Efficient synthesis of a heptasaccharide, the repeating unit of the O-chain lipopolysaccharide produced by Xanthomonas campestris strain 642

Article abstract of DOI:10.1016/S0008-6215(03)00080-6

α-L-Rhap-(1→3)-α-L-Rhap-(1→2)-α-L-Rhap- (1→3)-[β-D-Xylp-(1→2)-][β-D-Xylp-(1→4)-]α-L- Rhap-(1→3)-α-L-Rhap, the repeating unit of the O-chain lipopolysaccharide produced by Xanthomonas campestris strain 642 was synthesized as its methyl glycoside via 3-O-se

Full text of DOI:10.1016/S0008-6215(03)00080-6

Carbohydrate Research 338 (2003) 1023–1031
www.elsevier.com/locate/carres
Efficient synthesis of a heptasaccharide, the repeating unit of the
O-chain lipopolysaccharide produced by Xanthomonas campestris
strain 642
Jianjun Zhang, Jun Ning, Fanzuo Kong*
Research Center for Eco-En6ironmental Sciences, Academia Sinica, P.O. Box 2871, Beijing 100085, China
Received 17 December 2002; accepted 12 February 2003
Abstract
-Rhap-(1“3)-a-
a-
peating unit of the O-chain lipopolysaccharide produced by Xanthomonas campestris strain 642 was synthesized as its methyl
glycoside via 3-O-selective glycosylation of methyl a- -rhamnopyranosyl-(1“3)-2,4-di-O-benzoyl-a- -rhamnopyranoside (9) with
2,3,4-tri-O-benzoyl-a- -rhamnopyranosyl-(1“3)-2,4-di-O-benzoyl-a- -rhamnopyranosyl-(1“2)-3,4-di-O-benzoyl-a- -rhamno-
-xylopyranosyl trichloroacetimidate
L
L
-Rhap-(1“2)-a-
L
-Rhap-(1“3)-[b-
D
-Xylp-(1“2)-][b-
D
-Xylp-(1“4)-]a-
L
-Rhap-(1“3)-a-
L-Rhap, the re-
L
L
L
L
L
pyranosyl trichloroacetimidate (8), followed by dixylosylation with 2,3,4-tri-O-benzoyl-a,b-
(12) and subsequent deacylation. © 2003 Elsevier Science Ltd. All rights reserved.
D
Keywords: Oligosaccharide; Rhamnose; Xylose
1. Introduction
Synthesis of these compounds will need orthogonal
masking groups and multiple protection–deprotection
steps if a traditional stepwise method6,7 is used. Our
previous work described a highly regio- and stereoselec-
tive synthesis using glycosyl trichloroacetimidates as the
donors and partially protected sugars as the acceptors,
and a variety of branched rhamnans was obtained.8–11
Synthetic samples of new rhamnan structures would be
very valuable in research in plant pathology and in the
design of immunodiagnostic reagents. We present
Rhamnose-containing oligosaccharides are widely dis-
tributed in natural products,1–3 and they usually consist
of an a-(1“2)- and a-(1“3)-linked backbone with
xylose, glucose, ribose, or GlcNAc side chains. Xan-
thomonas campestris is a phytopathogenic bacterium
recognized to cause a serious disease in strawberries.4
Recently, a new O-polysaccharide chain has been iso-
lated and identified from the LPS fraction of the X.
campestris strain 642, whose repeating unit is a xylos-
ylated rhamnan heptasaccharide as shown below:5
herein
a
highly efficient synthesis of the title
heptasaccharide.
2. Results and discussion
As outlined in Scheme 1, condensation of 2,3,4-tri-O-
benzoyl-a- -rhamnopyranosyl trichloroacetimidate (1)
with unprotected allyl a- -rhamnopyranoside (2) selec-
* Corresponding
fax: +86-10-62923563
E-mail address: fzkong@mail.rcees.ac.cn (F. Kong).
author.
Tel.:
+86-10-62936613;
L
L
0008-6215/03/$ - see front matter © 2003 Elsevier Science Ltd. All rights reserved.
doi:10.1016/S0008-6215(03)00080-6

1024
J. Zhang et al. / Carbohydrate Research 338 (2003) 1023–1031
1
tively gave allyl 2,3,4-tri-O-benzoyl-a-
L
-rhamnopyran-
confirmed by benzoylation of 3 to give 4, and the H
NMR spectrum of 4 showed two newly emerged
downfield signals at l 5.51 (dd, J3,4=J4,5=9.8 Hz) for
H-4 and l 5.28 (dd, J1,2 1.4, J2,3 3.5) for H-2, respec-
tively, compared to 3. Deallylation with PdCl2, fol-
osyl-(1“3)-a-
L
-rhamnopyranoside (3)8 in satisfactory
yield (63.2%). Keeping the temperature below −20 °C
during the addition of TMSOTf was necessary in order
to avoid byproduct formation. The (1“3)-linkage was
Scheme 1. (a) TMSOTf, CH2Cl2; (b) BzCl–pyridine (dry); (c) PdCl2, 90% HOAc–NaOAc, rt, 12 h; then Cl3CN, DBU, CH2Cl2
8 h; (d) Ac2O–pyridine (dry); (e) satd NH3–MeOH, rt, 72 h.

J. Zhang et al. / Carbohydrate Research 338 (2003) 1023–1031
1025
lowed by trichloroacetimidation with CCl3CN in the
presence of DBU or K2CO3,12 gave the disaccharide
donor 5. Coupling of compound 5 with allyl 3,4-di-O-
tion of 20 with acetic anhydride in pyridine gave 21,
and the 1H NMR spectrum of 21 confirmed the regiose-
lectivity by showing characteristic peaks at l 4.85 (J2,3
2.9, J3,4 9.2 Hz) for H-3%, and 4.48 (J2,3 3.4, J3,4 9.8 Hz)
for H-3, respectively.
benzoyl-a-
-rhamnopyranoside (6)10 in the presence of
L
catalytic TMSOTf gave trisaccharide 7 in high yield
(88.2%), which could be activated by deallylation and
trichloroacetimidation to furnish the trisaccharide
Condensation of tetrasaccharide 20 with trisaccha-
ride donor 8 did not give the expected heptasaccharide,
but afforded only a byproduct and unreacted starting
materials. This indicated that the trisaccharide donor
was too big to get close to the 3%-OH that was severely
shielded by the two xylosyl residues at the 2%- and
4%-positions. However, when the tetrasaccharide 20 was
coupled with monosaccharide donor 22, pentasaccha-
ride 23 was obtained in 41.3% yield, revealing that a
smaller size of donor was allowed to react with 20,
albeit to a limited extent. However, subsequent selective
2¦-O-deacetylation of 23 in 2–3% CH3COCl–MeOH
did not work, even at elevated temperature (50 °C), and
only unchanged starting material was obtained. Here,
severe steric hindrance at the 2¦-OAc of the pentasac-
charide 23 rejected the deacetylation under normal
conditions. It seemed that the target heptasaccharide
was not readily obtained by any other methods, and
construction of the pentasaccharide backbone, followed
by attaching the side chains was the best choice.
In summary, a branched xylosylated rhamnan hep-
tasaccharide was synthesized in a highly regioselective
way with a simple procedure. Large-scale preparations
should be possible with this method.
donor 8. 3-O-Selective glycosylation of methyl a-
L
-
-
rhamnopyranosyl - (1“3) - 2,4 - di - O - benzoyl - a -
L
rhamnopyranoside (9)8 with the donor 8, promoted by
catalytic TMSOTf, gave pentasaccharide 10 in satisfac-
tory yield (57.3%). The structure of 10 was confirmed
by acetylation to give methyl 2,3,4-tri-O-benzoyl-
a-
rhamnopyranosyl - (1“2) - 3,4 - di - O - benzoyl - a -
rhamnopyranosyl-(1“3)-2,4-di-O-acetyl-a-
pyranosyl-(1“3)-2,4-di-O-benzoyl-a- -rhamnopyran-
oside (11). The H NMR spectrum of 11 showed newly
emerged downfield signals at l 4.99 (dd, H, J3,4
4,5=10.0 Hz) for H-4% and 4.93 (dd, J1,2 0.8, J2,3 2.9
L
-rhamnopyranosyl-(1“3)-2,4-di-O-benzoyl-a-
L
-
L-
L-rhamno-
L
1
=
J
Hz) for H-2%, respectively, compared to 10. With the
pentasaccharide diol 10 at hand, the heptasaccharide 13
was readily obtained in high yield (71.3%) by coupling
of 10 with the xylose donor 12 in dichloromethane in
the presence of TMSOTf. The 13C NMR spectrum of
13 showed all of the characteristic peaks, i.e., l 104.8,
104.8, 104.6, 104.0, 103.3, 103.2, 103.2 for seven C-1s
and 18.1, 17.9, 17.5, 17.4, 17.3 for five rhamnose C-6s.
Finally deacylation of 13 in ammonia–methanol gave
the target heptasaccharide 14.
Before the successful synthesis of the target heptasac-
charide by the route described above, we also tried
another route using a 4+3 (20+8) or 4+1+2 (20+
22+5) strategy (A) (Scheme 2). Although the target
compound was not obtained by the strategy, an inter-
esting effect of steric factors on the glycosylation was
observed as described below. Isopropylidenation of
compound 15 in DMF with 2,2-dimethoxypropane in
the presence of TsOH readily gave allyl 2,3-O-isopropy-
3. Experimental
3.1. General methods
Melting points were determined with a ‘Mel-Temp’
apparatus. Optical rotations were determined with a
Perkin–Elmer model 241-MC automatic polarimeter
for solutions in a 1-dm, jacketed cell. H, 13C, and 2D
1
lidene-a-
a- -rhamnopyranoside (16) in high yield (87.3%). The
structure of 16 was confirmed by acetylation to give
allyl 4-O-acetyl-2,3-O-isopropylidene-a- -rhamnopy-
-rhamnopyran-
L
-rhamnopyranosyl-(1“3)-2,4-di-O-benzoyl-
NMR spectra were recorded with Varian XL-400 spec-
trometers, for solutions in CDCl3 or in D2O as indi-
cated. Chemical shifts are expressed in l (ppm)
downfield from the Me4Si resonance. Mass spectra were
recorded with a VG PLATFORM mass spectrometer
using the ESI mode. Thin-layer chromatography (TLC)
was performed on silica gel HF with detection by
charring with 30% (v/v) H2SO4 in MeOH or by UV
detection. Column chromatography was conducted by
elution of a column (8×100, 16×240, 18×300, 35×
400 mm) of silica gel (100–200 mesh) with EtOAc–
petroleum ether (bp 60–90 °C) as the eluent. Analytical
LC was performed with a Gilson HPLC consisting of a
pump (model 306), stainless steel column packed with
silica gel (Spherisorb SiO2, 10×300 or 4.6×250 mm),
differential refractometer (132-RI Detector), UV–Vis
detector (model 118). EtOAc–petroleum ether (bp 60–
L
L
ranosyl-(1“3)-2,4-di-O-benzoyl-a-
L
oside (17), showing characteristic signals in its 1H
NMR spectrum at l 5.48 (dd, J3,4=J4,5=9.9 Hz) for
H-4, and 4.71 (dd, J3%,4%=8.0 Hz, J4%,5%=10.0 Hz) for
H-4%, respectively. Coupling of 16 with 2,3,4-tri-O-ben-
zoyl-a,b- -xylopyranosyl trichloroacetimidate (12) in
D
the presence of catalytic TMSOTf gave the trisaccha-
ride 18 (88.5%), and O-deisopropylidenation of 18 in
9:1 trifluoroacetic acid (TFA)–water at room tempera-
ture furnished the diol acceptor 19 (90.7%). Condensa-
tion of the diol acceptor 19 with 12 in dichloromethane
in the presence of TMSOTf at −20 °C selectively gave
2-O-glycosylated tetrasaccharide 20 (79.9%). Acetyla-

1026
J. Zhang et al. / Carbohydrate Research 338 (2003) 1023–1031
90 °C) was used as the eluent at a flow rate of 1–4
mL/min. Solutions were concentrated at a temperature
B60 °C under diminished pressure.
together under high vacuum for 2 h, then dissolved in
anhyd CH2Cl2 (40 mL). TMSOTf (36 mL, 0.2 mmol)
was added dropwise at −25 °C with N2 protection.
The reaction mixture was stirred for 3 h, during which
time the temperature was gradually warmed to ambient
temperature. Then the mixture was neutralized with
Et3N and concentrated to dryness to afford the crude
3.2. Allyl 2,3,4-tri-O-benzoyl-a-
L-rhamnopyranosyl-
(1“3)-2,4-di-O-benzoyl-a- -rhamnopyranoside (4)
L
2,3,4-Tri-O-benzoyl-a-
timidate (1) (6.20 g, 10.0 mmol) and allyl a-
rhamnopyranoside (2) (2.04 g, 10.0 mmol) were dried
L
-rhamnopyranosyl trichloroace-
allyl 2,3,4-tri-O-benzoyl-a-
a- -rhamnopyranoside (3). To the solution of crude 3
in pyridine (20 mL), benzoyl chloride (3.5 mL, 30
L
-rhamnopyranosyl-(1“3)-
L-
L
Scheme 2. 2,2-Di-methoxypropene, p-TsOH, DMF, rt, 2 h; (b) TMSOTf, CH2Cl2; (c) Ac2O–pyridine (dry); (d) 90% TFA, rt, 2
h; (e) 3–5% CH3COCl–methanol, rt, 14–24 h.

J. Zhang et al. / Carbohydrate Research 338 (2003) 1023–1031
1027
mmol) was added dropwise, and the mixture was stirred
overnight at room temperature (rt). TLC (3:1
petroleum ether–EtOAc) indicated that the reaction
was complete. Ice-water was added, and the mixture
was diluted with CH2Cl2, subsequently washed with M
HCl, water, and satd aq NaHCO3. The organic layers
were combined, dried, and concentrated. Purification
by column chromatography (3:1 petroleum ether–
EtOAc) gave 4 (5.50 g, 63.2% for two steps) as a syrup:
[h]D+122.3° (c 1.0, CHCl3); 1H NMR (400 MHz,
CDCl3): l 8.25–7.19 (m, 25 H, 5 PhH), 6.01–5.93 (m,
1 H, CH2ꢀCHCH2O), 5.61 (dd, 1 H, J3%,4%=J4%,5%=9.7
Hz, H-4%), 5.58 (dd, 1 H, J2%,3% 3.1 Hz, J3%,4% 9.7 Hz, H-3%),
5.54 (dd, 1 H, J1%,2% 1.5 Hz, J2%,3% 3.1 Hz, H-2%), 5.51 (dd,
1 H, J3,4=J4,5=9.8 Hz, H-4), 5.38–5.34 (m, 1 H,
CH2ꢀCHCH2O), 5.28 (dd, 1 H, J1,2 1.4 Hz, J2,3 3.5 Hz,
H-2), 5.29–5.25 (m, 1 H, CH2ꢀCHCH2O), 5.23 (d, 1 H,
J1%,2% 1.5 Hz, H-1%), 5.07 (d, 1 H, J1,2 1.4 Hz, H-1), 4.50
(dd, 1 H, J2,3 3.5 Hz, J3,4 9.8 Hz, H-3), 4.26–4.22 (m, 1
H, CH2ꢀCHCH2O), 4.15–4.07 (m, 3 H, H-5, H-5%,
CH2ꢀCHCH2O), 1.35 (d, 3 H, J5,6 6.2 Hz, H-6), 1.16 (d,
3 H, J5,6 6.2 Hz, H-6). Anal. Calcd for C50H46O14: C,
68.95; H, 5.32. Found: C, 69.24; H, 5.21.
(dd, 1 H, J3%,4%=J4%,5%=9.8 Hz, H-4%), 5.60 (dd, 1 H, J2%,3%
3.2 Hz, J3%,4% 9.8 Hz, H-3%), 5.52 (dd, 1 H, J3,4=J4,5
=
10.0 Hz, H-4), 5.33 (dd, 1 H, J1%,2% 1.6 Hz, J2%,3% 3.2 Hz,
H-2%), 5.24 (d, 1 H, J1%,2% 1.6 Hz, H-1%), 4.60 (dd, 1 H,
J2,3 3.5 Hz, J3,4 10.0 Hz, H-3), 4.29–4.20 (m, 2 H, H-5,
H-5%), 1.38 (d, 3 H, J5,6 6.3 Hz, H-6), 1.16 (d, 3 H, J5,6
6.2 Hz, H-6). Anal. Calcd for C49H42Cl3NO14: C, 60.35;
H, 4.34. Found: C, 60.50; H, 4.39.
3.4. Allyl 2,3,4-tri-O-benzoyl-a-
(1“3)-2,4-di-O-benzoyl-a- -rhamnopyranosyl-(1“2)-
3,4-di-O-benzoyl-a- -rhamnopyranoside (7)
L-rhamnopyranosyl-
L
L
Compound 5 (3.96 g, 3.0 mmol) and allyl 3,4-di-O-ben-
zoyl-a- -rhamnopyranoside (6) (1.25 g, 3.0 mmol) were
L
dried together under high vacuum for 2 h, then dis-
solved in anhyd CH2Cl2 (20 mL). TMSOTf (18 mL, 0.1
mmol) was added dropwise at 0 °C with N2 protection.
The reaction mixture was stirred for 3 h at rt, and then
neutralized with Et3N. Concentration of the reaction
mixture and purification of the crude product on a
silica gel column with 2:1 petroleum ether–EtOAc as
the eluent, furnished the trisaccharide 7 (3.24 g, 88.2%)
as a foamy solid: [h]D+124.0° (c 1.0, CHCl3); 1H NMR
(400 MHz, CDCl3): l 8.16–7.19 (m, 35 H, 7 PhH),
5.99–5.91 (m, 1 H, CH2ꢀCHCH2O), 5.80 (dd, 1 H, J2,3
3.3 Hz, J3,4 10.1 Hz, H-3), 5.72 (dd, 1 H, J1,2 1.8 Hz,
J2,3 3.3 Hz, H-2), 5.62 (dd, 2 H, J3,4=J4,5=9.8 Hz, 2
H-4), 5.60 (dd, 1 H, J2,3 3.2 Hz, J3,4 9.8 Hz, H-3), 5.52
(dd, 1 H, J3,4=J4,5=9.7 Hz, H-4), 5.41–5.37 (m, 1 H,
CH2ꢀCHCH2O), 5.34 (dd, 1 H, J1,2 1.7 Hz, J2,3 3.3 Hz,
H-2), 5.30 (d, 1 H, J1,2 1.8 Hz, H-1), 5.28–5.24 (m, 1 H,
CH2ꢀCHCH2O), 5.19 (d, 1 H, J1,2 1.6 Hz, H-1), 5.04 (d,
1 H, J1,2 1.6 Hz, H-1), 4.65 (dd, 1 H, J2,3 3.4 Hz, J3,4 9.8
Hz, H-3), 4.32 (dd, 1 H, J1,2 1.6 Hz, J2,3 3.2 Hz, H-2),
4.31–4.27 (m, 1 H, CH2ꢀCHCH2O), 4.26–4.08 (m, 4 H,
3 H-5, CH2ꢀCHCH2O), 1.37 (d, 3 H, J5,6 6.1 Hz, H-6),
1.31 (d, 3 H, J5,6 6.3 Hz, H-6), 1.22 (d, 3 H, J5,6 6.2 Hz,
H-6); 13C NMR (100 MHz, CDCl3): l 165.7, 165.6,
165.5, 165.5, 165.4, 164.7, 164.6 (7 C, 7 COPh), 99.4,
99.1, 97.6 (3 C, 3 C-1), 77.2, 74.9, 73.1, 71.9, 71.8, 71.6,
71.0, 70.4, 69.3, 68.2, 67.6, 67.4, 66.9, 17.6, 17.5, 17.3.
Anal. Calcd for C70H64O20: C, 68.62; H, 5.27. Found:
C, 68.48; H, 5.55.
3.3. 2,3,4-Tri-O-benzoyl-a-
L-rhamnopyranosyl-(1“3)-
2,4-di-O-benzoyl-a-L-rhamnopyranosyl trichloroacetimi-
date (5)
To a solution of allyl 2,3,4-tri-O-benzoyl-a-
L-rhamno-
pyranosyl-(1“3)-2,4-di-O-benzoyl-a- -rhamnopyran-
L
oside (4) (4.35 g, 5 mmol) in 90% HOAc (50 mL)
containing NaOAc (1.46 g, 15 mmol) was added PdCl2
(270 mg, 2.5 mmol), and the mixture was stirred for 12
h, at the end of which time TLC (2:1 petroleum ether–
EtOAc) indicated that the reaction was complete. The
mixture was diluted with CH2Cl2 (150 mL), washed
with water and satd aq NaHCO3. The organic layer
was concentrated, and the residue was passed through a
short silica gel column with 2:1 petroleum ether–
EtOAc as the eluent to give crude 2,3,4-tri-O-benzoyl-
a -
L
- rhamnopyranosyl - (1“3) - 2,4 - di - O - benzoyl - L-
rhamnopyranose as a foamy solid. Dried under high
vacuum for 2 h, the solid was was dissolved in CH2Cl2
(30 mL), and CCl3CN (1.0 mL, 10 mmol) and DBU
(135 mL, 0.9 mmol) were added. The reaction mixture
was stirred for 2 h, at the end of which time TLC (2:1
petroleum ether–EtOAc) indicated that the reaction
was complete. Concentration of the reaction mixture,
followed by purification of the crude product on a silica
gel column with 2:1 petroleum ether–EtOAc as the
eluent, furnished the disaccharide donor 5 (4.10 g,
84.1%) as a syrup: [h]D+114.7° (c 0.5, CHCl3); 1H
NMR (400 MHz, CDCl3): l 8.82 (s, 1 H, CNHCCl3),
8.27–7.19 (m, 25 H, 5 PhH), 6.51 (d, 1 H, J1,2 1.9 Hz,
H-1), 5.73 (dd, 1 H, J1,2 1.9 Hz, J2,3 3.5 Hz, H-2), 5.71
3.5. 2,3,4-Tri-O-benzoyl-a-
2,4-di-O-benzoyl-a- -rhamnopyranosyl-(1“2)-3,4-di-
O-benzoyl-a- -rhamnopyranosyl trichloroacetimidate (8)
L-rhamnopyranosyl-(1“3)-
L
L
Compound 7 (2.45 g, 2.0 mmol) was deallylated and
then trichloroacetimidated under the same conditions
as those used for the preparation of 5 from 4, giving 8
(2.11 g, 79.6% for two steps) as a foamy solid: [h]D+
1
99.8° (c 0.5, CHCl3); H NMR (400 MHz, CDCl3): l
8.75 (s, 1 H, CNHCCl3), 8.16–7.19 (m, 35 H, 7 PhH),

1028
J. Zhang et al. / Carbohydrate Research 338 (2003) 1023–1031
3.7. Methyl 2,3,4-tri-O-benzoyl-a-
(1“3)-2,4-di-O-benzoyl-a- -rhamnopyranosyl-(1“2)-
3,4-di-O-benzoyl-a- -rhamnopyranosyl-(1“3)-2,4-di-
O-acetyl-a- -rhamnopyranosyl-(1“3)-2,4-di-O-ben-
zoyl-a- -rhamnopyranoside (11)
L-rhamnopyranosyl-
6.48 (d, 1 H, J1,2 1.6 Hz, H-1), 5.83 (dd, 1 H, J2,3 3.4,
J3,4 10.0 Hz, H-3), 5.72 (dd, H, J3,4=J4,5=9.9 Hz,
H-4), 5.70 (dd, 1 H, J1,2 1.4 Hz, J2,3 3.4 Hz, H-2), 5.62
(dd, H, J3,4=J4,5=9.8 Hz, H-4), 5.60 (dd, 1 H, J2,3 3.1
Hz, J3,4 9.8 Hz, H-3), 5.54 (dd, 1 H, J3,4=J4,5=9.8 Hz,
H-4), 5.35 (dd, 1 H, J1,2 1.5 Hz, J2,3 3.2 Hz, H-2), 5.31
(d, 1 H, J1,2 1.0 Hz, H-1), 5.26 (d, 1 H, J1,2 1.3 Hz,
H-1), 4.64 (dd, 1 H, J2,3 3.1 Hz, J3,4 9.8 Hz, H-3), 4.55
(dd, 1 H, J1,2 1.6 Hz, J2,3 3.4 Hz, H-2), 4.39–4.36 (m, 1
H, H-5), 4.27–4.24 (m, 1 H, H-5), 4.21–4.18 (m, 1 H,
H-5), 1.43 (d, 3 H, J5,6 6.4 Hz, H-6), 1.34 (d, 3 H, J5,6
6.3 Hz, H-6), 1.19 (d, 3 H, J5,6 6.3 Hz, H-6). Anal.
Calcd for C69H60Cl3NO20: C, 62.33; H, 4.55. Found: C,
62.60; H, 4.31.
L
L
L
L
To a solution of 10 (85 mg, 0.05 mmol) in pyridine (5
mL) was added Ac2O (2.0 mL, 2 mmol). The reaction
mixture was stirred at rt for 12 h, at the end of which
time TLC (4:1 petroleum ether–EtOAc) indicated that
the reaction was complete. The reaction mixture was
concentrated, and then the residue was purified by flash
column chromatography on a silica gel column (2:1
petroleum ether–EtOAc) to give compound 11 (80 mg,
89.8%) as a foamy solid: [h]D+120.7° (c 1.0, CHCl3);
1H NMR (400 MHz, CDCl3): l 8.16–7.20 (m, 45 H, 9
PhH), 5.60–5.57 (m, 3 H), 5.53 (dd, H, J3,4=J4,5=9.7
Hz, H-4), 5.47 (dd, H, J3,4=J4,5=9.9 Hz, H-4), 5.45
(dd, 1 H, J1,2 1.2 Hz, J2,3 3.1 Hz, H-2), 5.41 (dd, 1 H,
3.6. Methyl 2,3,4-tri-O-benzoyl-a-
(1“3)-2,4-di-O-benzoyl-a- -rhamnopyranosyl-(1“2)-
3,4-di-O-benzoyl-a- -rhamnopyranosyl-(1“3)-a-
L-rhamnopyranosyl-
L
L
L-
J2,3 3.2 Hz, J3,4 9.8 Hz, H-3), 5.39 (dd, H, J3,4=J4,5
=
rhamnopyranosyl-(1“3)-2,4-di-O-benzoyl-a-L-rhamno-
9.7 Hz, H-4), 5.35 (dd, 1 H, J1,2 1.5 Hz, J2,3 3.0 Hz,
H-2), 5.29 (d, 1 H, J1,2 1.5 Hz, H-1), 5.03 (d, 1 H, J1,2
1.4 Hz, H-1), 4.99 (dd, H, J3,4=J4,5=10.0 Hz, H-4%),
4.96 (d, 1 H, J1,2 0.7 Hz, H-1), 4.94 (d, 1 H, J1,2 0.9 Hz,
H-1), 4.93 (dd, 1 H, J1,2 0.8 Hz, J2,3 2.9 Hz, H-2%), 4.84
(d, 1 H, J1,2 1.5 Hz, H-1), 4.59 (dd, 1 H, J2,3 3.2 Hz, J3,4
9.7 Hz, H-3), 4.38 (dd, 1 H, J2,3 3.2 Hz, J3,4 9.8 Hz,
H-3), 4.21–4.17 (m, 2 H, 2 H-5), 4.03 (dd, 1 H, J1,2 1.0
Hz, J2,3 3.1 Hz, H-2), 3.99 (m, 1 H, H-5), 3.96 (dd, 1 H,
J2,3 3.1 Hz, J3,4 9.9 Hz, H-3), 3.85–3.81 (m, 1 H, H-5),
3.80–3.76 (m, 1 H, H-5), 3.44 (s, 3 H, OCH3), 2.03 (s,
3 H, CH3CO), 1.97 (s, 3 H, CH3CO), 1.30 (d, 3 H, J5,6
6.2 Hz, H-6), 1.26 (d, 3 H, J5,6 6.4 Hz, H-6), 1.18 (d, 3
H, J5,6 6.4 Hz, H-6), 1.05 (d, 3 H, J5,6 6.3 Hz, H-6), 0.88
(d, 3 H, J5,6 6.4 Hz, H-6). Anal. Calcd for C98H94O32:
C, 65.98; H, 5.31. Found: C, 65.69; H, 5.50.
pyranoside (10)
Compound 8 (1.33 g, 1.0 mmol) and methyl a-
rhamnopyranosyl - (1“3) - 2,4 - di - O - benzoyl - a -
L
-
-
L
rhamnopyranoside (9) (530 mg, 1.0 mmol) were dried
together under high vacuum for 2 h, then dissolved in
anhyd CH2Cl2 (20 mL). TMSOTf (18 mL, 0.1mmol)
was added dropwise at −25 °C with N2 protection.
The reaction mixture was stirred for 3 h, during which
time the mixture was gradually warmed to ambient
temperature. Then the mixture was neutralized with
Et3N and concentrated to dryness. Purification of the
residue by column chromatography (1:1 petroleum
ether–EtOAc) gave 10 (974 mg, 57.3%) as a syrup:
[h]D+131.5° (c 1.0, CHCl3); 1H NMR (400 MHz,
CDCl3): l 8.15–7.19 (m, 45 H, 9 PhH), 5.64 (dd, 1 H,
J1,2 1.6 Hz, J2,3 3.3 Hz, H-2), 5.59–5.46 (m, 7 H), 5.33
(dd, 1 H, J1,2 1.4 Hz, J2,3 3.2 Hz, H-2), 5.26 (s, 2 H, 2
H-1), 5.11 (d, 1 H, J1,2 1.3 Hz, H-1), 4.95 (s, 1 H, H-1),
4.83 (d, 1 H, J1,2 1.4 Hz, H-1), 4.57 (dd, 1 H, J2,3 3.1
Hz, J3,4 9.6 Hz, H-3), 4.41 (dd, 1 H, J2,3 3.2 Hz, J3,4 9.8
Hz, H-3), 4.28 (dd, 1 H, J1,2 1.3 Hz, J2,3 3.0 Hz, H-2),
4.26–4.23 (m, 1 H, H-5), 4.17–4.14 (m, 1 H, H-5),
4.05–4.02 (m, 1 H, H-5), 3.93–3.90 (m, 1 H, H-5),
3.8. Methyl 2,3,4-tri-O-benzoyl-a-
(1“3)-2,4-di-O-benzoyl-a- -rhamnopyranosyl-(1“2)-
3,4-di-O-benzoyl-a- -rhamnopyranosyl-(1“3)-[2,3,4-
tri-O-benzoyl-b- -xylopyranosyl-(1“2)-][2,3,4-tri-O-
benzoyl-b- -xylopyranosyl-(1“4)]-a- -rhamnopyran-
osyl-(1“3)-2,4-di-O-benzoyl-a- -rhamnopyranoside (13)
L-rhamnopyranosyl-
L
L
D
D
L
L
Compound 10 (765 mg, 0.45 mmol) and 2,3,4-tri-O-
benzoyl-a,b- -xylopyranosyl trichloroacetimidate (12)
3.74–3.70 (m, 3 H, H-2, H-3, H-5), 3.56 (dd, H, J3,4
=
D
J4,5=9.3 Hz, H-4) 3.45 (s, 3 H, OCH3), 1.30 (d, 3 H,
(606 mg, 1.0 mmol) were coupled under the same
conditions as those used for the preparation of 7 from
5 and 6, giving 13 (830 g, 71.3%) as a foamy solid:
[h]D+97.3° (c 1.0, CHCl3); 1H NMR (400 MHz,
CDCl3, characteristic signals are given): l 5.92 (dd, 1
J5,6 6.4 Hz, H-6), 1.25–1.19 (m, 9 H, 3 H-6), 1.01 (d, 3
H, J5,6 6.2 Hz, H-6); 13C NMR (100 MHz, CDCl3): l
165.9, 165.8, 165.7, 165.5, 165.5, 165.5, 165.3, 164.7,
164.7 (9 C, 9 COPh), 101.4, 99.8, 99.2, 99.1, 98.3 (5 C,
5 C-1), 78.0, 76.7, 75.1, 74.9, 73.5, 73.0, 72.3, 72.2, 71.9,
71.7, 71.6, 70.9, 70.8, 70.4, 69.3, 69.2, 67.7, 67.4, 67.2,
66.4, 55.2, 17.6, 17.4, 17.3, 17.2, 17.1. Anal. Calcd for
C94H90O30: C, 66.42; H, 5.34. Found: C, 66.48; H,
5.25.
H, J3,4=J4,5=9.8 Hz, H-4-Rhap), 5.53 (dd, 1 H, J3,4
=
J4,5=9.8 Hz, H-4-Rhap), 5.48 (dd, 1 H, J1,2 1.3 Hz, J2,3
3.2 Hz, H-2-Rhap), 5.44 (dd, 1 H, J3,4=J4,5=9.9 Hz,
H-4-Rhap), 5.36 (dd, 1 H, J3,4=J4,5=9.8 Hz, H-4-
Rhap), 5.29 (dd, 1 H, J1,2 1.5 Hz, J2,3 3.4 Hz, H-2-

J. Zhang et al. / Carbohydrate Research 338 (2003) 1023–1031
1029
Rhap), 5.20 (s, 1 H, H-1-Rhap), 5.11 (s, 1 H, H-1-
Rhap), 5.04 (d, 1 H, J1,2 6.1 Hz, H-1-Xylp), 5.01 (s, 1
H, H-1-Rhap), 4.81 (d, 1 H, J1,2 1.5 Hz, H-1-Rhap),
4.74 (d, 1 H, J1,2 5.8 Hz, H-1-Xylp), 4.63 (s, 1 H,
H-1-Rhap), 3.45 (s, 3 H, OCH3), 1.35 (d, 3 H, J5,6 6.4
Hz, H-6), 1.29 (d, 3 H, J5,6 6.3 Hz, H-6), 1.22 (d, 3 H,
J5,6 6.2 Hz, H-6), 1.05 (d, 3 H, J5,6 6.4 Hz, H-6), 1.04
(d, 3 H, J5,6 6.4 Hz, H-6); 13C NMR (100 MHz,
CDCl3): l 166.6, 166.5, 165.6, 165.5, 165.4, 165.3,
165.3, 165.2, 165.1, 165.1, 165.1, 164.9, 164.6, 164.5,
164.5 (15 C, 15 COPh), 100.9, 100.9, 100.2, 98.9, 98.8,
98.8, 98.5 (7 C, 7 C-1), 18.1, 17.9, 17.5, 17.4, 17.3 (5 C,
5 C-6-Rhap). Anal. Calcd for C146H130O44: C, 67.74; H,
5.06. Found: C, 67.68; H, 5.35.
Hz, J2,3 3.0 Hz, H-2), 5.47 (dd, 1 H, J3,4=J4,5=9.9 Hz,
H-4), 5.38–5.25 (m, 2 H, OCH2CHꢀCH2), 5.07 (s, 1 H,
H-1%), 4.97 (s, 1 H, J1,2 0.7 Hz, H-1), 4.42 (dd, 1 H, J2,3
3.0 Hz, J3,4 9.9 Hz, H-3), 4.26–4.22 (m, 1 H,
OCH2CHꢀCH2), 4.10–4.04 (m,
2
H, H-4%,
OCH2CHꢀCH2), 3.82–3.75 (m, 2 H, H-2%, H-3%), 3.65–
3.61 (m, 1 H, H-5), 3.24–3.20 (m, 1 H, H-5), 1.35 (s, 3
H, isopropylidene), 1.31 (d, 3 H, J5,6 6.4 Hz, H-6), 1.20
(d, 3 H, J5,6 6.3 Hz, H-6), 0.96 (s, 3 H, isopropylidene).
Anal. Calcd for C32H38O11: C, 64.20; H, 6.40. Found:
C, 64.08; H, 6.51.
3.11. Allyl 4-O-acetyl-2,3-O-isopropylidene-a-L-
rhamnopyranosyl-(1“3)-2,4-di-O-benzoyl-a-L-rhamno-
pyranoside (17)
3.9. Methyl a-
rhamnopyranosyl-(1“2)-a-
[b- -xylopyranosyl-(1“2)-][b-
a- -rhamnopyranosyl-(1“3)-a-
L
-rhamnopyranosyl-(1“3)-a-
-rhamnopyranosyl-(1“3)-
-xylopyranosyl-(1“4)]-
-rhamnopyranoside (14)
L-
L
To a solution of 16 (180 mg, 0.3 mmol) in pyridine (5
mL) was added Ac2O (2.0 mL, 2 mmol). The reaction
mixture was stirred at rt for 12 h, at the end of which
time TLC (4:1 petroleum ether–EtOAc) indicated that
the reaction was complete. The reaction mixture was
concentrated, and the residue was purified by flash
column chromatography on a silica gel column (3:1
petroleum ether–EtOAc) to give compound 17 (158
D
D
L
L
Heptasaccharide 13 (520 mg, 0.20 mmol) was dissolved
in a saturated solution of NH3–MeOH (30 mL). After
96 h at rt, the reaction mixture was concentrated, and
the residue was purified by chromatography on Sep-
hadex LH-20 (MeOH) to afford 14 (143 mg, 69.8%) as
1
mg, 82.4%) as a syrup: [h]D+40.3° (c 1.0, CHCl3); H
1
a foamy solid: [h]D−52.8° (c 1.0, CHCl3); H NMR
NMR (400 MHz, CDCl3): l 8.14–7.45 (m, 10 H, 2
PhH), 6.01–5.93 (m, 1 H, OCH2CHꢀCH2), 5.48 (dd, 1
H, J3,4=J4,5=9.9 Hz, H-4), 5.40 (dd, 1 H, J1,2 1.0 Hz,
J2,3 2.9 Hz, H-2), 5.38–5.25 (m, 2 H, OCH2CHꢀCH2),
5.11 (s, 1 H, H-1%), 4.97 (s, 1 H, J1,2 1.6 Hz, H-1), 4.71
(dd, 1 H, J3%,4%=8.0 Hz, J4%,5%=10.0 Hz, H-4%), 4.41 (dd,
1 H, J2,3 3.0 Hz, J3,4 9.9 Hz, H-3), 4.25–4.21 (m, 1 H,
OCH2CHꢀCH2), 4.10–4.05 (m, 2 H, H-5, OCH2CHꢀ
CH2), 3.89 (dd, 1 H, J2%,3% 5.4 Hz, J3%,4% 8.0 Hz, H-3%),
3.74 (d, 1 H, J2%,3% 5.4 Hz, H-2%), 3.69–3.66 (m, 1 H,
H-5), 2.00 (s, 3 H, CH3CO), 1.39 (s, 3 H, isopropyli-
dene), 1.32 (d, 3 H, J5,6 6.3 Hz, H-6), 1.08 (d, 3 H, J5,6
6.3 Hz, H-6), 0.93 (s, 3 H, isopropylidene). Anal. Calcd
for C34H40O12: C, 63.74; H, 6.29. Found: C, 63.57; H,
6.13.
(400 MHz, CDCl3): l 5.05 (s 1 H, H-1), 5.03 (d, 1 H,
J1,2 1.5 Hz, H-1), 5.02 (d, 1 H, J1,2 1.5 Hz, H-1), 4.67
(d, 2 H, J1,2 1.6 Hz, 2 H-1), 4.61 (d, 1 H, J1,2 7.6 Hz,
H-1), 4.47 (d, 1 H, J1,2 7.6 Hz, H-1), 3.40 (s, 3 H,
OCH3), 1.35 (d, 3 H, J5,6 6.4 Hz, H-6), 1.32–1.29 (m,
12 H, 4 H-6); 13C NMR (100 MHz, CDCl3): l 104.8,
104.8, 104.6, 104.0, 103.3, 103.2, 103.2 (7 C, 7 C-1),
19.3, 19.3, 19.1, 19.1, 19.1 (5 C, 5 C-6); MS (m/z) Calcd
for C41H70O29: 1026.97 [M]+. Found: 1050.09 [M+
Na]+.
3.10. Allyl 2,3-O-isopropylidene-a-
L-rhamnopyranosyl-
(1“3)-2,4-di-O-benzoyl-a- -rhamnopyranoside (16)
L
To a solution of allyl a-
L
-rhamnopyranosyl-(1“3)-2,4-
di-O-benzoyl-a- -rhamnopyranoside (15) (5.58 g, 10
L
3.12. Allyl 2,3,4-tri-O-benzoyl-b-
4)-2,3-O-isopropylidene-a- -rhamnopyranosyl-(1“3)-
2,4-di-O-benzoyl-a- -rhamnopyranoside (18)
D-xylopyranosyl-(1“
mmol) in anhyd DMF (50 mL) was added p-
TsOH·H2O (190 mg, 1.0 mmol) and 2,2-di-
methoxypropane (3.7 mL, 30 mmol) under N2
protection. The mixture was stirred at rt for 12 h, and
TLC (3:1 petroleum ether–EtOAc) indicated that the
reaction was complete. Sodium bicarbonate (5.00 g, 60
mmol) was added to the reaction mixture, and the
mixture was stirred for additional 1 h. After filtration,
the mixture was concentrated in vacuo to give a residue
that was subjected to silica gel column chromatography
(2:1 petroleum ether–EtOAc) to give 16 (5.22 g, 87.3%)
L
L
2,3,4-Tri-O-benzoyl-a,b-
timidate (12) (3.03 g, 5.0 mmol) and allyl 2,3-O-iso-
propylidene-a- -rhamnopyranosyl-(1“3)-2,4-di-O-
benzoyl-a- -rhamnopyranoside (16) (3.0 g, 5.0 mmol)
D-xylopyranosyl trichloroace-
L
L
were dried together under high vacuum for 2 h, then
dissolved in anhyd CH2Cl2 (30 mL). TMSOTf (18.0 mL,
0.10 mmol) was added dropwise at −0 °C with N2
protection. The reaction mixture was stirred for 2 h and
then neutralized with Et3N. Concentration of the reac-
tion mixture and purification of the residue on a silica
gel column (3:1 petroleum ether–EtOAc) afforded com-
1
as a syrup: [h]D+52.1° (c 1.0, CHCl3); H NMR (400
MHz, CDCl3): l 8.12–7.45 (m, 10 H, 2 PhH), 6.03–
5.95 (m, 1 H, OCH2CHꢀCH2), 5.48 (dd, 1 H, J1,2 0.7

1030
J. Zhang et al. / Carbohydrate Research 338 (2003) 1023–1031
3.14. Allyl 2,3,4-tri-O-benzoyl-b-
D-xylopyranosyl-(1“
pound 18 (4.61 g, 88.5%) as a foamy solid: [h]D+41.2°
(c 0.5, CHCl3); H NMR (400 MHz, CDCl3): l 8.03–
1
2)-[2,3,4-tri-O-benzoyl-b- -xylopyranosyl-(1“4)]-a-L-
D
rhamnopyranosyl-(1“3)-2,4-di-O-benzoyl-a-L-
rhamnopyranoside (20)
7.31 (m, 25 H,
5 PhH), 6.01–5.93 (m, 1 H,
OCH2CHꢀCH2), 5.71 (dd, 1 H, J2¦,3¦=J3¦,4¦=7.8 Hz,
H-3¦), 5.45 (dd, 1 H, J1,2 1.2 Hz, J2,3 3.2 Hz, H-2), 5.40
(dd, 1 H, J3,4=J4,5=9.8 Hz, H-4), 5.36–5.30 (m, 1 H,
OCH2CHꢀCH2), 5.30–5.23 (m, 3 H, H-2¦, H-4¦,
OCH2CHꢀCH2), 5.22 (d, 1 H, J1,2 6.1 Hz, H-1¦), 5.04
(s, 1 H, H-1%), 4.97 (s, 1 H, J1,2 1.2 Hz, H-1), 4.40–4.32
Compound 19 (3.00 g, 3 mmol) and 2,3,4-tri-O-ben-
zoyl-a,b- -xylopyranosyl trichloroacetimidate (12)
D
(1.91 g, 3.15 mmol) were dried together under high
vacuum for 2 h, then dissolved in anhyd CH2Cl2 (50
mL). TMSOTf (18.0 mL, 0.10 mmol) was added drop-
wise at −20 °C with N2 protection. The reaction mix-
ture was stirred for 2 h, during which time the
temperature was gradually warmed to ambient temper-
ature. Then the mixture was neutralized with Et3N and
concentrated to dryness under reduced pressure. Purifi-
cation of the residue by column chromatography on a
silica gel column (2:1 petroleum ether–EtOAc) fur-
nished the tetrasaccharide 20 (3.47 mg, 79.9%) as a
(m,
2
H, H-3%, H-3), 4.25–4.21 (m,
1
H,
OCH2CHꢀCH2), 4.10–4.02 (m, 2 H), 3.84 (dd, 1 H,
J3%,4%=8.6 Hz, J4%,5%=9.7 Hz, H-4%), 43.66–3.62 (m, 2
H), 3.56–3.44 (m, 2 H), 1.36 (s, 3 H, isopropylidene),
1.30 (d, 3 H, J5,6 6.4 Hz, H-6), 1.25 (d, 3 H, J5,6 6.3 Hz,
H-6), 0.87 (s, 3 H, isopropylidene); 13C NMR (100
MHz, CDCl3): l 165.8, 165.6, 165.5, 165.4, 165.0 (5 C,
5 COPh), 117.8, 108.7 (2 C, OCH2CHꢀCH2 and
Me2CO2), 99.8, 99.2, 96.6 (3 C, 3 C-1), 27.6, 25.6 (2 C,
Me2CO2), 17.6, 17.2 (2 C, 2 C-6). Anal. Calcd
for C58H58O18: C, 66.78; H, 5.61. Found: C, 66.64; H,
5.45.
1
syrup: [h]D−2.3° (c 1.0, CHCl3); H NMR (400 MHz,
CDCl3): l 8.05–7.32 (m, 40 H, 8 PhH), 6.01–5.95 (m,
1 H, OCH2CHꢀCH2), 5.57 (dd, 1 H, J2,3=J3,4=9.0
Hz, H-3-Xylp), 5.56 (dd, 1 H, J2,3=J3,4=8.9 Hz,
H-3-Xylp), 5.47 (dd, 1 H, J1,2 1.4 Hz, J2,3 3.1 Hz,
H-2-Rhap), 5.44 (dd, 1 H, J3,4=J4,5=9.8 Hz, H-4-
Rhap), 5.36–5.32 (m, 1 H, OCH2CHꢀCH2), 5.29–5.20
(m, 3 H, 2 H-2-Xylp, OCH2CHꢀCH2), 5.18–5.15 (m, 1
H, H-4-Xylp), 4.97 (d, 1 H, J1,2 1.0 Hz, H-1-Rhap),
4.95 (d, 1 H, J1,2 1.4 Hz, H-1-Rhap), 4.94–4.91 (m, 1
H, H-4-Xylp), 4.60 (d, 1 H, J1,2 6.0 Hz, H-1-Xylp), 4.52
(d, 1 H, J1,2 7.1 Hz, H-1-Xylp), 4.44 (dd, 1 H, J2,3 3.1
Hz, J3,4 9.8 Hz, H-3-Rhap), 4.24–4.20 (m, 1 H,
OCH2CHꢀCH2), 4.12–4.03 (m, 3 H), 3.77–3.75 (m, 1
H, H-5-Rhap), 3.63 (dd, 1 H, J1,2 1.0 Hz, J2,3 3.1 Hz,
H-2-Rhap), 3.58–3.55 (m, 1 H), 3.44 (dd, 1 H, J2,3 3.0
3.13. Allyl 2,3,4-tri-O-benzoyl-b-
4)-a- -rhamnopyranosyl-(1“3)-2,4-di-O-benzoyl-a-
rhamnopyranoside (19)
D-xylopyranosyl-(1“
L
L-
Compound 18 (4.17 g, 4 mmol) was dissolved in 9:1
TFA–water (50 mL) and stirred for 2 h, at the end of
which time the reaction mixture was poured directly
into toluene (200 mL), and then the mixture was con-
centrated. The residue was purified by flash chromatog-
raphy (1:1 petroleum ether–EtOAc) to give 19 (3.63 g,
90.7%) as a syrup: [h]D+32.6° (c 1.0, CHCl3); 1H NMR
(400 MHz, CDCl3): l 8.18–7.34 (m, 25 H, 5 PhH),
6.03–5.97 (m, 1 H, OCH2CHꢀCH2), 5.69 (dd, 1 H,
Hz, J3,4 9.9 Hz, H-3-Rhap), 3.34 (dd, 1 H, J3,4=J4,5
=
9.9 Hz, H-4-Rhap), 3.02 (dd, 1 H, J 9.1, 11.0 Hz,
H-5b-Xylp), 2.78 (dd, 1 H, J 9.3, 11.7 Hz, H-5b-Xylp),
1.26 (d, 3 H, J5,6 6.4 Hz, H-6), 1.17 (d, 3 H, J5,6 6.2 Hz,
H-6); 13C NMR (100 MHz, CDCl3): l 165.6, 165.5,
165.4, 165.3, 165.3, 165.2, 165.0, 164.7 (8 C, 8 COPh),
117.8, (1 C, OCH2CHꢀCH2), 101.6, 100.5, 100.1, 96.7
(4 C, 4 C-1), 17.4, 17.4 (2 C, 2 C-6). Anal. Calcd for
C81H74O25: C, 67.21; H, 5.15. Found: C, 67.40; H, 5.07.
J2¦,3¦=J3¦,4¦=8.8 Hz, H-3¦), 5.52 (dd, 1 H, J1,2 1.6 Hz,
J2,3 3.2 Hz, H-2), 5.47 (dd, 1 H, J3,4=J4,5=9.9 Hz,
H-4), 5.39–5.29 (m, 3 H, H-2¦, OCH2CHꢀCH2), 5.24–
5.20 (m, 1 H, H-4¦), 4.98 (d, 1 H, J1%,2% 1.1 Hz, H-1%),
4.88 (d, 1 H, J1,2 1.6 Hz, H-1), 4.85 (d, 1 H, J1,2 6.9 Hz,
H-1¦), 4.40 (dd, 1 H, J2,3 3.2 Hz, J3,4 9.9 Hz, H-3),
4.29–4.25 (m, 1 H, OCH2CHꢀCH2), 4.19 (dd, 1 H, J2%,3%
3.9 Hz, J3%,4% 9.8 Hz, H-3%), 4.07–4.03 (m, 1 H,
OCH2CHꢀCH2), 4.04–4.01 (m, 1 H, H-5%), 3.84–3.80
(m, 1 H, H-5), 3.69–3.65 (m, 1 H, H-5¦a), 3.61 (dd, 1 H,
3.15. Allyl 2,3,4-tri-O-benzoyl-b-
2)-[2,3,4-tri-O-benzoyl-b- -xylopyranosyl-(1“4)]-3-O-
acetyl-a- -rhamnopyranosyl-(1“3)-2,4-di-O-benzoyl-a-
-rhamnopyranoside (21)
D-xylopyranosyl-(1“
D
L
L
J1%,2% 1.1 Hz, J2%,3% 3.9 Hz, H-2%), 3.55 (dd, 1 H, J3%,4%
=
J4%,5%=9.8 Hz, H-4%), 3.19 (dd, 1 H, J 9.0, 11.7 Hz,
To a solution of 20 (145 mg, 0.1 mmol) in pyridine
(5 mL) was added Ac2O (2.0 mL, 2 mmol). The reac-
tion mixture was stirred at rt for 12 h, at the end of
which time TLC (3:1 petroleum ether–EtOAc) indi-
cated that the reaction was complete. The reaction
mixture was concentrated, and then the residue was
purified by flash column chromatography on a silica gel
H-5¦), 1.31 (d, 3 H, J5,6 6.4 Hz, H-6), 1.07 (d, 3 H, J5,6
b
6.4 Hz, H-6); 13C NMR (100 MHz, CDCl3): l 165.8,
165.6, 165.5, 165.3, 164.9 (5 C, 5 COPh), 117.9, (1 C,
OCH2CHꢀCH2), 101.2, 98.6, 96.7 (3 C, 3 C-1), 17.5,
17.3 (2 C, 2 C-6). Anal. Calcd for C55H54O18: C, 65.86;
H, 5.43. Found: C, 66.00; H, 5.71.

J. Zhang et al. / Carbohydrate Research 338 (2003) 1023–1031
1031
column (3:1 petroleum ether–EtOAc) to give com-
pound 21 (113 mg, 75.8%) as a syrup: [h]D−11.4° (c
1.0, CHCl3); H NMR (400 MHz, CDCl3): l 8.05–7.33
(m, 40 H, 8 PhH), 6.00 (m, 1 H, OCH2CHꢀCH2), 5.57
(dd, 1 H, J2,3=J3,4=8.3 Hz, H-3-Xylp), 5.53 (dd, 1 H,
J1,2 1.7 Hz, J2,3 3.1 Hz, H-2-Rhap), 5.48 (dd, 1 H,
H-3-Xylp), 5.61 (dd, 1 H, J2,3=J3,4=8.4 Hz, H-3-
Xylp), 5.08 (d, 1 H, J1,2 1.1 Hz, H-1-Rhap), 5.06 (d, 1
H, J1,2 6.7 Hz, H-1-Xylp), 5.02 (s, 1 H, H-1-Rhap), 4.95
(d, 1 H, J1,2 6.6 Hz, H-1-Xylp), 4.93 (s, 1 H, H-1-
Rhap), 2.06 (s, 3 H, CH3CO), 1.32 (d, 3 H, J5,6 6.2 Hz,
H-6), 1.25 (d, 3 H, J5,6 6.3 Hz, H-6); 13C NMR (100
MHz, CDCl3): l 169.3 (1 C, 1 CH3CO), 165.7, 165.4,
165.4, 165.2, 165.1, 165.1, 165.1, 165.0, 164.9, 164.7 (10
C, 10 COPh), 117.9 (1 C, OCH2CHꢀCH2), 100.2, 99.8,
99.1, 98.4, 96.8 (5 C, 5 C-1), 20.5 (1 C, 1 CH3CO), 17.7,
17.5, 17.4 (3 C, 3 C-6). Anal. Calcd for C103H94O32: C,
67.09; H, 5.14. Found: C, 67.20; H, 5.26.
1
J
J
2,3=J3,4=8.7 Hz, H-3-Xylp), 5.47 (dd, 1 H, J3,4
4,5=9.8 Hz, H-4-Rhap), 5.38–5.34 (m,
=
H,
1
OCH2CHꢀCH2), 5.27–5.17 (m, 3 H, 2 H-2-Xylp,
OCH2CHꢀCH2), 5.14–5.10 (m, 1 H, H-4-Xylp), 5.01
(d, 1 H, J1,2 2.0 Hz, H-1-Rhap), 4.98 (d, 1 H, J1,2 1.7
Hz, H-1-Rhap), 4.85 (dd, 1 H, J2,3 2.9 Hz, J3,4 9.2 Hz,
H-3-Rhap), 4.82–4.78 (m, 1 H, H-4-Xylp), 4.63 (d, 1
H, J1,2 6.0 Hz, H-1-Xylp), 4.48 (dd, 1 H, J2,3 3.4 Hz,
J3,4 9.8 Hz, H-3-Rhap), 4.28–4.24 (m,
1
H,
Acknowledgements
OCH2CHꢀCH2), 4.24 (d, 1 H, J1,2 6.1 Hz, H-1-Xylp),
4.12–3.87 (m, 4 H), 3.77 (dd, 1 H, J1,2 2.0 Hz, J2,3 3.1
Hz, H-2-Rhap), 3.59 (dd, 1 H, J3,4=J4,5=9.8 Hz,
H-4-Rhap), 3.36–3.21 (m, 2 H), 1.45 (s, 3 H, CH3CO),
1.29 (d, 3 H, J5,6 6.3 Hz, H-6), 1.27 (d, 3 H, J5,6 6.4 Hz,
H-6). Anal. Calcd for C83H76O26: C, 66.93; H, 5.14.
Found: C, 66.70; H, 5.33.
This work was supported by The Chinese Academy
of Sciences (KZCX3-J-08) and by The National Natu-
ral Science Foundation of China (Projects 30070185
and 39970864).
References
3.16. Allyl 2-O-acetyl-3,4-di-O-benzoyl-a-
ranosyl-(1“3)-[2,3,4-tri-O-benzoyl-b- -xylopyranosyl-
(1“2)-][2,3,4-tri-O-benzoyl-b- -xylopyranosyl-(1“4)]-
a- -rhamnopyranosyl-(1“3)-2,4-di-O-benzoyl-a-
rhamnopyranoside (23)
L-rhamnopy-
D
1. Tommasi, N. D.; Piacente, S.; Gacs-Baitz, E.; De Si-
mone, F.; Pizza, C.; Aquino, R. J. Nat. Prod. 1998, 323,
61–66.
2. Jackson, G. E.; Ravenscroft, N.; Stephen, A. M. Carbo-
hydr. Res. 1990, 200, 409–418.
D
L
L-
3. Mcneil, M.; Chatterjee, D.; Hunter, S. W.; Brenna, P. J.
Methods Enzymol. 1989, 179, 215–228.
4. Mass, J. L.; Pooler, M. R.; Gallette, G. J. Ad6. Straberry
Res. 1995, 14, 18–24.
5. Molinaro, A.; Evidente, A.; Fiore, S.; Lacobellis, N. S.;
Lanzetta, R.; Parrilli, M. Carbohydr. Res. 2000, 325,
222–229.
6. Reimer, K. B.; Harris, S. L.; Varma, V.; Pinto, B. M.
Carbohydr. Res. 1992, 228, 399–414.
7. Albernas, J. M.; Harris, S. L.; Varma, V.; Pinto, B. M.
Carbohydr. Res. 1993, 245, 245–257.
8. Zhang, J.; Kong, F. J. Carbohydr. Chem. 2002, 21, 79–
87.
9. Zhang, J.; Kong, F. Carbohydr. Res. 2002, 337, 391–396.
10. Zhang, J.; Zhu, Y.; Kong, F. Carbohydr. Res. 2001, 336,
329–335.
11. Zhang, J.; Kong, F. J. Carbohydr. Chem. 2002, 21, 575–
585.
12. Schmidt, R. R.; Kinzy, W. Ad6. Carbohydr. Chem.
Biochem. 1994, 50, 21–125.
Compound 20 (2.89 g, 2.0 mmol) and allyl 2-O-acetyl-
3,4-di-O-benzoyl-a- -rhamnopyranosyl trichloroace-
L
timidate (22) (1.17 g, 2.1 mmol) were dried together
under high vacuum for 2 h, then dissolved in anhyd
CH2Cl2 (50 mL). TMSOTf (18 mL, 0.1 mmol) was
added dropwise at −20 °C with N2 protection. The
reaction mixture was stirred for 2 h, during which time
the temperature was gradually warmed to rt. Then the
mixture was neutralized with Et3N and concentrated to
dryness under reduced pressure. Purification of the
residue by column chromatography on a silica gel
column (2:1 petroleum ether–EtOAc) furnished the
pentasaccharide 23 (1.52 g, 41.3%) as a foamy solid:
[h]D+32.4° (c 1.0, CHCl3); 1H NMR (400 MHz,
CDCl3, characteristic signals are given): l 6.02 (m, 1 H,
OCH2CHꢀCH2), 5.93 (dd, 1 H, J2,3=J3,4=8.9 Hz,