A general method for the synthesis of oligosaccharides consisting of α-(1→2)- and α-(1→3)-linked rhamnan backbones and GlcNAc side chains

Article abstract of DOI:10.1016/S0040-4020(03)00075-9

A general method has been developed for the synthesis of oligosaccharides consisting of (1→2)- and (1→3)-linked rhamnans with GlcNAc side chains. As examples, highly effective and convergent syntheses of two decasaccharides in the O polysaccharide moiety of the lipopolysaccharide of the phytopathogenic bacterium Pseudomonas syringae pv. ribicola NCPPB 1010 were achieved. The two decasaccharides consist of O polysaccharide repeating units I+II and II+I, respectively. Allyl 3-O-acetyl-4-O-benzoyl-α-L-rhamnopyranoside, allyl 2-O-benzoyl-3-O-chloroacetyl-α-L-rhamnopyranoside, 2,4-di-O-benzoyl-3-O-chloroacetyl-α-L-rhamnopyranosyl trichloroacetimidate, and 3-O-acetyl-2,4-di-O-benzoyl-α-L-rhamnopyranosyl trichloroacetimidate, which were obtained by highly regioselective 3-O-acylations, were used as the key synthons to obtain the required α-(1→2)- and α-(1→3)-linked rhamnoocta saccharide acceptors with 3³- and 3⁷-free hydroxyl groups. Therefore, several disaccharides were synthesized, from which tetrasaccharides and hexasaccharides were then synthesized. Coupling of the hexasaccharide donors with the disaccharide acceptors gave the octasaccharide acceptors. Finally, the coupling of 3,4,6-tri-O-acetyl-2-deoxy-2-phthalimido-β-D-glucopyranosyl trichloroacetimidate with the octasaccharide acceptors, followed by deprotection, afforded the two target decasaccharides. A repeating hexasaccharide unit of the cell wall polysaccharide of β-hemolytic Streptococci Group A was also synthesized in a similar way.

Full text of DOI:10.1016/S0040-4020(03)00075-9

Tetrahedron 59 (2003) 1429–1441
A general method for the synthesis of oligosaccharides
consisting of a-(1!2)- and a-(1!3)-linked rhamnan backbones
and GlcNAc side chains
*
Jianjun Zhang and Fanzuo Kong
Research Center for Eco-Environmental Sciences, Academia Sinica, P.O. Box 2871, Beijing 100085, People’s Republic of China
Received 31 October 2002; revised 11 December 2002; accepted 9 January 2003
Abstract—A general method has been developed for the synthesis of oligosaccharides consisting of (1!2)- and (1!3)-linked rhamnans
with GlcNAc side chains. As examples, highly effective and convergent syntheses of two decasaccharides in the O polysaccharide moiety of
the lipopolysaccharide of the phytopathogenic bacterium Pseudomonas syringae pv. ribicola NCPPB 1010 were achieved. The two
decasaccharides consist of O polysaccharide repeating units IþII and IIþI, respectively. Allyl 3-O-acetyl-4-O-benzoyl-a-L-rhamnopyrano-
side, allyl 2-O-benzoyl-3-O-chloroacetyl-a-L-rhamnopyranoside, 2,4-di-O-benzoyl-3-O-chloroacetyl-a-L-rhamnopyranosyl trichloro-
acetimidate, and 3-O-acetyl-2,4-di-O-benzoyl-a-L-rhamnopyranosyl trichloroacetimidate, which were obtained by highly regioselective
3-O-acylations, were used as the key synthons to obtain the required a-(1!2)- and a-(1!3)-linked rhamnoocta saccharide acceptors with
33- and 37-free hydroxyl groups. Therefore, several disaccharides were synthesized, from which tetrasaccharides and hexasaccharides were
then synthesized. Coupling of the hexasaccharide donors with the disaccharide acceptors gave the octasaccharide acceptors. Finally, the
coupling of 3,4,6-tri-O-acetyl-2-deoxy-2-phthalimido-b-D-glucopyranosyl trichloroacetimidate with the octasaccharide acceptors, followed
by deprotection, afforded the two target decasaccharides. A repeating hexasaccharide unit of the cell wall polysaccharide of b-hemolytic
Streptococci Group A was also synthesized in a similar way. q 2003 Elsevier Science Ltd. All rights reserved.
1. Introduction
A similar structure (III) with alternate (1!2)- and (1!3)-
linked rhamnan backbone and 3-O-GlcNAc side chains on
the !2)-rhamnose residues occur in the cell wall poly-
saccharide of the b-hemolytic Streptococci Group A, which
is one of the primary infective agents in humans, causing
streptococcal pharyngitis, known as strep throat, and
sometimes rheumatic fever.2
The phytopathogenic bacterium Pseudomonas syringae
causes diseases in nearly all cultivated plants and in an
unknown number of wild plant species. Recently, Knirel
et al. reported that the O polysaccharide (OPS) moiety of the
lipopolysaccharide (LPS) of P. syringae pv. ribicola
NCPPB 1010 was composed of branched pentasaccharide
repeating units (O repeats) of two types, major I and minor
II, differing in the position of substitution of one of the
rhamnose residues.1
Synthetic samples of higher-order rhamnan structures
spanning two or more branch points would be very valuable
in the research of plant pathology and in the design of
immunodiagnostic reagents. However, the efficient syn-
thesis of complex rhamnans with a backbone of different
linkages, and multiple sugar side chains represents a
challenge task, since it is difficult to finish the synthesis
with a simple process. The synthesis of structure III3 and its
frame-shifted analogue,4 has been reported by Pinto’s group
using a procedure involving orthogonal masking groups and
multiple protection–deprotection steps. We present herein a
general and facile method for construction of (1!2)- and
(1!3)-linked rhamnans with GlcNAc side chains.
Keywords: Pseudomonas syringae; rhamnose; glycosylation.
*
Corresponding author. Tel.: þ86-10-629-366-13; fax: þ86-10-629-235-
63; e-mail: fzkong@mail.rcees.ac.cn
0040–4020/03/$ - see front matter q 2003 Elsevier Science Ltd. All rights reserved.
doi:10.1016/S0040-4020(03)00075-9

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J. Zhang, F. Kong / Tetrahedron 59 (2003) 1429–1441
2. Results and discussion
isopropylidenation with 2,2-dimethoxypropane, 4-O-
benzoylation, and removal of 2,3-O-isopropylidene.
Selective chloroacetylation and acetylation with chloro-
acetyl chloride and acetyl chloride, respectively, in pyridine
proceeded smoothly to give allyl 4-O-benzoyl-3-O-chloro-
acetyl- (3) and 3-O-acetyl-4-O-benzoyl-a-L-rhamnopyrano-
side (4) in high yields (88 and 93%, respectively). The
selective 3-O-chloroacetylation and 3-O-acetylation were
As a typical example of the method, the synthesis of the
decasaccharide consisting of two pentasaccharide repeating
units IþII of the O polysaccharide moiety of P. syringae pv.
ribicola NCPPB 1010 was carried out as outlined in
Scheme 1. Allyl a-L-rhamnoside (1) was converted to
allyl 4-O-benzoyl-a-L-rhamnopyranoside (2) by 2,3-O-
Scheme 1. Conditions and reagents: (also suitable for Scheme 2 and Scheme 3) (a) (i) 2,2-Dimethoxypropane, DMF, toluenesulfonic acid; (ii) BzCl–pyridine;
(iii) 90% HOAc. (b) For 3: ClCH2COCl, CH2Cl2, pyridine; for 4: CH3COCl, CH2Cl2, pyridine. (c) BzCl–pyridine. (d) 1–5% CH3COCl/CH3OH, 08C to room
temperature. (e) PdCl2, CH3COOH/CH3COONa, then CCl3CN, CH2Cl2, DBU, room temperature. (f) TMSOTf, CH2Cl2, 08C to room temperature. (g) Thiourea
in EtOH–CH2Cl2 (1:4), reflux. (h) (i) EtOH/10% hydrazine hydrate, reflux, 48 h; (ii) Ac2O–pyridine (dry), room temperature, 12 h; (iii) satd NH3/MeOH,
room temperature, 72 h.

J. Zhang, F. Kong / Tetrahedron 59 (2003) 1429–1441
1431
Scheme 2.
the key steps in the synthesis, because the resulting 3-O-
chloroacetyl rhamnoside 3 and the 3-O-acetyl rhamnoside 4
were not only the required acceptors for construction of
(1!2)-linked disaccharides, but could also be transformed
to the related donors. These rhamnose donors and acceptors
could then be assembled and transformed in an appropriate
way to build a (1!2)- and (1!3)-linked long chain with
acetyl groups as temporary hydroxyl protecting groups at
the branched points. Thus, 3 and 4 were benzoylated to
produce the corresponding allyl 2,4-di-O-benzoyl-3-O-
chloroacetyl- (5) and 3-O-acetyl-2,4-di-O-benzoyl-a-L-
rhamnopyranoside (6), respectively in quantitative yields.
Deallylation of 5 and 6 with PdCl2,5 followed by
trichloroacetimidation with trichloroacetonitrile6 gave the
donors 8 (83% for 2 steps) and 9 (87% for 2 steps),
respectively. Selective deacetylation7 of 6 gave acceptor 7.
Condensation of 4 with 2,3,4-tri-O-benzoyl-a-L-rhamno-
pyranosyl trichloroacetimidate (10) furnished the (1!2)-
linked disaccharide, 11. Subsequent deallylation and
trichloroacetimidation yielded the disaccharide donor, 12.
Glycosylation of acceptor 7 with imidate 9 gave disacchar-
ide 13. Subsequent deacetylation of 13 gave disaccharide
acceptor 14. Condensation of 12 with 14 offered the tail
(nonreducing end) tetrasaccharide 17. Deacetylation fol-
lowed to give the tetrasaccharide acceptor 18, which was the
key precursor for the construction of the pentasaccharide
structure I or II. Disaccharide 15, an inner moiety of the
backbone, was built by the coupling of 8 with 4.
Dechloroacetylation of 15 gave the disaccharide acceptor
16, while deallylation of 17 followed by trichloroacetimida-
tion gave the tetrasaccharide donor 19. Coupling of 16 with
19 furnished hexasaccharide 20, and reiteration of deallyl-
ation and trichloroacetimidation transformed 20 to the
hexasaccharide donor, 21. Octasaccharide 22 was obtained
by glycosylation of 14 with 21. All of the glycosylation
reactions described above gave satisfactory yields (84–92%
for the disaccharides, 86% for the tetrasaccharide, 81% for
the hexasaccharide, and 83% for the octasaccharide),
making large-scale preparation possible. Selective deacetyl-
ation of 22 gave the octasaccharide acceptor 23 with 33- and
37- hydroxyl groups free, and subsequent coupling with
3,4,6-tri-O-acetyl-2-deoxy-2-phthalimido-D-glucopyrano-
syl trichloroacetimidate (24) gave decasaccharide 25.
Compound 25 was identified by its 1H and 13C NMR
spectra which showed 8 rhamnose H-6 signals at d 1.25,
1.17, 0.99, 0.71, 0.67, 0.62, 0.47, and 0.40 ppm, 8 rhamnose
C-1 signals at 99.44, 99.27, 98.98, 98.81, 98.50, 98.46,
96.24, 96.02 ppm, and two C-1 signals for glucosamines at
100.31 and 100.16 ppm. Decasaccharide 39 consisting of
two pentasaccharide repeating units IIþI was synthesized in
a similar way (Scheme 2). Thus, the disaccharide acceptor
methyl 2,4-di-O-benzoyl-a-L-rhamnopyranosyl-(1!3)-2,4-
di-O-benzoyl-a-L-rhamnopyranoside (29) was obtained by
the coupling of 9 with methyl 2,4-di-O-benzoyl-a-L-
rhamnopyranoside (27), followed by deacetylation. The
other disaccharide acceptor allyl 3,4-di-O-benzoyl-a-L-

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J. Zhang, F. Kong / Tetrahedron 59 (2003) 1429–1441
rhamnopyranosyl-(1!2)-3-O-acetyl-4-O-benzoyl-a-L-
rhamnopyranoside (33) was obtained by the coupling of 4
with 3,4-di-O-benzoyl-2-O-chloroacetyl-a-L-rhamno-
pyranoside (31). Condensation of the tetrasaccharide
donor 19 with disaccharide acceptor 33 gave hexasacchar-
ide 34. Deallylation of 34, followed by trichloroacetimida-
tion, produced hexasaccharide donor 35, whose coupling
with disaccharide acceptor 29 and subsequent selective
deacetylation afforded the octasaccharide acceptor 37. The
final two steps to obtain 39 were exactly the same as those in
the preparation of decasaccharide 26 from 23. Protected
decasaccharide 38 clearly had all of the characteristic peaks
in its 1H NMR (d 1.39, 1.31, 1.11, 1.05, 0.72, 0.69, 0.59 and
0.55 ppm for 8 rhamnose H-6 signals) and 13C NMR
(100.05, 99.91, 99.59, 99.32, 99.32, 99.32, 99.16, 98.59,
98.13, 91.97 ppm for 10 C-1 signals) spectra.
Perkin–Elmer model 241-MC automatic polarimeter for
1
solutions in a 1-dm jacketed cell. H NMR and 13C NMR
spectra were recorded on Varian XL-400 and Varian
XL-200 spectrometers, for solutions in CDCl3 or in D2O
as indicated. Chemical shifts are expressed in ppm down-
field from the Me4Si absorption. Mass spectra were
recorded on 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) sulfuric acid in methanol or by UV
detection. Column chromatography was conducted by the
elution of columns (8£100 mm, 16£240 mm, 18£300 mm,
35£400 mm) of silica gel (100–200 mesh) with EtOAc/
petroleum ether (bp 60–908C) 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 mm or 4.6£250 mm), differential
refractometer (132-RI Detector), UV/vis detector (model
118). EtOAc–petroleum ether (bp 60–908C) was used as
the eluent at a flow rate of 1–4 mL/min. Solutions were
concentrated at a temperature ,608C under reduced
pressure.
With the disaccharide synthons 12 and 16 in hand,
hexasaccharide III can also be synthesized in a facile
manner. Thus, the coupling of donor 12 with acceptor 16
gave tetrasaccharide 40, and its subsequent deacetylation
furnished tetrasaccharide diol acceptor 41. Condensation of
24 with 41 produced the protected hexasaccharide, 42
(Scheme 3).
3.1.1. Allyl 4-O-benzoyl-a-L-rhamnopyranoside (2). To a
solution of allyl a-L-rhamnopyranoside (1) (2.04 g,
10 mmol) in DMF (10 mL) containing p-TsOH·H2O
(38 mg, 0.2 mmol) was added 2,2-dimethoxypropane
(2.5 mL, 20 mmol). The mixture was stirred for 12 h, at
the end of which time TLC (3:1 petroleum ether–EtOAc)
indicated that the reaction was complete. Then a solution of
pyridine (20 mL) containing benzoyl chloride (4.7 mL,
40 mmol) was added dropwise to the reaction mixture. After
stirring for 24 h at room temperature, the mixture was
diluted with CH2Cl2, and washed sequentially with 1 M
HCl, water, and satd NaHCO3 (aq). The organic layers were
combined, dried, and concentrated to give a residue. The
residue was dissolved in 90% acetic acid and refluxed for
1 h. The solution was concentrated. Purification of the
residue by flash column chromatography on silica gel (1:1
petroleum ether–EtOAc) gave compound 2 (2.63 g, 85%)
as a syrup; [a]D25¼271.3 (c 1.3, CHCl3); nmax (KBr) 3439,
2980, 1736, 1267, 1050, 826, 710; dH (400 MHz, CDCl3)
8.06–7.42 (m, 5H, Ph), 5.93 (m, 1H, OCH2CHvCH2),
5.32–5.21 (m, 2H, OCH2CHvCH2), 5.07 (dd, 1H,
J3,4¼9.9 Hz, J4,5¼9.9 Hz, H-4), 4.92 (d, 1H, J1,2¼0.8 Hz,
H-1), 4.24–3.98 (m, 5H), 3.07–2.90 (bs, 2H, 2 OH), 1.24
(d, 3H, J5,6¼6.4 Hz, H-6); dC (100 MHz, CDCl3) 165.4
(PhCO), 117.8 (OCH2CHvCH2), 98.6 (C-1), 71.6, 70.1,
67.7, 66.9, 17.3. Anal. calcd for C16H20O6: C, 62.32; H,
6.54. Found: C, 62.49; H, 6.76.
Conventional removal of phthalimido group from 25, 38,
and 42 using hydrazine worked well; however, the reaction
of 25 and 42 was accompanied by simultaneous reduction of
the allyl group to propyl.4 Subsequent acetylation of the
amino groups and deacylation of the protective hydroxyl
groups with sodium methoxide–methanol gave unprotected
decasaccharides 26 and 39, and hexasaccharide 43 (III),
respectively. The decasaccharides were characterized by
1
mass and H NMR spectroscopy, and the hexasaccharide
showed spectral data similar to those reported in the
literature.3
In summary, we have presented herein a general
and convergent method that can be applied to the
synthesis of (1!2)- and (1!3)-linked rhamnans with
arbitrary sugar side chains on the 3-OH of the rhamnose
residues.
3. Experimental
3.1. General methods
Melting points were determined using a ‘Mel-Temp’
apparatus. Optical rotations were determined using a
Scheme 3.

J. Zhang, F. Kong / Tetrahedron 59 (2003) 1429–1441
1433
3.1.2. Allyl 4-O-benzoyl-3-O-chloroacetyl-a-L-rhamno-
pyranoside (3). Compound 2 (3.08 g, 10 mmol) was
dissolved in dry CH2Cl2 (40 mL) containing pyridine
(8.1 mL, 100 mmol), then under N2, chloroacetyl chloride
(0.7 mL, 11 mmol) in anhydrous CH2Cl2 (10 mL) was
added dropwise to the solution over 30 min at 08C. The
reaction mixture was slowly raised to room temperature and
stirred for 2 h, at the end of which time TLC (3:1 petroleum
ether–EtOAc) indicated that the reaction was complete. The
reaction mixture was diluted with CH2Cl2 (100 mL),
washed with water, 1 M HCl, and dried (Na2SO4). The
solution was concentrated, and purification of the residue by
column chromatography on silica gel (3:1 petroleum ether–
EtOAc) gave compound 3 (3.20 g, 83%) as a syrup;
[a]2D5¼239.2 (c 0.7, CHCl3); nmax (KBr) 3443, 2970,
1733, 1271, 1079, 1026, 711; dH (400 MHz, CDCl3) 8.05–
7.43 (m, 5H, Ph), 5.93 (m, 1H, CH2vCH–CH2O), 5.50 (dd,
1H, J2,3¼3.1 Hz, J3,4¼10.0 Hz, H-3), 5.40 (dd, 1H,
J3,4¼10.0 Hz, J4,5¼10.0 Hz, H-4), 5.37–5.24 (m, 2H,
CH2vCH–CH2O), 4.91 (d, 1H, J1,2¼1.6 Hz, H-1), 4.24
(m, 1H, CH2vCH–CH2O), 4.18 (dd, 1H, J1,2¼1.6 Hz,
J2,3¼3.1 Hz, H-2), 4.08–4.02 (m, 2H, CH2vCH–CH2O,
graphy (4:1 petroleum ether–EtOAc) gave 5 (4.52 g, 92%)
as a syrup; [a]D25¼þ75.7 (c 1.3, CHCl3); nmax (KBr) 2974,
1729, 1274, 1079, 1022, 713; dH (400 MHz, CDCl3) 7.97–
7.26 (m, 10H, Ph), 5.95 (m, 1H, OCH2CHvCH2), 5.77 (dd,
1H, J2,3¼3.4, J3,4¼10.2 Hz, H-3), 5.55–5.50 (m, 2H, H-2,
H-4), 5.40–5.26 (m, 2H, OCH2CHvCH2), 4.94 (d, 1H,
J1,2¼1.7 Hz, H-1), 4.26 (m, 1H, OCH2CHvCH2), 4.20 (d,
1H, 2J¼8.9 Hz, ClCH2CO), 4.16 (d, 1H, 2J¼8.9 Hz,
ClCH2CO), 4.16–4.07 (m, 2H, H-5, OCH2CHvCH2),
1.32 (d, 3H, J5,6¼6.3 Hz, H-6); dC (100 MHz, CDCl3)
170.6 (ClCH2CO), 166.3, 165.7 (PhCO), 117.8 (OCH2-
CHvCH2), 98.6 (C-1), 71.8, 70.4, 68.7, 68.6, 40.0
(ClCH2CO), 17.7. Anal. calcd for C25H25ClO8: C, 61.41;
H, 5.15. Found: C, 61.22; H, 5.10.
3.1.5. Allyl 3-O-acetyl-2,4-di-O-benzoyl-a-L-rhamno-
pyranoside (6). Compound 4 (3.50 g, 10 mmol) was
benzoylated under the same conditions as those used for
the preparation of 5 from 3, giving 6 (4.30 g, 95%) as a
foamy solid; [a]D25¼þ76.3 (c 1.0, CHCl3); nmax (KBr) 1730,
1270, 1112, 1073, 716; dH (400 MHz, CDCl3) 8.13–7.26
(m, 10H, Ph), 5.98 (m, 1H, OCH2CHvCH2), 5.65 (dd, 1H,
J2,3¼3.4 Hz, J3,4¼10.1 Hz, H-3), 5.54 (dd, 1H, J1,2¼1.7 Hz,
J2,3¼3.4 Hz, H-2), 5.47 (t, 1H, J3,4¼10.1 Hz, J4,5¼10.1 Hz,
H-4), 5.39–5.25 (m, 2H, OCH2CHvCH2), 4.98 (d, 1H,
J1,2¼1.7 Hz, H-1), 4.21–4.06 (m, 3H, H-5, OCH2-
CHvCH2), 1.86 (s, 3H, CH3CO), 1.32 (d, 3H,
J5,6¼6.2 Hz, H-6); dC (100 MHz, CDCl3) 169.7 (CH3CO),
167.0, 166.3 (PhCO), 117.9 (OCH2CHvCH2), 97.4 (C-1),
70.9, 70.4, 69.3, 68.0, 20.6 (CH3CO), 17.8. Anal. calcd for
C25H26O8: C, 66.07; H, 5.77. Found: C, 66.19; H, 5.50.
2
H-5), 3.97 (d, 1H, J¼17.5 Hz, ClCH2CO), 3.93 (d, 1H,
2J¼17.5 Hz, ClCH2CO), 1.28 (d, 3H, J5,6¼6.4 Hz, H-6); dC
(100 MHz, CDCl3) 170.6 (ClCH2CO), 166.2 (PhCO), 117.8
(OCH2CHvCH2), 97.4 (C-1), 71.4, 70.6, 68.1, 66.7, 40.2
(ClCH2CO), 17.3. Anal. calcd for C18H21ClO7: C, 56.15; H,
5.50. Found: C, 56.03; H, 5.69.
3.1.3. Allyl 3-O-acetyl-4-O-benzoyl-a-L-rhamnopyrano-
side (4). Compound 2 (3.08 g, 10 mmol) was dissolved in
dry CH2Cl2 (40 mL) containing pyridine (8.1 mL,
100 mmol), then under N2, acetyl chloride (0.8 mL,
11 mmol) in anhydrous CH2Cl2 (10 mL) was added
dropwise to the solution over 30 min at 08C. The reaction
mixture was slowly raised to room temperature and stirred
for 2 h, at the end of which time TLC (3:1 petroleum ether–
EtOAc) indicated that the reaction was complete. The
reaction mixture was diluted with CH2Cl2 (100 mL),
washed with water, 1 M HCl, and dried (Na2SO4). The
solution was concentrated, and purification of the residue by
column chromatography on silica gel (3:1 petroleum ether–
EtOAc) gave compound 4 (3.24 g, 93%) as a syrup;
[a]2D5¼253.2 (c 1.1, CHCl3); dH (400 MHz, CDCl3)
8.02–7.43 (m, 5H, Ph), 5.93 (m, 1H, CH2vCH–CH2O),
5.46 (dd, 1H, J2,3¼3.2 Hz, J3,4¼10.0 Hz, H-3), 5.37 (dd,
1H, J3,4¼10.0 Hz, J4,5¼10.0 Hz, H-4), 5.37–5.23 (m, 2H,
CH2vCH–CH2O), 4.90 (d, 1H, J1,2¼1.6 Hz, H-1), 4.23 (m,
1H, CH2vCH–CH2O), 4.12 (dd, 1H, J1,2¼1.6 Hz,
J2,3¼3.2 Hz, H-2), 4.08–4.01 (m, 2H, CH2vCH–CH2O,
H-5), 1.97 (s, 3H, CH3CO), 1.27 (d, 3H, J5,6¼6.3 Hz, H-6).
Anal. calcd for C18H22O7: C, 61.70; H, 6.33. Found: C,
61.96; H, 6.24.
3.1.6. Allyl 2,4-di-O-benzoyl-a-L-rhamnopyranoside (7).
To a solution of 6 (2.27 g, 5 mmol) in anhydrous MeOH
(50 mL) was added acetyl chloride (1.5 mL) at 08C. The
solution was stirred at room temperature until TLC (3:1
petroleum ether–EtOAc) showed that the starting material
had been consumed. The solution was neutralized with
Et3N, then concentrated to dryness. The residue was passed
through a short silica gel column to give 7 (1.81 g, 88%) as a
syrup; [a]D¼þ46.7 (c 1.1, CHCl3); nmax (KBr) 3443, 1736,
1269, 1110, 1025, 713; dH (400 MHz, CDCl3) 8.12–7.45
(m, 10H, Ph), 5.97 (m, 1H, OCH2CHvCH2), 5.41 (dd, 1H,
J1,2¼1.7 Hz, J2,3¼3.5 Hz, H-2), 5.39–5.25 (m, 2H, OCH2-
CHvCH2), 5.28 (dd, 1H, J3,4¼10.0 Hz, J4,5¼10.0 Hz, H-4),
5.02 (d, 1H, J1,2¼1.7 Hz, H-1), 4.34 (dd, 1H, J2,3¼3.5 Hz,
J3,4¼10.0 Hz, H-3), 4.27–4.05 (m, 3H, H-5, OCH2-
CHvCH2), 1.33 (d, 3H, J5,6¼6.3 Hz, H-6); dC (100 MHz,
CDCl3) 166.8, 165.6 (PhCO), 117.8 (OCH2CHvCH2), 98.0
(C-1), 70.6, 70.0, 69.1, 68.4, 17.7. Anal. calcd for C23H24O7:
C, 66.98; H, 5.87. Found: C, 66.81; H, 5.68.
3.1.7. 2,4-Di-O-benzoyl-3-O-chloroacetyl-a-L-rhamno-
pyranosyl trichloroacetimidate (8). To a solution of
compound 5 (2.44 g, 5 mmol) in 90% acetic acid (50 mL)
containing sodium acetate (1.46 g, 15 mmol) was added
PdCl2 (270 mg, 2.5 mmol). The mixture was stirred for
12 h, at the end of which time TLC (3:1 petroleum ether–
EtOAc) indicated that the reaction was complete. The
reaction mixture was diluted with CH2Cl2 (150 mL),
washed with water and satd Na2CO3 (aq). The organic
layer was concentrated, and the residue was passed through
a short silica gel column with 2:1 petroleum ether–EtOAc
3.1.4. Allyl 2,4-di-O-benzoyl-3-O-chloroacetyl-a-L-
rhamnopyranoside (5). To the solution of compound 3
(3.85 g, 10 mmol) in pyridine (20 mL) was added benzoyl
chloride (2.4 mL, 20 mmol) dropwise, and the mixture was
stirred overnight at room temperature. Ice water was added,
and the mixture was diluted with CH2Cl2, washed with 1 M
HCl, water, and satd Na2CO3 (aq) sequentially. The organic
layers were combined, dried (Na2SO4), and concentrated.
Purification of the crude product by column chromato-

1434
J. Zhang, F. Kong / Tetrahedron 59 (2003) 1429–1441
as the eluent to give crude 2,4-di-O-benzoyl-3-O-chloro-
acetyl-a,b-L-rhamnopyranose as a syrup. A solution of the
above syrup in dry CH2Cl2 (30 mL), CCl3CN (1.0 mL,
10 mmol) and DBU (135 mL, 0.9 mmol) was stirred at room
temperature for 2 h. The solvents were removed in vacuo.
The residue was purified by silica gel flash column
chromatography to give trichloroacetimidate 8 (2.46 g,
83%) as a white foam; [a]2D5¼þ49.3 (c 1.1, CHCl3); nmax
(KBr) 3344, 1730, 1270, 1064, 711; dH (400 MHz, CDCl3)
8.80 (s, 1H, CNHCCl3), 8.14–7.25 (m, 10H, Ph), 6.42 (d,
acetimidate under the same conditions as those used for the
preparation of 8 from 5, giving 12 (3.90 g, 85%) as a foamy
solid; [a]D¼þ113.6 (c 0.6, CHCl3); nmax (KBr) 3339, 1730,
1270, 1107, 712; 1H NMR d 8.74 (s, 1H, CNHCCl3), 8.11–
7.26 (m, 20H, Ph), 6.44 (d, 1H, J1,2¼1.6 Hz, H-1), 5.94 (dd,
0
0
0
0
0
1H, J2 ,3 ¼3.4 Hz, J3 ,4 ¼10.0 Hz, H-3 ), 5.76 (dd, 1H,
0
0
0
0
0
0
0
J1 ,2 ¼1.0 Hz, J2 ,3 ¼3.4 Hz, H-2 ), 5.71 (t, 1H, J3 ,4
¼
0
0
0
10.0 Hz, J4 ,5 ¼10.0 Hz, H-4 ), 5.62–5.55 (m, 2H, H-3,
H-4), 5.23 (d, 1H, J1,2¼1.0 Hz, H-10), 4.44 (dd, 1H,
J1,2¼1.6 Hz, J2,3¼3.1 Hz, H-2), 4.38 (m, 1H, H-5), 4.28
1H, J1,2¼1.9 Hz, H-1), 5.77 (dd, 1H, J1,2¼1.9 Hz, J2,3
¼
(m, 1H, H-50), 2.06 (s, 3H, CH3CO), 1.43 (d, 3H,
0
0
0
3.2 Hz, H-2), 5.71 (dd, 1H, J2,3¼3.2 Hz, J3,4¼10.2 Hz,
H-3), 5.94 (dd, 1H, J3,4¼10.2 Hz, J4,5¼10.2 Hz, H-4), 4.30
(m, 1H, H-5), 3.93 (d, 1H, 2J¼15.2 Hz, ClCH2CO), 3.87 (d,
1H, 2J¼15.2 Hz, ClCH2CO), 1.40 (d, 3H, J5,6¼6.2 Hz,
H-6). Anal. calcd for C24H21Cl4NO8: C, 48.59; H, 3.57.
Found: C, 48.71; H, 3.50.
J5,6¼6.3 Hz, H-6), 1.40 (d, 3H, J5 ,6 ¼6.3 Hz, H-6 ). Anal.
calcd for C44H40Cl3NO14: C, 57.87; H, 4.42. Found: C,
57.72; H, 4.31.
3.1.11. Allyl 3-O-acetyl-2,4-di-O-benzoyl-a-L-rhamno-
pyranosyl-(1!3)-2,4-di-O-benzoyl-a-L-rhamnopyrano-
side (13). Compounds 7 (2.06 g, 5.0 mmol) and 9 (2.80 g,
5.0 mmol) were coupled under the same conditions as those
used for the preparation of 11 from 4 and 10, giving 13
(3.38 g, 84%) as a foamy solid; [a]2D5¼þ105.8 (c 1.3,
CHCl3); dH (400 MHz, CDCl3) 8.23–7.37 (m, 20H, Ph),
5.95 (m, 1H, OCH2CHvCH2), 5.46 (dd, 1H, J3,4¼9.8 Hz,
3.1.8. 3-O-Acetyl-2,4-di-O-benzoyl-a-L-rhamnopyrano-
syl trichloroacetimidate (9). Compound
6 (4.54 g,
10 mmol) was deallylated and subsequently converted to
the trichloroacetimidate under the same conditions as that
used for the preparation of 8 from 5, giving 9 (4.84 g, 87%)
as a foamy solid; [a]2D5¼þ50.8 (c 0.5, CHCl3); dH
(400 MHz, CDCl3) 8.77 (s, 1H, CNHCCl3), 8.10–7.27 (m,
10H, Ph), 6.42 (d, 1H, J1,2¼1.6 Hz, H-1), 5.60 (dd, 1H,
J2,3¼3.2 Hz, J3,4¼10.0 Hz, H-3), 5.57 (dd, 1H, J1,2¼1.6 Hz,
J2,3¼3.2 Hz, H-2), 5.42 (t, 1H, J3,4¼10.0 Hz, J4,5¼10.0 Hz,
H-4), 4.32 (m, 1H, H-5), 1.97 (s, 3H, COCH3), 1.44 (d, 3H,
J5,6¼6.2 Hz, H-6). Anal. calcd for C24H22Cl3NO8: C, 51.59;
H, 3.96. Found: C, 51.40; H, 3.74.
J4,5¼9.8 Hz, H-4), 5.51 (dd, 1H, J1,2¼1.8 Hz, J2,3¼3.5 Hz,
0
0
0
0
0
H-2), 5.37 (dd, 1H, J2 ,3 ¼3.1 Hz, J3 ,4 ¼9.7 Hz, H-3 ), 5.33
0
0
(m, 1H, OCH2CHvCH2), 5.29 (t, 1H, J3 ,4 ¼9.7 Hz,
0
0
0
J4 ,5 ¼9.7 Hz, H-4 ), 5.25 (m, 1H, OCH2CHvCH2), 5.15–
5.13 (m, 2H, H-10, H-20), 5.05 (d, 1H, J1,2¼1.8 Hz, H-1),
4.47 (dd, 1H, J2,3¼3.5 Hz, J3,4¼9.8 Hz, H-3), 4.22–4.04
(m, 4H, H-50, H-5, OCH2CHvCH2), 1.71 (s, 3H, CH3CO),
1.34 (d, 3H, J5,6¼6.3 Hz, H-6/H-60), 1.15 (d, 3H,
J5,6¼6.2 Hz, H-6/H-60); dC (100 MHz, CDCl3) 169.1
(CH3CO), 166.1, 165.6, 165.5, 164.9 (4PhCO), 117.9
(OCH2CHvCH2), 99.3, 96.4 (2C-1), 20.4 (CH3CO), 17.6,
17.3 (2C-6). Anal. calcd for C45H44O14: C, 66.82; H, 5.48.
Found: C, 66.70; H, 5.53.
3.1.9. Allyl 2,3,4-tri-O-benzoyl-a-L-rhamnopyranosyl-
(1!2)-3-O-acetyl-4-O-benzoyl-a-L-rhamnopyranoside
(11). To a cooled solution (08C) of 4 (1.75 g, 5 mmol) and
2,3,4-tri-O-benzoyl-a-L-rhamnopyranosyl trichloroacetimi-
date (10) (3.25 g, 5.3 mmol) in anhydrous CH2Cl2 (30 mL)
was added TMSOTf (36 mL, 0.2 mmol). The mixture was
stirred at this temperature for 2 h, then neutralized with
Et3N, and concentrated. The residue was purified by silica
gel column chromatography to give 11 (3.41 g, 84%) as a
foamy solid; [a]D25¼þ118.4 (c 1.0, CHCl3); nmax (KBr)
1730, 1267, 1112, 714; dH (400 MHz, CDCl3) 8.11–7.41
3.1.12. Allyl 2,4-di-O-benzoyl-a-L-rhamnopyranosyl-
(14).
(1!3)-2,4-di-O-benzoyl-a-L-rhamnopyranoside
Compound 13 (3.00 g, 3.7 mmol) was deacetylated under
the same conditions as those used for the preparation of 7
from 6, giving 14 (2.33 g, 82%) as a foamy solid;
[a]2D5¼þ92.2 (c 0.5, CHCl3); nmax (KBr) 3447, 1275,
1266, 1110, 712; dH (400 MHz, CDCl3) d 8.21–7.38 (m,
(m, 20H, Ph), 5.98 (m, 1H, OCH2CHvCH2), 5.92 (dd, 1H,
0
0
0
0
0
0
0
0
20H, Ph), 5.93 (m, 1H, CH2vCH–CH2), 5.56 (t, 1H, J3 ,4
0
J2 ,3 ¼3.2 Hz, J3 ,4 ¼9.8 Hz0, H-3 ), 5.74 (dd, 1H, J1 ,2
¼
¼
0
0
0
0
0
0
0
0
0
1.4 Hz, J2 ,3 ¼3.5 Hz, H-2 ), 5.70 (t, 1H, J3 ,4 ¼9.8 Hz,
9.9 Hz, J4 ,5 ¼9.9 0Hz, H-4 ), 5.51 (dd, 1H, J1 ,2 ¼1.8 Hz,
0
0
0
0
0
J4 ,5 ¼9.8 Hz, H-4 ), 5.54 (dd, 1H, J2,3¼3.2 Hz, J3,4
¼
J2 ,3 ¼3.5 Hz, H-2 ), 5.38–5.25 (m, 2H, CH2vCH–CH2),
0
0
0
10.1 Hz, H-3), 5.47 (dd, 1H, J3,4¼10.1 Hz, J4,5¼10.1 Hz,
H-4), 5.38–5.25 0 (m, 2H, OCH2CHvCH2), 5.14 (d, 1H,
5.18 (d, 1H, J1 ,2 ¼1.8 Hz, H-1 ), 5.07 (t, 1H, J3,4¼9.8 Hz,
J4,5¼9.8 Hz, H-4), 5.04 (d, 1H, J1,2¼1.7 Hz, H-1), 5.00 (dd,
1H, J1,2¼1.7 Hz, J2,3¼3.5 Hz, H-2), 4.47 (dd, 1H,
J2,3¼3.5 Hz, J3,4¼9.8 Hz, H-3), 4.23 (m, 1H, CH2vCH–
CH2), 4.10–4.04 (m, 3H, H-30, H-5, CH2vC0H–CH2), 3.98
0
0
J1 ,2 ¼1.4 Hz,H-1 ), 4.98 (d, 1H, J1,2¼1.5 Hz, H-1), 4.32–
4.24 (m, 2H, H-50, OCH2CHvCH2), 4.19 (dd, 1H,
J1,2¼1.5 Hz, J2,3¼3.2 Hz, H-2), 4.11–4.04 (m, 2H, H-5,
OCH2CHvCH2), 2.04 (s, 3H, CH3CO), 1.34 (d, 3H,
J5,6¼6.3 Hz, H-6/H-60), 1.15 (d, 3H, J5,6¼6.2 Hz, H-6/
H-60); dC (100 MHz, CDCl3) 170.6 (CH3CO), 165.8, 165.3,
165.2, 165.1 (4PhCO), 117.8 (OCH2CHvCH2), 99.5, 97.5
(2C-1), 20.7 (CH3CO), 17.6, 17.5 (2C-6). Anal. calcd for
C45H44O14: C, 66.82; H, 5.48. Found: C, 67.01; H, 5.74.
(m, 1H, H-50), 1.34 (d, 3H, J5 ,6 ¼6.4 Hz, H-6 ), 1.12 (d, 3H,
J5,6¼6.4 Hz, H-6); dC (100 MHz, CDCl3) 166.6, 166.3,
165.7, 165.0 (4PhCO), 117.8 (OCH2CHvCH2), 98.9, 97.4
(2C-1), 17.7, 17.3 (2C-6). Anal. calcd for C43H42O13: C,
67.35; H, 5.52. Found: C, 67.44; H, 5.40.
0
0
3.1.13. Allyl 2,4-di-O-benzoyl-3-O-chloroacetyl-a-L-
rhamnopyranosyl-(1!2)-3-O-acetyl-4-O-benzoyl-a-L-
rhamnopyranoside (15). Compound 4 (1.75 g, 5.0 mmol)
and 8 (2.97 g, 5.0 mmol) were coupled under the same
conditions as those used for the preparation of 11 from 4 and
3.1.10. 2,3,4-Tri-O-benzoyl-a-L-rhamnopyranosyl-
(1!2)-3-O-acetyl-4-O-benzoyl-a-L-rhamnopyranosyl
trichloroacetimidate (12). Compound 11 (4.04 g, 5 mmol)
was deallylated and subsequently converted to the trichloro-

J. Zhang, F. Kong / Tetrahedron 59 (2003) 1429–1441
1435
10, giving 15 as a foamy solid (3.44 g, 88%); [a]2D5¼þ66.2
(c 1.9, CHCl3); nmax (KBr) 1736, 1270, 1074, 1026, 713; dH
(400 MHz, CDCl3) 8.10–7.45 (m, 15H, Ph), 5.94 (m, 1H,
(d, 3H, J5,6¼6.4 Hz, H-6), 1.09 (d, 3H, J5,6¼6.4 Hz, H-6),
0.94 (d, 3H, J5,6¼6.2 Hz, H-6), 0.70 (d, 3H, J5,6¼6.3 Hz,
H-6); dC (100 MHz, CDCl3) 169.7 (CH3CO), 165.9
(2C), 165.8, 165.6, 165.2, 165.1 (2C), 165.0 (8PhCO),
118.0 (OCH2CHvCH2), 100.2, 99.3, 99.0, 96.3 (4C-1),
20.6 (CH3CO), 17.7, 17.3, 17.2, 16.8 (4C-6). Anal. calcd
for C85H80O26: C, 67.27; H, 5.31. Found: C, 67.42; H,
5.51.
0
0
0
0
OCH2CHvCH2), 5.78 (dd, 1H, J2 ,3 ¼3.4 Hz, J3 ,4
¼
10.1 Hz, H-30), 5.63 (dd, 1H, J1 ,2 ¼1.8 Hz, J2 ,3 ¼3.4 Hz,
0
0
0
0
H-20), 5.53 (t, 1H, J3 ,4 ¼10.1 Hz, J4 ,5 ¼10.1 Hz, H-4 ), 5.51
0
0
0
0
0
(dd, 1H, J2,3¼3.2 Hz, J3,4¼9.7 Hz, H-3), 5.42 (dd, 1H,
J3,4¼9.7 Hz, J4,5¼9.7 Hz, H-4), 5.37–5.08 (m, 2H, OCH2-
0
0
0
CHvCH2), 5.08 (d, 1H, J1 ,2 ¼1.8 Hz, H-1 ), 4.95 (d, 1H,
J1,2¼1.6 Hz, H-1), 4.26–4.22 (m, 2H, H-50, OCH2-
CHvCH2), 4.16 (dd, 1H, J1,2¼1.6 Hz, J2,3¼3.2 Hz, H-2),
4.09–4.04 (m, 2H, H-5, OCH2CHvCH2), 3.92 (d, 1H,
3.1.16. Allyl 2,3,4-tri-O-benzoyl-a-L-rhamnopyranosyl-
(1!2)-4-O-benzoyl-a-L-rhamnopyranosyl-(1!3)-2,4-
di-O-benzoyl-a-L-rhamnopyranosyl-(1!3)-2,4-di-O-
benzoyl-a-L-rhamnopyranoside (18). To a solution of 17
(455 mg, 0.3 mmol) in anhydrous MeOH (50 mL) was
added acetyl chloride (1.0 mL) at 08C. The solution was
stirred at room temperature until TLC (3:1 petroleum ether–
EtOAc) showed that the starting material had been
consumed. The solution was neutralized with Et3N, then
concentrated to dryness. The residue was passed through a
short silica gel column to give 18 (410 g, 93%) as a syrup;
[a]2D5¼þ107.3 (c 1.1, CHCl3); nmax (KBr) 3443, 1731,
1265, 1101, 1024, 711; dH (400 MHz, CDCl3) 8.19–7.21
(m, 40H, Ph), 5.96 (m, 1H, OCH2CHvCH2), 5.72 (dd, 1H,
J2,3¼3.1 Hz, J3,4¼9.9 Hz, H-3), 5.59–5.52 (m, 4H), 5.39
(m, 1H, OCH2CHvCH2), 5.31 (dd, 1H, J3,4¼9.8 Hz,
J4,5¼9.8 Hz, H-4), 5.25 (m, 1H, OCH2CHvCH2), 5.20 (d,
1H, J1,2¼1.0 Hz, H-1), 5.11 (dd, J1,2¼0.8 Hz, J2,3¼3.0 Hz,
H-2), 5.03 (d, 1H, J1,2¼0.8 Hz, H-1), 5.00 (d, 1H,
J1,2¼1.1 Hz, H-1), 4.90 (t, 1H, J3,4¼9.8 Hz, J4,5¼9.8 Hz,
H-4), 4.59 (d, J1,2¼1.0 Hz, H-1), 4.48 (dd, 1H, J2,3¼3.4 Hz,
J3,4¼9.8 Hz, H-3), 4.25–3.98 (m, 6H), 3.60–3.54 (m, 3H),
1.32 (d, 3H, J5,6¼6.2 Hz, H-6), 1.10 (d, 6H, J5,6¼6.1 Hz,
H-6), 0.72 (d, 3H, J5,6¼6.3 Hz, H-6); dC (100 MHz, CDCl3)
166.5, 165.9 (2C), 165.8, 165.4 (2C), 165.3, 164.9 (8PhCO),
118.0 (OCH2CHvCH2), 100.3, 99.5, 99.2, 96.3 (4C-1),
17.6, 17.4, 17.3, 16.9 (4C-6). Anal. calcd for C83H78O25: C,
67.56; H, 5.33. Found: C, 67.44; H, 5.18.
2J¼14.9 Hz, ClCH2CO), 3.84 (d, 1H, J¼14.9 Hz, ClCH2-
2
CO), 2.03 (s, 3H, CH3CO), 1.36 (d, 3H, J5,6¼6.2 Hz, H-6/
H-60), 1.29 (d, 3H, J5,6¼6.2 Hz, H-6/H-60); dC (100 MHz,
CDCl3) 170.5 (CH3CO), 166.3 (ClCH2CO), 165.7, 165.4,
165.3 (3PhCO), 117.9 (OCH2CHvCH2), 99.4, 97.4 (2C-1),
40.4 (ClCH2CO), 20.7 (CH3CO), 17.6, 17.4 (2C-6). Anal.
calcd for C40H41ClO14: C, 61.50; H, 5.30. Found: C, 61.31;
H, 5.42.
3.1.14. Allyl 2,4-di-O-benzoyl-a-L-rhamnopyranosyl-
(1!2)-3-O-acetyl-4-O-benzoyl-a-L-rhamnopyranoside
(16). To a solution of 15 (3.20 g, 4.1 mmol) in EtOH
(25 mL) CH2Cl2 (100 mL) was added thiourea (0.36 g), and
the mixture was refluxed for 16 h, at the end of which time
TLC (3:1 petroleum ether–EtOAc) indicated that the
reaction was complete. The mixture was concentrated.
The residue was passed through a silica-gel column with 3:1
petroleum ether–EtOAc as the eluent to give 16 (2.33 g,
81%) as a foamy solid; [a]2D5¼þ52.7 (c 1.0, CHCl3); dH
(400 MHz, CDCl3) 8.13–7.46 (m, 15H, Ph), 5.92 (m, 1H,
OCH2CHvCH2), 5.52 (dd, 1H, J2,3¼3.2 Hz, J3,4¼9.8 Hz,
0
0
0
0
0
H-3), 5.48 (dd, 1H, J1 ,2 ¼1.4 Hz, J2 ,3 ¼3.3 Hz, H-2 ), 5.40
0
0
0
0
0
(t, 1H, J3 ,4 ¼9.8 Hz, J4 ,5 ¼9.8 Hz, H-4 ), 5.33 (m, 1H,
OCH2CHvCH2), 5.32 (t, 1H, J3,4¼9.9 Hz, J4,5¼9.9 Hz,
H-4), 5.25 (m, 1H, OCH2CHvCH2), 5.07 (d, 1H,
0
0
0
J1 ,2 ¼1.4 Hz, H-1 ), 4.95 (d, 1H, J1,2¼1.6 Hz, H-1), 4.25
(m, 1H, H-5/H-50), 4.23–4.19 (m, 2H, H-5/H-50, OCH2-
CHvCH2), 4.16 (dd, 1H, J1,2¼1.6 Hz, J2,3¼3.2 Hz, H-2),
4.09–4.02 (m, 2H, H-30, OCH2CHvCH2), 2.04 (s, 3H,
CH3CO), 1.31 (d, 3H, J5,6¼6.3 Hz, H-6/H-60), 1.29 (d, 3H,
J5,6¼6.1 Hz, H-6/H-60). Anal. calcd for C38H40O13: C,
64.76; H, 5.72. Found: C, 64.70; H, 5.45.
3.1.17. 2,3,4-Tri-O-benzoyl-a-L-rhamnopyranosyl-
(1!2)-3-O-acetyl-4-O-benzoyl-a-L-rhamnopyranosyl-
(1!3)-2,4-di-O-benzoyl-a-L-rhamnopyranosyl-(1!3)-
2,4-di-O-benzoyl-a-L-rhamnopyranosyl trichloroaceti-
midate (19). Compound 17 (3.34 g, 2.2 mmol) was
deallylated and subsequently converted to the trichloro-
acetimidate under the same conditions as those used for the
preparation of 8 from 5, giving 19 (2.93 g, 82%) as a foamy
solid; [a]D¼þ116.0 (c 1.0, CHCl3); nmax (KBr) 3374, 1740,
1256, 1093, 1035, 716; dH (400 MHz, CDCl3) 8.80 (s, 1H,
CvNH), 8.19–7.23 (m, 40H, Ph), 6.47 (d, 1H, J1,2¼1.7 Hz,
H-1), 5.77 (dd, 1H, J2,3¼3.1 Hz, J3,4¼9.7 Hz, H-3), 5.70
(dd, 1H, J1,2¼1.5 Hz, J2,3¼3.3 Hz, H-2), 5.67 (t, 1H,
J3,4¼9.8 Hz, J4,5¼9.8 Hz, H-4), 5.56–5.51 (m, 3H), 5.34
(t, 1H, J3,4¼9.6 Hz, J4,5¼9.6 Hz, H-4), 5.24 (d, 1H,
J1,2¼1.6 Hz, H-1), 5.17–5.13 (m, 3H), 4.93 (d, 1H,
J1,2¼0.8 Hz, H-1), 4.63 (d, 1H, J1,2¼1.3 Hz, H-1), 4.54
(dd, 1H, J2,3¼3.4 Hz, J3,4¼9.9 Hz, H-3), 4.26 (m, 1H, H-5),
4.20 (dd, 1H, J2,3¼3.4 Hz, J3,4¼9.5 Hz, H-3), 4.05–4.01
(m, 2H), 3.75 (dd, 1H, J1,2¼0.8 Hz, J2,3¼3.3 Hz, H-2), 3.66
(m, 1H, H-5), 1.86 (s, 3H, CH3CO), 1.37 (d, 3H,
J5,6¼6.2 Hz), 1.12 (d, 3H, J5,6¼6.3 Hz), 0.97 (d, 3H,
J5,6¼6.3 Hz), 0.74 (d, 3H, J5,6¼6.3 Hz). Anal. calcd for
C84H76Cl3NO26: C, 62.20; H, 4.72. Found: C, 62.29; H,
4.70.
3.1.15. Allyl 2,3,4-tri-O-benzoyl-a-L-rhamnopyranosyl-
(1!2)-3-O-acetyl-4-O-benzoyl-a-L-rhamnopyranosyl-
(1!3)-2,4-di-O-benzoyl-a-L-rhamnopyranosyl-(1!3)-
2,4-di-O-benzoyl-a-L-rhamnopyranoside (17). Com-
pounds 12 (3.0 g, 3.3 mmol) and 14 (2.50 g, 3.3 mmol)
were coupled under the same conditions as those used for
the preparation of 11 from 4 and 10, giving 17 as a foamy
solid (4.32 g, 86%); [a]2D5¼þ126.6 (c 1.1, CHCl3); dH
(400 MHz, CDCl3) 8.20–7.20 (m, 40H, Ph), 5.95 (m, 1H,
OCH2CHvCH2), 5.78 (dd, 1H, J2,3¼3.3 Hz, J3,4¼10.1 Hz,
H-3), 5.59–5.52 (m, 4H), 5.37–5.23 (m, 4H), 5.15 (s, 1H,
H-1), 5.13 (dd, 1H, J3,4¼9.7 Hz, J4,5¼9.7 Hz, H-4), 5.08
(dd, J1,2¼1.0 Hz, J2,3¼2.9 Hz, H-2), 5.04 (d, J1,2¼0.8 Hz,
H-1), 4.89 (d, J1,2¼1.0 Hz, H-1), 4.64 (d, J1,2¼1.0 Hz, H-1),
4.47 (dd, 1H, J2,3¼3.1 Hz, J3,4¼9.8 Hz, H-3), 4.24 (m, 1H,
OCH2CHvCH2), 4.18 (dd, 1H, J2,3¼3.2 Hz, J3,4¼9.8 Hz,
H-3), 4.10–3.94 (m, 4H), 3.74 (dd, J1,2¼1.0 Hz, J2,3
¼
3.1 Hz, H-2), 3.64 (m, 1H, H-5), 1.86 (s, 3H, CH3CO), 1.32

1436
J. Zhang, F. Kong / Tetrahedron 59 (2003) 1429–1441
3.1.18. Allyl 2,3,4-tri-O-benzoyl-a-L-rhamnopyranosyl-
(1!2)-3-O-acetyl-4-O-benzoyl-a-L-rhamnopyranosyl-
(1!3)-2,4-di-O-benzoyl-a-L-rhamnopyranosyl-(1!3)-
2,4-di-O-benzoyl-a-L-rhamnopyranosyl-(1!3)-2,4-di-
O-benzoyl-a-L-rhamnopyranosy-(1!2)-3-O-acetyl-4-O-
benzoyl-a-L-rhamnopyranoside (20). Compounds 19
(1.45 g, 0.9 mmol) and 16 (750 mg, 1.05 mmol) were
dried together under high vacuum for 2 h, then dissolved
in anhydrous CH2Cl2 (20 mL). TMSOTf (18 mL, 0.1 mmol)
was added dropwise at 08C under N2 protection. The
reaction mixture was stirred for 3 h, during which time the
temperature was gradually raised to ambient temperature.
Then the mixture was neutralized with Et3N, and concen-
trated to dryness. Purification of the residue by column
chromatography (1:1 petroleum ether–EtOAc) gave 20
(1.57 g, 81%) as a foamy solid; [a]2D5¼þ122.8 (c 0.6,
CHCl3); nmax (KBr) 1736, 1269, 1110, 1024, 712; dH
(400 MHz, CDCl3) 8.03–7.21 (m, 55H, Ph), 5.60 (m, 1H,
OCH2CHvCH2), 5.29 (d, 1H, J1,2¼1.5 Hz, H-1), 5.09 (d,
J1,2¼1.4 Hz, H-1), 4.91 (d, J1,2¼1.4 Hz, H-1), 4.85 (d,
J1,2¼1.4 Hz, H-1), 4.84 (d, J1,2¼1.5 Hz, H-1), 4.59 (d,
J1,2¼1.4 Hz, H-1), 2.03 (s, 3H, CH3CO), 1.86 (s, 3H,
CH3CO), 1.32 (d, 3H, J5,6¼6.4 Hz, H-6), 1.25 (d, 3H,
J5,6¼6.3 Hz, H-6), 1.09 (d, 3H, J5,6¼6.4 Hz, H-6), 0.87 (d,
3H, J5,6¼6.3 Hz, H-6), 0.71 (d, 3H, J5,6¼6.4 Hz, H-6), 0.68
(d, 3H, J5,6¼6.3 Hz, H-6). dC (100 MHz, CDCl3) 170.6,
169.8 (2CH3CO), 165.9, 165.8, 165.7, 165.4 (3C), 165.3,
165.2 (2C), 165.0, 163.4 (11PhCO), 117.9 (OCH2-
CHvCH2), 100.1, 99.6, 99.0 (2C), 98.7, 97.6 (6C-1),
20.7, 20.5 (2CH3CO), 17.6 (2C), 17.3, 17.1, 16.9, 16.8
(6C-6). Anal. calcd for C120H114O38: C, 66.60; H, 5.31.
Found: C, 66.57; H, 5.02.
(1!2)-3-O-acetyl-4-O-benzoyl-a-L-rhamnopyranosyl-
(1!3)-2,4-di-O-benzoyl-a-L-rhamnopyranosyl-(1!3)-
2,4-di-O-benzoyl-a-L-rhamnopyranosy-(1!3)-2,4-di-O-
benzoyl-a-L-rhamnopyranosyl-(1!2)-3-O-acetyl-4-O-
benzoyl-a-L-rhamnopyranosyl-(1!3)-2,4-di-O-benzoyl-
a-L-rhamnopyranosyl-(1!3)-2,4-di-O-benzoyl-a-L-
rhamnopyranoside (22). Compounds 21 (568 mg,
0.25 mmol) and 14 (250 mg, 0.31 mmol) were coupled
under the same conditions as those used for the preparation
of 20 from 19 and 16, giving 22 as a foamy solid (593 mg,
83%); [a]D¼þ117.8 (c 0.5, CHCl3); nmax (KBr) 1740,
1266, 1110, 714; dH (400 MHz, CDCl3) 8.10–7.20 (m, 75H,
Ph), 5.95 (m, 1H, CH2vCH–CH2), 5.25 (d, 1H,
J1,2¼0.8 Hz, H-1), 5.08 (d, 1H, J1,2¼1.0 Hz, H-1), 5.03
(d, 1H, J¼1.4 Hz, H-1), 4.85 (d, 1H, J1,2¼1.0 Hz, H-1), 4.84
(s, 2H, H-1), 4.58 (d, 1H, J1,2¼1.0 Hz, H-1), 4.56 (d, 1H,
J1,2¼0.8 Hz, H-1), 1.84 (s, 6H, CH3CO), 1.31 (d, 3H,
J5,6¼6.3 Hz, H-6), 1.09 (d, 3H, J5,6¼6.2 Hz, H-6), 1.05 (d,
3H, J5,6¼6.2 Hz, H-6), 0.92 (d, 3H, J5,6¼6.4 Hz, H-6), 0.89
(d, 3H, J5,6¼6.3 Hz, H-6), 0.76 (d, 3H, J5,6¼6.2 Hz, H-6),
0.73 (d, 3H, J5,6¼6.2 Hz, H-6), 0.68 (d, 3H, J5,6¼6.2 Hz,
H-6); dC (100 MHz, CDCl3) 169.7, 169.6 (2CH3CO), 118.0
(OCH2CHvCH2), 100.3, 100.1, 99.3, 99.1, 99.0, 98.9, 98.7,
96.3 (8C-1), 20.5, 20.4 (2CH3CO), 17.7, 17.6, 17.3, 17.2,
17.1, 16.9, 16.8, 16.7 (8C-6). Anal. calcd for C160H150O50:
C, 66.89; H, 5.26. Found: C, 66.70; H, 5.17.
3.1.21. Allyl 2,3,4-tri-O-benzoyl-a-L-rhamnopyranosyl-
(1!2)-4-O-benzoyl-a-L-rhamnopyranosyl-(1!3)-2,4-
di-O-benzoyl-a-L-rhamnopyranosyl-(1!3)-2,4-di-O-
benzoyl-a-L-rhamnopyranosy-(1!3)-2,4-di-O-benzoyl-
a-L-rhamnopyranosyl-(1!2)-4-O-benzoyl-a-L-rhamno-
pyranosyl-(1!3)-2,4-di-O-benzoyl-a-L-rhamnopyrano-
syl-(1!3)-2,4-di-O-benzoyl-a-L-rhamnopyranoside
(23). To a solution of 22 (575 mg, 0.2 mmol) in anhydrous
MeOH (100 mL) was added acetyl chloride (4.0 mL) at 08C.
The solution was stirred at room temperature for 24 h. The
solution was neutralized with Et3N, then concentrated to
dryness. The residue was passed through a short silica gel
column to give 23 (476 g, 85%) as a syrup; [a]2D5¼þ113.4 (c
0.5, CHCl3); nmax (KBr) 3441, 1739, 1270, 1112, 712; dH
(400 MHz, CDCl3) 5.94 (m, 1H, CH2vCH–CH2), 5.12 (d,
1H, J1,2¼0.9 Hz, H-1), 5.04 (s, 2H, H-1), 4.99 (d, 2H, H-1),
4.83 (d, 1H, J1,2¼0.9 Hz, H-1), 4.55 (s, 2H, H-1), 1.32 (d,
3H, J5,6¼6.4 Hz, H-6), 1.13 (d, 3H, J5,6¼6.2 Hz, H-6), 1.09
(d, 6H, J5,6¼6.3 Hz, 2H-6), 0.86 (d, 3H, J5,6¼6.2 Hz, H-6),
0.78 (d, 6H, J5,6¼6.4 Hz, 2H-6), 0.73 (d, 3H, J5,6¼6.2 Hz,
H-6). dC (100 MHz, CDCl3) 118.0 (OCH2CHvCH2),
100.2, 100.1, 99.5, 99.3, 99.2, 98.8, 98.7, 96.3 (8C-1),
17.7, 17.5, 17.4, 17.3 (2C), 16.9 (2C), 16.8 (8C-6). Anal.
calcd for C156H146O48: C, 67.18; H, 5.28. Found: C, 67.32;
H, 5.40.
3.1.19. 2,3,4-Tri-O-benzoyl-a-L-rhamnopyranosyl-
(1!2)-3-O-acetyl-4-O-benzoyl-a-L-rhamnopyranosyl-
(1!3)-2,4-di-O-benzoyl-a-L-rhamnopyranosyl-(1!3)-
2,4-di-O-benzoyl-a-L-rhamnopyranosy-(1!3)-2,4-di-O-
benzoyl-a-L-rhamnopyranosyl-(1!2)-3-O-acetyl-4-O-
benzoyl-a-L-rhamnopyranosyl trichloroacetimidate
(21). Compound 20 (1.08 g, 0.5 mmol) was deallylated
and subsequently converted to the trichloroacetimidate
under the same conditions as those used for the preparation
of 8 from 5, giving 21 (840 mg, 74%) as a foamy solid;
[a]D¼þ144.3 (c 0.7, CHCl3); dH (400 MHz, CDCl3) 8.71
(s, 1H, CvNH), 8.03–7.20 (m, 55H, Ph), 6.37 (d, 1H,
J1,2¼0.8 Hz, H-1), 5.73 (dd, 1H, J2,3¼3.4 Hz, J3,4¼10.1 Hz,
H-3), 5.64 (dd, 1H, J1,2¼1.0 Hz, J2,3¼3.1 Hz, H-2), 5.60 (t,
1H, J3,4¼9.9 Hz, J4,5¼9.9 Hz, H-4), 5.51–5.54 (m, 4H),
5.40 (dd, 1H, J3,4¼9.8 Hz, J4,5¼9.8 Hz, H-4), 5.30 (d, 1H,
J1,2¼1.3 Hz, H-1), 5.20–5.12 (m, 5H), 4.99 (dd, 1H,
J1,2¼1.2 Hz, J2,3¼2.9 Hz, H-2), 4.86 (d, 1H, J1,2¼0.8 Hz,
H-1), 4.84 (d, 1H, J1,2¼0.7 Hz, H-1), 4.59 (d, 1H, J1,2
¼
1.0 Hz, H-1), 4.52 (dd, 1H, J2,3¼3.4 Hz, J3,4¼9.7 Hz, H-3),
4.37 (dd, 1H, J1,2¼0.8 Hz, J2,3¼3.0 Hz, H-2), 4.25–4.21
(m, 3H), 4.07 (dd, 1H, J2,3¼3.1 Hz, J3,4¼9.8 Hz, H-3),
4.01–3.97 (m, 2H), 3.71–3.63 (m, 3H), 2.04 (s, 3H,
CH3CO), 1.57 (s, 3H, CH3CO), 1.38 (d, 3H, J5,6¼6.2 Hz),
1.36 (d, 3H, J5,6¼6.2 Hz), 1.08 (d, 3H, J5,6¼6.1 Hz), 0.89
(d, 3H, J5,6¼6.2 Hz), 0.72 (d, 3H, J5,6¼6.2 Hz), 0.70 (d, 3H,
J5,6¼6.3 Hz). Anal. calcd for C119H110Cl3NO38: C, 63.00;
H, 4.89. Found: C, 63.21; H, 4.79.
3.1.22. Allyl 2,3,4-tri-O-benzoyl-a-L-rhamnopyranosyl-
(1!2)-[3,4,6-tri-O-acetyl-2-deoxy-2-phthalimido-b-D-
glucopyranosyl-(1!3)-]4-O-benzoyl-a-L-rhamnopyra-
nosyl-(1!3)-2,4-di-O-benzoyl-a-L-rhamnopyranosyl-
(1!3)-2,4-di-O-benzoyl-a-L-rhamnopyranosy-(1!3)-
2,4-di-O-benzoyl-a-L-rhamnopyranosyl-(1!2)-[3,4,6-
tri-O-acetyl-2-deoxy-2-phthalimido-b-D-glucopyrano-
syl-(1!3)-]4-O-benzoyl-a-L-rhamnopyranosyl-(1!3)-
2,4-di-O-benzoyl-a-L-rhamnopyranosyl-(1!3)-2,4-di-
O-benzoyl-a-L-rhamnopyranoside (25). Compounds 23
3.1.20. Allyl 2,3,4-tri-O-benzoyl-a-L-rhamnopyranosyl-

J. Zhang, F. Kong / Tetrahedron 59 (2003) 1429–1441
1437
(420 mg, 0.15 mmol) and 3,4,6-tri-O-acetyl-2-deoxy-2-
phthalimido-b-D-glucopyranosyl trichloroacetimidate (24)
(250 mg, 0.4 mmol) and were dried together under high
vacuum for 2 h, then dissolved in anhydrous CH2Cl2
(10 mL). TMSOTf (3 mL, 0.02 mmol) was added at
2258C under N2 protection. The reaction mixture was
stirred for 3 h, during which time the temperature was
gradually raised to ambient temperature. Then the mixture
was neutralized with Et3N, and concentrated to dryness.
Purification of the residue on a silica gel column with 1:1
petroleum ether–EtOAc as the eluent, furnished 25
(208 mg, 38%) as a syrup; [a]D¼þ102.2 (c 0.5, CHCl3);
nmax (KBr) 3440, 1733, 1274, 1108, 710; dH (400 MHz,
CDCl3) 8.07–7.02 (m, 83H, Ph), 5.86 (m, 1H, CH2vCH–
CH2), 5.76 (dd, 1H, J2,3¼3.2 Hz, J3,4¼9.9 Hz, H-3), 5.56–
5.50 (m, 2H), 5.47 (dd, 1H, J1,2¼1.2 Hz, J2,3¼3.1 Hz, H-2),
5.43–5.35 (m, 6H), 5.28–5.15 (m, 6H), 5.09–5.05 (m, 6H),
5.02 (dd, 1H, J1,2¼1.4 Hz, J2,3¼3.2 Hz, H-2), 4.97 (dd, 1H,
J1,2¼1.6 Hz, J2,3¼3.0 Hz, H-2), 4.94 (d, 1H, J1,2¼1.5 Hz,
H-1), 4.85–4.70 (m, 5H), 4.61 (dd, 1H, J1,2¼1.0 Hz,
OCH2CH2CH3), 1.37 (d, 3H, J5,6¼6.2 Hz, H-6), 1.29–1.19
(m, 12H, 4H-6), 1.15–1.12 (m, 6H, 2H-6), 1.08 (d, 3H,
J5,6¼6.4 Hz, H-6), 0.83 (t, 3H, J¼7.3 Hz, OCH2CH2CH3).
MALDI-TOF MS calcd for C67H114N2O43: 1635.6 [Mþ].
Found: 1658.6 [MþNaþ].
3.1.24. Methyl 3-O-acetyl-2,4-di-O-benzoyl-a-L-rhamno-
pyranosyl-(1!3)-2,4-di-O-benzoyl-a-L-rhamnopyrano-
side (28). Condensation of methyl 2,4-di-O-benzoyl-a-L-
rhamnopyranoside (27) (1.98 g, 5.0 mmol) and 9 (2.80 g,
5.0 mmol) under the same conditions as those used for the
preparation of 11 from 4 and 10, gave 28 as a foamy solid
(3.12 g, 80%); [a]2D5¼þ114.7 (c 1.0, CHCl3); dH (400 MHz,
0
0
CDCl3) 8.22–7.36 (m, 20H, Ph), 5.54 (dd, 1H, J3 ,4
¼
0
0
0
0
0
9.9 Hz, J4 ,5 ¼9.9 Hz, H-4 ), 5.59 (dd, 1H, J1 ,2 ¼1.2 Hz,
0
0
0
0
0
0
0
J2 ,3 ¼3.1 Hz, H-2 ), 5.84 (dd, 1H, J2 ,3 ¼3.1 Hz, J3 ,4
¼
9.9 Hz, H-30), 5.43 (dd, 1H, J3,4¼9.8 Hz, J4,5¼9.8 Hz, H-4),
5.14 (dd, J1,2¼1.5 Hz, J2,3¼3.2 Hz, H-2), 5.11 (d, 1H,
0
0
0
J1 ,2 ¼1.2 Hz, H-1 ), 4.89 (d, 1H, J1,2¼1.5 Hz, H-1), 4.43
(dd, 1H, J2,3¼3.2 Hz, J3,4¼9.8 Hz, H-3), 4.07–4.00 (m, 2H,
J2,3¼2.8 Hz, H-2), 4.36 (dd, 1H, J2,3¼3.4 Hz, J3,4
¼
H-5, H-50), 3.45 (s, 3H, OCH3), 1.70 (s, 3H, CH3CO), 1.34
0
0
0
9.8 Hz, H-3), 4.19–4.12 (m, 3H), 4.05–3.94 (m, 9H),
3.87–3.83 (m, 4H), 3.77–3.62 (m, 4H), 3.52–3.26 (m, 5H),
1.89 (s, 3H, CH3CO), 1.88 (s, 3H, CH3CO), 1.65 (s, 6H,
CH3CO), 1.45 (s, 3H, CH3CO), 1.44 (s, 3H, CH3CO), 1.25
(d, 3H, J5,6¼6.3 Hz, H-6), 1.17 (d, 3H, J5,6¼6.3 Hz, H-6),
0.99 (d, 3H, J5,6¼6.3 Hz, H-6), 0.71 (d, 3H, J5,6¼6.4 Hz,
H-6), 0.67 (d, 3H, J5,6¼6.2 Hz, H-6), 0.62 (d, 3H,
J5,6¼6.2 Hz, H-6), 0.47 (d, 3H, J5,6¼6.3 Hz, H-6), 0.40
(d, 3H, J5,6¼6.4 Hz, H-6); dC (100 MHz, CDCl3) 170.5,
170.4, 170.2, 170.1, 169.0, 168.9 (6CH3CO), 117. 9,
(CH2vCH–CH2), 100.3, 100.2, 99.4, 99.3, 99.0, 98.8,
98.5, 98.4, 96.2, 96.0 (10C-1), 20.6, 20.5, 20.4, 20.0, 19.9,
19.1 (6CH3CO), 17.6, 17.3, 17.2, 17.0 (2C), 16.9, 16.7, 16.6
(8C-6). Anal. calcd for C196H184N2O66: C, 64.96; H, 5.12.
Found: C, 65.03; H, 5.10.
(d, 3H, J5 ,6 ¼6.3 Hz, H-6 ), 1.17 (d, 3H, J5,6¼6.4 Hz, H-6);
dC (100 MHz, CDCl3) 169.1 (CH3CO), 166.1, 165.6, 165.4,
164.9 (4PhCO), 99.3, 98.3 (2C-1), 20.3 (CH3CO), 17.6, 17.3
(2C-6). Anal. calcd for C43H42O14: C, 65.98; H, 5.41.
Found: C, 65.80; H, 5.13.
3.1.25. Methyl 2,4-di-O-benzoyl-a-L-rhamnopyranosyl-
(29).
(1!3)-2,4-di-O-benzoyl-a-L-rhamnopyranoside
Compound 28 (2.90 g, 3.7 mmol) was deacetylated under
the same conditions as those used for the preparation of 7
from 6, giving 29 (2.40 g, 88%) as a foamy solid;
[a]2D5¼þ93.2 (c 0.5, CHCl3); nmax (KBr) 3440, 1723,
1261, 1070, 977, 712; dH (400 MHz, CDCl3) 8.20–7.39 (m,
0
0
0
0
0
20H, Ph), 5.60 (dd, 1H, J3 ,4 ¼9.7 Hz, J4 ,5 ¼9.7 Hz, H-4 ),
0
0
0
0
0 0
5.50 (dd, 1H, J1 ,2 ¼0.8 Hz, J2 ,3 ¼3.0 Hz, H-2 ), 5.17 (d, 1H,
0
0
J1 ,2 ¼0.8 Hz, H-1 ), 5.08 (dd, 1H, J3,4¼9.8 Hz, J4,5¼9.8 Hz,
H-4), 5.00 (dd, J1,2¼1.0 Hz, J2,3¼3.1 Hz, H-2), 4.90 (d, 1H,
J1,2¼1.0 Hz, H-1), 4.44 (dd, 1H, J2,3¼3.1 Hz, J3,4¼9.8 Hz,
3.1.23. Propyl a-L-rhamnopyranosyl-(1!2)-[2-aceta-
mido-2-deoxy-b-D-glucopyranosyl-(1!3)-]a-L-rhamno-
pyranosyl-(1!3)-a-L-rhamnopyranosyl-(1!3)-a-L-
rhamnopyranosy-(1!3)-a-L-rhamnopyranosyl-(1!2)-
[2-acetamido-2-deoxy-b-D-glucopyranosyl-(1!3)-]a-L-
rhamnopyranosyl-(1!3)-a-L-rhamnopyranosyl-(1!3)-
a-L-rhamnopyranoside (26) (I1II). Decasaccharide 25
(180 mg, 0.05 mmol) was dissolved in EtOH (36 mL).
Hydrazine hydrate (100%, 4 mL) was added, and the
solution was refluxed for 48 h. The solution was then
concentrated and co-evaporated several times with toluene.
The residue was taken up in pyridine (20 mL), and acetic
anhydride (15 mL) was added. The solution was allowed to
stand for 12 h at room temperature and then evaporated to
dryness. Purification of the residue by flash column
chromatography (EtOAc) gave a foamy solid intermediate,
which was taken up in a saturated solution of ammonia in
MeOH (30 mL). After 96 h at room temperature, the
reaction mixture was concentrated and the residue was
purified by chromatography on Sephadex LH-20 (MeOH) to
afford 26 as a foamy solid (52 mg, 64%); [a]D¼214.2 (c
0.2, H2O); dH (400 MHz, D2O) 5.22 (d, 1H, J1,2¼1.1 Hz,
H-1), 5.16 (s, 2H, 2H-1), 5.13 (d, 1H, J1,2¼1.4 Hz, H-1),
5.06 (m, 3H, 3H-1), 4.83 (d, 1H, J1,2¼1.5 Hz, H-1), 4.74 (d,
1H, J1,2¼7.6 Hz, H-1), 4.70 (d, 1H, J1,2¼8.1 Hz, H-1), 2.03
(s, 3H, CH3CONH), 1.98 (s, 3H, CH3CONH), 1.61 (m, 2H,
H-3), 4.07–3.98 (m, 3H, H-30, H-5, H-50), 3.47 (s, 3H,
0
0
0
OCH3), 1.34 (d, 3H, J5 ,6 ¼6.2 Hz, H-6 ), 1.13 (d, 3H,
J5,6¼6.4 Hz, H-6); dC (100 MHz, CDCl3) 166.7, 165.9,
165.0, 164.9 (4PhCO), 98.8, 98.4 (2C-1), 17.5, 17.2 (2C-6).
Anal. calcd for C41H40O13: C, 66.48; H, 5.44. Found: C,
66.76; H, 5.40.
3.1.26. 3,4-Di-O-benzoyl-2-O-chloroacetyl-a-L-rhamno-
pyranosyl trichloroacetimidate (31). Allyl 3,4-di-O-ben-
zoyl-a-L-rhamnopyranoside (30) (2.06 g, 5 mmol) was
dissolved in dry CH2Cl2 (20 mL) containing pyridine
(4.0 mL, 50 mmol). Under N2 protection, chloroacetyl
chloride (0.7 mL, 11 mmol) in anhydrous CH2Cl2 (10 mL)
was added dropwise to the solution over 30 min at 08C. The
reaction mixture was stirred for 2 h at room temperature, at
the end of which time TLC (4:1 petroleum ether–EtOAc)
indicated that the reaction was complete. The reaction
mixture was diluted with CH2Cl2 (100 mL), washed with
water, 1 M HCl, and dried (Na2SO4). The solution was
concentrated, and purification of the residue by flash column
chromatography on silica gel (4:1 petroleum ether–EtOAc)
gave allyl 3,4-di-O-benzoyl-2-O-chloroacetyl-a-L-rhamno-
pyranoside as a colorless syrup, which was deallylated and
converted to the trichloroacetimidate under the same

1438
J. Zhang, F. Kong / Tetrahedron 59 (2003) 1429–1441
conditions as those used for the preparation of 8 from 5,
giving 31 (2.18 g, 73% for 3 steps) as a foamy solid;
[a]2D5¼þ20.2 (c 1.0, CHCl3); dH (400 MHz, CDCl3) 8.84 (s,
1H, CNHCCl3), 8.14–7.25 (m, 10H, Ph), 6.60 (d, 1H,
J1,2¼1.5 Hz, H-1), 5.83 (dd, 1H, J1,2¼1.5 Hz, J2,3¼3.0 Hz,
H-2), 5.67 (dd, 1H, J2,3¼3.0 Hz, J3,4¼9.7 Hz, H-3), 5.90
(dd, 1H, J3,4¼9.7 Hz, J4,5¼9.7 Hz, H-4), 4.30 (m, 1H, H-5),
3.86 (q, 2H, J¼14.1 Hz, ClCH2CO), 1.44 (d, 3H,
J5,6¼6.2 Hz, H-6). Anal. calcd for C24H21Cl4NO8: C,
48.59; H, 3.57. Found: C, 48.43; H, 3.44.
benzoyl-a-L-rhamnopyranoside (34). Compounds 19
(1.45 g, 0.9 mmol) and 33 (750 mg, 1.05 mmol) were
coupled under the same conditions as those used for the
preparation of 20 from 16 and 19, giving 34 (1.71 g, 88%) as
a foamy solid; [a]D25¼þ112.6 (c 1.0, CHCl3); nmax (KBr)
1733, 1270, 1039, 712; dH (400 MHz, CDCl3) 8.11–7.23
(m, 55H, Ph), 5.95 (m, 1H, OCH2CHvCH2), 5.82 (dd, 1H,
J2,3¼3.1 Hz, J3,4¼9.8 Hz, H-3), 5.75 (dd, 1H, J2,3¼3.3 Hz,
J3,4¼9.9 Hz, H-3), 5.67 (dd, 1H, J1,2¼1.3 Hz, J2,3¼3.2 Hz,
H-2), 5.29 (d, 1H, J1,2¼1.4 Hz, H-1), 5.19 (d, J1,2¼1.5 Hz,
H-1), 5.14 (d, J1,2¼1.6 Hz, H-1), 4.94 (d, J1,2¼1.2 Hz, H-1),
4.92 (d, J1,2¼1.5 Hz, H-1), 4.62 (d, J1,2¼1.4 Hz, H-1), 4.59
(dd, 1H, J2,3¼3.1 Hz, J3,4¼9.7 Hz, H-3), 4.44 (dd, 1H,
J1,2¼1.5 Hz, J2,3¼3.1 Hz, H-2), 1.93 (s, 3H, CH3CO), 1.86
(s, 3H, CH3CO), 1.35 (d, 3H, J5,6¼6.2 Hz, H-6), 1.33 (d,
3H, J5,6¼6.3 Hz, H-6), 1.29 (d, 3H, J5,6¼6.3 Hz, H-6), 1.12
(d, 3H, J5,6¼6.2 Hz, H-6), 0.94 (d, 3H, J5,6¼6.2 Hz, H-6),
0.73 (d, 3H, J5,6¼6.4 Hz, H-6); dC (100 MHz, CDCl3)
170.1, 169.6 (2CH3CO), 165.9, 165.8, 165.5, 165.4 (3C),
165.3, 165.2, 165.1, 165.0, 164.9 (11PhCO), 117.9
(CH2vCH–CH2O), 100.6, 100.2, 99.6, 99.1, 99.0, 97.6
(6C-1), 20.7, 20.5 (2CH3CO), 17.5 (3C), 17.3, 17.2, 16.9
(6C-6). Anal. calcd for C120H114O38: C, 66.60; H, 5.31.
Found: C, 66.74; H, 5.13.
3.1.27. Allyl 3,4-di-O-benzoyl-2-O-chloroacetyl-a-L-
rhamnopyranosyl-(1!2)-3-O-acetyl-4-O-benzoyl-a-L-
rhamnopyranoside (32). Compounds 4 (1.75 g, 5.0 mmol)
and 31 (2.97 g, 5.0 mmol) were coupled under the same
conditions as those used for the preparation of 11 from 4 and
10, giving 32 as a foamy solid (3.41 g, 87%); [a]2D5¼þ50.5
(c 1.0, CHCl3); dH (400 MHz, CDCl3) 8.04–7.35 (m, 15H,
0
Ph), 5.95 (m, 1H, CH2vCHCH2O), 5.84 (dd, 1H, J2 ,3
0
¼
0
0
0
0
0
3.3 Hz, J3 ,4 ¼9.8 Hz, H-3 ), 5.59 (dd, 1H, J1 ,2 ¼1.1 Hz,
0
0
0
0
0
0
0
J2 ,3 ¼3.3 Hz, H-2 ), 5.54 (dd, 1H, J3 ,4 ¼9.8 Hz, J4 ,5
¼
9.8 Hz, H-40), 5.51 (dd, 1H, J2,3¼3.2 Hz, J3,4¼9.8 Hz, H-3),
5.43 (dd, 1H, J3,4¼9.8 Hz, J4,5¼9.8 Hz, H-4), 5.38–5.25
0
0
0
(m, 2H, CH2vCHCH2O), 5.02 (d, 1H, J1 ,2 ¼1.1 Hz, H-1 ),
4.95 (d, 1H, J1,2¼1.1 Hz, H-1), 4.27–4.22 (m, 2H, H-5,
CH2vCH–CH2O), 4.18 (s, 2H, ClCH2CO), 4.16 (dd,
J1,2¼1.1 Hz, J2,3¼3.2 Hz, H-2), 4.10–4.03 (m, 2H, H-5,
3.1.30. 2,3,4-Tri-O-benzoyl-a-L-rhamnopyranosyl-
(1!2)-3-O-acetyl-4-O-benzoyl-a-L-rhamnopyranosyl-
(1!3)-2,4-di-O-benzoyl-a-L-rhamnopyranosyl-(1!3)-
2,4-di-O-benzoyl-a-L-rhamnopyranosy-(1!2)-3,4-di-O-
benzoyl-a-L-rhamnopyranosyl-(1!2)-3-O-acetyl-4-O-
benzoyl-a-L-rhamnopyranosyl trichloroacetimidate
(35). Compound 34 (1.08 g, 0.5 mmol) was deallylated
and converted to the trichloroacetimidate under the same
conditions as those used for the preparation of 8 from 5,
giving 35 (861 mg, 76%) as a foamy solid; [a]D¼þ94.3 (c
0.7, CHCl3); dH (400 MHz, CDCl3) 8.73 (s, 1H, CvNH),
8.03–7.22 (m, 55H, Ph), 6.36 (s, 1H, J1,2¼0.8 Hz, H-1),
5.81 (dd, 1H, J2,3¼3.1 Hz, J3,4¼9.7 Hz, H-3), 5.76 (dd, 1H,
J2,3¼3.2 Hz, J3,4¼10.1 Hz, H-3), 5.68 (dd, 1H, J1,2¼0.9 Hz,
J2,3¼3.2 Hz, H-2), 5.60 (t, 1H, J3,4¼10.4 Hz, J4,5¼10.4 Hz,
H-4), 5.53 (t, 1H, J3,4¼10.0 Hz, J4,5¼10.0 Hz, H-4), 5.52–
5.48 (m, 4H), 5.34 (t, 1H, J3,4¼9.7 Hz, J4,5¼9.7 Hz, H-4),
5.28 (s, 1H, J1,2¼1.5 Hz, H-1), 5.22 (s, 1H, J1,2¼1.2 Hz, H-
1), 5.20 (s, 1H, J1,2¼1.4 Hz, H-1), 5.17–5.13 (m, 3H), 4.92
(s, 1H, J1,2¼1.3 Hz, H-1), 4.62 (s, 1H, J1,2¼1.3 Hz, H-1),
4.60 (dd, 1H, J2,3¼3.0 Hz, J3,4¼9.9 Hz, H-3), 4.47–4.44
(m, 2H), 4.27–4.03 (m, 6H), 3.76–3.70 (m, 2H), 1.95 (s,
3H, CH3CO), 1.86 (s, 3H, CH3CO), 1.40–1.37 (t, 6H,
J5,6¼6.1 Hz, 2H-6), 1.29 (d, 3H, J5,6¼6.3 Hz, H-6), 1.11
(d, 3H, J5,6¼6.2 Hz, H-6), 0.94 (d, 3H, J5,6¼6.2 Hz, H-6),
0.75 (d, 3H, J5,6¼6.2 Hz, H-6). Anal. calcd for
C119H110Cl3NO38: C, 63.00; H, 4.89. Found: C, 63.12; H,
5.01.
CH2vCH–CH2O), 2.00 (s, 3H, CH3CO), 1.35 (d, 3H,
0
0
0
J5 ,6 ¼6.4 Hz, H-6 ), 1.27 (d, 3H, J5,6¼6.4 Hz, H-6); dC
(100 MHz, CDCl3) 170.4 (CH3CO), 166.3 (ClCH2CO),
165.7, 165.4, 165.1 (3PhCO), 117.8 (OCH2CHvCH2),
98.9, 97.5 (2C-1), 40.4 (ClCH2CO), 20.6 (CH3CO), 17.5,
17.3 (2C-6). Anal. calcd for C40H41ClO14: C, 61.50; H, 5.30.
Found: C, 61.58; H, 5.09.
3.1.28. Allyl 3,4-di-O-benzoyl-a-L-rhamnopyranosyl-
(1!2)-3-O-acetyl-4-O-benzoyl-a-L-rhamnopyranoside
(33). Compound 32 (3.90 g, 5 mmol) was deprotected under
the same conditions as those used for the preparation of 16
from 15, giving 33 as a foamy solid (2.80 g, 80%);
[a]2D5¼19.6 (c 1.0, CHCl3); nmax (KBr) 3446, 1727, 1274,
1110, 1072, 1026, 713; dH (400 MHz, CDCl3) 8.03–7.37
(m, 15H, Ph), 5.94 (m, 1H, CH2vCH–CH2), 5.68 (dd, 1H,
0
0
0
0
0
0
0
J2 ,3 ¼3.2 Hz, J3 ,4 ¼9.8 Hz, H-3 ), 5.59 (dd, 1H, J3 ,4
¼
0
0
0
9.8 Hz, J4 ,5 ¼9.8 Hz, H-4 ), 5.54 (dd, 1H, J2,3¼3.4 Hz,
J3,4¼9.9 Hz, H-3), 5.41 (dd, 1H, J3,4¼9.9 Hz, J4,5¼9.9 Hz,
H-4), 5.37–5.25 (m, 2H, CH2vCH–CH2), 5.07 (d, 1H,
0
0
0
J1 ,2 ¼1.6 Hz, H-1 ), 4.96 (d, 1H, J1,2¼1.7 Hz, H-1), 4.47
0
0
0
0
0
(dd, 1H, J1 ,2 ¼1.6 Hz, J2 ,3 ¼3.2 Hz, H-2 ), 4.27 (m, 1H,
CH2vCH–CH2O), 4.20–4.16 (m, 2H, H-2, H-50), 4.09–
4.01 (m, 2H, H-5, CH2vCH–CH2O), 1.95 (s, 3H, CH3CO),
0
0
0
1.34 (d, 3H, J5 ,6 ¼6.3 Hz, H-6 ), 1.27 (d, 3H, J5,6¼6.4 Hz,
H-6); dC (100 MHz, CDCl3) 170.0 (CH3CO), 165.8,
165.5, 165.3 (3PhCO), 117.7 (OCH2CHvCH2), 101.3,
97.7 (2C-1), 20.6 (CH3CO), 17.5, 17.4 (2C-6). Anal. calcd
for C38H40O13: C, 64.76; H, 5.72. Found: C, 64.53; H,
5.60.
3.1.31. Methyl 2,3,4-tri-O-benzoyl-a-L-rhamnopyrano-
syl-(1!2)-3-O-acetyl-4-O-benzoyl-a-L-rhamnopyrano-
syl-(1!3)-2,4-di-O-benzoyl-a-L-rhamnopyranosyl-
(1!3)-2,4-di-O-benzoyl-a-L-rhamnopyranosyl-(1!2)-
3,4-di-O-benzoyl-a-L-rhamnopyranosyl-(1!2)-3-O-
acetyl-4-O-benzoyl-a-L-rhamnopyranosyl-(1!3)-2,4-di-
O-benzoyl-a-L-rhamnopyranosyl-(1!3)-2,4-di-O-ben-
zoyl-a-L-rhamnopyranoside (36). Compounds 35
(600 mg, 0.26 mmol) and 29 (300 mg, 0.40 mmol) were
3.1.29. Allyl 2,3,4-tri-O-benzoyl-a-L-rhamnopyranosyl-
(1!2)-3-O-acetyl-4-O-benzoyl-a-L-rhamnopyranosyl-
(1!3)-2,4-di-O-benzoyl-a-L-rhamnopyranosyl-(1!3)-
2,4-di-O-benzoyl-a-L-rhamnopyranosy-(1!2)-3,4-di-O-
benzoyl-a-L-rhamnopyranosyl-(1!2)-3-O-acetyl-4-O-

J. Zhang, F. Kong / Tetrahedron 59 (2003) 1429–1441
1439
coupled under the same conditions as those used for the
preparation of 20 from 19 and 16, giving 36 as a foamy solid
(640 mg, 85%); [a]2D5¼þ91.0 (c 0.5, CHCl3); dH (400 MHz,
(d, 3H, J5,6¼6.3 Hz, H-6), 1.09 (d, 3H, J5,6¼6.4 Hz, H-6),
0.97 (d, 3H, J5,6¼6.4 Hz, H-6), 0.76 (d, 3H, J5,6¼6.2 Hz,
H-6), 0.69 (d, 3H, J5,6¼6.4 Hz, H-6). dC (100 MHz, CDCl3)
166.9, 166.6, 166.1, 166.0, 165.9, 165.8, 165.6, 165.5 (3C),
165.4, 165.3 (3C), 165.0 (15PhCO), 100.9, 100.6, 100.3,
99.6, 99.3, 99.1, 99.0, 98.3 (8C-1), 17.8, 17.6, 17.4 (3C),
17.3, 17.0, 16.8 (8C-6). Anal. calcd for C154H144O48: C,
66.94; H, 5.25. Found: C, 66.73; H, 5.44.
CDCl3) d 8.10–7.24 (m, 75H, Ph), 5.75 (dd, 1H, J2,3
¼
3.4 Hz, J3,4¼10.2 Hz, H-3), 5.66 (dd, 1H, J2,3¼3.2 Hz,
J3,4¼9.9 Hz, H-3), 5.61 (dd, 1H, J1,2¼1.6 Hz, J2,3¼3.2 Hz,
H-2), 5.57–5.48 (m, 5H), 5.43 (dd, 1H, J3,4¼9.8 Hz,
J4,5¼9.8 Hz, H-4), 5.34 (dd, 1H, J3,4¼9.7 Hz, J4,5
¼
9.7 Hz, H-4), 5.30 (dd, 1H, J3,4¼9.7 Hz, J4,5¼9.7 Hz,
H-4), 5.28 (d, 1H, J1,2¼1.3 Hz, H-1), 5.21 (d, 1H,
J1,2¼1.6 Hz, H-1), 5.17–5.05 (m, 7H), 4.91 (d, 1H,
J1,2¼1.2 Hz, H-1), 4.89 (d, 1H, J1,2¼1.5 Hz, H-1), 4.82 (s,
2H, 2H-1), 4.62 (d, 1H, J1,2¼1.4 Hz, H-1), 4.50 (dd, 1H,
J2,3¼3.3 Hz, J3,4¼9.9 Hz, H-3), 4.45 (dd, 1H, J2,3¼3.2 Hz,
J3,4¼9.8 Hz, H-3), 4.28 (dd, 1H, J1,2¼1.8 Hz, J2,3¼3.2 Hz,
H-2), 4.22–4.18 (m, 2H), 4.07–3.86 (m, 6H), 3.79 (dd, 1H,
J1,2¼1.5 Hz, J2,3¼3.0 Hz, H-2), 3.75 (dd, 1H, J1,2¼1.0 Hz,
J2,3¼2.9 Hz, H-2), 3.72–3.62 (m, 2H), 3.45 (s, 3H, OCH3),
1.86 (s, 3H, CH3CO), 1.75 (s, 3H, CH3CO), 1.35 (d, 3H,
J5,6¼6.4 Hz, H-6), 1.15 (d, 3H, J5,6¼6.4 Hz, H-6), 1.12 (d,
3H, J5,6¼6.3 Hz, H-6), 1.09 (d, 3H, J5,6¼6.4 Hz, H-6), 0.93
(d, 3H, J5,6¼6.4 Hz, H-6), 0.88 (d, 3H, J5,6¼6.2 Hz, H-6),
0.75 (d, 3H, J5,6¼6.3 Hz, H-6), 0.69 (d, 3H, J5,6¼6.2 Hz,
H-6); dC (100 MHz, CDCl3) 170.0, 169.8 (2CH3CO), 117.8
(CH2vCH–CH2), 100.3, 100.2, 100.1, 99.3, 99.2, 99.0,
98.2, 91.9 (8C-1), 20.6, 20.6 (2 CH3CO), 17.7, 17.4, 17.4,
17.3, 17.2, 17.1, 16.9, 16.7 (8C-6). Anal. calcd for
C158H148O50: C, 66.66; H, 5.24. Found: C, 66.48; H, 5.12.
3.1.33. Methyl 2,3,4-tri-O-benzoyl-a-L-rhamnopyrano-
syl-(1!2)-[3,4,6-tri-O-acetyl-2-deoxy-2-phthalimido-b-
D-glucopyranosyl-(1!3)-]4-O-benzoyl-a-L-rhamnopyr-
anosyl-(1!3)-2,4-di-O-benzoyl-a-L-rhamnopyranosyl-
(1!3)-2,4-di-O-benzoyl-a-L-rhamnopyranosy-(1!2)-
3,4-di-O-benzoyl-a-L-rhamnopyranosyl-(1!2)-[3,4,6-
tri-O-acetyl-2-deoxy-2-phthalimido-b-D-glucopyrano-
syl-(1!3)-]4-O-benzoyl-a-L-rhamnopyranosyl-(1!3)-
2,4-di-O-benzoyl-a-L-rhamnopyranosyl-(1!3)-2,4-di-
O-benzoyl-a-L-rhamnopyranoside (38). Compounds 37
(497 mg, 0.18 mmol) and 3,4,6-tri-O-acetyl-2-deoxy-2-
phthalimido-b-D-glucopyranosyl trichloroacetimidate (24)
(300 mg, 0.5 mmol) were coupled under the same con-
ditions as those used for the preparation of 25 from 23 and
24, giving 38 (223 mg, 35%) as a syrup; [a]D¼þ102.2 (c
0.5, CHCl3); nmax (KBr) 1728, 1265, 1109, 712; dH
(400 MHz, CDCl3) 8.12–7.24 (m, 83H, Ph), 5.80 (dd, 1H,
J2,3¼3.0 Hz, J3,4¼9.8 Hz, H-3), 5.72 (dd, 1H, J1,2¼1.4 Hz,
J2,3¼2.8 Hz, H-2), 5.65 (dd, 1H, J2,3¼2.9 Hz, J3,4¼9.6 Hz,
H-3), 5.60–5.46 (m, 7H), 5.39 (dd, 1H, J3,4¼9.7 Hz,
3.1.32. Methyl 2,3,4-tri-O-benzoyl-a-L-rhamnopyrano-
syl-(1!2)-4-O-benzoyl-a-L-rhamnopyranosyl-(1!3)-
2,4-di-O-benzoyl-a-L-rhamnopyranosyl-(1!3)-2,4-di-
O-benzoyl-a-L-rhamnopyranosy-(1!2)-3,4-di-O-ben-
zoyl-a-L-rhamnopyranosyl-(1!2)-4-O-benzoyl-a-L-
rhamnopyranosyl-(1!3)-2,4-di-O-benzoyl-a-L-rhamno-
pyranosyl-(1!3)-2,4-di-O-benzoyl-a-L-rhamnopyrano-
side (37). To a solution of 36 (570 mg, 0.2 mmol) in
anhydrous MeOH (100 mL) was added acetyl chloride
(4.0 mL) at 08C. The solution was stirred at room
temperature for 24 h. The solution was neutralized with
Et3N, then concentrated to dryness. The residue was passed
through a short silica gel column to give 37 (510 g, 92%) as
a syrup; [a]2D5¼þ117.6 (c 1.0, CHCl3); nmax (KBr) 3442,
1740, 1268, 1070, 714; dH (400 MHz, CDCl3) 8.11–7.21
(m, 75H, Ph), 5.72 (dd, 1H, J2,3¼3.1 Hz, J3,4¼9.7 Hz, H-3),
5.69–5.66 (m, 2H, H-2, H-3), 5.57 (dd, 1H, J1,2¼1.4 Hz,
J2,3¼3.3 Hz, H-2), 5.55 (dd, 1H, J3,4¼9.8 Hz, J4,5¼9.8 Hz,
H-4), 5.52 (dd, 1H, J3,4¼9.8 Hz, J4,5¼9.8 Hz, H-4), 5.51
(dd, 1H, J1,2¼1.0 Hz, J2,3¼3.1 Hz, H-2), 5.49 (dd, 1H,
J3,4¼9.7 Hz, J4,5¼9.7 Hz, H-4), 5.44 (dd, 1H, J3,4¼9.8 Hz,
J4,5¼9.8 Hz, H-4), 5.36 (dd, 1H, J3,4¼9.8 Hz, J4,5¼9.8 Hz,
H-4), 5.29 (dd, 1H, J3,4¼9.8 Hz, J4,5¼9.8 Hz, H-4), 5.25 (d,
J4,5¼9.7 Hz, H-4), 5.32 (dd, 1H, J3,4¼9.8 Hz, J4,5
9.8 Hz, H-4), 5.29–4.70 (m, 17H), 4.57 (dd, 1H,
J1,2¼1.5 Hz, J2,3¼3.0 Hz, H-2), 4.41 (dd, 1H, J1,2
¼
¼
1.5 Hz, J2,3¼3.1 Hz, H-2), 4.30–3.49 (m, 21H), 3.43 (s,
3H, OCH3), 334–3.25 (m, 2H), 1.96 (s, 3H, CH3CO), 1.93
(s, 3H, CH3CO), 1.89 (s, 6H, 2CH3CO), 1.72 (s, 3H,
CH3CO), 1.55 (s, 3H, CH3CO), 1.39 (d, 3H, J5,6¼6.2 Hz,
H-6), 1.31 (d, 3H, J5,6¼6.3 Hz, H-6), 1.11 (d, 3H,
J5,6¼6.3 Hz, H-6), 1.05 (d, 3H, J5,6¼6.2 Hz, H-6), 0.72
(d, 3H, J5,6¼6.2 Hz, H-6), 0.69 (d, 3H, J5,6¼6.3 Hz, H-6),
0.59 (d, 3H, J5,6¼6.3 Hz, H-6), 0.55 (d, 3H, J5,6¼6.4 Hz,
H-6); dC (100 MHz, CDCl3) 170.5, 170.3, 170.1, 169.8,
169.0, 168.9 (6CH3CO), 100.1, 99.9, 99.6, 99.3, 99.3, 99.2,
99.2, 98.6, 98.1, 98.1 (10C-1), 20.6, 20.5, 20.3, 20.2, 19.9,
19.0 (6 CH3CO), 18.0, 17.6, 17.4, 17.2, 17.1, 16.9, 16.7,
16.6 (8C-6). Anal. calcd for C194H182N2O66: C, 64.77; H,
5.10. Found: C, 64.99; H, 5.41.
3.1.34. Methyl a-L-rhamnopyranosyl-(1!2)-[2-aceta-
mido-2-deoxy-b-D-glucopyranosyl-(1!3)-]a-L-rhamno-
pyranosyl-(1!3)-a-L-rhamnopyranosyl-(1!3)-a-L-
rhamnopyranosy-(1!2)-a-L-rhamnopyranosyl-(1!2)-
[2-acetamido-2-deoxy-b-D-glucopyranosyl-(1!3)-]a-L-
rhamnopyranosyl-(1!3)-a-L-rhamnopyranosyl-(1!3)-
a-L-rhamnopyranoside (39) (II1I). Decasaccharide 38
(215 mg, 0.06 mmol) was dissolved in EtOH (36 mL).
Hydrazine hydrate (100%, 4 mL) was added, and the
solution was refluxed for 48 h. The solution was then
concentrated and co-evaporated several times with toluene.
The residue was taken up in pyridine (20 mL), and acetic
anhydride (15 mL) was added. The solution was allowed to
stand for 12 h at room temperature and then evaporated to
dryness. Purification of the residue by flash column
chromatography (EtOAc) gave a foamy solid intermediate,
1H, J1,2¼1.5 Hz, H-1), 5.17 (dd, 1H, J1,2¼1.5 Hz, J2,3
¼
3.2 Hz, H-2), 5.10 (dd, 1H, J1,2¼1.3 Hz, J2,3¼3.0 Hz, H-2),
5.09 (d, 1H, J1,2¼1.0 Hz, H-1), 5.06 (d, 1H, J1,2¼1.0 Hz,
H-1), 4.93 (dd, 1H, J3,4¼9.7 Hz, J4,5¼9.7 Hz, H-4), 4.88 (d,
1H, J1,2¼1.5 Hz, H-1), 4.86 (d, 1H, J1,2¼1.4 Hz, H-1), 4.81
(dd, 1H, J3,4¼9.0 Hz, J4,5¼9.0 Hz, H-4), 4.55 (d, 1H,
J1,2¼1.3 Hz, H-1), 4.51 (dd, 1H, J2,3¼3.3 Hz, J3,4¼9.9 Hz,
H-3), 4.51 (dd, 1H, J2,3¼3.4 Hz, J3,4¼9.8 Hz, H-3), 4.30
(dd, 1H, J1,2¼1.3 Hz, J2,3¼3.3 Hz, H-2), 3.45 (s, 3H,
OCH3), 1.34 (d, 3H, J5,6¼6.2 Hz, H-6), 1.19 (d, 3H,
J5,6¼6.3 Hz, H-6), 1.14 (d, 3H, J5,6¼6.3 Hz, H-6), 1.12

1440
J. Zhang, F. Kong / Tetrahedron 59 (2003) 1429–1441
which was taken up in a saturated solution of ammonia in
MeOH (30 mL). After 96 h at room temperature, the
reaction mixture was concentrated and the residue was
purified by chromatography on Sephadex LH-20 (MeOH) to
afford 39 as a foamy solid (57 mg, 59%); [a]D¼217.3 (c
0.2, H2O); dH (400 MHz, D2O) 5.18–5.15 (m, 3H, 3H-1),
5.09 (d, 1H, J1,2¼1.4 Hz, H-1), 5.03–5.01 (m, 3H, 3H-1),
4.84 (d, 1H, J1,2¼1.1 Hz, H-1), 4.77 (d, 1H, J1,2¼8.0 Hz,
H-1), 4.75 (d, 1H, J1,2¼8.1 Hz, H-1), 3.39 (s, 3H, OCH3),
1.97 (s, 3H, CH3CONH), 1.90 (s, 3H, CH3CONH), 1.26 (d,
3H, J5,6¼6.2 Hz, H-6), 1.29–1.14 (m, 18H, 6H-6), 1.10 (d,
3H, J5,6¼6.4 Hz, H-6). MALDI-TOF MS calcd for
C65H110N2O43: 1607.5 [Mþ]. Found: 1630.7 [MþNaþ].
glucopyranosyl-(1!3)-]4-O-benzoyl-a-L-rhamnopyra-
nosyl-(1!3)-2,4-di-O-benzoyl-a-L-rhamnopyranosyl-
(1!2)-[3,4,6-tri-O-acetyl-2-deoxy-2-phthalimido-b-D-
glucopyranosyl-(1!3)-]4-O-benzoyl-a-L-rhamnopyra-
noside (42). Compounds 41 (685 mg, 0.5 mmol) and 3,4,6-
tri-O-acetyl-2-deoxy-2-phthalimido-b-D-glucopyranosyl
trichloroacetimidate (24) (900 mg, 1.5 mmol) were coupled
under the same conditions as those used for the preparation
of 25 from 23 and 24, giving 42 (455 mg, 41%) as a syrup;
[a]2D5¼þ43.2 (c 0.5, CHCl3); dH (400 MHz, CDCl3) 8.03–
7.02 (m, 35H, Ph), 5.85 (m, 1H, CH2vCH–CH2O), 5.82
(dd, 1H, J2,3¼3.4 Hz, J3,4¼9.8 Hz, H-3), 5.52 (d, 1H,
J1,2¼7.6 Hz, H-1), 5.48 (d, 1H, J1,2¼8.0 Hz, H-1), 5.29 (d,
1H, J1,2¼1.1 Hz, H-1), 5.23 (d, 1H, J1,2¼1.3 Hz, H-1), 5.05
(d, 1H, J1,2¼1.3 Hz, H-1), 4.73 (d, 1H, J1,2¼1.0 Hz, H-1),
4.46 (dd, 1H, J2,3¼3.3 Hz, J3,4¼9.7 Hz, H-3), 4.21 (dd, 1H,
J1,2¼1.5 Hz, J2,3¼3.1 Hz, H-2), 1.93 (s, 3H, CH3CO), 1.91
(s, 3H, CH3CO), 1.74 (s, 3H, CH3CO), 1.67 (s, 6H,
2CH3CO), 1.57 (s, 3H, CH3CO), 1.18 (d, 3H, J5,6¼6.1 Hz,
H-6), 1.15 (d, 3H, J5,6¼6.3 Hz, H-6), 1.03 (d, 3H,
J5,6¼6.0 Hz, H-6), 0.80 (d, 3H, J5,6¼6.4 Hz, H-6); dC
(100 MHz, CDCl3) 170.7, 170.6, 170.1, 170.1, 169.2, 169.1
(6CH3CO), 166.0, 165.7, 165.2, 164.9, 164.8, 164.5, 164.3
(7C6H5CO), 117.9 (CH2vCH–CH2), 100.2, 99.4, 99.4,
99.3, 98.7, 98.00 (6C-1), 20.6, 20.5, 20.4, 20.4, 20.2, 20.1
(6CH3CO), 17.5, 17.4, 17.2, 17.2 (4C-6). Anal. calcd for
C116H112N2O42: C, 63.15; H, 5.12. Found: C, 63.32; H, 5.21.
3.1.35. Allyl 2,3,4-tri-O-benzoyl-a-L-rhamnopyranosyl-
(1!2)-3-O-acetyl-4-O-benzoyl-a-L-rhamnopyranosyl-
(1!3)-2,4-di-O-benzoyl-a-L-rhamnopyranosyl-(1!2)-
3-O-acetyl-4-O-benzoyl-a-L-rhamnopyranoside
(40).
Compounds 12 (912 mg, 1.0 mmol) and 16 (704 mg,
1.0 mmol) were coupled under the same conditions as
those used for the preparation of 20 from 16 and 19, giving
40 as a foamy solid (1.21 g, 83%); [a]2D5¼þ103.5 (c 1.0,
CHCl3); dH (400 MHz, CDCl3) 8.20–7.23 (m, 35H, Ph),
5.94 (m, 1H, OCH2CHvCH2), 5.22 (d, J1,2¼1.0 Hz, H-1),
5.13 (d, J1,2¼0.9 Hz, H-1), 4.95 (d, J1,2¼1.0 Hz, H-1), 4.74
(d, J1,2¼0.8 Hz, H-1), 2.04 (s, 3H, CH3CO), 1.90 (s, 3H,
CH3CO), 1.32 (d, 3H, J5,6¼6.2 Hz, H-6), 1.30 (d, 3H,
J5,6¼6.3 Hz, H-6), 1.26 (d, 3H, J5,6¼6.2 Hz, H-6), 1.11 (d,
3H, J5,6¼6.4 Hz, H-6); dC (100 MHz, CDCl3) 170.5, 169.9
(2CH3CO), 165.9, 165.8, 165.6, 165.4, 165.3, 165.2, 165.1
(7PhCO), 118.0 (OCH2CHvCH2), 100.2, 99.5, 99.2, 97.6
(4C-1), 20.6, 20.5 (2CH3CO) 17.6, 17.5, 17.4, 17.3 (4C-6).
Anal. calcd for C80H78O26: C, 61.77; H, 5.05. Found: C,
62.01; H, 5.16.
3.1.38. Propyl a-L-rhamnopyranosyl-(1!2)-[2-acet-
amido-2-deoxy-b-D-glucopyranosyl-(1!3)-]a-L-rham-
nopyranosyl-(1!3)-a-L-rhamnopyranosyl-(1!2)-[2-
acetamido-2-deoxy-b-D-glucopyranosyl-(1!3)-]a-L-
rhamnopyranoside (43). Compound 42 (220 mg,
0.1 mmol) was deprotected under conditions similar to
those used for the preparation of 26 from 25, giving 43
(66 mg, 63%) as a foamy solid; [a]D¼223.6 (c 0.2, H2O);
3.1.36. Allyl 2,3,4-tri-O-benzoyl-a-L-rhamnopyranosyl-
(1!2)-4-O-benzoyl-a-L-rhamnopyranosyl-(1!3)-2,4-
di-O-benzoyl-a-L-rhamnopyranosyl-(1!2)-4-O-ben-
zoyl-a-L-rhamnopyranoside (41). Compound 40 (1.16 g,
0.8 mmol) was deacetylated under the same conditions as
those used for the preparation of 23 from 22, giving 41
(820 mg, 75%) as a foamy solid; [a]2D5¼þ77.5 (c 1.0,
CHCl3); nmax (KBr) 3440, 1730, 1263, 1107, 709; dH
(400 MHz, CDCl3) 8.18–7.24 (m, 35H, Ph), 5.92 (m, 1H,
OCH2CHvCH2), 5.74 (dd, 1H, J2,3¼3.3 Hz, J3,4¼9.8 Hz,
H-3), 5.65 (dd, 1H, J1,2¼1.2 Hz, J2,3¼3.3 Hz, H-2), 5.62
(dd, 1H, J1,2¼1.1 Hz, J2,3¼3.2 Hz, H-2), 5.60 (dd, 1H,
J3,4¼9.7 Hz, J4,5¼9.7 Hz, H-4), 5.52 (dd, 1H, J3,4¼9.9 Hz,
J4,5¼9.9 Hz, H-4), 5.33 (m, 1H, OCH2CHvCH2), 5.32 (d,
J1,2¼1.0 Hz, H-1), 5.26 (d, J1,2¼1.1 Hz, H-1), 5.24 (m, 1H,
OCH2CHvCH2), 5.16 (dd, 1H, J3,4¼9.8 Hz, J4,5¼9.8 Hz,
H-4), 5.08 (dd, 1H, J3,4¼9.8 Hz, J4,5¼9.8 Hz, H-4), 5.01 (d,
J1,2¼1.2 Hz, H-1), 4.67 (d, J1,2¼1.4 Hz, H-1), 4.47 (dd, 1H,
J2,3¼3.4 Hz, J3,4¼9.8 Hz, H-3), 3.91 (dd, 1H, J2,3¼3.2 Hz,
J3,4¼9.9 Hz, H-3), 1.32–1.24 (m, 12H, 4H-6); dC
(100 MHz, CDCl3) 166.9, 166.6, 165.8, 165.8, 165.6,
165.3, 164.9 (7PhCO), 117.7 (OCH2CHvCH2), 100.3,
99.9, 99.6, 97.5 (4C-1), 17.6, 17.6, 17.5, 17.5 (4C-6). Anal.
calcd for C76H74O24: C, 66.56; H, 5.44. Found: C, 66.70; H,
5.31.
1
the H NMR data of compound 43 were identical to those
reported in the literature.3
Acknowledgements
This work was supported by the Chinese Academy of
Sciences (KZCX3-J-08) and the National Natural Science
Foundation of China (39970864 and 30070815), and the
Ministry of Science and Technology.
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