2.13 (2 s, 6 H, 2 CH3CO), 3.40–3.46 (m, 1 H,
one proton of OCH2(CH2)10CH3), 3.83–3.88
(m, 1 H, one proton of OCH2(CH2)10CH3),
3.98 (dt, 1 H, J4,5 1.8, J5,6 6.1 Hz, H-5),
4.15–4.20 (m, 2 H, H-3 and H-4), 4.31 (d, 1
H, J1,2 8.2 Hz, H-1), 4.36 (d, 2 H, 2 H-6), 4.96
(dd, 1 H, J2,3 6.9 Hz, H-2). Anal. Calcd for
C25H44O8: C, 63.56; H, 9.32. Found: C, 63.55;
H, 9.32.
Dodecyl
furanosyl-(1“2)-6-O-tert-butyldiphenylsilyl-
3,4 - O - isopropylidene - i - - galactopyranoside
2,3,5-tri-O-benzoyl-h- -arabino-
L
Dodecyl 3,4-di-O-isopropylidene-6-O-tert-
butyldiphenylsilyl - i -
D
- galactopyranoside
D
(8).—Compound 7 (2.0 g, 5.15 mmol) was
dissolved in CH2Cl2 (10 mL) and tert-
butyldiphenylsilyl chloride (1.7 g, 6.18 mmol),
Et3N (10 mL) and 4-dimethylaminopyridine
(30 mg) were added to the soln. The mixture
was stirred at rt for 16 h, then poured into
cold water, extracted with CH2Cl2 (2×30
mL), and the organic layer was dried over
Na2SO4 and concd. Column chromatography
(4:1 petroleum ether–EtOAc) of the residue
gave 8 as a syrup (2.94 g, 91%); [h]2D5+1° (c
0.9, CHCl3); 1H NMR (CDCl3): l 0.87 (t, 3 H,
CH3), 1.06 (s, 9 H, t-Bu), 1.21–1.31 (bs, 18 H,
9 CH2), 1.35, 1.51 (2 s, 6 H, 2 CH3), 1.56–1.62
(10).—To a mixture of 8 (760 mg, 1.19 mmol)
,
and 9b (788 mg, 1.3 mmol), 4 A molecular
sieves, and anhyd CH2Cl2 (15 mL) was added
Me3SiOTf (20 mL, 0.11 mmol) under a N2
atmosphere at −15 °C. The mixture was
stirred under these conditions for 1 h, at the
end of which time TLC (3:1 petroleum ether–
EtOAc) indicated that all starting material 9b
was consumed. The reaction mixture was neu-
tralized with Et3N, then filtered, and the
filtrate was concd. Purification of the product
by column chromatography (3:1 petroleum
ether–EtOAc) gave 10 as a syrup (1.13 g,
1
87%); [h]2D5+82° (c 1.0, CHCl3); H NMR

Y. Du et al. / Carbohydrate Research 323 (2000) 28–35
33
Column chromatography (1:1 petroleum
ether–EtOAc) of the residue gave 12 as a
syrup (91 mg, 59%); [h]2D5+18° (c 0.2, CHCl3);
12 was converted into its acetylated derivative,
(CDCl3): l 0.87 (t, 3 H, CH3), 1.06 (bs, 25 H,
8 CH2 and (CH3)3C), 1.08–1.25 (m, 4 H, 2
CH2), 1.29, 1.55 (2 s, 6 H, 2 CH3), 3.29–3.35
(m, 1 H one proton of OCH2R), 3.77–3.81
(m, 1 H, one proton of OCH2R), 3.83–3.90
(m, 2 H, H-2, H-5), 3.92–4.01 (m, 2 H, J5,6a
6.2, J5,6b 7.4, J6a,6b 9.9 Hz, H-6a, H-6b), 4.25–
4.30 (m, 3 H, J1,2 8.5 Hz, H-1, H-3, H-4), 4.71
(dd, 1 H, J4%,5%a 5.5, J5%a,5%b 12.3 Hz, H-5%a),
4.77–7.82 (m, 2 H, J4%,5%b 3.0 Hz, H-4%, H–5%b),
5.54 (d, 1 H, J3%,4% 4.5 Hz, H-3%), 5.64 (s, 1 H,
H-1%/H-2%), 5.72 (s, 1 H, H-2%/H-1%), 7.23–8.13
(m, 25 H, 5 Ph). Anal. Calcd for C63H78O13Si:
C, 70.65; H, 7.29. Found: C, 70.71; H, 7.23.
dodecyl 2,3,4,6-tetra-O-acetyl-b-
ranosyl-(1“6)-2,3,4-tri-O-acetyl-b-
pyranosyl-(1“6)-2-O-acetyl-3,4-O-isopro-
D
-galactopy-
D
-galacto-
pylidene-b- -galactopyranoside, showing the
D
following physical data: [h]2D5 +7° (c 0.5,
1
CHCl3); H NMR (CDCl3): l 0.88 (t, 3 H,
CH3), 1.25 (bs, 18 H, 9 CH2), 1.31 (s, 3 H,
CH3), 1.54 (s, 3 H, CH3), 1.55–1.61 (m, 2 H,
CH2), 1.97, 1.98, 2.03, 2.06, 2.07, 2.09, 2.15,
2.16 (8 s, 24 H, 8 CH3CO), 3.39–3.42 (m, 1 H,
one proton of OCH2), 3.78–3.94 (m, 7 H,
H-6a, H-6b, one proton of OCH2, H-6%a, H-
6%b, H-5, H-5%), 4.07–4.10 (m, 5 H, H-5%%, H-4,
H-3, H-6%%a, H-6%%b), 8.28 (d, 1 H, J1,2 8.3 Hz,
H-1), 4.55, 4.61 (2 d, 2 H, J 8.0 Hz, H-1%/H-
1%%), 4.91–5.00 (m, 3 H, H-2, H-3%, H-3%%),
5.52–5.23 (m, 2 H, J 8.0, 10.8 Hz, H-2%/H-2%%),
5.38 (d, 2 H, H-4%, H-4%%). Anal. Calcd for
C49H76O24: C, 56.11; H, 7.25. Found: C, 56.02;
H, 7.31.
Dodecyl
2,3,5-tri-O-benzoyl-h- -arabino-
L
furanosyl-(1“2)-3,4-O-isopropylidene-i-
D
-
galactopyranoside (11).—To a soln of 10 (1.1
g, 1.03 mmol) in THF (10 mL) was added
nBu4NF trihydrate (480 mg, 1.5 mmol). The
mixture was stirred at rt for 5 h, then poured
into cold water and extracted with EtOAc.
The organic phase was washed with satd
NaHCO3, then dried over Na2SO4 and concd.
Column chromatography (3:2 petroleum
ether–EtOAc) of the residue gave 11 as a
syrup (812 mg, 95%). [h]2D5+61° (c 1.1,
Dodecyl 2,3,4,6-tetra-O-acetyl-i-
topyranosyl-(1“6)-2,3,4-tri-O-acetyl-i-
galactopyranosyl-(1“6)-[2,3,5-tri-O-benzoyl-
h- -arabinofuranosyl-(1“2)]-3,4-O-isopropyl-
idene-i- -galactopyranoside (13).—Method
D
-galac-
D
-
1
CHCl3); H NMR (CDCl3): l 0.87 (t, 3 H,
CH3), 1.07–1.25 (m, 20 H, 10 CH2), 1.28, 1.54
(2 s, 6 H, 2 CH3), 2.99 (bs, 1 H, OH), 3.30–
3.34 (m, 1 H one proton of OCH2R), 3.77–
3.80 (m, 1 H, one proton of OCH2R),
3.82–3.89 (m, 2 H, H-2, H-5), 3.90–4.00 (m, 2
H, H-6a, 6b), 4.25–4.30 (m, 3 H, J1,2 8.7 Hz,
H-1, H-3, H-4), 4.71 (dd, 1 H, J4%,5%a 5.5, J5%a,5%b
12.6 Hz, H-5%a), 4.77–4.82 (m, 2 H, J4%,5%b 3.2
Hz, H-4%, H-5%b), 5.54 (d, 1 H, J3%,4% 4.2 Hz,
H-3%), 5.64 (s, 1 H, H-1%/H-2%), 5.72 (s, 1 H,
H-2%/H-1%), 7.23–8.13 (m, 25 H, 5 Ph). Anal.
Calcd for C47H60O13: C, 67.79; H, 7.21.
Found: C, 67.81; H, 7.27.
L
D
A. To a soln of 4c (190 mg, 0.24 mmol) and
11 (202 mg, 0.24 mmol) in anhyd CH2Cl2 (15
,
mL) was added activated 4 A molecular
sieves. The mixture was cooled to −42 °C,
then Me3SiOTf (10 mL, 0.055 mmol) was
added under N2 protection. The mixture was
stirred at rt for 1 h, neutralized with Et3N (0.2
mL), then concd. Column chromatography
(1:1 petroleum ether–EtOAc) of the residue
gave 13 as a syrup (321 mg, 91%). Method B.
The same procedure was used in the coupling
reaction of 9b (34 mg, 0.055 mmol) with 12
(50 mg, 0.05 mmol) to give 13 (53 mg, 74%);
Dodecyl 2,3,4,6-tetra-O-acetyl-i-
topyranosyl-(1“6)-2,3,4-tri-O-acetyl-i-
galactopyranosyl-(1“6)-3,4-O-isopropylidene-
i-
D
-galac-
D
-
1
[h]2D5−16° (c 0.2, CHCl3); H NMR (CDCl3):
D
-galactopyranoside (12).—To a soln of 4c
l 0.88 (t, 3 H, CH3), 1.07–1.33 (m, 18 H, 9
CH2), 1.23, 1.53 (2 s, 6 H, 2 CH3C), 1.97 (s, 6
H, 2 CH3CO), 2.01, 2.05, 2.07, 2.14, 2.15 (5 s,
15 H, 5 CH3CO), 3.33–3.38 (m, 1 H, one
proton of OCH2R), 3.80–3.93 (m, 8 H, H-
2,4,5,6a,6b,6%a,6%b and one proton of
OCH2R), 4.04–4.17 (m, 4 H, H-3, H-5%, H-5%%,
H-6%%a), 4.26–4.29 (m, 2 H, J1,2 8.8 Hz, H-1
(120 mg, 0.15 mmol) and 7 (60 mg, 0.15
mmol) in anhyd CH2Cl2 (15 mL) was added
,
activated 4 A molecular sieves. The mixture
was cooled to −42 °C, then Me3SiOTf (5.7
mL, 0.029 mmol) was added under N2 protec-
tion. The mixture was stirred at rt for 1 h,
neutralized with Et3N (0.2 mL), and concd.

34
Y. Du et al. / Carbohydrate Research 323 (2000) 28–35
5.00 (dd, 1 H, J3%%,4%% 3.4 Hz, H-3%%), 5.08 (dd, 1
H, J3,4 4.4 Hz, H-3), 5.12–5.16 (m, 2 H, H-2%
and H-2%%), 5.36–5.39 (m, 4 H, Hara-3, H-4%
and H-4%%, Hara-1/Hara-2), 5.16 (s, 1 H, Hara-2/
Hara-1), 5.59 (d, 1 H, H-4), 7.32–8.08 (m, 15
H, 3 Ph). Anal. Calcd for C74H94O32: C, 59.44;
H, 6.29. Found: C, 59.39; H, 6.27.
and H-6%%b), 4.54 (d, 1 H, J1%,2% 8.0 Hz, H-1%),
4.62 (d, 1 H, J1%%,2%% 8.0 Hz, H-1%%), 4.71 (dd, 1
H, J4,5a 5.5, J5a,5b 11.2 Hz, HAra-5a), 4.78–4.80
(m, 2 H, Hara-4, Hara-5b), 4.97 (dd, 2 H,
J2%,3%=J2%%,3%%=10.5, J3%,4%=J3%%,4%%=3.3 Hz, H-3%,
H-3%%), 5.18 (dd, 1 H, H-2%), 5.18 (dd, 1 H,
H-2%%), 5.37 (bs, 2 H, H-4% and H-4%%), 5.53 (d,
1 H, J3,4 4.6 Hz, Hara-3), 5.61, 5.67 (2 s, 2 H,
Hara-1 and Hara-2), 7.254–8.108 (m, 15 H, 3
Ph); 13C NMR (CDCl3, 100 MHz): l 14.1–
31.9 (CAlkyl), 61.2 (CAra-5), 63.8 (C-6%%), 66.1
(C-6%), 66.9 (C-6), 67.4 (C-5%%), 68.4 (C-4%), 68.9
(C-4%%), 69.1 (CH2O), 69.9 (C-5%), 70.8 (C-5),
70.9 (2 C, C-2%%, C-3%%), 72.0 (C-4), 74.9 (C-3),
78.1 (C-2), 79.4 (C-4), 81.5 (C-3), 81.7 (C-2),
100.6 (C-1%%), 101.3 (C-1%), 101.4 (C-1), 104.2
(CAra-1), 110.6 (acetal C), 128.3–133.5 (CAr),
165.4, 165.8, 166.2 (3 PhCO), 169.3, 169.4,
170.0, 170.04, 170.1, 170.2, 170.4 (7 CH3CO).
Anal. Calcd for C73H94O30: C, 60.41; H, 6.48.
Found: C, 60.51; H, 6.44.
Dodecyl i-
galactopyranosyl - (1“6) - [h -
osyl(1“2)]-i- -galactopyranoside
D
-galactopyranosyl-(1“6)-i-
- arabinofuran -
(15).—
D
-
L
D
Compound 14 (810 mg, 0.54 mmol) was
treated with NaOMe in MeOH (keep pH at 9)
at rt for 24 h, then neutralized with Dowex-
50W (H+) resin and concd. One portion of the
product (from about 230 mg of 14) was dis-
solved in 1:1 MeOH–water (10 mL) and
transferred into a dialysis tubing (with molec-
ular-weight cut-off 500). The soln was dia-
lyzed for 48 h and then concd under reduced
pressure to give a crude product 15 (44 mg,
35%). Another portion of the fully deacylated
product (from about 500 mg of 14) was
purified directly on Sephadex LH-20 column
chromatography using MeOH as the eluent to
afford 15 (214 mg, 80%); [h]2D5−6° (c 1.5, 5:1
Dodecyl 2,3,4,6-tetra-O-acetyl-i-
topyranosyl-(1“6)-2,3,4-tri-O-acetyl-i-
galactopyranosyl-(1“6)-[2,3,5-tri-O-benzoyl-
h- -arabinofuranosyl-(1“2)]-3,4-di-O-acetyl-
i- -galactopyranoside (14).—Compound 13
D-galac-
D
-
L
1
MeOH–H2O); H NMR (D2O, 400 MHz): l
D
0.8–1.4 (m, 23 H, alkyl), 3.30–3.40 (m, 2 H),
(950 mg, 0.66 mmol) was dissolved in aq 90%
TFA (8 mL), and the mixture was stirred at rt.
The reaction was monitored by TLC (3:2
petroleum ether–EtOAc) until all of the start-
ing material was consumed (about 40 min).
The mixture was diluted with toluene and then
concd to dryness. After acetylation of the
residue with Ac2O (1 mL) in pyridine (2 mL),
the soln was co-evaporated with toluene.
Purification of the product on column chro-
matography (2:3 petroleum ether–EtOAc)
gave pure 14 as a syrup (861 mg, 88%);
3.60–4.12 (m, 34 H), 4.20 (bs, 1 H, HAra-2),
4.31 (d, 1 H, J
8.0 Hz, H-1), 4.49 (d, 1 H,
1,2
J 7.4 Hz, H-1%/H-1%%), 4.54 (d, 1 H, J 7.6 Hz,
H-1%%/H-1%), 5.25 (bs, 1 H, HAra-1). 13C NMR
(MeOD:D2O, 4:1, 100 MHz): l 13.5–31.6 (11
C, OCH2(CH2)10CH3), 62.2 (C-6%%), 63.2 (CAra
-
5), 69.9, 69.8 (C-6, C-6%), 70.9, 71.6, 72.1, 74.1,
74.3, 74.4, 74.8, 74.9, 75.0, 76.4, 76.7, 77.0,
78.0, 80.0, 83.3, 86.8 (C-2,3,4,5, C-2%,3%,4%,5%,
C-2%%, 3%%, 4%%,5%%, CAra-2, CAra-3, CAra-4, CH2O),
104.2, 105.2, 105.8 (C-1, C-1%, C-1%%), 110.6
(CAra-1). ESMS Calcd for C35H64O20 (804).
Found ESIMS (+): 827.6 [M+Na]+; ESIMS
(−): 803.7 [M]−.
1
[h]2D5−23° (c 0.3, CHCl3); H NMR (CDCl3):
l 0.86 (t, 3 H, CH3), 1.07–1.54 (m, 20 H, 10
CH2), 1.96, 1.98, 1.99, 2.03, 2.04, 2.05, 2.11,
2.14, 2.15 (9 s, 27 H, 9 CH3CO), 3.32–3.35
(m, 1 H, one proton of OCH2R), 3.66–3.92
(m, 7 H, H-5, H-5%, H-6a, H-6b, H-6%a, H-6%b,
one proton of OCH2R), 4.08 (dd, 1 H, J1,2 7.8,
J2,3 10.5 Hz, H-2), 4.10–4.15 (m, 3 H, H-5%%,
H-6%%a, H-6%%b), 4.43 (d, 1 H, J1,2 7.8 Hz, H-1),
4.48, 4.50 (2 d, 2 H, J1%,2% 7.9, J1%%,2%% 8.0 Hz, H-1%
and H-1%%), 4.69–4.70 (dd, 1 H, J 4.6 and 11.4
Hz, Hara-5a), 4.80–4.85 (m, 2 H, Hara-4 and
Hara-5b), 4.95 (dd, 1 H, J3%,4% 3.2 Hz, H-3%),
Acknowledgements
This work was supported by The Chinese
Academy of Sciences (Project KJ952J1510)
and The National Natural Science Founda-
tion of China (Projects 29672049 and
29802009). Y.D. also acknowledges the sup-
port from SRF for ROCS, SEM.

Y. Du et al. / Carbohydrate Research 323 (2000) 28–35
35
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