Toward synthesis of the regular sequence of heparin: synthesis of two tetrasaccharide precursors

Article abstract of DOI:10.1016/j.carres.2006.02.020

Two fully protected tetrasaccharides, which represent precursors for the synthesis of the regular sequence of heparin, were synthesized via coupling of a pair of disaccharide trichloroacetimidates with a thioglycoside and a glucosamine derivative, respectively, in a sequential manner.

Full text of DOI:10.1016/j.carres.2006.02.020

Carbohydrate Research 341 (2006) 1619–1629
Toward synthesis of the regular sequence of heparin: synthesis
of two tetrasaccharide precursors
Ying Zhou, Feng Lin, Jianfang Chen and Biao Yu*
State Key Laboratory of Bio-organic and Natural Products Chemistry, Shanghai Institute of Organic Chemistry,
Chinese Academy of Sciences, Shanghai 200032, China
Received 10 January 2006; received in revised form 15 February 2006; accepted 21 February 2006
Available online 10 March 2006
Abstract—Two fully protected tetrasaccharides, which represent precursors for the synthesis of the regular sequence of heparin,
were synthesized via coupling of a pair of disaccharide trichloroacetimidates with a thioglycoside and a glucosamine derivative,
respectively, in a sequential manner.
Ó 2006 Elsevier Ltd. All rights reserved.
Keywords: Heparin; Synthesis; Glycosylation; Thioglycoside; L-Idopyranuronic acid; One pot
1. Introduction
synthesis is a lack of highly efficient (1!4) glycosidic
couplings (e.g., >90% yield) between D-GlcpA/L-IdopA
and D-GlcpN residues, which has rarely been achieved.
In fact, the well-developed one-pot sequential glycosyl-
ation strategy4 has never been used for the synthesis of
heparin oligosaccharides, although a sequential glyco-
sylation protocol has been reported.5 Using the regular
sequence of heparin as a target, we set out to examine
the combined use of two orthogonal classes of glycosyl
donors, glycosyl trichloroacetimidates and thioglyco-
sides, in a sequential glycosylation approach for the syn-
thesis of heparin oligosaccharides.6
The structure of heparin is composed of a repetitive
disaccharide in which a uronic acid is b-(1!4)-linked
to 2-amino-2-deoxy-a-D-glucopyranose (D-GlcpN). A
number of structural variations of this disaccharide exist
leading to tremendous microheterogeneity in the poly-
saccharide. Those structural variations include sulfon-
ation of the hydroxyl groups, various substitutions
(sulfonation, acetylation or none) of the amino group
of the D-GlcpN residue and the alternating occurrence
of L-idopyranosyluronic acid (L-IdopA) and D-glucopyr-
anosyluronic acid (D-GlcpA). Associated with its com-
plex structure, heparin displays numerous biological
activities via interaction with diverse proteins.1 A few
of these heparin-protein interactions have been shown
to be sequence-specific by employing homogeneous hep-
arin fragments as probes.1,2 Chemical synthesis is there-
fore a powerful tool for obtaining these diverse heparin
and heparin-like oligosaccharides. However, the synthe-
sis of heparin oligosaccharides still remains as one of the
most formidable tasks for carbohydrate chemists.3
Among the difficulties posed by heparin oligosaccharide
2. Results and discussion
Adopting the common protecting-group strategy for
heparin synthesis,3 we envisioned tetrasaccharides 1 as
precursors to the regular sequence of heparin (Scheme
1). In this approach, benzyl groups were used as a per-
manent protecting group, acetyl/benzoyl groups were
used for protection of the hydroxyl groups destined
for sulfonation and an azide as the precursor to the
2-amino group of the D-GlcpN residues. In addition,
a levulinoyl group at the 4-hydroxyl group of the non-
reducing end residue would enable further elongation
*
Corresponding author. Tel.: +86 21 54925131; fax: +86 21
64166128; e-mail: byu@mail.sioc.ac.cn
0008-6215/$ - see front matter Ó 2006 Elsevier Ltd. All rights reserved.
doi:10.1016/j.carres.2006.02.020

1620
Y. Zhou et al. / Carbohydrate Research 341 (2006) 1619–1629
O-
-
OSO3
O
O
O
HO
O
-
O
HO
OSO3
O
-O3SO
-O3SHN
O
O
O
HO
-O3SHN
HO
-O3SO
O-
O
O
regular sequence of heparin
OMe
O
OR
O
O
LevO
BnO
O
BnO
OR
O
N3
RO
O
O
BnO
O
BnO
1 (R = Ac or Bz)
RO
N3
OMe
O
OMe
OAc
O
O
LevO
BnO
O
O
CCl3
NH
BnO
OBz
O
N3
BzO
O
HO
BnO
OMe
O
SPh
2
HO
+
+
BnO
BzO
OMe
OMe
O
OAc
O
O
N3
OMe
O
5
4
LevO
BnO
O
BnO
O
CCl3
N3
NH
OAc
3
Scheme 1. Retrosynthesis for tetrasaccharides 1.
upon selective removal. To test a sequential glycosyl-
ation protocol for the synthesis of the tetrasaccharides
1, we attempted to employ trichloroacetimidate 2/3,
thioglycoside 4,5,7 and glucosamine derivative 58 as
building blocks.
O-benzyl-b-L-idopyranoside 6, a versatile L-idose build-
ing block recently developed by Hung and co-workers,8
was subjected to acetolysis in the presence of a catalytic
amount of TMSOTf, affording triacetate 79 (89%),
which was converted readily into ethyl thioglycoside 8
1
Disaccharide trichloroacetimidate 2 was prepared as
shown in Scheme 2. Thus, 1,6-anhydro-2-O-benzoyl-3-
(91%, a/b, 3:2 from H NMR) in the presence of EtSH
and BF3ÆEt2O. Coupling of 8 with 1,6-anhydro-2-azido-
O
O
OBn
O
O
AcO
BnO
O
AcO
BnO
HO
BnO
a
b
SEt
OAc
+
BzO
BzO
OAc
BzO
OAc
O
OH
N3
8
7
6
9
O
O
OBn
O
OBn
O
e
d
c
O
HO
BnO
O
AcO
BnO
N3
N3
O
O
BzO
OH
BzO
OAc
10
11
O
O
OBn
O
OBn
O
g
f
O
O
LevO
BnO
O
HO
N3
N3
O
BnO
BzO
BzO
OMe
O
OMe
O
12
13
OAc
OAc
O
O
i
LevO
BnO
O
O
O
OH
h
LevO
BnO
2
O
OAc
BnO
OMe
BnO
OMe
BzO
N3
O
BzO
N3
O
14
15
Scheme 2. Synthesis of the disaccharide trichloroacetimidate 2. Reagents and conditions: (a) TMSOTf, Ac2O, CH2Cl2, 0 °C, 89%; (b) EtSH,
˚
BF3ÆEt2O, CH2Cl2, 0 °C, 91%; (c) AgOTf, NIS, 4 A MS, toluene, 0 °C!rt, 95%; (d) 0.1 M HCl/methanol, rt, 88%; (e) (i) TEMPO, Ca(ClO)2,
NaHCO3–KBr–tBu4NBr, CH2Cl2/H2O, 0 °C; (ii) CH2N2, THF, rt, 84%; (f) Levulinic acid, DCC, DMAP, CH2Cl2, 0 °C, 92%; (g) TMSOTf, Ac2O,
CH2Cl2, 0 °C, 88%; (h) NH3, THF/methanol (7:3), 0 °C, 77%; (i) CCl3CN, K2CO3, CH2Cl2, 0 °C–rt, 95%.

Y. Zhou et al. / Carbohydrate Research 341 (2006) 1619–1629
1621
3-O-benzyl-2-deoxy-b-D-glucopyranoside 910 under the
action of NIS/AgOTf provided the a-linked disaccha-
ride 10 in an excellent 95% yield. The 4,6-O-acetyl
groups in 10 were then selectively removed with HCl
in methanol (0.1 M) to give diol 1111 (88%). Subjection
of 11 to the modified TEMPO oxidation protocol with
addition of solid Ca(ClO)2 as the co-oxidant and subse-
quent methyl ester formation with CH2N2,12 provided
the desired a-L-IdopA-(1!4)-D-GlcpN disaccharide
1212 in a satisfactory 84% yield. The remaining 40-hydro-
xyl group was protected with levulinoyl ester giving 13
(92%), which was then subjected to acetolysis to provide
1,6-diacetate 1413 (88%). Selective removal of the ano-
meric acetyl group (77%) followed by addition with
CCl3CN led to the desired trichloroacetimidate 2 (95%).
Disaccharide trichloroacetimidate 3 was synthesized
starting from 1,2-di-O-acetyl-3-O-benzyl-4,6-O-benzyl-
idene-D-glucopyranoside 1614 (Scheme 3). Selective re-
moval of the 4,6-O-benzylidene group in 16 with 80%
HOAc gave diol 17 (79%), which was subjected to TEM-
PO oxidation and methylation under similar conditions
for 11!12 to provide methyl uronate 18 in a good 70%
yield. Blocking the remaining 4-hydroxyl group as a lev-
ulinate ester, followed by selective removal of the ano-
meric acetyl group (with Bu2SnO in methanol)15 and
subsequent reaction of the resulting lactol with CCl3CN
and DBU led to trichloroacetimidate 21. Coupling of 21
with 9 in the presence of TMSOTf afforded the desired
D-GlcpA-b-(1!4)-D-GlcpN disaccharide 22 in good
(70%) yield. In this reaction, the corresponding ortho-
1
ester was initially formed (as indicated by TLC and H
NMR analysis), which was gradually transformed into
the glycoside (22) upon continued stirring of the mixture
at room temperature overnight. Acetolysis of 1,6-anhy-
dride 22 was achieved with 1:5 CF3COOH/Ac2O and
the same transformations used to convert 14 into 2 were
applied for the conversion of acetate 23 into trichloro-
acetimidate 3.
Phenyl thioglycoside 45,7 was prepared by adopting,
for the most part, transformations previously reported
in the literature (Scheme 4).13 In contrast to the conver-
sion of idose acetate 7 to ethyl thioglycoside 8 (above),
where an a/b mixture was produced, treatment of 7 with
PhSH and BF3ÆEt2O under similar conditions provided
only the a anomer of the phenyl thioglycoside 25 (89%).
The 2-azidoglucoside 58 was synthesized from D-glu-
cosamine hydrochloride in six steps (Scheme 5). Thus,
the crude diazo transfer product 2716 was treated with
10% HCl in methanol and the resulting methyl glycoside
2817 was subsequently subjected to 4,6-O-benzylidene
OMe
O
HO
O
Ph
c
b
a
O
O
HO
O
O
HO
OAc
OAc
OAc
BnO
BnO
BnO
OAc
OAc
OAc
16
17
18
OMe
OMe
O
O
OMe
O
O
d
e
O
O
LevO
LevO
CCl3
LevO
O
OH
OAc
BnO
BnO
BnO
OAc
OAc
NH
OAc
21
20
19
O
OAc
OBn
O
OMe
O
O
g
f
h
OMe
O
O
O
LevO
BnO
O
OAc
BnO
LevO
BnO
O
9
N3
N3
OAc
22
OAc
23
OAc
O
OMe
O
O
i
LevO
BnO
O
OH
3
BnO
N3
OAc
24
Scheme 3. Synthesis of the disaccharide trichloroacetimidate 3. Reagents and conditions: (a) 80% HOAc/H2O, 70 °C, 79%; (b) (i) TEMPO,
Ca(ClO)2, NaHCO3–KBr–tBu4NBr, CH2Cl2/H2O, 0 °C; (ii) CH2N2, THF, rt, 70%; (c) Levulinic acid, DCC, DMAP, CH2Cl2, 0 °C, 95%; (d)
˚
Bu2SnO, methanol, 55 °C, 87%; (e) CCl3CN, DBU, CH2Cl2, rt, 93%; (f) TMSOTf, 4 A MS, CH2Cl2, rt, 70%; (g) CF3COOH/Ac2O (1:5), 0 °C, 96%;
(h) NH3, THF/methanol (7:3), 0 °C, 92%; (i) CCl3CN, K2CO3, CH2Cl2, rt, 92%.
O
SPh
OMe
O
SPh
OAc
LevO
BnO
AcO
BnO
ref. 13
a
b
4
7
BzO
BzO
5 steps
O
25
26
Scheme 4. Synthesis of IdoA thioglycoside 4. Reagents and conditions: (a) PhSH, BF3ÆEt2O, CH2Cl2, rt, 89%; (b) H2NNH2ÆHOAc, CH2Cl2, rt, 90%.

1622
Y. Zhou et al. / Carbohydrate Research 341 (2006) 1619–1629
OH
O
OH
O
OH
O
c
a
d
b
HO
HO
HO
HO
HO
HO
OH
OMe
OH
.
N3
N3
NH2 HCl
27
28
HO
O
O
Ph
O
HO
f
Ph
O
e
O
O
O
HO
5
BnO
BnO
N3
OMe
N3
N3
OMe
OMe
31
29
30
Scheme 5. Synthesis of glucosamine derivative 5. Reagents and conditions: (a) TfN3, NaOMe/MeOH, DMAP, rt; (b) 10% HCl/methanol, reflux; (c)
p-TsOH, PhCH(OMe)2, DMF, 40 °C, 51% (three steps for 29); (d) NaH, BnBr, THF, rt, 85%; (e) 80% HOAc/H2O, 70 °C, 71%; (f) BzCl, pyridine,
CH2Cl2, 0 °C, 96%.
formation. The desired a-anomer 2917,18 was isolated in
51% yield via column chromatography and the corre-
sponding b-anomer was also obtained in 20% yield. Pro-
tection of the remaining 3-hydroxyl group as a benzyl
ether followed by removal of the 4,6-O-benzylidene ace-
tal13 and selective protection of the resulting 6-hydroxyl
group as a benzoate ester8 furnished the desired com-
pound 5.
With all of the building blocks 2–5 available, we
examined the final glycosidic coupling to elaborate the
target tetrasaccharides 1a and 1b (Scheme 6). Coupling
between trichloroacetimidate 2 and thioglycoside 4 was
found to be problematic,19 leading unavoidably to com-
plex mixtures under a variety of conditions. A modest
56% yield of the desired trisaccharide 32 was obtained
under the promotion of TMSOTf in toluene at
ꢀ78 °C. Promotion with TBSOTf, Zn(OTf)2 or BF3Æ
Et2O, in CH2Cl2 or Et2O, and at varying temperatures
did not improve the yield of the coupling product (32).
In comparison, coupling between imidate 3 and thiogly-
coside 4 led to fewer by-products; up to a 70% yield of
the corresponding trisaccharide 33 was obtained under
the same conditions leading to a 56% yield of 32 (from
2+4). The a-stereochemistry of nascent glycosidic link-
ages in 32 and 33 was established by the resonances of
the C-10 signals, which were appeared at 97.8 and
99.7 ppm, respectively.20,21 Recently, thioglycosides of
the idouronate type were found by van der Marel and
co-workers5 to be effective glycosyl donors under the ac-
tion of BSP (1-benzenesulfinyl-piperidine)/Tf2O, a pow-
erful promoter system developed by Crich et al.22 In our
hands, after failing to couple thioglycoside 32 with sugar
alcohol 5 under the promotion of NIS/AgOTf (or
TfOH, no reaction took place at all), we found indepen-
dently that BSP/Tf2O could promote this coupling reac-
tion effectively, furnishing the desired tetrasaccharide 1a
in an impressive 87% yield. Coupling of thioglycoside 33
with 5 under similar conditions gave 1b in 79% yield.
It should be noted that a successful one-pot procedure
for the coupling of imidate 2/3, thioglycoside 4, and
sugar alcohol 5 (and related derivatives for the synthesis
of heparin oligosaccharides) still waits for improvement
in the efficiency of each coupling step. Nevertheless, we
examined a one-pot procedure for sequential coupling
of 2/3, 4, and 5 adopting the present coupling condi-
tions. Thus, treatment of imidate 2/3 (1.2 equiv) with
thioglycoside 4 (1.0 equiv) in the presence of TMSOTf
(0.05 equiv) in CH2Cl2 under argon (ꢀ78 °C to rt) fol-
lowed by subsequent addition of BSP (1.2 equiv), Tf2O
(1.2 equiv, at ꢀ60 °C), and 5 in CH2Cl2 (2.0 equiv, at
ꢀ40 °C) afforded the desired tetrasaccharides 1a and
1b in a low 10% and 17% isolated yield, respectively.
In summary, tetrasaccharides 1a and 1b are
synthesized via coupling of trichloroacetimidate 2/3,
OAc
O
OAc
O
O
O
LevO
BnO
O
LevO
BnO
O
BnO
BnO
5
4
OBz
O
N3
BzO
N3
BzO
2
3
OMe
O
OMe
O
O
O
O
O
b
a
SPh
O
BnO
BnO
BnO
32
1a
BzO
BzO
N3
OMe
O
OMe
O
OMe
OMe
O
OAc
O
O
OMe
OAc
O
O
LevO
BnO
O
O
LevO
BnO
O
5
BnO
4
BnO
N3
OAc
N3
O
OBz
O
OAc
O
b
a
O
O
SPh
OMe
BnO
O
BnO
33
1b
BnO
OMe
BzO
BzO
O
O
N3
OMe
˚
Scheme 6. Sequential glycosylation for the synthesis of tetrasaccharides 1a and 1b. Reagents and conditions: (a) TMSOTf, 4 A MS, toluene, ꢀ78 °C,
56% for 32; 70% for 33; (b) BSP, Tf2O, CH2Cl2, ꢀ60 °C, 30 min, then ꢀ40 °C, 5, 15 min, !rt, 87% for 1a, 79% for 1b.

Y. Zhou et al. / Carbohydrate Research 341 (2006) 1619–1629
1623
thioglycoside 4, and glucosamine derivative 5 in a
sequential manner. A successful one-pot procedure
requires further improvement of the efficiency of each
coupling steps, especially of the one between the
2-azidoglucopyranosyl imidates (e.g., 2/3) and the ido-
pyranosyluronate thioglycosides (e.g., 4). It should be
mentioned that a tetrasaccharide similar to 1a en route
(262 mg, 91%) as a colorless syrup (a/b, 1.5:1).
Rf = 0.78 (2:1, petroleum ether/EtOAc); 1H NMR
(300 MHz, CDCl3): d 8.18–8.07 (m, 2H), 7.57 (m, 1H),
7.47–7.32 (m, 7H, ArH), 5.44 (s, 0.4H), 5.27 (t, 0.4H,
J = 1.5 Hz), 5.22 (m, 0.6H), 5.13 (d, 0.6H, J = 1.8 Hz),
4.92–4.68 (m, 4H), 4.25 (m, 2H), 3.97 (t, 0.6H,
J = 3.0 Hz), 3.82 (m, 0.4H), 2.78 (m, 1.2H), 2.71–2.66
(m, 0.8H), 2.06 (s, 3H, Ac), 1.97 (s, 1.2H, Ac), 1.79 (s,
1.8H, Ac), 1.34 (m, 3H); 13C NMR (75 MHz, CDCl3):
d 170.6, 170.1, 165.5, 165.1, 137.2, 133.5, 130.0, 129.8,
129.5, 128.6, 128.4, 128.2, 127.9, 127.8, 82.6, 81.5,
73.0, 72.8, 72.7, 72.6, 72.0, 69.6, 69.0, 67.2, 66.0, 64.1,
62.8, 26.8, 26.0, 20.7, 20.6, 15.1, 15.0; IR: 2968, 2930,
to heparin fragments has been prepared by Sinay and
¨
co-workers employing a convergent 2+2 coupling
approach.21 In addition, the present preparation of the
useful building blocks 2–5 employs routine transforma-
tions but in new sequences.
1746, 1453, 1268, 1235, 1112, 1070, 1027, 713 cmꢀ1
;
3. Experimental
ESIMS m/z calcd for [C26H30O8S]Na+: 525.1554.
Found: 525.1561.
3.1. General methods23
3.1.3. 4,6-Di-O-acetyl-2-O-benzoyl-3-O-benzyl-a-L-ido-
pyranosyl-(1!4)-1,6-anhydro-2-azido-3-O-benzyl-2-deoxy-
b-D-glucopyranoside (10). A mixture of thioglycoside 8
(117 mg, 0.227 mmol), alcohol 9 (53 mg, 0.189 mmol),
3.1.1. 1,4,6-Tri-O-acetyl-2-O-benzoyl-3-O-benzyl-L-ido-
pyranose (7). To a cooled solution of 1,6-anhydride
68 (366 mg, 1.03 mmol) in dry CH2Cl2 (5 mL) and
Ac2O (2 mL) at 0 °C, TMSOTf (three drops) was added.
After stirring for 10 min, the reaction was quenched by
the addition of Et3N (0.5 mL), and the mixture was con-
centrated in vacuo. The residue was purified by silica gel
column chromatography (4:1, petroleum ether/EtOAc)
to give 79 (456 mg, 89%) as a colorless syrup. A small
amount of the mixture was separated for 1H NMR mea-
surement. Compound 7a: Rf = 0.79 (petroleum ether/
˚
and freshly activated 4 A MS (100 mg) in dry toluene
(1.5 mL) was stirred under argon at rt for 30 min. The
mixture was cooled in an ice bath and then NIS
(65 mg, 0.28 mmol) and a solution of AgOTf in
toluene (0.09 M, 0.4 mL) were added. The ice bath was
removed and stirring continued for 1 h. The reaction
was then quenched by the addition of Et3N (0.2 mL).
The mixture was filtered and concentrated under
reduced pressure. Silica gel column chromatography
(2:1, petroleum ether/EtOAc) of the residue provided
10 (129 mg, 95%) as a colorless syrup. Rf = 0.62 (2:1,
1
EtOAc 2:1); H NMR (300 MHz, CDCl3): d 8.12 (m,
2H), 7.60 (t, 1H, J = 7.5 Hz), 7.46 (t, 2H, J = 7.8 Hz),
7.37–7.26 (m, 5H, ArH), 6.20 (d, 1H, J = 1.2 Hz, H-1),
5.30 (m, 1H, H-2), 4.93 (t, 1H, J = 2.1 Hz, H-4), 4.78
(d, 2H, J = 12.3 Hz, PhCH2), 4.47 (m, 1H, H-5), 4.27
(m, 2H, H-6), 4.00 (t, 1H, J = 3.0 Hz, H-3), 2.07, 1.92
(s each, 3H each, Ac). Compound 7b: Rf = 0.82 (2:1,
19
petroleum ether/EtOAc); ½aꢁD ꢀ9.4 (c 1.1, CHCl3);
1H NMR (300 MHz, CDCl3): d 8.01–7.24 (m, 15H,
ArH), 5.55 (s, 1H), 5.31 (d, 1H, J = 3.3 Hz), 5.27
(s, 1H), 4.95 (br, 1H), 4.89 (d, 1H, J = 11.5 Hz), 4.78
(d, 1H, J = 4.8 Hz), 4.73–4.57 (m, 4H), 4.51 (t, 1H,
J = 6.3 Hz), 4.27–4.06 (m, 3H), 3.88 (br, 1H), 3.82–
3.72 (m, 2H), 3.21 (br, 1H), 1.99, 1.97 (s each, 3H
each, Ac); 13C NMR (75 MHz, CDCl3): d 170.3, 169.9,
164.9, 137.3, 137.2, 133.5, 129.6, 129.2, 128.3, 127.7,
127.6, 127.5, 100.9, 95.0, 77.8, 73.0, 72.7, 72.0, 71.9,
71.8, 66.8, 66.3, 65.4, 64.0, 62.8, 60.3, 20.6, 20.6; IR:
2103, 1745, 1725, 1234, 1113, 1027, 714 cmꢀ1; ESIMS
m/z calcd for [C37H39N3O12]Na+: 740.2426. Found:
740.2428.
1
petroleum ether/EtOAc); H NMR (300 MHz, CDCl3):
d 8.07 (m, 2H), 7.59 (t, 1H, J = 7.5 Hz), 7.46 (t, 2H,
J = 7.8 Hz), 7.37–7.26 (m, 5H, ArH), 6.22 (s, 1H, H-
1), 5.21 (m, 1H, H-2), 4.99 (br, 1H, H-4), 4.81 (d, 2H,
J = 12.3 Hz, PhCH2), 4.61 (m, 1H, H-5), 4.31 (m, 2H,
H-6), 3.90 (br, 1H, H-3), 2.09, 1.94 (s each, 3H each,
Ac); IR: 2928, 1745, 1371, 1272, 1223, 1114, 1097,
1056, 715 cmꢀ1; ESIMS m/z calcd for [C26H28O10]Na+
523.1575. Found: 523.1579.
3.1.2. Ethyl 4,6-di-O-acetyl-2-O-benzoyl-3-O-benzyl-1-
thio-L-idopyranoside (8). To a solution of acetate 7
(281 mg, 0.56 mmol) and ethanethiol (0.063 mL,
0.84 mmol) in anhydrous CH2Cl2 (4 mL) at 0 °C, BF3Æ
Et2O (0.028 mL, 0.21 mmol) was added. After stirring
at rt for 5 h, a saturated aqueous solution of NaHCO3
was added. The organic layer was washed with water,
dried over Na2SO4, and then filtered and concentrated.
The residue was purified by silica gel column chromato-
graphy (4:1, petroleum ether/EtOAc) to provide 8
3.1.4. 2-O-Benzoyl-3-O-benzyl-a-L-idopyranosyl-(1!4)-
1,6-anhydro-2-azido-3-O-benzyl-2-deoxy-b-D-glucopyran-
oside (11). A solution of 10 (1.154 g, 1.6 mmol) in
0.1 M HCl/CH3OH (20 mL) was stirred at rt for 5 h.
The mixture was neutralized with Et3N, and then con-
centrated. The residue was purified by silica gel column
chromatography (2:1:1, petroleum ether/EtOAc/CH2Cl2)
to provide 1111 (900 mg, 88%) as a colorless syrup.
Rf = 0.11 (2:1, petroleum ether/EtOAc).

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Y. Zhou et al. / Carbohydrate Research 341 (2006) 1619–1629
3.1.5. Methyl (2-O-benzoyl-3-O-benzyl-a-L-idopyranosyl)-
uronate-(1!4)-1,6-anhydro-2-azido-3-O-benzyl-2-deoxy-
b-D-glucopyranoside (12). The same procedure de-
scribed for the preparation of methyl glucuronate 18
(from diol 17) was employed for the preparation of 12
from 11. Purification by silica gel column chromatogra-
phy (3:1:1, petroleum ether/EtOAc/CH2Cl2) gave 1212
(84%) as a colorless syrup. Rf = 0.34 (2:1:1, petroleum
(1.34 g, 1.56 mmol) in a mixture of THF/CH3OH (7:3,
15 mL) at 0 °C for 20 min. The solvent was then concen-
trated under reduced pressure to give a residue that was
purified by silica gel column chromatography (1:1, petro-
leum ether/EtOAc) to afford 15 (988 mg, 77%) as a color-
less syrup (a/b, 4:1). Rf = 0.21 (2:1, petroleum ether/
1
EtOAc); H NMR (300 MHz, CDCl3): d 8.03 (m, 2H),
7.58 (m, 1H), 7.46–7.23 (m, 12H), 5.33 (d, 0.8H,
J = 2.1 Hz), 5.31 (d, 0.2H, J = 2.8 Hz), 5.27 (t, 0.8H,
J = 3.3 Hz), 5.20 (m, 1H), 5.14 (t, 0.8H, J = 3.0 Hz),
5.11 (t, 0.2H, J = 3.0 Hz), 5.01 (d, 0.2H, J = 3.3 Hz),
4.99 (d, 0.2H, J = 3.0 Hz), 4.83–4.67 (m, 4H), 4.58 (m,
0.8H), 4.46 (d, 0.8H, J = 12.6 Hz), 4.28 (m, 1H), 4.11
(d, 0.8H, J = 9.6 Hz), 4.01–3.79 (m, 3.2H), 3.49 (s,
0.8H), 3.47 (s, 3H), 3.43 (m, 1H), 3.33 (m, 0.8H), 2.68
(m, 2H), 2.48 (m, 2H), 2.12 (s, 3H), 2.06 (s, 3H); 13C
NMR (75 MHz, CDCl3): d 206.0, 171.6, 171.0, 170.9,
168.7, 165.3, 137.6, 137.4, 137.1, 133.6, 129.8, 129.0,
128.4, 128.2, 128.1, 128.0, 127.9, 127.8, 127.7, 127.5,
127.3, 97.5, 96.3, 91.7, 81.0, 78.1, 74.9, 74.6, 74.3, 73.1,
72.8, 69.0, 68.2, 68.0, 67.3, 67.1, 67.0, 63.9, 62.1, 52.1,
37.5, 29.6, 27.7, 20.9, 20.8; IR: 3456, 2111, 1745, 1720,
1270, 1233, 1109, 1070 cmꢀ1; MALDIMS m/z calcd for
[C41H45N3O15]Na+: 842.2743. Found: 842.2781.
20
ether/EtOAc/CH2Cl2); ½aꢁD ꢀ22.1 (c 1.2, CHCl3);
13C NMR (75 MHz, CDCl3): d 169.5, 164.9, 137.3–
127.7, 101.1, 96.3, 78.0, 75.0, 74.0, 73.1, 73.0, 72.0,
68.2, 68.0, 67.2, 65.7, 61.2, 52.3; IR: 3577, 3031,
2111, 1749, 1720, 1271, 1108, 714, 696 cmꢀ1; ESIMS
m/z calcd for [C34H35N3O11]Na+: 684.2164. Found:
684.2166.
3.1.6. Methyl (2-O-benzoyl-3-O-benzyl-4-O-levulinoyl-a-
L-idopyranosyl)uronate-(1!4)-1,6-anhydro-2-azido-3-O-
benzyl-2-deoxy-b-D-glucopyranoside (13). The same
procedure described for the preparation of levulinoyl
ester 19 (from 18) was employed for the preparation of
13 from 12. Purification by silica gel column chromato-
graphy (2:1, petroleum ether/EtOAc) gave 13 (92%) as a
colorless syrup. Rf = 0.11 (3:4:1, petroleum ether/tolu-
21
ene/acetone); ½aꢁD ꢀ11.8 (c 0.9, CHCl3); 1H NMR
(300 MHz, CDCl3): d 8.05–7.20 (m, 15H), 5.50 (s, 1H),
5.38 (s, 1H), 5.25 (d, 2H, J = 6.3 Hz), 4.87 (d, 2H,
J = 11.1 Hz), 4.74 (m, 2H), 4.55 (s, 2H), 4.01 (d, 1H,
J = 7.2 Hz), 3.94 (s, 1H), 3.80 (m, 1H), 3.74 (s, 4H),
3.64 (t, 1H, J = 3.3 Hz), 3.24 (d, 1H, J = 3.0 Hz), 2.63
(m, 2H), 2.43 (m, 2H), 2.10 (s, 3H); 13C NMR (75 MHz,
CDCl3): d 205.8, 171.5, 168.5, 165.1, 137.2, 137.1, 133.6,
129.7, 129.2, 128.4, 128.3, 127.9, 127.8, 127.7, 127.6,
101.1, 95.7, 77.8, 74.7, 73.2, 72.3, 71.9, 67.8, 66.5, 66.2,
65.7, 61.4, 52.5, 37.6, 29.6, 29.5, 27.8; IR: 2104, 1746,
1721, 1269, 1112, 1029 cmꢀ1; ESIMS m/z calcd for
[C39H41N3O13]Na+: 782.2532. Found: 782.2540.
3.1.9. Methyl (2-O-benzoyl-3-O-benzyl-4-O-levulinoyl-
a-L-idopyranosyl)uronate-(1!4)-6-O-acetyl-2-azido-3-O-
benzyl-2-deoxy-D-glucopyranosyl
(2). To
trichloroacetimidate
solution of compound 15 (269 mg,
a
0.33 mmol) in dry CH2Cl2 (5 mL) at 0 °C was added
anhydrous K2CO3 (114 mg, 0.82 mmol) followed by
CCl3CN (0.22 mL, 2.00 mmol). After stirring at rt for
30 min, the mixture was filtered and the filtrate was con-
centrated. The residue was purified by silica gel column
chromatography (1:1, petroleum ether/EtOAc) provid-
ing 2 (306 mg, 95%, a/b, 2:7) as a colorless syrup. A
small amount of the mixture was separated. Compound
1
2b: Rf = 0.68 (1:1, petroleum ether/EtOAc); H NMR
3.1.7. Methyl (2-O-benzoyl-3-O-benzyl-4-O-levulinoyl-a-
L-idopyranosyl)uronate-(1!4)-1,6-di-O-acetyl-2-azido-3-
O-benzyl-2-deoxy-D-glucopyranose (14). To a solution
of 1,6-anhydride 13 (2.55 g, 3.35 mmol) in dry CH2Cl2
(10 mL) was added Ac2O (10 mL). The mixture was
cooled to 0 °C and TMSOTf (three drops) was added
under argon. After stirring at 0 °C for 10 min, the reac-
tion was quenched by the addition of Et3N (1 mL). The
resulting mixture was concentrated in vacuo to give a
residue, which was purified by silica gel column chroma-
tography (4:1, petroleum ether/EtOAc) to provide 1413
(2.55 g, 88%) as a colorless syrup (a/b, 4:1). Rf = 0.60
(1:1, petroleum ether/EtOAc).
(300 MHz, CDCl3): d 8.72 (s, 1H), 8.04 (m, 2H), 7.58
(m, 1H), 7.46–7.25 (m, 12H), 5.62 (d, 1H, J = 8.7 Hz),
5.30 (br, 1H), 5.21 (t, 1H, J = 3.3 Hz), 5.12 (br, 1H),
5.02 (d, 1H, J = 3.0 Hz), 4.78 (d, 2H, J = 11.4 Hz),
4.74 (s, 2H), 4.48 (d, 1H, J = 12.2 Hz), 4.32 (dd, 1H,
J = 4.2, 12.2 Hz), 4.07 (t, 1H, J = 9.6 Hz), 3.94 (t, 1H,
J = 3.0 Hz), 3.72 (t, 1H, J = 8.7 Hz), 3.64 (d, 1H, J =
9.6 Hz), 3.50 (s, 3H), 3.43 (t, 1H, J = 9.0 Hz), 2.67 (m,
2H), 2.48 (m, 2H), 2.12, 2.05 (s each, 3H each); 13C
NMR (75 MHz, CDCl3): d 205.8, 171.6, 170.4, 168.5,
165.2, 160.8, 137.4, 137.1, 133.5, 129.7, 129.0, 128.4,
128.2, 128.0, 127.9, 127.5, 97.5, 96.5, 90.2, 81.0, 74.9,
73.9, 72.9, 72.8, 67.9, 67.8, 66.9, 65.5, 61.7, 52.1, 37.5,
29.6, 27.7, 20.8. Compound 2a: Rf = 0.52 (1:1, petro-
leum ether/EtOAc); 1H NMR (300 MHz, CDCl3): d
8.71 (s, 1H), 8.10 (m, 2H), 7.57 (m, 1H), 7.49–7.18 (m,
12H), 5.56 (d, 1H, J = 7.8 Hz), 5.29 (s, 1H), 5.26 (br,
1H), 5.20 (br, 1H), 4.85 (d, 2H, J = 10.8 Hz), 4.72 (d,
3.1.8. Methyl (2-O-benzoyl-3-O-benzyl-4-O-levulinoyl-
a-L-idopyranosyl)uronate-(1!4)-6-O-acetyl-2-azido-3-O-
benzyl-2-deoxy-D-glucopyranose (15). Ammonia gas
was bubbled through a solution of compound 14

Y. Zhou et al. / Carbohydrate Research 341 (2006) 1619–1629
1625
2H, J = 11.7 Hz), 4.62 (m, 2H), 4.37 (m, 1H), 3.99 (t,
1H, J = 2.7 Hz), 3.93 (d, 1H, J = 9.6 Hz), 3.79 (s, 3H),
3.65 (m, 2H), 3.50 (t, 1H, J = 9.0 Hz), 2.55 (m, 2H),
2.34 (m, 2H), 2.06, 2.03 (s each, 3H each); 13C NMR
(75 MHz, CDCl3): d 205.8, 171.6, 170.4, 168.5, 165.2,
160.4, 137.3, 137.0, 133.5, 129.8, 129.0, 128.4, 128.1,
128.0, 127.6, 127.4, 97.6, 94.3, 90.7, 78.4, 77.4, 74.8,
74.1, 72.9, 72.7, 71.8, 68.0, 67.8, 67.2, 63.0, 61.6, 52.1,
37.5, 29.6, 27.7, 20.8; IR: 2114, 1744, 1722, 1677, 1272,
1070 cmꢀ1; ESIMS m/z calcd for [C43H45Cl3N4O15]Na+:
985.1839. Found 985.1838.
by silica gel column chromatography (petroleum ether/
EtOAc/CH2Cl2 3:1:1 to 2:1:1, then CH2Cl2/acetone
23:1) to provide 18 (5.25 g, 70%, a/b, 1:1) as a colorless
syrup. Rf = 0.30 (2:1, petroleum ether/EtOAc); 1H
NMR (300 MHz, CDCl3): d 7.35–7.25 (m, 5H), 6.33
(d, 0.5H, J = 3.3 Hz), 5.65 (d, 0.5H, J = 7.5 Hz), 5.07
(t, 0.5H, J = 8.7 Hz), 5.01 (dd, 0.5H, J = 3.3, 9.6 Hz),
4.87 (d, 0.5H, J = 11.7 Hz), 4.84 (d, 0.5H, J =
12.0 Hz), 4.74 (d, 0.5H, J = 11.7 Hz), 4.70 (d, 0.5H,
J = 12.0 Hz), 4.29 (d, 0.5H, J = 9.6 Hz), 3.91 (m,
1.5H), 3.78 (s, 1.5H), 3.77 (s, 1.5H), 3.62 (m, 1.5H),
2.14 (s, 1.5H), 2.06 (s, 1.5H), 1.96 (s, 1.5H), 1.91 (s,
1.5H); 13C NMR (75 MHz, CDCl3): d 169.7, 169.3,
169.2, 169.0, 168.8, 168.6, 138.0, 137.7, 128.2, 127.6,
127.5, 127.3, 91.6, 89.2, 80.6, 78.0, 74.9, 74.6, 74.4,
72.4, 71.4, 71.2, 70.8, 70.4, 52.6, 20.6, 20.5, 20.4, 20.3;
IR: 3498, 1752, 1239, 1216, 1052 cmꢀ1; ESIMS m/z
calcd for [C18H22O9]Na+: 405.1156, found: 405.1151.
Anal. Calcd for C18H22O9: C, 56.54; H, 5.80. Found:
C, 56.19; H, 5.90.
3.1.10. 1,2-di-O-acetyl-3-O-benzyl-D-glucopyranose (17).
A solution of compound 16 (2.61 g, 5.9 mmol) in 80%
aqueous HOAc (30 mL) was heated at 70 °C for 6 h
and then concentrated. The residue was purified by silica
gel column chromatography (2:1, petroleum ether/
EtOAc) providing 17 (1.64 g, 79%, a/b, 1:1) as a color-
1
less syrup. Rf = 0.35 (2:1, petroleum ether/EtOAc); H
NMR (300 MHz, CDCl3): d 7.37–7.26 (m, 5H), 6.27
(d, 0.5H, J = 3.6 Hz), 5.61 (d, 0.5H, J = 8.1 Hz), 5.05
(t, 0.5H, J = 8.7 Hz), 4.97 (dd, 0.5H, J = 3.3, 9.3 Hz),
4.82 (m, 1.5H), 4.72 (m, 0.5H), 3.97 (br, 0.5H), 3.82
(m, 4H), 3.59 (t, 0.5H, J = 9.0 Hz), 3.46 (m, 0.5H),
3.20 (br, 1H), 2.13 (s, 1.5H), 2.06 (s, 1.5H), 1.96 (s,
1.5H), 1.95 (s, 1.5H); 13C NMR (75 MHz, CDCl3): d
170.0, 169.5, 169.4, 138.2, 137.9, 128.5, 128.3, 127.7,
127.6, 127.4, 92.0, 89.7, 82.0, 79.2, 76.2, 75.0, 74.6,
73.8, 71.6, 71.4, 69.6, 69.1, 61.2, 61.1, 20.8, 20.7, 20.6,
20.5; IR: 3448, 1751, 1240, 1059 cmꢀ1; ESIMS m/z calcd
for [C17H22O8]Na+: 377.1207. Found: 377.1212.
3.1.12. Methyl (1,2-di-O-acetyl-3-O-benzyl-4-O-levulinoyl-
D-glucopyranosyl)uronate (19). A mixture of DCC
(4.27 g, 20.6 mmol) and DMAP (173 mg, 1.37 mmol) in
dry CH2Cl2 (5 mL) was added to a solution of compound
18 (5.25 g, 13.7 mmol) and levulinic acid (2.14 mL,
20.6 mmol) in dry CH2Cl2 (50 mL) at 0 °C under argon.
After stirring overnight, the precipitate was removed by
filtration through Celite and washed with CH2Cl2. The
solution was concentrated in vacuo and the residue was
purified by silica gel column chromatography (2:1, petro-
leum ether/EtOAc) to afford 19 (6.26 g, 95%, a/b, 3:7) as
a colorless syrup. Rf = 0.16 (3:1, petroleum ether/
3.1.11. Methyl (1,2-di-O-acetyl-3-O-benzyl-D-glucopyran-
osyl)uronate (18). To a solution of diol 17 (6.951 g,
19.6 mmol) in CH2Cl2 (30 mL) containing TEMPO
(76 mg, 0.02 equiv) was added a solution of saturated
aqueous NaHCO3 (20 mL) containing KBr (1.077 g,
1
EtOAc); H NMR (300 MHz, CDCl3): d 7.31–7.23 (m,
5H), 6.35 (d, 0.7H, J = 3.3 Hz), 5.67 (d, 0.3H,
J = 7.5 Hz), 5.23–5.10 (m, 1.3H), 5.08 (dd, 0.7H,
J = 3.9, 13.5 Hz), 4.68 (m, 1.7H), 4.61 (m, 0.3H), 4.32
(d, 0.7H, J = 9.6 Hz), 4.09 (d, 0.3H, J = 9.6 Hz), 3.98
(t, 0.7H, J = 9.3 Hz), 3.80 (t, 0.3H, J = 8.7 Hz), 3.68 (s,
2.1H), 3.67 (s, 0.9H), 2.69 (m, 2H), 2.52 (m, 2H), 2.16
(s, 2.1H), 2.15 (s, 2.1H), 2.13 (s, 0.9H), 2.06 (s, 0.9H),
1.96 (s, 2.1H), 1.94 (s, 0.9H); 13C NMR (75 MHz,
CDCl3): d 206.0, 176.6, 171.3, 169.4, 169.0, 168.9,
168.4, 167.5, 167.2, 137.7, 137.4, 128.3, 128.2, 127.8,
127.7, 127.6, 127.5, 91.3, 88.9, 78.6, 76.1, 74.8, 74.1,
73.0, 70.8, 70.6, 70.5, 70.4, 52.9, 37.6, 37.4, 29.7, 27.5,
20.7, 20.5, 20.4; IR: 1747, 1719, 1213 cmꢀ1; ESIMS m/z
calcd for [C23H28O11]Na+: 503.1524. Found: 503.1526.
t
0.5 equiv) and Bu4NBr (451 mg, 0.07 equiv). The mix-
ture was cooled to 0 °C, and then Ca(ClO)2 (8.512 g,
3.0 equiv) was added slowly in portions under vigorous
stirring. After TLC indicated complete conversion of the
starting material, the reaction was quenched by the
addition of a saturated solution of NaCl (20 mL) and
NaHSO3 (7.66 g, 3 equiv). After further stirring for
5 min, HOAc was added to adjust the final pH value
of the mixture to pH 3. The resulting mixture was
diluted with EtOAc (50 mL). The organic phase was sep-
arated and the remaining aqueous phase was extracted
with EtOAc. The combined organic phase was washed
with brine, dried with Na2SO4, and then filtered and
concentrated in vacuo to yield the corresponding crude
glucuronic acid, which was used without further purifi-
cation. The crude glucuronic acid was dissolved in
THF (30 mL) and treated with CH2N2 in ether at rt.
After complete disappearance of the glucuronic acid,
the mixture was concentrated. The residue was purified
3.1.13. Methyl (2-O-acetyl-3-O-benzyl-4-O-levulinoyl-D-
glucopyranosyl)uronate (20). To a solution of 19
(848 mg, 1.76 mmol) in dry MeOH (8 mL) was added
Bu2SnO (100 mg, 0.40 mmol). The mixture was stirred
at 55 °C until the starting material disappeared and then
was filtered and concentrated in vacuo. Silica gel column
chromatography of the residue (2:1, petroleum ether/

1626
Y. Zhou et al. / Carbohydrate Research 341 (2006) 1619–1629
EtOAc) provided 20 (672 mg, 87%) as a colorless syrup.
Rf = 0.17 (1:1, petroleum ether/EtOAc); 1H NMR
(300 MHz, CDCl3) (data for b anomer): d 7.35–7.25
(m, 5H), 5.49 (d, 1H, J = 3.3 Hz), 5.14 (t, 1H,
J = 9.3 Hz), 4.87 (dd, 1H, J = 3.6, 9.3 Hz), 4.69 (s,
2H), 4.51 (d, 1H, J = 9.6 Hz), 4.09 (t, 1H, J = 9.0 Hz),
3.69 (s, 3H), 2.70 (m, 2H), 2.47 (m, 2H), 2.17 (s, 3H),
The residue was subjected to silica gel column chroma-
tography (4:1, petroleum ether/EtOAc) to provide disac-
charide 22 (1.63 g, 70%) as a colorless syrup. Rf = 0.20
19
(2:1, petroleum ether/EtOAc); ½aꢁD ꢀ3.4 (c 0.5, CHCl3);
1H NMR (300 MHz, CDCl3): d 7.35–7.24 (m, 10H), 5.44
(s, 1H), 5.26 (t, 1H, J = 9.3 Hz), 5.11 (dd, 1H, J = 7.5,
9.0 Hz), 4.74 (d, 1H, J = 7.5 Hz), 4.70–4.59 (m, 5H),
4.07 (dd, 1H, J = 0.9, 7.5 Hz), 3.95 (d, 1H, J =
9.9 Hz), 3.86 (br, 1H), 3.75 (m, 3H), 3.71 (s, 3H), 3.23
(s, 1H), 2.68 (m, 2H), 2.48 (m, 2H), 2.17 (s, 3H), 1.99
(s, 3H); 13C NMR (75 MHz, CDCl3): d 206.0, 171.3,
169.1, 167.3, 137.6, 137.3, 128.4, 128.3, 127.9, 127.8,
127.7, 100.6, 98.6, 79.0, 77.4, 74.7, 73.7, 73.2, 72.7,
72.5, 71.7, 70.9, 65.0, 59.6, 52.8, 37.5, 29.8, 29.6, 27.6,
1
2.05 (s, 3H); H NMR (data for a anomer): d 7.35–
7.25 (m, 5H), 5.69 (d, 1H, J = 7.8 Hz), 5.20 (m, 1H),
4.94 (t, 1H, J = 8.7 Hz), 4.66 (d, 2H, J = 12.0 Hz),
4.01 (d, 1H, J = 9.6 Hz), 3.78 (m, 1H), 3.70 (s, 1H),
2.65 (m, 2H), 2.46 (m, 2H), 2.16 (s, 3H), 2.01 (s, 3H);
13C NMR (75 MHz, CDCl3): d 206.4, 206.3, 171.5,
171.4, 170.5, 170.2, 168.9, 168.0, 137.9, 137.5, 128.3,
128.2, 127.7, 127.6, 127.5, 95.3, 89.9, 78.7, 76.0, 74.7,
74.2, 74.1, 73.9, 72.8, 72.4, 72.3, 71.0, 70.9, 70.6, 68.3,
52.8, 52.7, 37.4, 29.7, 29.5, 27.8, 27.5, 20.7, 20.5; IR:
3448, 1749, 1721, 1236, 1158, 1071 cmꢀ1; ESIMS m/z
calcd for [C21H26O10]Na+: 461.1418. Found: 461.1421.
Anal. Calcd for C21H26O10: C, 57.53; H, 5.98. Found:
C, 57.37; H, 6.12.
20.7; IR: 2109, 1755, 1742, 1720, 1154, 742 cmꢀ1
;
ESIMS m/z calcd for [C34H39N3O13]Na+: 720.2375.
Found: 720.2371.
3.1.16. Methyl (2-O-acetyl-3-O-benzyl-4-O-levulinoyl-b-
D-glucopyranosyl)uronate-(1!4)-1,6-di-O-acetyl-2-azido-
3-O-benzyl-2-deoxy-D-glucopyranose (23). Compound
22 (43 mg, 0.06 mmol) was dissolved in Ac2O (0.7 mL)
and cooled in an ice bath. Then a mixture of
CF3COOH/Ac2O (1:5, 0.9 mL) was added. After stirring
for 10 min, the solvent was removed under reduced pres-
sure. The crude residue was purified by silica gel column
chromatography (1:1, petroleum ether/EtOAc) to afford
23 (47 mg, 96%) as a colorless syrup. Rf = 0.32 (1:1,
3.1.14. Methyl (2-O-acetyl-3-O-benzyl-4-O-levulinoyl-D-
glucopyranosyl)uronate trichloroacetimidate (21). To a
solution of compound 20 (1.991 g, 4.54 mmol) in dry
CH2Cl2 (20 mL) in an ice bath was added CCl3CN
(2.51 mL, 25.0 mmol) followed by addition of DBU
(three drops). The mixture was stirred at rt until TLC
showed the reaction was complete. The mixture was then
concentrated to give a residue that was purified by silica
gel column chromatography (1:1, petroleum ether/
EtOAc) to afford 21 (2.46 g, 93%) as a colorless syrup.
Rf = 0.67 (1:1, petroleum ether/EtOAc); 1H NMR
(300 MHz, CDCl3) (data for a anomer): d 8.68 (s, 1H),
7.36–7.27 (m, 5H), 6.61 (d, 1H, J = 3.3 Hz), 5.25 (t,
1H, J = 9.3 Hz), 5.10 (dd, 1H, J1 = 3.6, 9.6 Hz), 4.73
(d, 2H, J = 11.4 Hz), 4.40 (d, 1H, J = 9.9 Hz), 4.12 (t,
1H, J1 = 9.3 Hz, J2 = 9.9 Hz), 3.72 (s, 3H), 2.72 (m,
1
petroleum ether/EtOAc); H NMR (300 MHz, CDCl3)
(data for a anomer): d 7.42–7.23 (m, 10H), 6.17 (d, 1H,
J = 3.6 Hz), 5.20 (m, 2H), 4.72 (d, 2H, J = 11.4 Hz),
4.58 (d, 2H, J = 10.2 Hz), 4.35 (dd, 1H, J = 0.6,
12.1 Hz), 4.15 (dd, 1H, J = 5.1, 12.3 Hz), 3.85 (m, 4H),
3.70 (t, 1H, J = 9.0 Hz), 3.52 (m, 1H), 3.49 (s, 3H),
2.67 (m, 2H), 2.48 (m, 2H), 2.17 (s, 3H), 2.16 (s, 3H),
2.10 (s, 3H), 1.99 (s, 3H); 13C NMR (75 MHz, CDCl3):
d 205.9, 171.3, 170.4, 169.1, 168.8, 167.0, 138.1, 137.5,
128.4, 128.2, 127.8, 127.7, 127.5, 127.4, 101.0, 90.1,
79.5, 78.2, 77.8, 75.3, 74.2, 72.9, 72.4, 71.1, 70.7, 62.2,
61.6, 52.7, 37.5, 29.8, 27.6, 21.0, 20.8, 20.7; IR: 2117,
1765, 1746, 1720, 1240, 1219 cmꢀ1; ESI-MS: 817.4
[M+NH4]+. Anal. Calcd for C38H45N3O16: C, 57.07;
H, 5.67; N, 5.25. Found: C, 57.24; H, 5.81; N, 4.91.
1
2H), 2.54 (m, 2H), 2.18 (s, 3H), 1.96 (s, 3H); H NMR
(data for b anomer): d 8.70 (s, 1H), 7.38–7.27 (m, 5H),
5.85 (d, 1H, J = 7.2 Hz), 5.36 (m, 2H), 4.69 (d, 2H,
J = 12.0), 4.18 (d, 1H, J = 9.3 Hz), 3.84 (t, 1H,
J = 8.7 Hz), 3.72 (s, 3H), 2.72 (m, 2H), 2.55 (m, 2H),
2.18 (s, 3H), 1.97 (s, 3H); ESI-MS: 604.2 [M+Na+].
3.1.17. Methyl (2-O-acetyl-3-O-benzyl-4-O-levulinoyl-b-
D-glucopyranosyl)uronate-(1!4)-6-O-acetyl-2-azido-3-
O-benzyl-2-deoxy-D-glucopyranose (24). The same
procedure employed for the preparation of lactol 15
(from acetate 14) was employed for the preparation of
24 from 23. Purification by silica gel column chromato-
graphy (1:1, petroleum ether/EtOAc) afforded 24 (92%,
a/b, 1:1) as a colorless syrup. Rf = 0.29 (1:1, petroleum
ether/EtOAc); 1H NMR (300 MHz, CDCl3): d 7.41–
7.23 (m, 10H), 5.24 (t, 0.5H, J = 3.0 Hz), 5.20 (m,
0.5H), 5.19 (s, 0.5H), 5.15 (t, 0.5H, J = 3.0 Hz), 5.11
(s, 0.5H), 5.09–5.00 (m, 1.5H), 4.82 (s, 0.5H), 4.78 (s,
3.1.15. Methyl (2-O-acetyl-3-O-benzyl-4-O-levulinoyl-b-
D-glucopyranosyl)uronate-(1!4)-1,6-anhydro-2-azido-3-
O-benzyl-2-deoxy-b-D-glucopyranoside (22). A mixture
of glycosyl imidate 21 (2.478 g, 4.25 mmol), sugar alco-
˚
hol 9 (907 mg, 3.27 mmol), and freshly activated 4 A
molecular sieves (500 mg) in dry CH2Cl2 (20 mL) was
stirred at rt under argon for 30 min. Then TMSOTf
(0.06 mL, 0.327 mmol) was added dropwise. After stir-
ring overnight at rt, the reaction was quenched by the
addition of Et3N (0.5 mL). The mixture was filtered
through a pad of Celite and concentrated in vacuo.

Y. Zhou et al. / Carbohydrate Research 341 (2006) 1619–1629
1627
0.5H), 4.72 (d, 0.5H, J = 13.2 Hz), 4.66 (s, 1H), 4.57 (m,
2H), 4.42 (m, 1H), 4.17–4.05 (m, 1H), 3.97 (t, 0.5H,
J = 8.4, 9.9 Hz), 3.81–3.66 (m, 4H), 3.51 (s, 1.5H),
3.49 (s, 1.5H), 3.45 (m, 1H), 3.34 (t, 0.5H, J = 8.1 Hz),
3.33 (t, 0.5H, J = 10.5 Hz), 2.66 (m, 2H), 2.48 (m,
2H), 2.15 (s, 3H), 2.10 (s, 1.5H), 2.08 (s, 1.5H), 1.98 (s,
1.5H), 1.95 (s, 1.5H); 13C NMR (75 MHz, CDCl3): d
206.1, 171.3, 170.7, 169.2, 167.2, 138.2, 137.6, 137.5,
128.4, 128.2, 127.8, 127.7, 127.7, 127.5, 127.3, 100.9,
95.9, 91.7, 80.8, 79.5, 78.5, 78.1, 77.7, 75.0, 74.9, 74.2,
72.8, 72.7, 72.6, 72.4, 71.1, 68.4, 67.1, 63.5, 62.3, 52.7,
37.5, 29.7, 29.6, 27.5, 20.9, 20.8, 20.6; IR: 3443, 2116,
1766, 1744, 1702, 1235, 1031 cmꢀ1; ESIMS m/z calcd
for [C36H43N3O15]Na+: 780.2586. Found: 780.2587.
1068 cmꢀ1; ESIMS m/z calcd for [C30H3O8S]Na+:
573.1554. Found: 573.1552.
3.1.20. Methyl (phenyl 2-O-benzoyl-3-O-benzyl-1-thio-a-
L-idopyranoside)uronate (4). To a solution of 26
(951 mg, 1.61 mmol) in dry CH2Cl2 (15 mL) was added
a solution of hydrazine acetate (297 mg, 3.23 mmol) in
MeOH (10 mL). After stirring at rt for 1 h, the solvent
was removed under reduced pressure. The residue was
purified by silica gel column chromatography (2:1,
petroleum ether/EtOAc) to afford 45,7 (725 mg, 90%)
as a colorless syrup. Rf = 0.61 (2:1, petroleum ether/
EtOAc).
3.1.21. Methyl 2-azido-4,6-O-benzylidene-2-deoxy-a-D-
glucopyranoside (29). Crude 27, prepared from D-glu-
cosamine hydrochloride (0.5 g, 2.3 mmol),16 was dis-
solved in 10% HCl/CH3OH (25 mL), and the reaction
temperature was then raised to 90 °C. When TLC
showed that the reaction was complete, the mixture
was concentrated and the residue was dissolved in
CH3OH (30 mL) and treated with NaHCO3 until the
pH was neutral. The mixture was filtered and concen-
trated to give the crude methyl glycoside 2817 (1.5 g).
Crude 28 was dissolved in DMF (10 mL) and p-TsOH
(20 mg) and benzaldehyde dimethyl acetal (0.8 mL) were
added. After stirring at 40 °C under reduced pressure for
10 h, the mixture was concentrated in vacuo. The ob-
tained anomers (a/b, 6:4) were purified by silica gel col-
umn chromatography (petroleum ether/EtOAc 10:1 to
4:1) affording the a anomer 2918 (346 mg, 51%) as a
white solid. Rf = 0.85 (3:1, petroleum ether/EtOAc).
3.1.18. Methyl (2-O-acetyl-3-O-benzyl-4-O-levulinoyl-b-
D-glucopyranosyl)uronate-(1!4)-6-O-acetyl-2-azido-3-
O-benzyl-2-deoxy-D-glucopyranosyl trichloroacetimidate
(3). The same procedure described for the preparation
of trichloroacetimidate 21 (from lactol 20) was em-
ployed for the preparation of 3 from 24. Purification
by silica gel column chromatography (1:1, petroleum
ether/EtOAc) afforded 3 (92%) as a colorless syrup.
Rf = 0.41 (1:1, petroleum ether/EtOAc); 1H NMR
(300 MHz, CDCl3) (data for a anomer): d 8.73 (s, 1H),
7.42–7.24 (m, 10H), 6.34 (d, 1H, J = 3.6 Hz), 5.21 (m,
2H), 5.09 (t, 1H, J = 9.6 Hz), 4.77 (d, 1H, J =
11.4 Hz), 4.69 (d, 1H, J = 11.7 Hz), 4.59 (m, 2H), 4.39
(dd, 1H, J = 2.1, 12.3 Hz), 4.18 (dd, 1H, J = 4.2,
12.3 Hz), 4.01–3.80 (m, 3H), 3.72 (dd, 1H, J = 6.6,
11.7 Hz), 3.62 (dd, 1H, J = 3.6, 9.9 Hz), 3.54 (s, 1H),
3.51 (s, 3H), 2.67 (m, 2H), 2.53 (m, 2H), 2.16, 2.10,
1.99 (s each, 3H each); IR: 2115, 1751, 1720, 1677,
1229, 1151, 1068, 1029 cmꢀ1; ESIMS m/z calcd for
[C38H43Cl3N4O15]Na+: 923.1683. Found: 923.1679.
3.1.22. Methyl 2-azido-6-O-benzoyl-3-O-benzyl-2-deoxy-
a-D-glucopyranoside (5). To a cooled (0 °C) solution of
29 (575 mg, 1.95 mol) in dry THF (10 mL), NaH (60%
dispersion in mineral oil, 114 mg, 2.92 mmol) was
added. After the mixture had been stirred for 1 h, benzyl
bromide (0.3 mL, 2.53 mmol) was added. Stirring con-
tinued at rt for 24 h, and then CH3OH (0.5 mL) was
added. The resulting mixture was filtered through a
pad of Celite and the filtrate concentrated in vacuo.
The residue was purified by silica gel column chroma-
tography (5:1, petroleum ether/EtOAc) to afford 3013
(640 mg, 85%) as a white solid. Rf = 0.82 (2:1, petroleum
ether/EtOAc). Compound 30 (425 mg, 1.10 mmol) was
converted into diol 31 (234 mg, 71%) accordingly.13
Rf = 0.12 (2:1, petroleum ether/EtOAc). Compound 31
(215 mg, 0.74 mmol) was dissolved in CH2Cl2 (3 mL),
and pyridine (0.18 mL, 2.23 mmol) and benzoyl chloride
(0.12 mL, 1.12 mmol) were added consecutively at 0 °C
under argon. After stirring at 0 °C for 30 min, the reac-
tion was quenched by the addition of CH3OH (0.2 mL)
and the solvent was evaporated under reduced pressure.
The residue was purified by silica gel column chroma-
tography (5:1, petroleum ether/EtOAc) to provide 58
3.1.19. Phenyl 4,6-di-O-acetyl-2-O-benzoyl-3-O-benzyl-1-
thio-a-L-idopyranoside (25). To a solution of 79 (5.77 g,
11.5 mmol) and thiophenol (1.414 mL, 13.8 mmol) in
anhydrous CH2Cl2 (60 mL) at 0 °C was added BF3ÆEt2O
(0.3 mL, 2.3 mmol). After stirring at rt for 5 h, the mix-
ture was treated with a saturated aqueous solution of
NaHCO3. The organic layer was washed with water,
dried over Na2SO4, and then filtered and concentrated.
The residue was subjected to silica gel column chroma-
tography (6:1, petroleum ether/EtOAc), affording 25
(5.65 g, 89%) as a colorless syrup. Rf = 0.53 (3:1, petro-
20
leum ether/EtOAc); ½aꢁD ꢀ79.3 (c 0.8, CHCl3); 1H
NMR (300 MHz, CDCl3): d 8.07–7.29 (m, 15H), 5.64
(s, 1H), 5.47 (m, 1H), 5.12 (m, 1H), 4.99 (m, 1H), 4.94
(d, 1H, J = 12.0 Hz), 4.77 (d, 1H, J = 12.0 Hz), 4.28
(m, 2H), 3.92 (m, 1H), 2.06, 1.97 (s each, 3H each); 13C
NMR (75 MHz, CDCl3): d 170.6, 170.0, 165.0, 137.0,
135.7, 133.6, 131.7, 129.7, 129.3, 128.9, 128.4, 127.9,
127.6, 127.5, 86.0, 72.6, 71.6, 68.7, 66.9, 64.5, 62.9,
20.7, 20.7; IR: 1745, 1722, 1269, 1230, 1111,

1628
Y. Zhou et al. / Carbohydrate Research 341 (2006) 1619–1629
(280 mg, 96%) as a colorless syrup. Rf = 0.3 (5:1, petro-
0.14 mmol) with thioglycoside 4 (57 mg, 0.12 mmol) after
purification by silica gel column chromatography (2:1,
petroleum ether/EtOAc), afforded 33 (99 mg, 70%) as a
colorless syrup. Rf = 0.44 (1:1, petroleum ether/EtOAc);
20
leum ether/EtOAc); ½aꢁD +60.5 (c 0.9, CHCl3); 1H NMR
(300 MHz, CDCl3): d 8.06–7.32 (m, 10H, ArH), 4.94
and 4.83 (AB, 2H, J = 10.8 Hz, CH2Ph), 4.83 (d, 1H,
J = 3.6 Hz, H-1), 4.77 (dd, 1H, J = 12.0, 3.9 Hz, H-
6a), 4.47 (dd, 1H, J = 12.0, 1.8 Hz, H-6b), 3.91–3.83
(m, 2H), 3.62–3.54 (m, 1H, H-4), 3.46 (s, 3H, OMe),
3.37 (m, 1H, H-2), 2.83 (d, 1H, OH); IR: 3375, 2113,
20
½aꢁD ꢀ27.7 (c 1.2, CHCl3); 1H NMR (300 MHz, CDCl3):
d 8.12–7.15 (m, 25H), 5.79 (s, 1H), 5.42 (s, 1H), 5.34 (d,
1H, J = 1.5 Hz), 5.25 (t, 1H, J = 9.3 Hz), 5.14 (t, 1H,
J = 8.7 Hz), 4.98 (d, 1H, J = 11.7 Hz), 4.80–4.51 (m,
7H), 4.20 (m, 2H), 4.09 (s, 1H), 3.95 (d, 1H,
J = 9.9 Hz), 3.84 (d, 1H, J = 10.2 Hz), 3.82 (s, 3H),
3.73 (m, 2H), 3.58 (d, 1H, J = 10.8 Hz), 3.43 (s, 4H),
3.17 (dd, 1H, J = 3.6, 10.2 Hz), 2.69 (m, 2H), 2.45 (m,
2H), 2.10, 2.03, 2.00 (s each, 3H each); 13C NMR
(75 MHz, CDCl3): d 205.8, 171.2, 170.3, 169.2, 169.0,
167.0, 165.6, 138.2, 137.7, 137.1, 135.0, 133.7, 131.8,
130.0, 129.3, 129.0, 128.8, 128.4, 128.0, 127.8, 127.7,
127.6, 127.5, 127.1, 100.9, 99.7, 86.9, 79.8, 78.0, 77.9,
77.4, 74.9, 74.3, 73.3, 72.8, 72.6, 72.4, 71.3, 69.8, 69.2,
68.4, 63.2, 61.5, 52.6, 52.4, 37.6, 29.7, 27.7, 22.6, 20.9,
20.7; IR: 2925, 2112, 1753, 1720, 1223, 1149, 1071,
1696, 1110, 837 cmꢀ1
;
ESIMS m/z calcd for
[C21H23N3O6]Na+: 436.1479. Found: 436.1483.
3.1.23. Phenyl [methyl (2-O-benzoyl-3-O-benzyl-4-O-
levulinoyl-a-L-idopyranosyl)uronate]-(1!4)-6-O-acetyl-2-
azido-3-O-benzyl-2-deoxy-a-D-glucopyranosyl-(1!4)-
(2-O-benzoyl-3-O-benzyl-1-thio-a-L-idopyranoside)uronate
(32). A mixture of trichloroacetimidate 2 (257 mg,
0.27 mmol) and thioglycoside 4 (95 mg, 0.19 mmol) in
dry toluene (6 mL) was stirred in the presence of freshly
˚
activated powdered 4 A molecular sieves (100 mg) for
30 min at rt under argon. After cooling to ꢀ78 °C,
TMSOTf (0.19 mL, 0.05 M) was added dropwise. The
reaction was stirred at ꢀ78 °C until TLC indicated com-
plete conversion of the donor 2 and then was quenched
by the addition of Et3N (0.2 mL). The resulting mixture
was filtered through a pad of Celite and concentrated.
The residue was purified by silica gel column chroma-
tography (2:1, petroleum ether/EtOAc) to provide tri-
saccharide 32 (125 mg, 56%) as a colorless syrup.
1029, 745 cmꢀ1
;
MALDIMS m/z calcd for
[C63H67N3O21S]Na+: 1256.3880. Found: 1256.3843.
3.1.25. Methyl [methyl (2-O-benzoyl-3-O-benzyl-4-O-
levulinoyl-a-L-idopyranosyl)uronate]-(1!4)-6-O-acetyl-2-
azido-3-O-benzyl-2-deoxy-b-D-glucopyranosyl-(1!4)-meth-
yl (2-O-benzoyl-3-O-benzyl-a-L-idopyranosyl)uronate-(1!4)-
2-azido-6-O-benzoyl-3-O-benzyl-2-deoxy-a-D-glucopyran-
oside (1a). A solution of trisaccharide thioglycoside 32
(37 mg, 0.029 mmol) and BSP (8 mg, 0.04 mmol) in dry
CH2Cl2 (2 mL) was stirred for 30 min over freshly acti-
20
Rf = 0.67 (1:1, petroleum ether/EtOAc); ½aꢁD ꢀ41.3 (c
1
1.1, CHCl3); H NMR (300 MHz, CDCl3): d 8.07–7.04
(m, 30H), 5.75 (s, 1H), 5.32 (s, 1H), 5.30 (d, 1H,
J = 1.8 Hz), 5.26 (d, 1H, J = 3.3 Hz), 5.15 (t, 1H, J=
3.7 Hz), 5.06 (t, 1H, J = 3.6 Hz), 4.93 (d, 1H,
J = 11.7 Hz), 4.78–4.67 (m, 4H), 4.58 (d, 1H,
J = 3.6 Hz), 4.30 (s, 2H), 4.24 (d, 1H, J = 10.5 Hz),
4.15 (br, 1H), 3.96 (br, 1H), 3.87–3.74 (m, 3H), 3.67
(d, 1H, J = 10.2 Hz), 3.61 (s, 3H), 3.48 (s, 3H), 3.35 (t,
1H, J = 9.1 Hz), 3.22 (dd, 1H, J = 3.6, 10.5 Hz), 2.61
(m, 2H), 2.47 (m, 2H), 2.08, 2.01 (s each, 3H each);
13C NMR (75 MHz, CDCl3): d 205.8, 171.5, 170.7,
169.2, 168.8, 165.6, 165.0, 137.4, 137.2, 137.0, 135.2,
133.5, 133.4, 131.2, 129.9, 129.8, 129.5, 129.1, 129.0,
128.6, 128.5, 128.1, 128.0, 127.8, 127.5, 127.4, 99.4,
97.8, 86.7, 78.5, 76.3, 75.1, 74.4, 74.2, 73.3, 72.7, 71.6,
69.9, 69.5, 69.3, 68.5, 68.3, 68.1, 63.7, 61.6, 52.2, 52.0,
37.6, 29.7, 27.7, 20.7; IR: 2925, 2111, 1741, 1720, 1269,
1110, 1071, 1027, 713 cmꢀ1; ESIMS m/z calcd for
[C68H69N3O21S]Na+: 1318.4036. Found: 1318.4039.
˚
vated powdered 3 A molecular sieves (100 mg). The mix-
ture was cooled to ꢀ60 °C, and Tf2O (5 lL, 0.037 mmol)
was added. The temperature was raised to ꢀ40 °C and
stirring continued for 15 min. Then a solution of the
monosaccharide alcohol 5 (30 mg, 0.057 mmol) in dry
CH2Cl2 (0.5 mL) was added and the resulting mixture
was allowed to warm slowly to rt. The reaction was
quenched by the addition of Et3N (0.05 mL) and the
mixture filtered through a pad of Celite. The filtrate
was concentrated and purified by silica gel column chro-
matography (2:1, petroleum ether/EtOAc) affording 1a
(39 mg, 87%) as a colorless syrup. Rf = 0.45 (2:1, petro-
20
1
leum ether/EtOAc); ½aꢁD 20.9 (c 1.0, CHCl3); H NMR
(300 MHz, CDCl3): d 8.07–7.16 (m, 35H), 5.56 (d, 1H,
J = 4.2 Hz), 5.30 (d, 1H, J = 3.6 Hz), 5.19 (m, 2H),
5.12 (t, 1H, J = 3.6 Hz), 4.91 (d, 1H, J = 10.5 Hz),
4.83 (m, 2H), 4.79–4.72 (m, 7H), 4.69 (d, 1H,
J = 4.2 Hz), 4.61 (dd, 1H, J = 4.2, 12.0 Hz), 4.54–4.43
(m, 2H), 4.29 (br, 2H), 4.17–4.11 (m, 2H), 4.03–3.71
(m, 7H), 3.51 (s, 3H), 3.50–3.42 (m, 3H), 3.39 (s, 3H),
3.33 (s, 4H), 3.32 (s, 1H), 3.28 (dd, 1H, J = 3.6,
10.2 Hz), 2.12, 2.07 (s each, 3H each); 13C NMR
(75 MHz, CDCl3): d 205.7, 171.6, 170.6, 169.2, 168.8,
166.0, 165.4, 165.1, 137.8, 137.5, 137.3, 137.2, 133.6,
133.4, 133.0, 129.8, 129.2, 129.1, 128.6, 128.5, 128.3,
3.1.24. Phenyl [methyl (2-O-acetyl-3-O-benzyl-4-O-levu-
linoyl-b-D-glucopyranosyl)uronate]-(1!4)-6-O-acetyl-2-
azido-3-O-benzyl-2-deoxy-a-D-glucopyranoside-(1!4)-
(2-O-benzoyl-3-O-benzyl-1-thio-a-L-idopyranoside)uro-
nate (33). The same procedure described for the prepa-
ration of trisaccharide 32 was employed for the synthesis
of 33. Thus, treatment of trichloroacetimidate 3 (130 mg,

Y. Zhou et al. / Carbohydrate Research 341 (2006) 1619–1629
1629
2. For the most successful example, see: Petitou, M.; van
Boeckel, C. A. A. Angew. Chem., Int. Ed. 2004, 43, 3118–
3133.
3. Recent review: Poletti, L.; Lay, L. Eur. J. Org. Chem.
2003, 2999–3024.
128.1, 127.9, 127.8, 127.6, 127.4, 98.4, 98.3, 98.2, 97.7,
78.5, 78.3, 76.2, 75.1, 75.0, 74.6, 74.4, 74.1, 73.6, 73.3,
70.5, 70.1, 69.8, 69.4, 69.1, 68.4, 68.0, 63.5, 63.4, 62.7,
61.7, 55.4, 52.1, 51.7, 37.6, 29.6, 27.7, 20.8; IR: 2925,
2110, 1741, 1722, 1270, 1110, 1070, 1027, 713 cmꢀ1
;
4. Recent review: Yu, B.; Yang, Z.; Cao, H. Curr. Org.
Chem. 2005, 9, 179–194.
ESIMS m/z calcd for [C83H86N6O27]Na+: 1621.5433.
´
5. Codee, J. D. C.; Stubba, B.; Schiattareklla, M.; Overkleeft,
Found: 1621.5438.
H. S.; van Boeckel, C. A. A.; van Boom, J. H.; van der
Marel, G. A. J. Am. Chem. Soc. 2005, 127, 3767–3773.
6. Early examples on one-pot sequential glycosylation using
glycosyl imidates and thioglycosides: (a) Yamada, H.;
Harada, T.; Miyazaki, H.; Takahashi, T. Tetrahedron
Lett. 1994, 35, 3979–3982; (b) Yamada, H.; Harada, T.;
Takahashi, T. J. Am. Chem. Soc. 1994, 116, 7919–7920; (c)
Yu, B.; Yu, H.; Hui, Y.; Han, X. Tetrahedron Lett. 1999,
40, 8591–8594; (d) Yu, H.; Yu, B.; Wu, X.; Hui, Y.; Han,
X. J. Chem. Soc., Perkin Trans. 1 2000, 1445–1453.
7. de Paz, J.-L.; Ojeda, R.; Reichardt, N.; Martin-Lomas, M.
Eur. J. Org. Chem. 2003, 3308–3324.
8. Lee, J.-C.; Lu, X.-A.; Kulkarni, S. S.; Wen, Y.-S.; Hung,
S.-C. J. Am. Chem. Soc. 2004, 126, 476–477.
9. Lee, J.-C.; Tai, C.-A.; Hung, S.-C. Tetrahedron Lett. 2002,
43, 851–855.
10. (a) Tailler, D.; Jacquinet, J.-C.; Noirot, A.-M.; Beau,
J.-M. J. Chem. Soc., Perkin Trans. 1 1992, 3163–3164; (b)
Hori, H.; Nishida, Y.; Ohrui, H.; Meguro, H. J. Org.
Chem. 1989, 54, 1346–1353.
11. Ichikawa, Y.; Monden, R.; Kuzuhara, H. Carbohydr. Res.
1988, 172, 37–64.
3.1.26. Methyl [methyl (2-O-acetyl-3-O-benzyl-4-O-levu-
linoyl-b-D-glucopyranosyl)uronate]-(1!4)-6-O-acetyl-2-
azido-3-O-benzyl-2-deoxy-b-D-glucopyranosyl-(1!4)-
(methyl 2-O-benzoyl-3-O-benzyl-a-L-idopyranosyl)uronate-
(1!4)-2-azido-6-O-benzoyl-3-O-benzyl-2-deoxy-a-D-gluco-
pyranoside (1b). The same procedure described for the
preparation of tetrasaccharide 1a was employed for the
synthesis of 1b. Thus, reaction of thioglycoside 33
(43 mg, 0.035 mmol) with alcohol 5 (36 mg, 0.087 mmol)
after purification by silica gel column chromatography
(2:1, petroleum ether/EtOAc) afforded 1b (42 mg, 79%)
as a colorless syrup. Rf = 0.15 (2:1, petroleum ether/
20
EtOAc); ½aꢁD 26.9 (c 1.1, CHCl3); 1H NMR
(300 MHz, CDCl3): d 8.06 (m, 4H), 7.44–7.24 (m,
26H), 5.62 (d, 1H, J = 4.7 Hz), 5.23 (m, 2H), 5.10 (t,
1H, J = 8.1 Hz), 4.94–4.88 (m, 3H), 4.77–4.70 (m, 5H),
4.68–4.59 (m, 4H), 4.50 (t, 1H, J = 7.9 Hz), 4.47–4.39
(m, 2H), 4.21–4.09 (m, 3H), 4.01 (m, 2H), 3.89–3.82
(m, 5H), 3.72 (m, 2H), 3.50 (m, 1H), 3.47 (s, 3H), 3.46
(s, 3H), 3.43 (dd, 1H, J = 3.6, 10.2 Hz), 3.38 (s, 3H),
3.19 (dd, 1H), 2.67 (m, 2H), 2.48 (m, 2H), 2.15, 2.06,
1.95 (s each, 3H each); 13C NMR (75 MHz, CDCl3): d
205.8, 171.2, 170.3, 169.4, 168.9, 167.0, 166.0, 165.3,
138.1, 137.7, 129.9, 129.8, 128.8, 128.4, 128.3, 128.2,
128.1, 128.0, 127.9, 127.8, 127.7, 127.6, 100.8, 98.7,
98.4, 98.3, 79.7, 78.5, 77.7, 77.3, 75.2, 75.1, 74.8, 74.3,
73.2, 72.4, 71.3, 69.2, 63.5, 55.4, 52.6, 52.0, 37.6, 29.7,
27.7, 20.8, 20.6; IR: 2927, 2111, 1749, 1722, 1272,
1224, 1149, 1110, 1070, 1029, 714 cmꢀ1; ESI-MS:
1559.7 [M+Na+]; ESIMS m/z calcd for [C78H84N6O27]-
Na+: 1559.5277. Found: 1559.5281.
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Acknowledgment
This work is supported by the Committee of Science and
Technology of Shanghai (04DZ19213) and the National
Natural Science Foundation of China (20572122).
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