Efficient and practical syntheses of mannose tri-, tetra-, penta-, hexa-, hepta-, and octasaccharides existing in N-glycans

Article abstract of DOI:10.1016/S0957-4166(02)00107-6

An efficient and practical regio- and stereoselective synthesis of mannose tri-, tetra-, penta-, hexa-, hepta-, and octasaccharides of N-glycans was achieved using simple mannosyl derivatives as the starting materials.

Full text of DOI:10.1016/S0957-4166(02)00107-6

TETRAHEDRON:
ASYMMETRY
Pergamon
Tetrahedron: Asymmetry 13 (2002) 243–252
Efficient and practical syntheses of mannose tri-, tetra-, penta-,
hexa-, hepta-, and octasaccharides existing in N-glycans
Jianjun Zhang and Fanzuo Kong*
Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, PO Box 2871, Beijing 100085, China
Received 16 January 2001; accepted 21 February 2002
Abstract—An efficient and practical regio- and stereoselective synthesis of mannose tri-, tetra-, penta-, hexa-, hepta-, and
octasaccharides of N-glycans was achieved using simple mannosyl derivatives as the starting materials. © 2002 Elsevier Science
Ltd. All rights reserved.
1. Introduction
required because such homogeneous oligosaccharide
samples are obtainable in only very small amounts
from natural sources. Remarkable progress has been
made in the field of N-glycan synthesis,4 however,
multiple steps and orthogonal masking groups are
needed in most of the syntheses making the work
complex and time consuming. We present herein a very
efficient and practical method for the synthesis of man-
nose oligosaccharides (Man3, Man4, Man5, Man6,
Man7, and Man8) for N-glycans,5 as shown in Scheme
1.
N-Linked glycans play a vital role in fundamental
biological processes such as cell differentiation, malig-
nant transformation, viral, bacterial and parasitic infec-
tions and protein transportations.1 Recent studies have
revealed that the mannose oligosaccharides in N-gly-
cans are required for human CD2 adhesion function2
and high mannose oligosaccharides are related to HIV
infection.3 For a study of the details of the recognition
mechanism, chemically synthesized oligosaccharides are
Scheme 1.
* Corresponding author. E-mail: fzkong@mail.rcees.ac.cn
0957-4166/02/$ - see front matter © 2002 Elsevier Science Ltd. All rights reserved.
PII: S0957-4166(02)00107-6

244
J. Zhang, F. Kong / Tetrahedron: Asymmetry 13 (2002) 243–252
2. Results and discussion
tion with regioselective glycosylation and one-pot
multistep transformation protocols.
Previous syntheses of mannose oligosaccharides
involved the use of permanent and temporary protect-
ing groups as well as complex protection and deprotec-
tion procedures.4 Thus, it is difficult to obtain the
oligosaccharide samples in sufficient quantity through
these syntheses. In the work described here we designed
a new method for mannose oligosaccharide syntheses
using solely temporary protecting groups in combina-
Scheme 2 depicts the syntheses of Man3, Man4, and
Man 5, and Scheme 3 shows the syntheses of Man6,
Man7, and Man8. In our synthetic route, the target
oligosaccharides were constructed from the coupling of
fully acylated mannose mono- and oligosaccharide
trichloroacetimidate donors with the mannose di-, tri-,
and terasaccharide acceptors having free 4,6-hydroxyl
Scheme 2. Reagents and conditions: (a) PhCHO, HC(OEt)3, toluenesulfonic acid, rt, 12 h (88%); (b) TMSOTf, CH2Cl2, 0°C, 2 h;
(c) 0.1% HCl–MeOH, rt, 12 h (88%); (d) 90% CF3COOH, rt, 2–5 h; (e) Ac2O/pyridine (dry), rt, 6 h; (f) 1.0 M NH3/MeOH, 3 h;
(g) CCl3CN, DBU, CH2Cl2 3 h (for 15: 82% from 12; for 19: 82% from 16); (h) satd NH3/MeOH, rt, 7 days (76%).

J. Zhang, F. Kong / Tetrahedron: Asymmetry 13 (2002) 243–252
245
Scheme 3. Reagents and conditions: (a) TMSOTf, CH2Cl2, 0°C, 2 h (79% for 23, 82% for 26, 80% for 29); (b) 90% CF3COOH,
rt, 2–5 h (81% for 24, 87% for 27, 85% for 30); (c) satd NH3/MeOH, rt, 7 days (72% for 25, 76% for 28, 82% for 31).
groups at the reducing end. This strategy ensures good
reactivity and selectivity of the couplings because of the
primary hydroxyl in the acceptors,6 while the prepara-
tions of the trichloroacetimidate donors are relatively
followed by debenzylidenation furnished the tetra-
saccharide acceptor 11 (92%).
With these acceptors in hand, the required mannosyl
oligosaccharides were synthesized readily. Thus, con-
densation of 5 with the monosaccharide donor 3 gave
the 6-linked trisaccharide 12 with high selectivity (87%).
Subsequent hydrolysis to remove the ethylidene protect-
ing group, acetylation with Ac2O in pyridine, selective
1-O-deacetylation with dilute NH3–MeOH solution,
followed by trichloroacetimidation produced the trisac-
charide donor 15 (overall yield for the four steps 82%).
These four steps were carried out consecutively without
chromatographic separation for the first three steps,
making large scale preparation possible with high
yields. The 1H NMR spectrum of 15 showed three
easy. Thus, 4,6-O-benzylidene-1,2-O-ethylidene-b-
mannopyranose 2, which was obtained from 1,2-O-eth-
ylidene-b-
-mannopyranose,7 was chosen as the
D-
D
starting material. Condensation of 2 with perbenzoy-
lated mannopyransyl trichloroacetimidate 3 afforded
the disaccharide 4 in high yield (83%). Selective removal
of the benzylidene protecting group with 0.1% HCl–
MeOH at room temperature from 4 was carried out
smoothly, yielding the disaccharide acceptor 5 (88%).
Coupling of 2 with the disaccharide donor 6, which was
readily prepared by self condensation of 1,2-O-allyl-
oxyethylidene-3,4,6-tri-O-benzoyl-b-D-mannopyranose
followed by deallylation and trichloroacetimidation,8
gave 7 in high yield (92%), and subsequent debenzylide-
nation gave the trisaccharide acceptor 8 (95%). Cou-
pling of 2 with the trisaccharide donor 99 (“10, 86%),
triplets for C(4)H of the mannose at l 6.22 (J3,4=J4,5
9.8 Hz), 6.11 (J3,4=J4,5=9.9 Hz), 5.51 ppm (J3,4=J4,5
=
=
9.8 Hz), confirming the 6-selective mannosylation of 5
as the third downfield triplet was obtained through

246
J. Zhang, F. Kong / Tetrahedron: Asymmetry 13 (2002) 243–252
acetylation of the upfield C(4)H of 12. The tetra-
saccharide donor 19 was prepared in the same way, i.e.
coupling of 5 with 6 gave 16 (78%), and subsequent
silica gel (100–200 mesh) with EtOAc–petroleum ether
(60–90°C) as the eluent. Solutions were concentrated
at <60°C under reduced pressure. In the syntheses,
compound 2 containing an ethylidene group was
composed of (R)- and (S)-isomers in a 4:1 ratio. The
two isomers were separated on a silica gel column
with 2:1 petroleum ether–EtOAc as the eluent. Thus,
pure (R)-2 was used in further reactions in most
cases, yielding products predominantly consisting of
the (R)-isomer as the major compound and less than
10% of the (S)-form as the minor isomer. An excep-
tion was the synthesis of 26, in which (S)-2 was used
at the beginning and thus the (S)-form was obtained
as the predominant isomer for 26. The (R)- and (S)-
isomers had no difference in reactivity and thus no
separation was conducted in the synthesis. However,
for convenience of identification by NMR spectrome-
try, the predominant isomer in each synthesis was
isolated in pure form. The assignments of (R)- and
(S)-forms were based on the data reported by
Kochetkov.7
hydrolysis,
acetylation,
1-O-deacetylation,
and
trichloroacetimidation gave 19 (overall yield 84%).
Condensation of the trisaccharide donor 15 with the
disaccharide acceptor 5 gave the pentasaccharide 20 in
satisfactory yield (85%). Subsequent hydrolysis to
remove the ethylidene group, followed by acetylation
and deacylation afforded the free pentasaccharide 22.
The same strategy was applied for the synthesis of
higher mannose oligosaccharides. Therefore, conden-
sation of the trisaccharide donor 15 with the trisac-
charide acceptor 8 gave the hexasaccharide 23, while
condensation with the tetrasaccharide acceptor 11
gave the heptasaccharide 26. Meanwhile, coupling of
the tetrasaccharide acceptor 11 with the tetra-
saccharide donor 19 afforded the octasaccharide 29.
Deethylidenation of 23, 26, and 29, followed by deac-
ylation gave the free hexasaccharide 25, heptasaccha-
ride 28, and octasaccharide 31, respectively. To the
best of our knowledge, these are the first reported
syntheses of mannoheptaose 28 and mannooctaose 31.
4.2. 4,6-O-Benzylidene-1,2-O-ethylidene-b-D-manno-
pyranose 2
It was found that the size of either donor or acceptor
did not have a significant influence on the yield of
the coupling. Owing to the use of convenient materi-
als and the simplicity of the procedure, this method is
readily amenable to large-scale production of man-
nose oligosaccharides.
p-Toluenesulfonic acid monohydrate (190 mg,
1
mmol) was added to a solution of 1 (2.06 g, 10
mmol), triethyl orthoformate (4.2 mL, 25 mmol) and
benzaldehyde (3.0 mL, 30 mmol) in anhydrous DMF
(25 mL). The mixture was stirred at room tempera-
ture for 12 h, when TLC (2:1 petroleum ether–
EtOAc) indicated that the reaction was complete.
Sodium bicarbonate (2.52 g, 30 mmol) was added to
the reaction mixture, and the mixture was stirred for
an additional hour. After filtration, the solvents were
evaporated in vacuo to give a residue, which was
subjected to silica gel column chromatography (2:1
petroleum ether–EtOAc) to give 2 as a white solid
(2.58 g, 88%) consisting of (R)- and (S)-isomers in a
4:1 ratio. Separation of the mixture with 2:1
petroleum ether–EtOAc as the eluent gave pure (R)-
and (S)-isomers. For the (R)-isomer: [h]D −47.6 (c
1.3, CHCl3); 1H NMR (400 MHz, CDCl3) l 7.37–
7.50 (m, 5H, Ph), 5.58 (s, 1H, PhCH), 5.33 (q, 1H,
J=4.8, MeCH), 5.26 (d, 1H, J1,2=2.0, H-1), 4.31
(dd, 1H, J5,6=5.1, J6,6%=10.6, H-6), 4.20 (dd, 1H,
3. Conclusion
In summary, we have presented herein a very facile
and practical method for the synthesis of multi
branched mannose oligosaccharides of N-glycans.
Sufficient quantities of mannose oligosaccharide sam-
ples can be obtained and this will greatly facilitate
the biological studies.
4. Experimental
4.1. General
Optical rotations were determined at 25°C with a
Perkin–Elmer Model 241-Mc automatic polarimeter.
Melting points were determined with a ‘Mel-Temp’
apparatus. 1H and 13C NMR spectra were recorded
with Bruker ARX 400 spectrometers (400 MHz for
1H, 100 MHz for 13C) for solutions in CDCl3 or D2O
as indicated. Chemical shifts are given in ppm
downfield from internal Me4Si. Mass spectra were
measured using MALTI-TOF-MS with CCA as
matrix or recorded with a VG PLATFORM mass
spectrometer using the ESI mode. Thin-layer chro-
matography (TLC) was performed on silica gel HF254
with detection by charring with 30% (v/v) H2SO4 in
MeOH or in some cases by a UV detector. Column
J
J
1,2=2.0, J2,3=3.2, H-2), 4.07 (dd, 1H, J2,3=3.2,
3,4=9.4, H-3), 3.92 (dd, 1H, J3,4=J4,5=9.4, H-4),
3.77 (dd, 1H, J5,6%=2.7, J6,6%=10.6, H-6%), 3.38 (ddd,
1H, J4,5=9.4, J5,6=5.1, J5,6%=2.7, H-5), 2.44–2.48 (br,
1H, OH), 1.52 (d, 3H, J=4.9, MeCH). Anal. calcd
for C15H18O6: C, 61.21; H, 6.16. Found: C, 61.32; H,
6.25%. For the (S)-isomer: [h]D −42.1 (c 1.1, CHCl3);
1H NMR (400 MHz, CDCl3) l 7.33–7.51 (m, 5H,
Ph), 5.57 (q, 1H, J=4.8, MeCH), 5.56 (s, 1H,
PhCH), 5.40 (d, 1H, J1,2=1.9, H-1), 4.00 (dd, 1H,
J
5,6=5.1, J6,6%=10.6, H-6), 3.83–3.73 (m, 4H, H-2, H-
3, H-4 and H-6%), 3.35 (ddd, 1H, J4,5=9.4, J5,6=5.1,
J5,6%=2.7, H-5), 2.44–2.48 (br, 1H, OH), 1.36 (d, 3H,
J=4.9, MeCH). Anal. calcd for C15H18O6: C, 61.21;
H, 6.16. Found: C, 61.18; H, 6.15%.
chromatography was conducted by elution of
a
column (16×240 mm, 18×300 mm, 35×400 mm) of

J. Zhang, F. Kong / Tetrahedron: Asymmetry 13 (2002) 243–252
247
4.3. 2,3,4,6-Tetra-O-benzoyl-a-
D
-mannopyranosyl-(1“
added TMSOTf (25 mL, 0.14 mmol). The mixture was
stirred at this temperature for 2 h, and then quenched
with Et3N (two drops). After evaporation of the sol-
vents, the crude residue was subjected to silica gel
column chromatography (2:1 petroleum ether–EtOAc)
to give trisaccharide 7 as a foamy solid (2.94 g, 92%).
For the (R)-isomer: [h]2D5 −31.9 (c 1.0, CHCl3); 1H
NMR (400 MHz, CDCl3) l 8.06–7.18 (m, 35H, 7Ph),
5.98 (dd, 1H, J2,3=3.1, J3,4=9.6, H-3), 5.95 (dd, 1H,
3)-4,6-O-benzylidene-1,2-O-ethylidene-b-D-mannopyran-
ose 4
To a cooled solution (0°C) of 2 (2.94 g, 10 mmol) and
3 (7.40 g, 10 mmol) in anhydrous CH2Cl2 (50 mL) was
added TMSOTf (50 mL, 0.28 mmol). The mixture was
stirred at this temperature for 2 h, and then quenched
with Et3N (two drops). The solvents were evaporated in
vacuo to give a residue, which was purified by silica gel
column chromatography (2:1 petroleum ether–EtOAc)
to give disaccharide 4 as a syrup (4.72 g, 83%). For the
J
3,4=J3,4=9.6, H-4), 5.89 (dd, 1H, J2,3=3.2, J3,4=9.8,
H-3), 5.78 (dd, 1H, J3,4=J3,4=9.8, H-4), 5.66 (dd, 1H,
1,2=1.6, J2,3=3.1, H-2), 5.58 (d, 1H, J1,2=1.6, H-1),
J
1
(R)-isomer: [h]D −39.7 (c 1.1, CHCl3); H NMR (400
MHz, CDCl3) l 8.07–7.37 (m, 25H, 5Ph), 6.07 (dd, 1H,
5.37 (q, 1H, J=4.9, MeCH), 5.34 (s, 1H, PhCH), 5.06
(d, 1H, J1,2=1.4, H-1), 4.93 (d, 1H, J1,2=0.9, H-1), 4.68
J
3,4=J4,5=9.8, H-4), 6.01 (dd, 1H, J2,3=3.0, J3,4=9.8,
(dd, 1H, J2,3=3.2, J3,4=10.0, H-3), 4.63 (dd, 1H, J5,6
=
H-3), 5.86 (dd, 1H, J1,2=1.0, J2,3=3.0, H-2), 5.66 (s,
1H, PhCH), 5.59 (d, 1H, J1,2=1.0, H-1), 5.41 (q, 1H,
J=4.7, MeCH), 5.07 (d, 1H, J1,2=1.6, H-1), 4.69 (dd,
1H, J2,3=2.0, J3,4=9.7, H-3), 4.62 (ddd, 1H, J4,5=9.8,
4.9, J6,6%=11.7, H-6), 4.54 (ddd, 1H, J4,5=9.4, J5,6=5.1,
J5,6%=3.3, H-5), 4.48 (dd, 1H, J1,2=1.9, J2,3=3.1, H-2),
4.31 (ddd, 1H, J4,5=9.6, J5,6=4.9, J5,6%=4.3, H-5), 4.19
(dd, 1H, J5,6=5.1, J6,6%=10.6, H-6), 4.13–4.00 (m, 5H),
3.65 (dd, 1H, J3,4=J3,4=10.0, H-4), 3.13 (ddd, 1H,
J
5,6=4.2, J5,6%=2.6, H-5), 4.70 (dd, 1H, J5,6=4.5, J6,6%=
13.5, H-6), 4.34–4.23 (m, 4H, H-2, H-6 and 2H-6%), 3.81
(dd, 1H, J3,4=J4,5=9.7, H-4), 3.36 (ddd, 1H, J4,5=9.7,
J4,5=9.8, J5,6=5.5, J5,6%=2.4, H-5), 2.03 (s, 3H,
CH3CO), 1.56 (d, 1H, J=4.9, MeCH); 13C NMR (100
MHz, CDCl3) l 168.8 (CH3CO), 165.8, 165.3, 165.2,
165.1, 165.0, 164.6 (6C, PhCO), 136.5–125.5 (PhCO
and PhCH), 104.3 (CH3CH), 101.1 (PhCH), 99.5, 98.6,
96.4 (3C-1), 79.2, 75.7, 73.6, 70.1, 69.2, 69.2, 68.8, 68.1,
67.7, 66.6, 65.1, 63.6, 62.5 (15C, C-2–6, some signals
overlapped), 21.3, 20.1 (CH3CH and CH3CO). Anal.
calcd for C71H64O23: C, 66.35; H, 5.02. Found: C,
66.48; H, 4.93%.
J5,6=4.5, J5,6%=4.3, H-5), 1.58 (d, 3H, J=4.7, MeCH).
Anal. calcd for C49H44O15: C, 67.42; H, 5.08. Found: C,
67.56; H, 5.12%.
4.4. 2,3,4,6-Tetra-O-benzoyl-a-
D-mannopyranosyl-(1“
3)-1,2-O-ethylidene-b- -mannopyranose 5
D
To a solution of 4 (8.72 g, 10.0 mmol) in anhydrous
MeOH (100 mL) was added acetyl chloride (0.1 mL).
The solution was sealed in a flask and stirred at rt until
TLC (2:1 petroleum ether–EtOAc) showed that all
starting material was consumed. The solution was neu-
tralized with Et3N, then concentrated to dryness. The
residue was passed through a short silica gel column
(1:2 petroleum ether–EtOAc) to give 5 as a white solid
(6.90 g, 88%). For the (R)-isomer: [h]D −49.7 (c 1.2,
4.6.
osyl-(1“2)-3,4,6-tri-O-benzoyl-a-
“3)-1,2-O-ethylidene-b- -mannopyranose 8
2-O-Acetyl-3,4,6-tri-O-benzoyl-a-
D-mannopyran-
D
-mannopyranosyl-(1
D
To a solution of 7 (2.57 g, 2 mmol) in anhydrous
MeOH (100 mL) was added acetyl chloride (0.1 mL).
The solution was sealed in a flask and stirred at room
temperature until TLC (2:1 petroleum ether–EtOAc)
showed that the starting material disappeared. The
solution was neutralized with Et3N, then concentrated
to dryness. The residue was passed through a short
silica gel column (1:2 petroleum ether–EtOAc) to give 8
as a white solid (2.27 g, 95%). For the (R)-isomer: [h]D25
1
CHCl3); H NMR (400 MHz, CDCl3) l 8.08–7.27 (m,
20H, 4Ph), 6.13 (dd, 1H, J3,4=J4,5=10.2, H-4), 5.97
(dd, 1H, J2,3=3.4, J3,4=10.2, H-3), 5.83 (dd, 1H, J1,2
1.1, J2,3=3.4, H-2), 5.42 (d, 1H, J1,2=1.1, H-1), 5.31 (q,
1H, J=4.8, MeCH), 5.23 (d, 1H, J1,2=2.1, H-1), 4.74
(ddd, 1H, J4,5=10.2, J5,6=4.4, J5,6%=2.3, H-5), 4.65
=
(dd, 1H, J2,3=2.4, J3,4=9.4, H-3), 4.51 (dd, 1H, J5,6
=
1
−3.8 (c 0.5, CHCl3); H NMR (400 MHz, CDCl3) l
4.4, J6,6%=12.1, H-6), 4.38 (dd, 1H, J1,2=2.0, J2,3=2.4,
H-2) 4.17 (dd, 1H, J3,4=J4,5=9.4, H-4), 3.91–3.83 (m,
3H, H-6, and 2H-6%), 3.43 (ddd, 1H, J4,5=9.4, J5,6=5.1,
J5,6%=2.2, H-5), 1.53 (d, 3H, J=4.8, MeCH); 13C NMR
(100 MHz, CDCl3) l 165.7, 165.3, 165.1, 164.9 (4C,
4PhCO), 133.0–127.9 (PhCO), 103.9 (CH3CH), 99.5,
96.4 (2C-1), 81.3, 78.9, 74.8, 69.9, 69.8, 69.0, 66.4, 65.8,
62.5, 61.9 (10C, C-2–6), 21.3 (CH3CH). Anal. calcd for
C42H40O15: C, 64.28; H, 5.14. Found: C, 64.24; H,
5.15%.
8.06–7.18 (m, 30H, 6Ph), 6.05–5.86 (m, 4H, 2H-3,
2H-4), 5.63 (dd, 1H, J1,2=1.5, J2,3=3.1, H-2), 5.58 (d,
1H, J1,2=1.5, H-1), 5.24 (q, 1H, J=4.7, MeCH), 5.16
(d, 1H, J1,2=1.7, H-1), 5.04 (d, 1H, J1,2=2.2, H-1),
4.64–4.69 (m, 7H), 4.18 (dd, 1H, J1,2=2.2, J2,3=3.6,
H-2), 4.08 (dd, 1H, J3,4=J3,4=9.5, H-4), 3.83–3.76 (m,
3H), 3.26 (ddd, 1H, J4,5=9.5, J5,6=5.1, J5,6%=2.3, H-5),
2.04 (s, 3H, CH3CO), 1.49 (d, 1H, J=4.7, MeCH); 13C
NMR (100 MHz, CDCl3) l 168.9 (CH3CO), 166.0,
165.8, 165.4, 165.2, 164.9, 164.7 (6C, PhCO), 133.0–
127.9 (PhCO), 103.9 (CH3CH), 100.3, 98.7, 96.3 (3C,
3C-1), 79.6, 78.8, 74.8, 70.4, 69.2, 68.9, 67.2, 67.0, 66.1,
63.4, 63.0, 61.8 (15C, 3C-2–6, some signals overlapped),
21.2 (CH3CH), 20.1 (CH3CO). Anal. calcd for
C42H40O15: C, 64.21; H, 5.05. Found: C, 64.04; H,
4.90%.
4.5.
2-O-Acetyl-3,4,6-tri-O-benzoyl-a-
D
-mannopyran-
osyl-(1“2)-3,4,6-tri-O-benzoyl-a-
D-mannopyranosyl-(1
“3)-4,6-O-benzylidene-1,2-O-ethylidene-b-D-mannopy-
ranose 7
To a cooled solution (0°C) of 2 (0.74 g, 2.5 mmol) and
6 (2.88 g, 2.5 mmol) in anhydrous CH2Cl2 (50 mL) was

248
J. Zhang, F. Kong / Tetrahedron: Asymmetry 13 (2002) 243–252
4.7. 2,3,4,6-Tetra-O-benzoyl-a-
D
-mannopyranosyl-(1“
5.3, J5,6%=2.0, H-5), 1.45 (d, 1H, J=4.8, MeCH); 13C
NMR (100 MHz, CDCl3) l 166.2, 165.9, 165.7, 165.3,
165.2, 165.1, 165.0, 164.9, 164.6, 164.4 (10C, PhCO),
132.9–127.8 (PhCO), 103.8 (CH3CH), 100.2, 99.1, 98.6,
96.3 (4C, 4C-1), 78.9, 78.8, 75.0, 70.0, 69.8, 69.6, 69.4,
69.1, 69.0, 68.9, 67.8, 67.4, 66.8, 66.2, 63.5, 63.3, 62.2,
62.0 (20C, 4C-2–6, some signals overlapped), 21.1
(CH3CH). Anal. calcd for C42H40O15: C, 66.51; H, 4.88.
Found: C, 66.32; H, 4.96%.
2)-3,4,6-tri-O-benzoyl-a-
D
-mannopyranosyl-(1“2)-3,4,6-
-mannopyranosyl-(1“3)-4,6-O-
benzylidene-1,2-O-ethylidene-b- -mannopyranose 10
tri-O-benzoyl-a-
D
D
TMSOTf (25 mL, 0.14 mmol) was added to a cooled
solution (0°C) of 2 (0.59 g, 2.0 mmol) and 9 (3.38 g, 2.0
mmol) in anhydrous CH2Cl2 (50 mL). The mixture was
stirred at this temperature for 2 h, and then quenched
with Et3N (two drops). The solvents were evaporated in
vacuo to give a residue, which was purified by silica gel
column chromatography (2:1 petroleum ether–EtOAc)
to give tetrasaccharide 10 as a syrup (3.17 g, 86%). For
4.9. 2,3,4,6-Tetra-O-benzoyl-a-
3)-[2,3,4,6-tetra-O-benzoyl-a- -mannopyranosyl-(1“6)]-
1,2-O-ethylidene-b- -mannopyranose 12
D-mannopyranosyl-(1“
D
D
1
the (R)-isomer: [h]2D5 −33.1 (c 1.2, CHCl3); H NMR
(400 MHz, CDCl3) l 8.11–7.27 (m, 55H, 11Ph), 6.06
(dd, 1H, J3,4=J4,5=9.6, H-4), 5.99–5.94 (m, 2H, 2H-3),
To a cooled solution (0°C) of 5 (3.92 g, 5 mmol) and 3
(3.70 g, 5 mmol) in anhydrous CH2Cl2 (50 mL) was
added TMSOTf (50 mL, 0.28 mmol). The mixture was
stirred at this temperature for 2 h, and then quenched
with Et3N (four drops). The solvents were evaporated
in vacuo to give a residue, which was purified by silica
gel column chromatography (2:1 petroleum ether–
EtOAc) to give trisaccharide 12 as a syrup (5.92 g,
87%). For the (R)-isomer: [h]2D5 −42.2 (c 1.0, CHCl3);
1H NMR (400 MHz, CDCl3) l 8.06–7.28 (m, 40H,
8Ph), 6.18 (dd, 1H, J3,4=J3,4=9.8, H-4), 6.15 (dd, 1H,
5.93 (dd, 1H, J3,4=J3,4=9.8, H-4), 5.88 (dd, 1H, J2,3
=
3.0, J3,4=9.8, H-3), 5.81 (dd, 1H, J1,2=1.5, J2,3=3.1,
H-2), 5.73 (dd, 1H, J3,4=J3,4=9.7, H-4), 5.60 (d, 1H,
J
1,2=1.6, H-1), 5.52 (s, 1H, PhCH), 5.38 (d, 1H, J1,2
1.0, H-1), 5.31 (q, 1H, J=4.7, MeCH), 5.11 (d, 1H,
1,2=1.5, H-1), 4.99 (d, 1H, J1,2=1.9, H-1), 4.74 (dd,
=
J
1H, J2,3=3.2, J3,4=9.7, H-3), 4.65 (dd, 1H, J5,6=5.2,
J6,6%=11.8, H-6), 4.54 (ddd, 1H, J4,5=9.4, J5,6=5.0,
J5,6%=2.3, H-5), 4.50–4.45 (m, 3H), 4.28 (ddd, 1H,
J
4,5=9.6, J5,6=5.0, J5,6%=2.1, H-5), 4.20 (dd, 1H, J5,6
4.9, J6,6%=10.5, H-6), 4.15–4.04 (m, 7H), 3.82 (dd, 1H,
3,4=J3,4=9.9, H-4), 3.40 (ddd, 1H, J4,5=9.8, J5,6=5.4,
=
J3,4=J3,4=9.6, H-4), 6.03 (dd, 1H, J2,3=2.9, J3,4=9.8,
H-3), 5.98 (dd, 1H, J2,3=3.1, J3,4=9.6, H-3), 5.89 (dd,
1H, J1,2=0.9, J2,3=3.0, H-2), 5.81 (dd, 1H, J1,2=1.2,
J
J5,6%=2.6, H-5), 1.52 (d, 1H, J=4.9, MeCH); 13C NMR
(100 MHz, CDCl3) l 165.9, 165.8, 165.4, 165.3, 165.2,
165.1, 165.0, 164.4 (10C, 10PhCO, some signals over-
lapped), 136.5–125.5 (PhCO and PhCH), 103.9
(CH3CH), 100.8 (PhCH), 99.1, 99.0, 97.3, 96.9 (4C,
4C-1), 79.8, 75.5, 74.9, 73.5, 73.6, 70.1, 69.3, 69.2, 68.9,
68.1, 67.0, 66.7, 65.4, 64.0, 62.1 (20C, 4C-2–6, some
signals overlapped), 21.3 (CH3CH). Anal. calcd for
C103H88O31: C, 67.91; H, 4.87. Found: C, 68.12; H,
4.85.
J2,3=3.1, H-2), 5.44 (d, 1H, J1,2=0.9, H-1), 5.37 (q, 1H,
J=4.7, MeCH), 5.28 (d, 1H, J1,2=1.2, H-1), 5.21 (d,
1H, J1,2=1.5, H-1), 4.85–4.72 (m, 2H), 4.67 (dd, 1H,
J
2,3=2.7, J3,4=9.9, H-3), 4.55–4.49 (m, 3H), 4.45 (dd,
1H, J1,2=1.5, J2,3=2.7, H-2), 4.24 (dd, 1H, J3,4=J3,4
=
9.9, H-4), 4.15 (dd, 1H, J5,6=4.9, J6,6%=10.8, H-6), 3.59
(ddd, 1H, J4,5=9.8, J5,6=4.9, J5,6%=2.2, H-5), 1.58 (d,
1H, J=4.7, MeCH); 13C NMR (100 MHz, CDCl3) l
165.8, 165.7, 165.3, 165.2, 165.1, 165.0, 164.9, 164.8
(8C, 8PhCO), 133.1–127.8 (PhCO and PhCH), 104.2
(CH3CH), 99.6, 97.5, 96.4 (3C, 3C-1), 82.9, 78.8, 73.7,
70.0, 69.1, 68.3, 66.7, 66.6, 66.4, 65.5, 62.5 (15C, 3C-2–
6, some signals overlapped), 21.5 (CH3CH). Anal. calcd
for C76H66O24: C, 66.95; H, 4.88. Found: C, 66.76; H,
4.85%.
4.8. 2,3,4,6-Tetra-O-benzoyl-a-
2)-3,4,6-tri-O-benzoyl-a- -mannopyranosyl-(1“2)-3,4,6-
tri-O-benzoyl-a- -mannopyranosyl-(1“3)-1,2-O-ethyl-
idene-b- -mannopyranose 11
D-mannopyranosyl-(1“
D
D
D
To a solution of 10 (3.00 g, 1.65 mmol) in anhydrous
MeOH (100 mL) was added acetyl chloride (0.1 mL).
The solution was sealed in a flask and stirred at rt until
TLC (1:1 petroleum ether–EtOAc) showed that the
starting material disappeared. The solution was neutral-
ized with Et3N, and then concentrated. Purification of
the residue on a short silica gel column (1:2 petroleum
ether–EtOAc) gave acceptor 11 as a white foam (2.60 g,
92%). For the (R)-isomer: [h]2D5 −33.3 (c 0.5, CHCl3);
1H NMR (400 MHz, CDCl3) l 8.06–7.18 (m, 50H,
10Ph), 6.10 (dd, 1H, J3,4=J4,5=10.1, H-4), 5.99 (dd,
1H, J3,4=J4,5=9.9, H-4), 5.95–5.93 (m, 2H, H-2 and
H-3), 5.84–5.80 (m, 3H, 2H-3 and H-4), 5.57 (d, 1H,
4.10. 2,3,4,6-Tetra-O-benzoyl-a-
3)-[2,3,4,6-tetra-O-benzoyl-a- -mannopyranosyl-(1“6)]-
-mannopyranosyl
D-mannopyranosyl-(1“
D
2,4-di-O-acetyl-a-
D
trichloroacetimidate 15
Compound 12 (5.45 g, 6.69 mmol) was dissolved in 90%
TFA (70 mL) and stirred for 2 h, at the end of which
time the reaction mixture was poured directly into 250
mL toluene and concentrated. Drying the residue under
high vacuum gave a white foamy solid. This foamy
solid was dissolved in pyridine (20 mL), and then Ac2O
(10 mL) was added. The reaction mixture was stirred at
rt for 12 h, and TLC (4:1 petroleum ether–EtOAc)
indicated that the reaction was complete. The reaction
mixture was concentrated to dryness. The resultant
crude product 13 was dissolved in a 1 M solution of
ammonia–methanol (200 mL) and stirred at rt for 3 h,
at the end of which time TLC (3:1 petroleum ether–
EtOAc) indicated that the reaction was complete. The
J1,2=2.1, H-1), 5.53 (d, 1H, J1,2=1.0, H-1), 5.23 (q, 1H,
J=4.8, MeCH), 5.05 (2d, 2H, 2H-1, overlapped), 4.63–
4.50 (m, 9H), 4.39 (dd, 1H, J1,2=1.0, J2,3=3.1, H-2),
4.24 (dd, 1H, J2,3=3.1, J3,4=9.6, H-3), 4.17 (dd, 1H,
J
1,2=2.1, J2,3=3.1, H-2), 4.11 (dd, 1H, J3,4=J3,4=9.7,
H-4), 3.89–3.78 (m, 3H), 3.26 (ddd, 1H, J4,5=9.6, J5,6
=

J. Zhang, F. Kong / Tetrahedron: Asymmetry 13 (2002) 243–252
249
4.12. 2,3,4,6-Tetra-O-benzoyl-a-
D
-mannopyranosyl-(1“
solution was concentrated to give compound 14 as a
syrup. A mixture of 14, trichloroacetonitrile (4.2 mL,
20 mmol), and 1,8-diazabicyclo[5.4.0]undecene (DBU)
(0.50 mL, 4.04 mmol) in dry dichloromethane (50 mL)
was stirred under nitrogen for 3 h and then concen-
trated. The residue was purified by flash chromatogra-
phy (4:1 petroleum ether–EtOAc) to give 15 as a white
foam (5.10 g, 82% for four steps): [h]D −33.9 (c 1.4,
3)-[2-O-acetyl-3,4,6-tri-O-benzoyl-a-D-mannopyranosyl-
(1“2)-3,4,6-tri-O-benzoyl-a-
D
-mannopyranosyl-(1“6)]-
2,4-di-O-acetyl-a-
D-mannopyranosyl trichloroaceti-
midate 19
Compound 16 (2.50 g, 1.41 mmol) was dissolved in 30
mL 90% TFA and stirred for 2 h, and then the reaction
mixture was poured directly into toluene (150 mL) and
concentrated. Drying the residue under high vacuum
gave a white foamy solid. This foamy solid was dis-
solved in pyridine (20 mL) and Ac2O (10 mL) was
added. The reaction mixture was stirred at rt for 12 h,
TLC (4:1 petroleum ether–EtOAc) indicated that the
reaction was complete. The reaction mixture was con-
centrated to dryness. The resultant crude product 17
was dissolved in a 1 M solution of ammonia–methanol
(100 mL) and stirred at rt for 3 h, at the end of which
time TLC (3:1 petroleum ether–EtOAc) indicated that
the reaction was complete. The solution was concen-
trated to give compound 18 as a syrup. A mixture of
18, trichloroacetonitrile (1.1 mL, 5 mmol), and 1,8-
diazabicyclo[5.4.0]undecene (DBU) (0.10 mL, 0.80
mmol) in dry dichloromethane (10 mL) was stirred
under nitrogen for 3 h and then concentrated. Purifica-
tion of the residue by flash chromatography (3:1
petroleum ether–EtOAc) gave 19 as a white foam (2.34
1
CHCl3); H NMR (400 MHz, CDCl3) l 8.96 (s, 1H,
CNHCCl3), 8.06–7.27 (m, 40H, 8Ph), 6.35 (d, 1H,
J
1,2=1.4, H-1), 6.22 (dd, 1H, J3,4=J4,5=9.8, H-4), 6.11
(dd, 1H, J3,4=J4,5=9.9, H-4), 5.89 (dd, 1H, J2,3=3.2,
3,4=9.8, H-3), 5.81 (dd, 1H, J2,3=3.2, J3,4=9.8, H-3),
5.69 (dd, 1H, J1,2=1.8, J2,3=3.2, H-2), 5.64 (dd, 1H,
1,2=1.5, J2,3=3.1, H-2), 5.54 (dd, 1H, J1,2=1.0, J2,3
J
J
=
3.1, H-2), 5.51 (dd, 1H, J3,4=J4,5=9.8, H-4), 5.42 (d,
1H, J1,2=1.8, H-1), 5.11 (d, 1H, J1,2=1.5, H-1), 4.68
(dd, 1H, J2,3=3.1, J3,4=9.9, H-3), 4.64–4.46 (m, 3H,
H-5, H-6, H-6%), 4.51–4.46 (m, 3H, H-5, H-6, H-6%),
4.22 (ddd, 1H, J4,5=9.8, J5,6=4.7, J5,6%=2.2, H-5), 3.99
(dd, 1H, J5,6=4.7, J6,6%=11.0, H-6), 3.75 (dd, 1H, J5,6%
=
2.1, J6,6%=11.0, H-6), 2.37 (s, 3H, MeCO), 2.29 (s, 3H,
MeCO). Anal. calcd for C80H68Cl3NO26: C, 61.36; H,
4.38. Found: C, 61.52; H, 4.40%.
4.11. 2,3,4,6-Tetra-O-benzoyl-a-
3)-[2-O-acetyl-3,4,6-tri-O-benzoyl-a-
(1“2)-3,4,6-tri-O-benzoyl-a- -mannopyranosyl-(1“6)]-
1,2-O-ethylidene-b- -mannopyranose 16
D
-mannopyranosyl-(1“
1
D
-mannopyranosyl-
g, 84% for four steps): [h]D +3.6 (c 1.1, CHCl3); H
NMR (400 MHz, CDCl3) l 9.04 (s, 1H, CNHCCl3),
8.11–7.27 (m, 50H, 10Ph), 6.33 (d, 1H, J1,2=0.8, H-1),
D
D
6.22 (dd, 1H, J3,4=J4,5=10.0, H-4), 5.99 (dd, 1H, J3,4
4,5=9.7, H-4), 5.90–5.79 (m, 4H, H-2, 3H-3 and H-4),
5.68 (dd, 1H, J1,2=0.8, J2,3=2.6, H-2), 5.64 (dd, 1H,
1,2=1.0, J2,3=3.1, H-2), 5.52–5.48 (m, 2H, H-2 and
H-4), 5.42 (d, 1H, J1,2=1.0, H-1), 5.17 (d, 1H, J1,2=0.9,
H-1), 5.09 (d, 1H, J1,2=1.1, H-1), 4.65–4.49 (m, 10H),
4.33 (dd, 1H, J1,2=1.0, J2,3=2.9, H-2), 4.19 (ddd, 1H,
=
TMSOTf (25 mL, 0.14 mmol) was added to a cooled
solution (0°C) of 5 (1.57 g, 2 mmol) and 6 (2.30 g, 2
mmol) in anhydrous CH2Cl2 (50 mL), and the mixture
was stirred at this temperature for 2 h and then
quenched with Et3N (two drops). The solvents were
evaporated in vacuo to give a residue, which was
purified by silica gel column chromatography (2:1
petroleum ether–EtOAc) to give tetrasaccharide 16 as a
white foamy solid (2.93 g, 83%). For the (R)-isomer:
[h]2D5 −21.6 (c 1.3, CHCl3); 1H NMR (400 MHz, CDCl3)
J
J
J4,5=9.8, J5,6=4.7, J5,6%=2.0, H-5), 3.93 (dd, 1H, J5,6=
4.3, J6,6=11.2, H-6), 3.61 (dd, 1H, J5,6%=2.3, J6,6%=11.2,
H-6%), 2.35 (s, 3H, MeCO), 2.29 (s, 3H, MeCO), 2.22 (s,
3H, MeCO). Anal. calcd for C102H88Cl3NO34: C, 61.93;
H, 4.48. Found: C, 61.71; H, 4.41%.
l 8.09–7.27 (m, 50H, 10Ph), 6.17 (dd, 1H, J3,4=J4,5
=
4.13. 2,3,4,6-Tetra-O-benzoyl-a-
3)-{2,3,4,6-tetra-O-benzoyl-a- -mannopyranosyl-(1“3)-
[2,3,4,6-tetra-O-benzoyl-a- -mannopyranosyl-(1
“6)]-2,4-di-O-acetyl-a- -mannopyranosyl-(1“6)}-1,2-
O-ethylidene-b- -mannopyranose 20
D-mannopyranosyl-(1“
D
D
D
D
1.3, J2,3=3.1, H-2), 4.11 (dd, 1H, J3,4=J3,4=9.6, H-4),
4.01 (dd, 1H, J5,6=5.5, J6,6%=10.9, H-6), 3.90 (dd, 1H,
To a cooled solution (0°C) of 5 (784 mg, 1 mmol) and
15 (1.56 g, 1 mmol) in anhydrous CH2Cl2 (25 mL) was
added TMSOTf (25 mL, 0.14 mmol). The mixture was
stirred at this temperature for 2 h, and then quenched
with Et3N (two drops). The solvents were evaporated in
vacuo to give a residue, which was purified by silica gel
column chromatography (1:1 petroleum ether–EtOAc)
to give pentasaccharide 20 as a syrup (1.86 g, 85%). For
J
2,3=3.1, J3,4=9.6, H-3), 3.76 (dd, 1H, J5,6%=2.1, J6,6%
=
=
10.9, H-6%), 3.48 (ddd, 1H, J4,5=9.6, J5,6=5.5, J5,6%
2.1, H-5), 2.02 (s, 3H, MeCO), 1.53 (d, 1H, J=4.8,
MeCH); 13C NMR (100 MHz, CDCl3) l 168.9
(MeCO), 166.1, 165.7, 165.7, 165.3, 165.2, 165.2, 165.1,
165.0, 164.9, 164.6 (10C, PhCO), 132.1–127.8 (PhCO),
104.2 (CH3CH), 99.7, 99.3, 98.1, 96.4 (4C, 4C-1), 81.8,
78.8, 73.4, 70.5, 69.9, 69.8, 69.3, 69.2, 69.1, 68.1, 67.1,
66.7, 66.6, 66.3, 65.6, 63.3, 62.9, 62.4 (20C, 4C-2–6,
some signals overlapped), 21.5 (MeCO), 20.1
(CH3CH). Anal. calcd for C98H86O32: C, 66.28; H, 4.88.
Found: C, 66.11; H, 5.02%.
1
(R)-isomer: [h]2D5 −44.3 (c 1.0, CHCl3); H NMR (400
MHz, CDCl3) l 8.05–7.04 (m, 60H, 12Ph), 6.17 (dd,
1H, J3,4=J4,5=10.0, H-4), 6.03 (dd, 1H, J3,4=J4,5
10.0, H-4), 6.00 (dd, 1H, J3,4=J4,5=10.4, H-4), 5.93
(dd, 1H, J2,3=3.5, J3,4=10.0, H-3), 5.87 (dd, 1H, J2,3
3.0, J3,4=10.0, H-3), 5.75–5.72 (m, 2H, H-2 and H-3),
=
=

250
J. Zhang, F. Kong / Tetrahedron: Asymmetry 13 (2002) 243–252
5.66 (dd, 1H, J1,2=1.3, J2,3=3.2, H-2), 5.48 (dd, 1H,
1,2=1.0, J2,3=3.5, H-2), 5.46 (dd, 1H, J1,2=1.5, J2,3
3.0, H-2), 5.38 (d, 1H, J1,2=1.3, H-1), 5.32 (dd, 1H,
3,4=J4,5=10.5, H-4), 5.26 (q, 1H, J=4.5, MeCH),
5.22 (d, 1H, J1,2=0.9, H-1), 5.20 (d, 1H, J1,2=1.0, H-1),
5.13 (d, 1H, J1,2=0.8, H-1), 5.10 (d, 1H, J1,2=1.0, H-1),
4.68–4.62 (m, 3H), 4.57–4.50 (m, 3H), 4.45–4.36 (m,
4H), 4.29 (dd, 1H, J1,2=2.0, J2,3=2.9, H-2), 4.19–4.09
1H, J3,4=J4,5=9.8, H-4), 6.13 (dd, 1H, J3,4=J4,5=10.2,
H-4), 5.99 (dd, 1H, J3,4=J4,5=10.1, H-4), 5.96 (dd, 1H,
J
=
J2,3=3.2, J3,4=10.1, H-3), 5.87 (dd, 1H, J2,3=3.1, J3,4=
J
9.8, H-3), 5.89 (dd, 1H, J3,4=J4,5=9.7, H-4), 5.86 (dd,
1H, J1,2=1.4, J2,3=3.1, H-2), 5.81 (dd, 1H, J2,3=3.0,
J3,4=10.5, H-3), 5.76 (dd, 1H, J1,2=1.5, J2,3=3.2, H-2),
5.64 (dd, 1H, J1,2=1.3, J2,3=3.1, H-2), 5.55–5.52 (m, 3H,
H-1, H-2 and H-3), 5.44 (dd, 1H, J3,4=J4,5=9.6, H-4),
5.41 (d, 1H, J1,2=1.0, H-1), 5.28 (q, 1H, J=4.6, MeCH),
5.20 (d, 1H, J1,2=1.5, H-1), 5.04 (d, 1H, J1,2=0.7, H-1),
5.02 (d, 1H, J1,2=1.1, H-1), 5.00 (d, 1H, J1,2=0.8, H-1),
4.73–4.46 (m, 15H), 4.25–4.16 (m, 3H), 4.04 (ddd, 1H,
(m, 3H, H-4 and 2H-6), 3.97 (ddd, 1H, J4,5=9.8, J5,6
=
4.9, J5,6%=2.4, H-5), 3.85 (dd, 1H, J5,6=5.2, J6,6=11.3,
H-6), 3.78 (dd, 1H, J2,3=2.9, J3,4=9.5, H-3), 3.76 (dd,
1H, J5,6%=1.9, J6,6%=11.9, H-6%), 3.48 (ddd, 1H, J4,5
=
9.8, J5,6=5.2, J5,6%=2.2, H-5), 2.21 (s, 3H, MeCO), 2.20
(s, 3H, MeCO), 1.48 (d, 1H, J=4.5, MeCH); 13C NMR
(100 MHz, CDCl3) l 170.4, 170.3 (2C, 2MeCO), 166.1,
166.0, 165.9, 165.8, 165.7, 165.4, 165.3, 165.2, 165.1,
165.0, 164.9, 164.8 (12C, 12PhCO), 133.2–128.1
(PhCO), 104.6 (CH3CH), 100.1, 98.7, 97.2, 96.9, 96.6
(5C, 5C-1), 81.6, 79.3, 74.4, 73.6, 70.6, 70.5, 70.4, 70.1,
69.9, 69.8, 69.4, 69.2, 68.8, 68.6, 66.7, 66.6, 66.2, 66.0,
65.8, 62.8, 62.7, 62.3 (25C, 5C-2–6, some signals over-
lapped), 21.9 (MeCO), 20.9, 20.7 (2C, 2CH3CH). Anal.
calcd for C120H106O40: C, 65.86; H, 4.88. Found C,
65.62; H, 4.80%.
J4,5=9.6, J5,6=5.1, J5,6%=2.2, H-5), 3.92 (dd, 1H, J5,6=
5.6, J6,6=12.4, H-6), 3.78 (dd, 1H, J2,3=3.3, J3,4=9.8,
H-3), 3.70 (dd, 1H, J5,6%=2.3, J6,6%=12.4, H-6%), 3.38
(ddd, 1H, J4,5=9.7, J5,6=5.1, J5,6%=2.3, H-5), 2.30 (s, 3H,
MeCO), 2.26 (s, 3H, MeCO), 1.93 (s, 3H, MeCO), 1.52
(d, 1H, J=4.6, MeCH); 13C NMR (100 MHz, CDCl3)
l 170.1, 170.0, 168.7 (3C, 3MeCO), 165.8, 165.7, 165.6,
165.5, 165.3, 165.1, 165.0, 164.9, 164.8, 164.6 (14C,
14PhCO, some signals overlapped), 133.1–127.9 (PhCO),
104.2 (CH3CH), 100.6, 99.1, 98.5, 97.2, 96.9, 96.3 (6C,
6C-1), 80.5, 78.9, 74.4, 73.8, 70.6, 70.4, 70.2, 70.0, 69.2,
69.0, 68.9, 68.8, 68.5, 68.1, 67.3, 67.0, 66.4, 66.0, 65.7,
63.4, 63.0, 62.5, 61.9 (30C, 6C-2–6, some signals over-
lapped), 21.6 (CH3CH), 20.5, 20.3, 20.1 (3C, 3MeCO).
Anal. calcd for C142H126O48: C, 65.58; H, 4.88. Found C,
65.78; H, 4.75%.
4.14. a-
(1“3)-[a-
osyl-(1“6)}-a-
D
-Mannopyranosyl-(1“3)-{a-
-mannopyranosyl-(1“6)]-a-
-mannopyranose 22
D
-mannopyranosyl-
D
D-mannopyran-
D
Compound 20 (1.00 g, 0.457 mmol) was dissolved in 90%
TFA (15 mL) and stirred for 2 h, and then the reaction
mixture was poured directly into toluene (50 mL) and
concentrated. The residue was purified by flash chro-
matography (1:2 petroleum ether–EtOAc) to give 21 as
a white foam (0.931 g, 94%). Compound 21 was dissolved
in a saturated ammonia–MeOH solution (50 mL). After
1 week at rt, the reaction mixture was concentrated and
the residue was purified by chromatography on Sephadex
LH-20 (MeOH) to afford 22 (288 mg, 76%) as a syrup
with predominant a-anomer at the reducing end; [h]D25
4.16. a-
D
-Mannopyranosyl-(1“2)-a-
-mannopyranosyl-(1“3)-[a-
-mannopyranosyl-(1“6)}-a-D
D
-mannopyranosyl-
-mannopyranosyl-
-mannopyranose
(1“3)-{a-
D
D
(1“6)]-a-
25
D
Compound 23 (910 mg, 0.35 mmol) was dissolved in 90%
TFA (15 mL) and stirred for 2 h, and then the reaction
mixture was poured directly into toluene (50 mL) and
concentrated. The residue was purified by flash chro-
matography (1:2 petroleum ether–EtOAc) to give 24 as
a foamy solid (730 mg, 81%). Compound 24 was dis-
solved in a saturated ammonia–MeOH solution (50 mL).
After 1 week at rt, the reaction mixture was concentrated
and the residue was purified by chromatography on
Sephadex LH-20 (MeOH) to afford 25 as a syrup (203
mg, 72%) with predominant a-anomer at the reducing
end: [h]2D5 +80.0 (c 1.0, D2O); 1H NMR (400 MHz, D2O)
l 5.24, 5.03, 4.93, 4.78, 4.73, 4.71 (d, 6H, J1,2:0, 6H-1),
4.13–3.50 (m, 36H, 6H-2–6); 13C NMR (100 MHz, D2O)
l 104.7, 104.6, 103.0, 102.0, 101.8, 101.7 (6C, 6C-1).
MALDI-TOF MS calcd for C36H62O31: 990.86 [M].
Found: 1013.74 [M+Na].
1
+46.5 (c 1.0, D2O); H NMR (400 MHz, D2O) l 5.03,
5.01, 4.94, 4.71, 4.70 (d, 5H, J1,2:0, 5H-1), 4.13–3.50 (m,
30H, 5H-2–6); 13C NMR (100 MHz, D2O) l 105.0, 104.8,
102.1, 101.9, 96.5 (5C, 5C-1); MALDI-TOF MS calcd for
C30H52O26: 828.72 [M]. Found: 851.55 [M+Na].
4.15. 2-O-Acetyl-3,4,6-tri-O-benzoyl-a-
osyl-(1“2)-3,4,6-tri-O-benzoyl-a- -mannopyranosyl-(1
“3)-{2,3,4,6-tetra-O-benzoyl-a- -mannopyranosyl-(1“
3)-[2,3,4,6-tetra-O-benzoyl-a- -mannopyranosyl-(1“6)]-
2,4-di-O-acetyl-a- -mannopyranosyl-(1“6)}-1,2-O-ethyl-
idene-b- -mannopyranose 23
D-mannopyran-
D
D
D
D
D
4.17. 2,3,4,6-Tetra-O-benzoyl-a-
2)-3,4,6-tri-O-benzoyl-a- -mannopyranosyl-(1“2)-3,4,6-
-mannopyranosyl-(1“3)-{2,3,4,6-
D-mannopyranosyl-(1“
To a cooled solution (0°C) of 8 (598 mg, 0.5 mmol) and
15 (782 mg, 0.5 mmol) in anhydrous CH2Cl2 (25 mL) was
added TMSOTf (9.0 mL, 0.05 mmol). The mixture was
stirred at this temperature for 2 h, and then quenched
with Et3N (two drops). The solvents were evaporated in
vacuo to give a residue, which was purified by silica gel
column chromatography (1:1 petroleum ether–EtOAc)
to give hexaccharide 23 as a foamy solid (1.02 g, 79%).
For the (R)-isomer: [h]2D5 −14.3 (c 1.5, CHCl3); 1H NMR
(400 MHz, CDCl3) l 8.14–7.18 (m, 70H, 14Ph), 6.24 (dd,
D
tri-O-benzoyl-a-
D
tetra-O-benzoyl-a-
tetra-O-benzoyl-a-
D
-mannopyranosyl-(1“3)-[2,3,4,6-
-mannopyranosyl-(1“6)]-2,4-di-O-
D
acetyl-a-
D
-mannopyranosyl-(1“6)}-1,2-O-ethylidene-
b- -mannopyranose 26
D
To a cooled solution (0°C) of 11 (866 mg, 0.5 mmol) and
15 (782 mg, 0.5 mmol) in anhydrous CH2Cl2 (25 mL) was
added TMSOTf (9 mL, 0.05 mmol). The mixture was

J. Zhang, F. Kong / Tetrahedron: Asymmetry 13 (2002) 243–252
251
stirred at this temperature for 2 h, and then quenched
with Et3N (two drops). Evaporation of the solvents in
vacuo gave a residue, and purification of the residue by
silica gel column chromatography (1:1 petroleum ether–
EtOAc) gave heptasaccharide 26 as a white foam (1.29
g, 82%). For the (S)-isomer: [h]2D5 −17.5 (c 1.0, CHCl3);
1H NMR (400 MHz, CDCl3) l 8.05–7.22 (m, 90H,
18Ph), 6.22 (dd, 1H, J3,4=J4,5=10.1, H-4), 6.14 (dd,
1H, J3,4=J4,5=10.0, H-4), 6.06–5.89 (m, 6H), 5.82–5.76
(m, 4H), 5.66 (q, 1H, J=4.9, MeCH), 5.54–5.52 (m,
2H, 2H-2), 5.02 (dd, 1H, J3,4=J4,5=9.9, H-4), 5.47–
5.46 (2d, 2H, J1,2=1.4, 2H-2), 5.36 (d, 1H, J1,2=1.3,
H-1), 5.23 (d, 1H, J1,2=1.5, H-1), 5.16 (d, 1H, J1,2=1.0,
H-1), 5.02 (d, 1H, J1,2=1.3, H-1), 4.98 (d, 1H, J1,2=1.0,
H-1), 4.73–4.39 (m, 18H), 4.19–3.96 (m, 6H), 3.78 (dd,
1H, J2,3=3.4, J3,4=9.4, H-3), 3.70 (dd, 1H, J5,6%=2.2,
J6,6%=11.3, H-6%), 3.38 (ddd, 1H, J4,5=9.4, J5,6=5.5,
J5,6%=2.2, H-5), 2.35 (s, 3H, MeCO), 2.24 (s, 3H,
MeCO), 1.32 (d, 1H, J=4.9, MeCH); 13C NMR (100
MHz, CDCl3) l 170.8, 170.4 (2C, 2MeCO), 166.6,
166.4, 166.3, 166.2, 166.1, 165.6, 165.5, 165.4, 165.1,
164.8 (18C, 18PhCO, some signals overlapped), 133.5–
128.4 (PhCO), 103.8 (CH3CH), 101.3, 99.7, 99.7, 99.1,
97.7, 97.6, 97.5 (7C, 7C-1), 81.5, 75.3, 74.4, 71.0, 70.8,
70.5, 70.3, 70.1, 69.9, 69.6, 69.2, 69.0, 68.3, 67.9, 66.9,
66.7, 66.4, 66.1, 64.0, 63.5, 63.0, 62.6, 62.5 (35C, 7C-2–
6, some signals overlapped), 21.2 (CH3CH), 21.0, 20.8
(2C, 2MeCO). Anal. calcd for C174H150O56: C, 66.62;
H, 4.82. Found C, 66.84; H, 4.77%.
and 19 (494 mg, 0.25 mmol) in anhydrous CH2Cl2 (25
mL) was added TMSOTf (9 mL, 0.05 mmol). The
mixture was stirred at this temperature for 2 h, and
then quenched with Et3N (two drops). The solvents
were evaporated in vacuo to give a residue, which was
purified by silica gel column chromatography (1:1
petroleum ether–EtOAc) to give octasaccharide 29 as a
syrup (710 mg, 80%). For the (R)-isomer: [h]2D5 −9.9 (c
1
1.0, CHCl3); H NMR (400 MHz, CDCl3) l 8.05–7.22
(m, 100H, 20Ph), 6.21 (dd, 1H, J3,4=J4,5=10.0, H-4),
6.04–5.90 (m, 9H), 5.81–5.78 (m, 3H), 5.65 (dd, 1H,
J1,2=1.1, J2,3=3.2, H-2), 5.53–5.50 (m, 3H), 5.46 (d,
1H, J1,2=1.2, H-1), 5.43 (d, 1H, J1,2=1.5, H-1), 5.37
(d, 1H, J1,2=1.2, H-1), 5.27 (q, 1H, J=4.8, MeCH),
5.25 (d, 1H, J1,2=1.3, H-1), 5.14 (d, 1H, J1,2=1.5,
H-1), 5.07 (d, 1H, J1,2=1.4, H-1), 5.01 (d, 1H, J1,2
=
1.4, H-1), 4.97 (d, 1H, J1,2=1.2, H-1), 4.70–4.26 (m,
21H), 4.18–4.08 (m, 5H), 3.98–3.92 (m, 2H), 3.88 (dd,
1H, J2,3=3.2, J3,4=9.6, H-3), 3.57 (dd, 1H, J5,6%=2.0,
J6,6%=10.8, H-6%), 3.42 (ddd, 1H, J4,5=9.8, J5,6=4.9,
J5,6%=2.1, H-5), 2.21 (s, 3H, MeCO), 2.18 (s, 3H,
MeCO), 1.95 (s, 3H, MeCO), 1.48 (d, 1H, J=4.8,
MeCH); 13C NMR (100 MHz, CDCl3) l 170.9, 169.8,
167.4 (3C, 3MeCO), 165.6–164.6 (PhCO), 133.0–128.0
(PhCO), 104.1 (CH3CH), 100.8, 99.5, 99.3, 99.2, 98.5,
97.6, 97.2, 96.2 (7C, 7C-1), 81.6–61.9 (C-2–6), 21.6
(CH3CH), 20.5, 20.4, 20.1 (3C, 3MeCO). Anal. calcd
for C196H170O64: C, 66.32; H, 4.83. Found C, 66.55; H,
4.88%.
4.18. a-
(1“2)-a-
syl-(1“3)-[a-
pyranosyl-(1“6)}-a-
D
-Mannopyranosyl-(1“2)-a-
-mannopyranosyl-(1“3)-{a-
-mannopyranosyl-(1“6)]-a-
-mannopyranose 28
D
-mannopyranosyl-
-mannopyrano-
-manno-
4.20. a-
(1“2)-a-
syl-(1“3)-[a-
D
-Mannopyranosyl-(1“2)-a-
-mannopyranosyl-(1“3)-{a-
-mannopyranosyl-(1“2)-a-
D
-mannopyranosyl-
-mannopyrano-
-manno-
-mannopyranosyl-(1“6)}-a-
D
D
D
D
D
D
D
D
D
pyranosyl-(1“6)]-a-
D
D-
Compound 26 (1.00 g, 0.32 mmol) was dissolved in 90%
TFA (15 mL) and stirred for 2 h, and then the reaction
mixture was poured directly into toluene (50 mL) and
concentrated. The residue was purified by flash chro-
matography (1:2 petroleum ether–EtOAc) to give 27 (860
mg, 87%) as a white foam. Compound 27 was dissolved
in a saturated ammonia–MeOH solution (50 mL). After
1 week at rt, the reaction mixture was concentrated and
the residue was purified by chromatography on Sephadex
LH-20 (MeOH) to afford 28 (242 mg, 76%) as a foamy
solid with predominant a-anomer at the reducing end:
mannopyranose 31
Compound 29 (600 mg, 0.17 mmol) was dissolved in
90% TFA (15 mL) and stirred for 2 h, and then the
reaction mixture was poured directly into toluene (50
mL) and concentrated. The residue was purified by
flash chromatography (1:2 petroleum ether–EtOAc) to
give 30 (510 mg, 86%) as a white foam. Compound 30
was dissolved in a saturated ammonia–MeOH solution
(50 mL). After 1 week at rt, the reaction mixture was
concentrated and the residue was purified by chro-
matography on Sephadex LH-20 (MeOH) to afford 31
(154 mg, 82%) as a syrup with predominant a-anomer
1
[h]2D5 +74.5 (c 1.0, D2O); H NMR (400 MHz, D2O) l
5.22, 5.17, 5.01, 5.00, 4.91, 4.77, 4.72 (d, 7H, J1,2:0,
7H-1), 4.02–3.50 (m, 42H, 7H-2–6); 13C NMR (100 MHz,
D2O) l 103.4, 103.1, 103.0, 102.9, 102.1, 101.9, 101.9 (7C,
7C-1). MALDI-TOF MS calcd for C42H72O36: 1152.99
[M]. Found: 1175.87 [M+Na].
1
at the reducing end: [h]2D5 +30.7 (c 1.0, D2O); H NMR
(400 MHz, D2O) l 5.43, 5.39, 5.34, 5.27, 5.11, 5.08,
5.02, 5.00 (d, 8H, J1,2:0, 8H-1), 4.11–3.31 (m, 48H,
8H-2–6); 13C NMR (100 MHz, D2O) l 105.4, 105.3,
105.0, 104.8, 103.9, 101.8, 101.4, 100.9 (8C, 8C-1).
MALDI-TOF MS calcd for C48H82O41: 1315.14 [M].
Found: 1338.27 [M+Na].
4.19. 2,3,4,6-Tetra-O-benzoyl-a-
2)-3,4,6-tri-O-benzoyl-a- -mannopyranosyl-(1“2)-3,4,6-
tri-O-benzoyl-a- -mannopyranosyl-(1“3)-{2,3,4,6-tetra-
O-benzoyl-a- -mannopyranosyl-(1“3)-[2-O-acetyl-
3,4,6-tri-O-benzoyl-a- -mannopyranosyl-(1“2)-3,4,6-
tri-O-benzoyl-a- -mannopyranosyl-(1“6)]-2,4-di-
O-acetyl-a- -mannopyranosyl-(1“6)}-1,2-O-ethylidene-
b- -mannopyranose 29
D-mannopyranosyl-(1“
D
D
D
D
Acknowledgements
D
D
This work was supported by CAS KIP-RCEES9904,
NNSF of China (Projects 39970864, and 30070815),
and the Ministry of Science and Technology.
D
To a cooled solution (0°C) of 11 (433 mg, 0.25 mmol)

252
J. Zhang, F. Kong / Tetrahedron: Asymmetry 13 (2002) 243–252
Ogawa, T.; Sasajima, K. Tetrahedron 1981, 37, 2787; (d)
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