Synthesis of the tetrasaccharide repeat unit of the O-antigen polysaccharide from Escherichia coli O77 employing the 2′-carboxybenzyl glycoside

Article abstract of DOI:10.1139/V06-030

The synthesis of the suitably protected form (1) of the tetrasaccharide repeat unit, →2)-α-D-Manp-(1→2)-β-D-Manp-(1→3)- α-D-GlcpNAc-(1→6)-α-D-Manp-(1→ (A), of the O-antigen polysaccharide of the lipopolysaccharide from Escherichia coli O77 has been accomp

Full text of DOI:10.1139/V06-030

506
Synthesis of the tetrasaccharide repeat unit of the
O-antigen polysaccharide from Escherichia coli
O77 employing the 2′-carboxybenzyl glycoside1
Bo Ram Lee, Joo Mi Jeon, Jae Hyuk Jung, Heung Bae Jeon, and Kwan Soo Kim
Abstract: The synthesis of the suitably protected form (1) of the tetrasaccharide repeat unit, →2)-α-D-Manp-(1→2)-β-D-
Manp-(1→3)-α-D-GlcpNAc-(1→6)-α-D-Manp-(1→ (A), of the O-antigen polysaccharide of the lipopolysaccharide from
Escherichia coli O77 has been accomplished by latent–active glycosylation employing the 2′-carboxybenzyl (CB) gly-
coside method. In addition to previously used latent glycosyl donors, 2′-(benzyloxycarbonyl)benzyl (BCB) glycosides,
new latent glycosyl donors, 2′-(allyloxycarbonyl)benzyl (ACB) glycosides, have been introduced as a direct precursor
for the active CB glycosides. We also demonstrate that 4,6-O-benzylidene-2-azido-2-deoxy-α-D-mannopyranoside (7)
has been readily prepared from D-glucosamine in good yield.
Key words: Escherichia coli O77, glycosylation, 2′-carboxybenzyl (CB) glycosides, 2′-(allyloxycarbonyl)benzyl (ACB)
glycosides, glycosyl donor.
Résumé : Faisant appel à une glycosilation latente active à l’aide de la méthode du glycoside de 2′-carboxybenzyle
(CB), on a réalisé la synthèse de la forme adéquatement protégée du composé 1, le tétrasaccharide →2)-α-D-Manp-
(1→2)-β-D-Manp-(1→3)-α-D-GlcpNAc-(1→6)-α-D-Manp(1→ (A) qui est le motif constitutif du polysaccharide O-
antigène du lipopolysaccharide du Escherichia coli O77. En plus des donneurs latents de glycosyle utilisés antérieure-
ment, les glycosides de 2′-benzyloxycarbonyl)benzyle (BCB), on a introduit de nouveaux donneurs latents de glycosyle,
les glycosides de 2′-(allylcarbonyl)benzyle (ACB), comme précurseurs directs de glycosides de CB actifs. On a aussi
préparé facilement le 4,6-O-benzylidène-2-azido-2-désoxy-α-D-mannopyranoside (7) à partir de la D-glucosamine avec
un bon rendement.
Mots clés : Escherichia coli O77, glycosylation, glycoside de 2′-carboxybenzle (CB), glycosides de 2′-(allyloxycarbo-
nyl)benzyle (ACB), donneur de glycosyle.
[Traduit par la Rédaction] Lee et al. 515
Introduction
from the E. coli O77 contains the O-antigen polysaccharide
as its substructure. As shown in Fig. 1, this particular poly-
saccharide is composed of a series of the repeat unit of a
tetrasaccharide with the following structure: →2)-α-D-Manp-
(1→2)-β-D-Manp-(1→3)-α-D-GlcpNAc-(1→6)-α-D-
Manp-(1→ (A).
One of the challenges in the synthesis of this tetra-
saccharide repeat unit would be the elaboration of the β-
mannopyranosyl linkage. Although several strategies for the
β-mannopyranosylation have been developed (9), including
Crich and co-workers’ recent approach (10) employing
4,6-O-benzylidene-protected glycosyl sulfoxides or thiogly-
cosides as glycosyl donors, the construction of β-manno-
pyranosyl linkages still poses a great challenge. Recently, we
have developed an efficient glycosylation method that em-
Escherichia coli is a facultative anaerobic Gram-negative
rod and is a predominant specie of the human colonic flora.
Normal nonpathogenic strains of E. coli usually remain
harmlessly confined to the intestinal lumen. However, infec-
tions owing to inherently pathogenic E. coli strains result in
clinical syndromes such as urinary tract infections, sepsis/
meningitis, and enteric/diarrheal disease. The species is sub-
divided into different serotypes based on the immunogeni-
city of bacterial surface structures (1, 2). E. coli O77, which
belongs to an O-serotype, causes diarrheal infections (3) and
has been identified as producing a Shiga-like toxin in both
humans and animals (4–7). Recently, Widmalm and co-
workers (8) have reported that the lipopolysaccharide (LPS)
Received 8 August 2005. Published on the NRC Research Press Web site at http://canjchem.nrc.ca on 11 April 2006.
Dedicated to Professor Walter A. Szarek, in recognition of his many achievements in carbohydrate chemistry, on the occasion of
his 65th birthday.
B.R. Lee, J.M. Jeon, J.H. Jung, H.B. Jeon, and K.S. Kim.2 Center for Bioactive Molecular Hybrids and Department of
Chemistry, Yonsei University, Seoul 120-749, Korea.
1This article is part of a Special Issue dedicated to Professor Walter A. Szarek.
2Corresponding author (e-mail: kwan@yonsei.ac.kr).
Can. J. Chem. 84: 506–515 (2006)
doi:10.1139/V06-030
© 2006 NRC Canada

Lee et al.
507
Scheme 1. Retrosynthesis of tetrasaccharide 1.
OLev
O
Ph
O
O
BnO
Ph
Ph
O
O
O
O
O
O
O
O
BnO
AcHN
OPiv
O
O
BnO
BnO
OBCB
1
OLev
O
Ph
O
O
OPiv
BnO
Ph
HO
BnO
BnO
O
O
O
Ph
O
O
O
+
O
O
BnO
O
OBCB
N3
OCB
3
2
OH
O
OLev
O
Ph
O
Ph
O
O
BnO
O
Ph
O
O
+
O
O
BnO
N3
OCB
OACB
4
5
OPMB
O
Ph
O
O
HO
O
Ph
O
O
BnO
+
N3
OCB
OACB
7
6
CH2
O
CH2
O
CH2 O
CB =
BCB =
ACB =
OAll
OH
OBn
going effort to explore the application and to understand the
limitation of the CB-glycoside-mediated glycosylation, we
disclose the synthesis of the protected tetrasaccharide 1,
which represents the elemental subunit of the O-antigen
polysaccharide of the LPS from E. coli O77.
Fig. 1. The repeat unit of the O-antigen polysaccharide in Esche-
richia coli O77.
O
HO
HO
O
HO
HO
O
O
HO
HO
HO
O
HO
Results and discussion
O
AcHN
HO
OH
O
O
The protective groups were carefully chosen in synthesiz-
ing the target tetrasaccharide 1, since it was of importance to
realize the selective deprotection during the future synthesis
of an octasaccharide or a dodecasaccharide from 1 by
dimerization or trimerization, respectively. Thus, the latent
2′-(benzyloxycarbonyl)benzyl (BCB) group at C-1 in the re-
ducing end of the tetrasaccharide 1 would be readily con-
verted into the active CB group to give a tetrasaccharide
donor. The levulinyl (Lev) group at the C-2 in the
nonreducing end of 1 would be selectively cleaved to pro-
vide a tetrasaccharide acceptor.
HO
O
n
A
ploys a new type of glycosyl donor, 2′-carboxybenzyl (CB)
glycoside. This methodology has been employed in the
stereoselective β-mannopyranosylation and 2-deoxygly-
cosylation of various glycosyl acceptors (11–14). As an on-
© 2006 NRC Canada

508
Can. J. Chem. Vol. 84, 2006
Scheme 2. Synthesis of monosaccharide building blocks 3, 4, and 6.
OH
OAc
O
OH
OAc
O
OBn AcO
HO
HO
HO
AcO
AcO
AcO
HgBr2, Hg(CN)2,
O
O
NaOMe
MeOH
93%
AcO
AcO
CH3CN, 0 oC
86%
OBCB
OBCB
Br
10
8
9
PhCH(OMe) 2, CSA
DMF, 50 oC
70%
1. Bu2SnO
MeOH, 50 oC
2. BnBr
OH
O
OH
O
Ph
O
Ph
O
O
O
HO
BnO
DMF, 90 oC
OBCB
OBCB
12
11
85%
PMBCl,NaH
DMF, 90%
PivCl
Et3N, DMAP
levulinic acid
DCC, DMAP
CH2Cl2, 88%
CH2Cl2, 88%
OPMB
O
Ph
O
O
OPiv
BnO
OLev
O
O
O
Ph
Ph
O
O
OBCB
O
BnO
13
BnO
OBCB
OBCB
15
Pd/C, H2, NH4OAc
MeOH, 86%
14
.
BH3 THF
Bu2BOTf
THF, 87%
Pd/C, H2, NH4OAc
MeOH, 92%
OPMB
O
Ph
O
O
BnO
OPiv
O
OLev
O
HO
BnO
BnO
Ph
O
O
BnO
OCB
6
OBCB
OCB
3
4
Retrosynthesis of 1 leads to trisaccharide donor 2 and
pivaloyl (Piv)-protected mannosyl acceptor 3, then further
analysis of 2 provides levulinyl-protected mannosyl donor 4
and 2′-(allyloxycarbonyl)benzyl (ACB) glycoside 5 as an
acceptor (Scheme 1). The acceptor 5 can be derived from p-
methoxybenzyl(PMB)-protected mannosyl donor 6 and 2-
azido-2-deoxy-glucospyranosyl acceptor 7.
The monosaccharide building blocks 3, 4, and 6 were syn-
thesized from a common intermediate 12, which was pre-
pared by the dibutyltinoxide-mediated selective benzylation
of diol 11 (Scheme 2) (14). Diol 11 was efficiently prepared
from tetraacetylmannosyl bromide (8) by the following se-
quence: (i) coupling of 8 and crystalline benzyl 2-
(hydroxymethyl)benzoate, which was readily obtained in
large quantities from inexpensive phthalide, in the presence
of HgBr2 and Hg(CN)2 in acetonitrile; (ii) deacetylation of
the resulting tetraacetylmannoside 9 under basic conditions;
and (iii) subsequent benzylidenation of the resulting tetrol
10 (11). P-Methoxybenzylation of 12 followed by selective
hydrogenolysis of the resulting BCB glycoside 13 in the
presence of NH4OAc gave the desired CB glycoside 6.
Pivaloylation of 12 and subsequent reductive cleavage of the
resultant benzylidene acetal 15 with borane – dibutylboron
triflate (15) provided C-6 alcohol 3. Protection of 12 with
levulinic acid in the presence of dicyclohexylcarbodiimide
(DCC) and 4-(N,N-dimethylamino)pyridine (DMAP) fol-
lowed by hydrogenolysis of the resulting levulinyl BCB
glycoside 14 in the presence of NH4OAc afforded the CB
glycoside 4.
For the synthesis of the azidomonosaccharide building
block 7, 8 was used as a starting material (Scheme 3). The
ACB mannoside 16 was prepared by coupling of 8 and allyl
2-(hydroxymethyl)benzoate in the presence of HgBr2 and
Hg(CN)2. Introduction of the new ACB group in the place of
the previously used BCB group was necessary because the
azide functionality at C-2 was also reduced during the con-
version of the BCB group into the CB group under the
hydrogenolysis conditions. Deacetylation of 16 by NaOMe
followed by benzylidenation of the resulting tetrol 17 af-
forded 4,6-O-benzylidene-protected ACB mannoside 18.
The hydroxy group at C-3 of diol 18 was selectively pro-
tected with the p-methoxybenzyl (PMB) group by using the
dibutyltin oxide method to give PMB-protected alcohol 19.
Then, compound 19 was treated with triflic anhydride in the
presence of pyridine to afford triflate 20. Treating 20 with
sodium azide in DMF gave the desired 2-azido-2-deoxy-
glucospyranoside 21 in only 34% yield. The major by-
product was the C-2,3 alkene, which was presumably to be
© 2006 NRC Canada

Lee et al.
509
Scheme 3. Synthesis of monosaccharide building block 7 from 8.
OH
OAll AcO
OAc
O
HO
HO
HO
OH
O
HgBr2, Hg(CN)2,
O
NaOMe
MeOH
93%
AcO
AcO
8
o
CH3CN, 0 C
86%
OACB
OACB
17
16
PhCH(OMe) 2, CSA
DMF, 50 oC
70%
1. Bu2SnO
OH
O
Ph
O
OH
O
MeOH, 50 oC
2. PMBCl, n-Bu4NI
DMF, 90 oC
Tf2O, Py.
CH2Cl2, -40 oC
Ph
O
O
O
PMBO
HO
88%
OACB
OACB
19
18
85%
OTf
O
Ph
PMBO
Ph
O
O
Ph
PMBO
NaN3
DMF
34%
O
DDQ
CH2Cl2:H2O
(10/1)
O
O
O
O
O
HO
N3
OACB
N3
OACB
OACB
20
21
92%
7
Scheme 4. Synthesis of monosaccharide building block 7 from glucosamine 22.
1. CuSO4, K2CO3, TfN3
CH2Cl2, MeOH, H2O
HO
HO
HO
AcO
AcO
AcO
AcO
AcO
AcO
O
O
O
ZnCl2
DCMME
97%
OH
2. Ac2O, DMAP, Py.
72%
N3
Cl
NH2
HCl
N3 OAc
22
23
24
OH
OAll
AgClO4,
CH2Cl2, rt
91%
O
AcO
AcO
AcO
Ph
O
1. NaOMe, MeOH, 91%
O
O
O
2. PhCH(OMe)2, CSA
DMF, 50 oC, 70 %
HO
N3
N3
OACB
OACB
7
25
formed via the E2 mechanism. To favor the nucleophilic
substitution, a number of different reaction conditions were
attempted. Unfortunately, there was no improvement.
NaOMe followed by benzylidenation with benzaldehyde
dimethyl acetal afforded the C-3 alcohol 7.
The stage was set for the assembly of the properly pro-
tected monosaccharide building blocks 3, 4, 6, and 7 to
make tetrasaccharide 1. The crucial stereoselective β-
mannopyranosylation was achieved by activation of the
glycosyl donor 6 with Tf2O in the presence of 2,6-di-tert-
butyl-4-methylpyridine (DTBMP) and 4 Å molecular sieves
in CH2Cl2, followed by the addition of the acceptor 7 at
–78 °C. The desired β-mannopyranosyl disaccharide 26 was
obtained in 59% yield along with α-disaccharide as a by-
product in 14% yield, as shown in Scheme 5. It was essen-
tial to activate the donor 6 with Tf2O in the presence of
DTBMP before the addition of the acceptor 7 to maximize
the yield of 26. The stereochemistry at the newly generated
anomeric center of the disaccharide 26 was determined on
the basis of its 1H and 13C NMR spectral data, especially the
chemical shift in the 13C NMR: δ 101.6 ppm for the β-
A different route to compound 7 was realized using D-
glucosamine hydrochloride (22) as a starting material
(Scheme 4). Treating 22 with triflyl azide (TfN3) in the pres-
ence of a catalytic amount of CuSO4 in a cosolvent of
CH2Cl2, MeOH, and H2O to make a homogenous solution
followed by acetylation provided tetraacetyl 2-azido-2-
deoxyglucopyranoside (23) in 72% yield (16). Compound 23
was smoothly transformed into glucopyranosyl chloride 24
by using dichloromethyl methyl ether (DCMME) in the
presence of a catalytic amount of zinc chloride (17). Reac-
tion of 24 with allyl 2-(hydroxymethyl)benzoate using
AgClO4 as a promoter afforded α-ACB glycoside 25 as a
single isomer in 91% yield, while the same reaction using
AgOTf as a promoter gave 25 in 86% yield as a mixture of α
and β anomers in a ratio of 4:1. Deacetylation of 25 with
© 2006 NRC Canada

510
Can. J. Chem. Vol. 84, 2006
Scheme 5. Completion of the synthesis of tetrasaccharide 1.
Tf2O, DTBMP
OPMB
Ph
O
OPMB
4Å MS
O
Ph
O
O
Ph
O
CH2Cl2, -78 oC;
O
O
DDQ
CH2Cl2:H2O
(10/1)
O
O
O
BnO
BnO
then 7
N3
OCB
-78 oC to rt
73%
OACB
6
26
85%
4
, DTBMP
OLev
Ph
O
OH
Ph
O
O
4 Å MS
O
O
O
Ph
O
O
BnO
O
CH2Cl2, -78 oC;
BnO
Ph
O
Ph
O
O
O
O
O
O
then Tf2O
-78 oC to rt
44%
N3
O
O
BnO
OACB
5
N3
OACB
2
O
N
H
(Ph3P)4Pd,
THF, 77%
OLev
O
Ph
O
O
OLev
O
3
, DTBMP
Ph
O
BnO
O
Ph
O
O
O
4Å MS
O
O
O
Ph
BnO
Ph
O
CH2Cl2, -78 oC;
O
BnO
Ph
O
O
O
O
N3
O
O
then Tf2O
-78 oC to rt
65%
OPiv
O
O
BnO
O
O
BnO
BnO
N3
OCB
27
OBCB
28
1. Ph3P, H2O, THF
2. Ac2O, py.
58%
Ph
OLev
O
Ph
O
O
BnO
Ph
O
O
O
O
O
O
O
O
BnO
AcHN
OPiv
O
O
BnO
BnO
OBCB
1
disaccharide in comparison with δ 100.1 ppm for the α-
disaccharide. Removal of the PMB group in 26 with DDQ
and the subsequent glycosylation of the resulting mono-
hydroxy disaccharide acceptor 5 with the CB glycosyl donor
4 provided the desired α-trisaccharide 2 in 44% yield and
the β-trisaccharide in 21% yield. Then, the ACB tri-
saccharide 2 was readily converted into the active CB
trisaccharide 27 in 77% yield by deallylation with a catalytic
amount of Pd(Ph3P)4 in the presence of morpholine (18).
This result indicated that ACB glycosides were a useful pre-
cursor for CB glycosides, especially in the presence of the
azide functionality, which could not survive during the con-
version of the BCB glycosides into CB glycosides by
hydrogenolysis. Finally, the coupling of the CB trisaccharide
donor 27 and the BCB monosaccharide acceptor 3 in the
presence of Tf2O and DTBMP afforded α-tetrasaccharide 28
as a single isomer in 65% yield. Reduction of the azido
group by treatment of 28 with triphenylphosphine (19), fol-
lowed by acetylation of the resulting amine, furnished the
desired target tetrasaccharide 1 in 58% yield.
Conclusion
We have described the synthesis of the suitably protected
tetrasaccharide repeat unit 1 of the O-antigen polysaccharide
of the LPS from E. coli O77. The 2′-carboxybenzyl (CB)
glycoside method proved to be effective in the coupling of
four monosaccharide components of the tetrasaccharide, 3,
4, 6, and 7. The newly introduced ACB glycoside was readily
converted into the active CB glycosyl donors without affect-
ing the azide functionality. Additionally, 4,6-O-benzylidene-
2-azido-2-deoxy-α-D-mannopyranoside (7) was readily pre-
pared from D-glucosamine hydrochloride in good yield.
© 2006 NRC Canada

Lee et al.
511
Pd/C (10%, 63 mg) and ammonium acetate (46 mg,
0.59 mmol) in MeOH (10 mL) at rt for 1 h, the reaction mix-
ture was filtered through Celite and the filtrate was concen-
trated in vacuo. The residue was purified by flash column
chromatography (hexane–EtOAc, 1:1) to afford compound 6
(330 mg, 91%) as a white solid; mp 81 to 82. Rf 0.12
Experimental
The known compounds 9 (11), 10 (11), 11 (11), 23 (16),
and 24 (17) were prepared according to the procedures re-
ported previously.
(hexane–EtOAc, 2:1, v/v). [α]20 +53.7° (c 1.3, CHCl3). IR
BCB 3-O-benzyl-4,6-O-benzylidene-␣-D-
mannopyranoside (12)
D
(CHCl3, film, cm–1): 2920, 1720, 1624, 1454, 1460, 1430,
1
A
solution of BCB 4,6-O-benzylidene-α-D-manno-
1381, 1088, 1021, 979. H NMR (250 MHz, CDCl3) δ: 3.77
pyranoside (11) (450 mg, 0.9 mmol) and Bu2SnO (228 mg,
0.9 mmol) in MeOH (40 mL) was stirred at 50 °C for 1 h. Af-
ter removal of the solvent in vacuo, the residue was dissolved
in DMF (10 mL) and then BnBr (0.19 mL, 1.6 mmol) was
added to the reaction mixture. After stirring at 90 °C for 3 h,
the reaction mixture was quenched with H2O and then ex-
tracted with EtOAc. The combined organic layer was washed
with satd. aq. NH4Cl and brine, dried over MgSO4, and con-
centrated in vacuo. The residue was purified by flash column
chromatography (hexane–EtOAc, 2:1) to afford compound 12
(506 mg, 85%) as a colorless oil. Rf 0.36 (hexane–EtOAc, 2:1,
(s, 3H), 3.84–3.93 (m, 3H), 4.04 (dd, J = 3.2, 10.0 Hz, 1H),
4.25–4.32 (m, 2H), 4.65 and 4.86 (ABq, J = 12.0 Hz, 2H),
4.67 and 4.74 (ABq, J = 12.0 Hz, 2H), 4.88 and 5.05 (ABq,
J = 14.0 Hz, 2H), 4.89 (d, J = 1.2 Hz, 1H), 5.64 (s, 1H) 6.84
(d, J = 8.5 Hz, 2H), 7.14–7.55 (m, 36H), 8.00 (d, J = 7.5 Hz,
1H). 13C NMR (63 MHz, CDCl3) δ: 55.3, 64.6, 66.9, 67.8,
71.6, 72.2, 74.2 78.5, 78.8, 100.0, 101.4, 101.7, 126.1, 126.2,
127.4, 127.6, 127.7, 128.2, 128.4, 128.5, 128.7, 128.9, 130.4,
130.6, 130.8, 132.6, 137.6, 138.4, 138.9, 139.5, 159.2, 171.9.
Anal. calcd. for C36H36O9: C 70.57, H 5.92; found: C 70.52,
H 5.92.
v/v). [α]20 +42.9° (c 6.75, CHCl3). IR (CHCl3, film, cm–1):
D
3447, 2921, 1637, 1460, 1381, 1098, 979. 1H NMR
(250 MHz, CDCl3) δ: 2.79 (s, 1H), 3.83–3.89 (m, 2H), 3.97
(dd, J = 3.5, 9.5 Hz, 1H), 4.07–4.19 (m, 2H), 4.26 (dd, J =
2.7, 8.0 Hz, 1H), 4.71 (d, J = 11.7 Hz, 1H), 4.87 (d, J =
11.7 Hz, 1H), 4.93 (d, J = 14.0 Hz, 1H), 4.96 (s, 1H), 5.11 (d,
J = 14.0 Hz, 1H), 5.31 (s, 2H), 5.61 (s, 1H) 7.25–7.54 (m,
18H), 8.00 (d, J = 7.5 Hz, 1H). 13C NMR (63 MHz, CDCl3)
δ: 63.7, 66.9, 67.6, 68.9, 70.1, 73.2, 75.9, 79.0, 99.9, 101.6,
125.9, 127.3, 127.8, 127.8, 128.0, 128.1, 128.2, 128.3, 128.5,
128.7, 130.6, 132.5, 135.9, 137.7, 138.1, 139.5, 166.7.
BCB 3-O-benzyl-4,6-O-benzylidene-2-O-levulinyl-␣-D-
mannopyranoside (14)
After a solution of 12 (360 mg, 0.62 mmol), levulinic acid
(107 mg, 0.93 mmol), DMAP (75 mg, 0.62 mmol), and
DCC (191 mg, 0.93 mmol) in CH2Cl2 (10 mL) was stirred at
rt for 1 h, the reaction mixture was filtered and the filtered
solid was washed with further CH2Cl2. The filtrate was
washed with satd. aq. NaHCO3 and brine, dried over
MgSO4, and concentrated in vacuo. The residue was purified
by flash column chromatography (hexane–EtOAc, 3:1) to af-
ford compound 14 (371 mg, 88%) as a white solid. Rf 0.25
BCB 3-O-benzyl-4,6-O-benzylidene-2-O-p-methoxybenzyl-
␣-D-mannopyranoside (13)
(hexane–EtOAc, 2:1, v/v). [α]20 +51.3° (c 1.5, CHCl3). IR
D
(CHCl3, film, cm–1): 3027, 2925, 2854, 1754, 713, 1617,
1499, 1372, 1275, 1036, 924, 751, 700. 1H NMR (250 MHz,
CDCl3) δ: 2.16 (s, 3H), 2.65–2.80 (m, 4H), 3.78–3.94 (m,
2H), 4.02–4.12 (m, 2H), 4.24 (dd, J = 3.5, 9.0 Hz, 1H), 4.65
(s, 2H), 4.95 and 5.17 (ABq, J = 12.0 Hz, 2H), 4.93 (d, J =
1.5 Hz, 1H), 5.32 (s, 2H), 5.47 (br s, 1H), 5.63 (s, 1H),
7.23–7.53 (m, 18H), 8.02 (d, J = 7.7 Hz, 1H). 13C NMR
(63 MHz, CDCl3) δ: 28.2, 29.9, 35.0, 38.1, 64.2, 66.9, 67.8,
68.9, 70.0, 72.3, 74.1, 78.5, 98.8, 101.7, 126.2, 127.6, 127.7,
127.9, 128.2, 128.3, 128.5, 129.0, 130.9, 132.7, 135.9,
137.6, 138.1, 139.4, 166.7, 172.1, 206.3. Anal. calcd. for
C40H40O10: C 70.57, H 5.92; found: C 70.58, H 5.93.
A solution of 12 (622 mg, 1.07 mmol), PMBCl (0.24 mL,
1.39 mmol), and NaH (51 mg, 2.14 mmol) in DMF (4 mL)
was stirred at 0 °C for 10 min and at room temperature (rt)
for 1 h. The reaction mixture was quenched with H2O and
then extracted with EtOAc. The combined organic layer was
washed with satd. aq. NH4Cl and brine, dried over MgSO4,
and concentrated in vacuo. The residue was purified by flash
column chromatography (hexane–EtOAc, 2:1) to afford
compound 13 (675 mg, 90%) as a colorless oil. Rf 0.47
(hexane–EtOAc, 2:1, v/v). [α]20 +52.9° (c 1.3, CHCl3). IR
D
(CHCl3, film, cm–1): 3420, 2920, 1720, 1624, 1430, 1381,
1
1088, 1021, 979. H NMR (250 MHz, CDCl3) δ: 3.78 (s,
3H), 3.79–3.91 (m, 3H), 4.02 (dd, J = 3.2, 10.0 Hz, 1H),
4.20–4.30 (m, 2H), 4.65 and 4.86 (ABq, J = 12.0 Hz, 2H),
4.67 and 4.74 (ABq, J = 12.0 Hz, 2H), 4.88 and 5.05 (ABq,
J = 14.0 Hz, 2H), 4.89 (d, J = 1.2 Hz, 1H), 5.21 (s, 2H),
5.64 (s, 1H), 6.82–6.90 (m, 2H), 7.24–7.51 (m, 21H), 7.95
(d, J = 7.5 Hz, 1H). 13C NMR (63 MHz, CDCl3) δ: 55.3,
55.4, 64.6, 66.7, 67.4, 68.9, 73.1, 73.3, 75.8, 76.5, 79.3,
99.3, 101.5, 113.9, 114.1, 126.1, 127.3, 127.6, 127.7, 128.0,
128.2, 128.4, 128.8, 129.8, 130.2, 130.8, 132.4, 137.8,
139.6, 159.4, 159.8, 166.8. Anal. calcd. for C43H42O9: C
73.49, H 6.02; found: C 73.47, H 6.03.
CB 3-O-benzyl-4,6-O-benzylidene-2-O-levulinyl-␣-D-
mannopyranoside (4)
Compound 14 was subjected to the same reaction condi-
tions as that for the preparation of 6 from 13 to give the title
compound 4 (92%) as a white solid. Rf 0.05 (hexane–EtOAc,
2:1, v/v). [α]20D +61.6° (c 3.7, CHCl3). IR (CHCl3, film, cm–1):
3027, 2920, 1718, 1693, 1454, 1377, 1224, 1097, 914, 756,
1
695. H NMR (250 MHz, CDCl3) δ: 2.16 (s, 3H), 2.65–2.82
(m, 4H), 3.80–3.97 (m, 2H), 4.09 (dd, J = 1.2, 5.0 Hz, 1H),
4.26 (dd, J = 3.5, 9.0 Hz, 1H), 4.67 and 4.72 (ABq, J =
12.5 Hz, 2H), 4.95 and 5.16 (ABq, J = 12.0 Hz, 2H), 4.98
(d, J = 1.5 Hz, 1H), 5.48 (brs, 1H), 5.63 (s, 1H), 7.24–7.61
(m, 13H), 8.08 (d, J = 7.7 Hz, 1H). 13C NMR (63 MHz,
CDCl3) δ: 28.2, 29.9, 38.1, 64.2, 67.8, 68.8, 70.1, 72.3, 73.9,
78.5, 98.8, 101.6, 126.1, 127.1, 127.5, 127.6, 127.7, 127.9,
CB 3-O-benzyl-4,6-O-benzylidene-2-O-p-methoxybenzyl-
␣-D-mannopyranoside (6)
After compound 13 (416 mg, 0.59 mmol) was stirred under
a hydrogen atmosphere using a balloon in the presence of
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Can. J. Chem. Vol. 84, 2006
128.2, 128.4, 128.9, 131.6, 133.4, 137.5, 138.0, 140.0,
171.8, 172.1, 206.6. Anal. calcd. for C33H34O10: C 67.11, H
5.80; found: C 67.10, H 5.80.
7.63 (dd, J = 0.6, 8.1 Hz, 1H), 8.01 (dd, J = 1.5, 8.1 Hz,
1H). 13C NMR (63 MHz, CDCl3) δ: 20.7 (3), 20.9, 62.3,
66.1, 66.8, 67.8, 68.7, 69.3, 69.5, 97.5, 127.6, 127.8, 128.1,
128.2, 128.3, 128.6, 130.8, 132.7, 135.9, 139.0, 166.4,
169.7, 169.9, 170.0, 170.6. HRMS calcd. for [M + Na]+:
545.1635; found: 545.1647.
BCB 3-O-benzyl-4,6-O-benzylidene-2-O-pivaloyl-␣-D-
mannopyranoside (15)
A solution of 12 (645 mg, 1.11 mmol), pivaloyl chloride
(0.27 mL, 2.21 mmol), DMAP (67 mg, 0.55 mmol), and
Et3N (0.17 mL, 1.22 mmol) in CH2Cl2 (10 mL) was stirred
at rt for 3 h. The reaction mixture was quenched with H2O
and then extracted with further CH2Cl2. The combined or-
ganic layer was washed with satd. aq. NH4Cl and brine,
dried over MgSO4, and concentrated in vacuo. The residue
was purified by flash column chromatography (hexane–
EtOAc, 9:1) to afford compound 15 (650 mg, 88%) as a col-
orless oil. Rf 0.28 (hexane–EtOAc, 9:1, v/v). [α]20D +21.8° (c
ACB 4,6-O-benzylidene-␣-D-mannopyranoside (18)
The title compound 18 was prepared from 17, which was
obtained from 16 in 93% yield, according to the known pro-
cedure (11) and in 70% yield. Rf 0.25 (hexane–EtOAc, 1:2,
v/v). [α]20 +90.0° (c 0.1, CHCl3). IR (CHCl3, film, cm–1):
D
3345, 3226, 2912, 1718, 1453, 1384, 1257, 1114, 1098,
1
1064, 1030, 1010, 740, 701. H NMR (250 MHz, CDCl3) δ:
3.04 (br s, 2H), 3.78–3.99 (m, 3H), 4.12 (s, 1H), 4.20–4.32
(m, 1H), 4.79–4.82 (dd, J = 1.1, 5.6 Hz, 2H), 4.92 and 5.12
(ABq, J = 14.0 Hz, 2H), 5.56 (s, 1H), 5.92–6.12 (m, 1H),
7.34–7.62 (m, 8H), 8.01 (dd, J = 1.0, 7.7 Hz, 1H). 13C NMR
(63 MHz, CDCl3) δ: 63.5, 65.8, 67.8, 68.9, 71.1, 79.0,
100.2, 102.3, 118.7, 126.4, 127.6, 128.0, 128.4, 129.4,
130.8, 132.1, 132.6, 137.3, 139.5, 166.7. HRMS calcd. for
[M + Na]+: 465.1525; found: 465.1540.
1
3.0, CHCl3). H NMR (250 MHz, CDCl3) δ: 1.26 (s, 9H),
3.78–4.12 (m, 4H), 4.24 (dd, J = 3.6, 9.1 Hz, 1H), 4.68 (s,
2H), 4.91 (d, J = 1.5 Hz, 1H), 4.96 (d, J = 14.0 Hz, 1H),
5.13 (d, J = 14.0 Hz, 1H), 5.33 (s, 2H), 5.46–5.48 (m, 1H),
5.63 (s, 1H), 7.23–7.56 (m, 18H), 8.00 (d, J = 7.7 Hz, 1H).
13C NMR (63 MHz, CDCl3) δ: 27.1, 27.3, 27.3, 64.2, 66.9,
67.8, 69.0, 69.4, 72.0, 74.2, 78.9, 99.0, 101.7, 126.3, 127.5,
127.6, 127.7, 127.8, 128.4, 128.4, 128.4, 128.7, 130.0,
130.9, 132.7, 136.0, 137.6, 138.3, 139.5, 166.7, 177.7.
ACB 4,6-O-benzylidene-3-O-p-methoxybenzyl-␣-D-
mannopyranoside (19)
A solution of 18 (523 mg, 1.18 mmol) and Bu2SnO
(324 mg, 1.30 mmol) in MeOH (40 mL) was stirred at 50 °C
for 2 h. After removal of the solvent in vacuo, the residue
was dissolved in DMF (10 mL) and then PMBCl (0.27 mL,
2.01 mmol) was added to the reaction mixture. After stirring
at 90 °C for 1 h, the reaction mixture was quenched with
H2O and then extracted with EtOAc. The combined organic
layer was washed with satd. aq. NH4Cl and brine, dried over
MgSO4, and concentrated in vacuo. The residue was purified
by flash column chromatography (hexane–EtOAc, 2:1) to af-
ford compound 19 (565 mg, 85%) as a colorless oil. Rf 0.28
BCB 3,4-di-O-benzyl-2-O-pivaloyl-␣-D-mannopyranoside (3)
To a solution of 15 (61 mg, 0.09 mmol) in THF (2 mL)
was added BH3–THF (0.91 mL) and Bu2BOTf (0.09 mL) at
0 °C. After stirring at 0 °C for 3 h, the reaction mixture was
quenched with Et3N (0.2 mL) and stirred at rt for another
hour. The reaction mixture was diluted with MeOH and then
concentrated in vacuo. The residue was purified by flash col-
umn chromatography (hexane–EtOAc, 3:1) to afford the
compound 3 (53 mg, 87%) as a colorless oil. Rf 0.3 (hexane–
EtOAc, 3:1, v/v). [α]20 +42.9° (c 6.75, CHCl3). IR (CHCl3,
D
film, cm–1): 3531, 3037, 2981, 2935, 2874, 1734, 1459,
(hexane–EtOAc, 2:1, v/v). [α]20 +61.2° (c 0.1, CHCl3). IR
D
1
1260, 1143, 1062, 746, 700. H NMR (250 MHz, CDCl3) δ:
(CHCl3, film, cm–1): 3486, 2930, 2912, 1718, 1611, 1513,
1
1.23 (s, 9H), 3.70–3.87 (m, 4H), 4.06 (dd, J = 3.2, 10.1 Hz,
1H), 4.53 and 4.89 (ABq, J = 12.0 Hz, 2H), 4.63 and 4.72
(ABq, J = 12.0 Hz, 2H), 4.91 (s, 1H), 4.94 and 5.09 (ABq,
J = 14.0 Hz, 2H), 5.32 (s, 2H), 5.42 (dd, J = 1.2, 1.3 Hz,
1H), 7.23–7.54 (m, 18H), 8.00 (d, J = 7.5 Hz, 1H). 13C
NMR (63 MHz, CDCl3) δ: 27.3, 39.1, 62.1, 66.9, 67.6, 68.1,
71.5, 72.1, 73.9, 75.3, 78.3, 97.9, 127.4, 127.7, 127.8, 127.9,
128.1, 128.2, 128.3, 128.4, 128.5, 128.7, 130.8, 132.6,
135.9, 138.1, 138.2, 139.5, 166.7, 177.6. Anal. calcd. for
C40H44O9: C 71.84, H 6.63; found: C 71.80, H 6.65.
1451, 1376, 1251, 1134, 1034, 916, 820, 747, 700. H NMR
(250 MHz, CDCl3) δ: 3.04 (br s, 1H), 3.74 (s, 3H) 3.83–3.88
(m, 2H), 3.96 (dd, J = 3.3, 7.5 Hz, 1H), 4.05–4.16 (m, 2H),
4.26 (dd, J = 2.7, 8.0 Hz, 1H), 4.64 and 4.79 (ABq, J =
11.3 Hz, 2H) 4.77 (d, J = 5.5 Hz, 2H), 4.92 and 5.13 (ABq,
J = 14.0 Hz, 2H), 4.97 (s, 1H), 5.23–5.29 (m, 1H), 5.35–
5.43 (m, 1H), 5.59 (s, 1H), 5.93–6.09 (m, 1H), 6.85 (d, J =
8.5 Hz, 2H), 7.25–7.54 (m, 10H), 7.99 (d, J = 7.7 Hz, 1H).
13C NMR (63 MHz, CDCl3) δ: 55.2, 63.7, 65.6, 67.5, 68.8,
70.7, 72.8, 75.5, 78.8, 100.0, 101.5, 113.8 (2), 118.5, 126.0,
127.4, 127.9, 128.2 (2), 128.3, 128.5, 128.9, 129.6(2), 130.1,
130.7, 132.1, 132.4, 137.6, 139.5, 159.4, 166.5.
ACB 2,3,4,6-tetra-O-acetyl-␣-D-mannopyranoside (16)
The title compound 16 was prepared from 8 according to
the known procedure (11) in 86% yield. Rf 0.2 (hexane–
ACB 4,6-O-benzylidene-2-azido-2-deoxy-3-O-p-
methoxybenzyl-␣-D-glucopyranoside (21)
EtOAc, 2:1, v/v). [α]20 +60.8° (c 0.2, CHCl3). IR (CHCl3,
D
film, cm–1): 3474, 3077, 2953, 1752, 1436, 1370, 1248,
1227, 1139, 1050, 978, 797, 744. 1H NMR (250 MHz,
CDCl3) δ: 2.01 (s, 3H), 2.04 (s, 3H), 2.09 (s, 3H), 2.16 (s,
3H), 4.03–4.14 (m, 2H), 4.31 (dd, J = 5.1, 12.3 Hz, 1H),
4.96 (d, J = 1.5 Hz, 1H), 4.98 (d, J = 13.8 Hz, 1H), 5.18 (d,
J = 13.8 Hz, 1H), 5.33 (s, 2H), 5.34 (t, J = 9.9 Hz, 1H), 5.38
(dd, J = 1.5, 3.3 Hz, 1H), 5.44 (dd, J = 3.3, 9.9 Hz, 1H),
7.30–7.46 (m, 6H), 7.56 (td, Jt = 8.1 Hz, Jd = 1.5 Hz, 1H),
To a solution of 20 (310 mg, 0.45 mmol), which was pre-
pared from 19 according to the known procedure (17), in
DMF (10 mL) was added sodium azide (116 mg,
1.79 mmol). After stirring at 40 °C for 10 h, the reaction
mixture was quenched with NH4Cl and then extracted with
EtOAc. The combined organic layer was washed with brine,
dried over MgSO4, and concentrated in vacuo. The residue
was purified by flash column chromatography (hexane–
© 2006 NRC Canada

Lee et al.
513
EtOAc, 3:1) to afford compound 21 (89 mg, 34%) as a col-
orless oil. Rf 0.53 (hexane–EtOAc, 2:1, v/v). [α]20D +81.0° (c
0.1, CHCl3). IR (CHCl3, film, cm–1): 3704, 3580, 3411,
2921, 2865, 2553, 2392, 2106, 1716, 1613, 1514, 1452,
1371, 1257, 1139, 1086, 1036, 971, 738, 696. 1H NMR
(250 MHz, CDCl3) δ: 3.46 (dd, J = 3.6, 9.9 Hz, 1H), 3.69–
3.77 (m, 2H), 3.79 (s, 3H), 3.87–3.99 (m, 1H), 4.16 (t, J =
9.5 Hz, 1H), 4.28 (dd, J = 4.5, 5.5 Hz, 1H), 4.76 and 4.91
(ABq, J = 10.5 Hz, 2H), 4.81 (d, J = 5.7 Hz, 2H), 5.02 and
5.19 (ABq, J = 14.2 Hz, 2H), 5.05 (s, 1H), 5.27–5.32 (m,
1H), 5.38–5.45 (m, 1H), 5.59 (s, 1H), 5.96–6.12 (m, 1H),
6.86 (d, J = 8.6 Hz, 2H), 7.31–7.75 (m, 10H), 8.04 (d, J =
7.8 Hz, 1H). 13C NMR (63 MHz, CDCl3) δ: 29.8, 55.4, 63.1,
63.3, 65.8, 67.9, 69.0, 74.9, 76.2, 82.9, 98.3, 101.5, 113.9,
118.6, 126.1 (2), 127.5, 127.9, 128.4, 129.1, 130.0 (2),
130.1, 130.8, 132.2, 132.8, 137.3, 139.6, 159.5, 166.5.
HRMS calcd. for [M + Na]+: 610.2165; found: 610.2186.
2H), 4.27–4.34 (m, 1H), 4.24–4.33 (m, 2H), 4.80 (d, J =
5.6 Hz, 2H), 5.03 and 5.22 (ABq, J = 14.0 Hz, 2H), 5.08 (t,
J = 10.0 Hz, 1H), 5.16 (t, J = 3.5 Hz, 1H), 5.28–5.33 (m,
1H), 5.38–5.45 (m, 1H), 5.93–6.12 (m, 1H), 7.37–7.73 (m,
3H), 8.05 (d, J = 6.9 Hz, 1H). 13C NMR (63 MHz, CDCl3)
δ: 20.8, 20.9 (2), 61.3, 61.9, 65.8, 67.9, 68.3, 68.7, 70.8,
97.6, 118.7, 127.8, 128.1, 128.2, 130.9, 132.2, 132.9, 139.0,
166.4, 169.8, 170.2, 170.8. Anal. calcd. for C23H27N3O10: C
54.56, H 5.38, N 8.31; found: C 54.56, H 5.36, N 8.51.
ACB 4,6-O-benzylidene-2-azido-2-deoxy-␣-D-
glucopyranoside (7) (from 25)
To a solution of 25 (700 mg, 1.38 mmol) in MeOH
(10 mL) was added NaOMe (8 mg, 0.15 mmol) at 0 °C. Af-
ter stirring at 0 °C for 2 h, the reaction mixture was neutral-
ized with DOWEX-MAC-3 (H+ mode), filtered through Celite,
and concentrated in vacuo. The residue was purified by flash
column chromatography (CHCl3–MeOH, 9:1) to afford the
trihydroxy intermediate (478 mg, 91%) as a white solid.
The trihydroxy intermediate (300 mg, 0.79 mmol) was
dissolved in DMF (5 mL) and then benzaldehyde dimethyl-
acetal (0.14 mL, 0.87 mmol) and camphorsulfonic acid
(10 mg, 0.04 mmol) were added to the solution. After stir-
ring at 50 °C for 2 h, the reaction mixture was quenched
with satd. aq. NaHCO3 and then extracted with EtOAc. The
combined organic layer was washed with satd. aq. NH4Cl
and brine, dried over MgSO4, and concentrated in vacuo.
The residue was purified by flash column chromatography
(hexane–EtOAc, 3:1) to afford compound 7 (259 mg, 70%)
as a colorless oil.
ACB 4,6-O-benzylidene-2-azido-2-deoxy-␣-D-
glucopyranoside (7) (from 21)
To a solution of 21 (42 mg, 0.071 mmol) in CH2Cl2–H2O
(2.2 mL, 10:1, v/v) was added DDQ (32 mg, 0.14 mmol).
After stirring at rt for 3 h, the reaction mixture was
quenched with satd. aq. NaHCO3 and then extracted with
CH2Cl2. The combined organic layer was washed with satd.
aq. NaHCO3 and brine, dried over MgSO4, and concentrated
in vacuo. The residue was purified by flash column chroma-
tography (hexane–EtOAc, 3:1) to afford compound 7
(31 mg, 92%) as a colorless oil. Rf 0.25 (hexane–EtOAc, 3:1,
v/v). [α]20 +112.0° (c 0.1, CHCl3). IR (CHCl3, film, cm–1):
D
3583, 3387, 2915, 2864, 2107, 1716, 1261, 1139, 1089,
1
1030, 739, 699. H NMR (250 MHz, CDCl3) δ: 2.96 (br s,
ACB (3-O-benzyl-4,6-O-benzylidene-2-O-p-
1H), 3.36 (dd, J = 3.6, 10.0 Hz, 1H), 3.54 (t, J = 9.2 Hz 1H),
3.72 (t, J = 10.2 Hz, 1H), 3.85–3.95 (m, 1H), 4.24–4.33 (m,
2H), 4.81 (d, J = 5.7 Hz, 2H), 5.02 and 5.20 (ABq, J =
14.2 Hz, 2H), 5.07 (d, J = 3.6 Hz, 1H), 5.27–5.32 (m, 1H),
5.38–5.45 (m, 1H), 5.53 (s, 1H), 5.96–6.12 (m, 1H), 7.35–
7.75 (m, 8H), 8.04 (d, J = 6.9 Hz, 1H). 13C NMR (63 MHz,
CDCl3) δ: 29.8, 62.7, 63.4, 65.8, 68.1, 69.1, 81.9, 98.3,
102.2, 118.6, 126.4 (2), 127.6, 127.9, 128.5 (2), 129.5, 130.9,
132.2 (2), 132.9, 137.0, 139.5, 166.5. Anal. calcd. for
C24H25N3O7: C 61.66, H 5.39, N 8.99; found: C 61.87, H
5.58, N 9.16.
methoxybenzyl-␤-D-mannopyranosyl)-(1→3)-4,6-O-
benzylidene-2-azido-2-deoxy-␣-D-glucopyranoside (26)
A solution of donor 6 (55 mg, 0.089 mmol) and DTBMP
(44 mg, 0.26 mmol) in CH2Cl2 (5 mL) in the presence of
4 Å molecular sieves was stirred for 30 min at rt and cooled
to –78 °C, then Tf2O (18 µL, 0.11 mmol) was added. After
the resulting solution was stirred at –78 °C for 10 min,
acceptor 7 (50 mg, 0.11 mmol) was added and stirred at
–78 °C for 1 h and allowed to warm over 2 h to 0 °C. The
reaction mixture was quenched with satd. aq. NaHCO3 and
then extracted with CH2Cl2. The combined organic layer
was washed with satd. aq. NaHCO3 and brine, dried over
MgSO4, and concentrated in vacuo. The residue was purified
by flash column chromatography (hexane–EtOAc, 3:1) to af-
ford compound 26 (61 mg, 73%, α:β = 1:4) as a colorless
ACB 3,4,6-tri-O-acetyl-2-azido-2-deoxy-␣-D-
glucopyranoside (25)
A solution of 24 (650 mg, 1.85 mmol), allyl 2-
(hydroxymethyl)benzoate (550 mg, 2.9 mmol), and DMAP
(350 mg, 2.9 mmol) in CH2Cl2 (15 mL) was added to a solu-
tion of AgClO4 (640 mg, 3.1 mmol) in CH2Cl2 (20 mL) at rt
via cannula. After stirring at rt for 3 h, the reaction mixture
was quenched with satd. aq. Na2S2O3 and then filtered
through Celite. The filtrate was washed with brine, dried
over MgSO4, and concentrated in vacuo. The residue was
purified by flash column chromatography (hexane–EtOAc,
3:1) to afford compound 25 (900 mg, 91%) as a colorless
oil. Rf 0.20 (hexane–EtOAc, 3:1, v/v). [α]20 +37.0° (c 0.1,
D
CHCl3). IR (CHCl3, film, cm–1): 2922, 2855, 2105, 1717,
1
1513, 1454, 1373, 1251, 1095, 1037, 744, 698. H NMR
(250 MHz, CDCl3) δ: 3.19 (m, 1H), 3.39 (dd, J = 3.7,
9.9 Hz, 1H), 3.57 (dd, J = 3.1, 9.8 Hz, 1H), 3.70 (d, J =
9.4 Hz, 1H), 3.76–3.82 (m, 2H), 3.77 (s, 3H), 3.86–3.94 (m,
2H), 4.03 (d, J = 2.9 Hz, 2H), 4.06–4.30 (m, 4H), 4.56 and
4.71 (ABq, J = 12.5 Hz, 2H), 4.75 (s, 1H), 4.80 and 4.90
(ABq, J = 11.7 Hz, 2H), 4.80 (t, J = 1.3 Hz, 1H), 4.83 (d,
J = 0.9 Hz, 1H), 5.04 and 5.20 (ABq, J = 13.9 Hz, 2H), 5.13
(d, J = 3.7 Hz, 1H), 5.28–5.46 (m, 2H), 5.54 (s, 2H), 5.97–
6.12 (m, 1H), 6.80 (d, J = 8.7 Hz, 2H), 7.28–7.72 (m, 20H),
8.05 (dd, J = 1.2, 7.8 Hz, 1H). 13C NMR (63 MHz, CDCl3)
δ: 29.9, 55.3, 63.1, 63.3, 65.8, 67.6, 68.2, 68.7, 68.9, 72.5,
oil. Rf 0.25 (hexane–EtOAc, 3:1, v/v). [α]20 +145.0° (c 0.1,
D
CHCl3). IR (CHCl3, film, cm–1): 3480, 3352, 3077, 2946,
1
2222, 2113, 1754, 1718, 1450, 1238, 1050, 742. H NMR
(250 MHz, CDCl3) δ: 2.04 (s, 3H), 2.10 (s, 3H), 3.44 (dd,
J = 3.5, 10.5 Hz, 1H), 3.85–3.95 (m, 1H), 4.02–4.15 (m,
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514
Can. J. Chem. Vol. 84, 2006
74.7, 77.0, 78.0, 78.5, 80.6, 98.3, 101.4, 101.6, 102.6, 113.5
(2), 118.6, 126.1 (2), 126.2 (2), 127.6 (3), 127.7, 128.1,
128.2 (3), 128.3 (2), 128.4 (2), 128.9, 129.3, 130.1 (2),
130.9 (2), 132.2, 132.8, 137.1, 137.7, 138.5, 139.2, 159.2,
166.4. Anal. calcd. for C52H53N3O13: C 67.30, H 5.76, N
4.53; found: C 67.41, H 5.73, N 4.26.
9.8 Hz, 1H), 4.59 (m, 1H), 4.68 and 4.87 (ABq, J = 12.6 Hz,
2H), 4.79 (d, J = 5.6 Hz, 2H), 4.82 (s, 1H), 5.01 and 5.13
(ABq, J = 13.6 Hz, 2H), 5.09 (d, J = 3.0 Hz, 1H), 5.24 (s,
1H), 5.29 (d, J = 10.0 Hz, 1H), 5.38 (s, 1H), 5.39 (d, J =
17.5 Hz, 1H), 5.58 (s, 1H), 5.64 (s, 1H), 5.66 (s, 1H), 5.99–
6.05 (m, 1H), 7.15–7.66 (m, 28H), 8.01 (d, J = 7.5 Hz, 1H).
13C NMR (125 MHz, CDCl3) δ: 28.3, 29.8, 38.3, 63.5, 64.0,
65.7, 67.5, 68.1, 68.4, 68.9, 70.1, 72.4, 73.1, 74.1, 74.3,
74.9, 78.0, 78.7, 79.1, 79.4, 98.3, 99.4, 99.7, 100.3, 101.2,
101.7, 118.6, 126.1, 126.2, 127.5, 127.6, 127.8, 128.1,
128.2, 128.3, 128.5, 128.8, 128.9, 129.0, 130.9, 132.2,
132.8, 137.6, 137.8, 138.4, 138.5, 139.1, 166.5, 171.8,
206.2. MALDI-TOF calcd. for [M + Na]+: 1268.4579;
found: 1268.4485.
ACB (3-O-benzyl-4,6-O-benzylidene-␤-D-
mannopyranosyl)-(1→3)-4,6-O-benzylidene-2-azido-2-
deoxy-␣-D-glucopyranoside (5)
To a solution of 26 (85 mg, 0.09 mmol) in CH2Cl2–H2O
(4.4 mL, 10:1, v/v) was added DDQ (42 mg, 0.18 mmol).
After stirring at rt for 1.5 h, the reaction mixture was
quenched with satd. aq. NaHCO3 and then extracted with
CH2Cl2. The combined organic layer was washed with satd.
aq. NaHCO3 and brine, dried over MgSO4, and concentrated
in vacuo. The residue was purified by flash column chroma-
tography (hexane–EtOAc, 2:1) to afford compound 5
(63 mg, 85%) as a colorless oil. Rf 0.18 (hexane–EtOAc, 2:1,
CB (3-O-Benzyl-4,6-O-benzylidene-2-O-levulinyl-␣-D-
mannopyranosyl)-(1→2)-(3-O-benzyl-4,6-O-benzylidene-
␤-D-mannopyranosyl)-(1→3)-4,6-O-benzylidene-2-azido-
2-deoxy-␣-D-glucopyranoside (27)
v/v). [α]20 +81.8° (c 0.1, CHCl3). IR (CHCl3, film, cm–1):
To a solution of 2 (34 mg, 0.027 mmol) and (Ph3P)4Pd
(3 mg, 0.003 mmol) in THF (3 mL) was added morpholine
(24 µL, 0.27 mmol). After stirring at rt for 1 h, the reaction
mixture was diluted with EtOAc. The organic solution was
washed with aq. 1 N HCl and brine, dried over MgSO4, and
concentrated in vacuo. The residue was purified by flash col-
umn chromatography (hexane–EtOAc, 1:1) to afford com-
pound 27 (25 mg, 77%) as a white solid. Rf 0.05 (hexane–
D
3498, 3064, 2921, 2106, 1717, 1453, 1378, 1258, 1094,
1
1039, 1010, 796, 745, 698. H NMR (250 MHz, CDCl3) δ:
2.76 (br s, 1H), 3.29 (m, 1H), 3.65 (dd, J = 3.3, 9.5 Hz, 1H),
3.68–3.85 (m, 2H), 3.91 (dd, J = 4.3, 9.7 Hz, 1H), 4.07–4.35
(m, 5H), 4.75 and 4.84 (ABq, J = 12.3 Hz, 2H), 4.79 (t, J =
12.3 Hz, 1H), 4.82 (s, 2H), 5.03 and 5.18 (ABq, J =
12.9 Hz, 2H), 5.12 (d, J = 3.6 Hz, 1H), 5.27–5.44 (m, 2H),
5.52 (s, 1H), 5.54 (s, 1H), 5.96–6.11 (m, 1H), 7.27–7.71 (m,
18H), 8.04 (d, J = 6.8 Hz, 1H). 13C NMR (63 MHz, CDCl3)
δ: 60.47, 63.1, 63.3, 65.7, 67.0, 68.1, 68.6, 68.8, 70.0, 72.6,
76.6, 76.8, 78.2, 80.4, 98.1, 101.0, 101.4, 101.5, 118.6,
126.0, 126.1, 127.7, 127.9, 128.0, 128.2, 128.3, 128.5,
129.0, 129.2, 130.9, 132.1, 132.8, 132.8, 137.1, 137.5,
138.0, 139.1, 166.4. MALDI-TOF calcd. for [M + Na]+:
846.2640; found: 846.2263.
EtOAc, 2:1, v/v). [α]20 +4.0° (c 0.1, CHCl3). IR (CHCl3,
D
film, cm–1): 3350, 2923, 2854, 2393, 2105, 1718, 1602,
1454, 1371, 1095, 1028, 916, 750, 698. 1H NMR (250 MHz,
CDCl3) δ: 2.14 (s, 3H), 2.57–2.75 (m, 4H), 3.31–3.46 (m,
3H), 3.65–3.72 (m, 2H), 3.86–3.98 (m, 5H), 4.02–4.15 (m,
4H), 4.25 (s, 2H), 4.30–4.42 (m, 2H), 4.55–4.62 (m, 1H),
4.67 and 4.88 (ABq, J = 12.4 Hz, 2H), 4.82 (s, 1H), 5.01
and 5.21 (ABq, J = 13.6 Hz, 2H), 5.12 (d, J = 3.8 Hz, 2H),
5.38 (s, 1H), 5.59 (br s, 1H), 5.66 (d, J = 6.3 Hz, 2H), 7.15–
7.66 (m, 29H), 8.01 (d, J = 7.5 Hz, 1H). 13C NMR
(125 MHz, CDCl3) δ: 28.3, 29.8, 30.0, 38.3, 30.0, 63.3,
64.0, 66.9, 67.4, 67.7, 68.3, 68.8, 70.0, 71.6, 72.4, 73.0,
73.9, 74.4, 75.4, 77.4, 77.9, 78.6, 79.1, 79.3, 97.9, 98.1,
99.4, 99.7, 100.3, 101.0, 101.6, 126.1, 126.2, 127.5, 127.6,
127.7, 128.0, 128.1, 128.2, 128.3, 128.4, 128.5, 128.8,
128.9, 129.1, 130.8, 132.7, 136.0, 137.6, 137.8, 138.1,
138.3, 138.4, 138.5, 139.5, 166.7, 171.8, 177.7, 206.4.
MALDI-TOF calcd. for [M + Na]+: 1228.4266; found:
1228.4352.
ACB (3-O-benzyl-4,6-O-benzylidene-2-O-levulinyl-␣-D-
mannopyranosyl)-(1→2)-(3-O-benzyl-4,6-O-benzylidene-
␤-D-mannopyranosyl)-(1→3)-4,6-O-benzylidene-2-azido-
2-deoxy-␣-D-glucopyranoside (2)
A solution of donor 4 (53 mg, 0.089 mmol), acceptor 5
(60 mg, 0.065 mmol), and DTBMP (27 mg, 0.13 mmol) in
CH2Cl2 (5 mL) in the presence of 4 Å molecular sieves was
stirred for 30 min at rt and cooled to –78 °C. After addition
of Tf2O (18 µL, 0.11 mmol), the resulting solution was
stirred at –78 °C for 1 h and allowed to warm over 3 h to
10 °C. The reaction mixture was quenched with satd. aq.
NaHCO3 and then extracted with CH2Cl2. The combined or-
ganic layer was washed with satd. aq. NaHCO3 and brine,
dried over MgSO4, and concentrated in vacuo. The residue
was purified by flash column chromatography (hexane–
EtOAc–CH2Cl2, 5:2:1) to afford compound 2 (41 mg, 44%)
BCB (3-O-benzyl-4,6-O-benzylidene-2-O-levulinyl-␣-D-
mannopyranosyl)-(1→2)-(3-O-benzyl-4,6-O-benzylidene-
␤-D-mannopyranosyl)-(1→3)-(4,6-O-benzylidene-2-azido-
2-deoxy-␣-D-glucopyranosyl)-(1→6)-3,4-di-O-benzyl-2-O-
pivaloyl-␣-D-mannopyranoside (28)
A solution of donor 27 (18 mg, 0.015 mmol), acceptor 3
(12 mg, 0.018 mmol), and DTBMP (7 mg, 0.036 mmol) in
CH2Cl2 (5 mL) in the presence of 4 Å molecular sieves was
stirred for 30 min at rt and cooled to –78 °C. After addition
of Tf2O (3 µL, 0.018 mmol), the resulting solution was
stirred at –78 °C for 1 h and allowed to warm over 3 h to
10 °C. The reaction mixture was quenched with satd. aq.
NaHCO3 and then extracted with CH2Cl2. The combined or-
ganic layer was washed with satd. aq. NaHCO3 and brine,
as a colorless oil. Rf 0.8 (hexane–EtOAc, 1:1, v/v). [α]20
D
+37.3° (c 0.1, CHCl3). IR (CHCl3, film, cm–1): 3372, 2923,
2853, 2397, 2104, 1743, 1718, 1454, 1262, 1138, 1095,
1028, 916, 748, 698. 1H NMR (500 MHz, CDCl3) δ: 2.12 (s,
3H), 2.64–2.69 (m, 4H), 3.32–3.36 (m, 2H), 3.41 (dd, J =
3.6, 9.8 Hz, 1H), 3.65–3.70 (m, 2H), 3.82–3.89 (m, 4H),
3.97 (t, J = 9.6 Hz, 1H), 4.04 (dd, J = 4.6, 10.0 Hz, 1H),
4.15 (d, J = 10.0 Hz, 2H), 4.26–4.31 (m, 4H), 4.36 (t, J =
© 2006 NRC Canada

Lee et al.
515
dried over MgSO4, and concentrated in vacuo. The residue
was purified by flash column chromatography (hexane–
EtOAc–CH2Cl2, 5:2:1) to afford compound 28 (17 mg, 65%)
137.1, 138.0, 138.2, 138.4, 138.6, 138.8, 139.3, 167.3,
177.3, 171.8, 171.8, 206.1. MALDI-TOF calcd. for [M +
Na]+: 1760.6979; found: 1760.6322.
as a colorless oil. Rf 0.25 (hexane–EtOAc, 2:1, v/v). [α]20
D
–0.2° (c 0.1, CHCl3). IR (CHCl3, film, cm–1): 3350, 2923,
2853, 2105, 1721, 1658, 1602, 1454, 1371, 1259, 1137,
1094, 748, 698. 1H NMR (250 MHz, CDCl3) δ: 1.25 (s, 9H),
2.14 (s, 3H), 2.59–2.68 (m, 4H), 3.24–3.37 (m, 3H), 3.63–
3.71 (m, 2H), 3.77–3.87 (m, 7H), 3.96 (t, J = 9.5 Hz, 1H),
4.05–4.30 (m, 10H), 4.39 (t, J = 9.4 Hz, 1H), 4.50 and 4.70
(ABq, J = 11.0 Hz, 2H), 4.63 (q, J = 5.7 Hz, 3H), 4.80 (d,
J = 15.1 Hz, 2H), 4.88–4.95 (m, 3H), 5.14 (d, J = 3.2 Hz,
1H), 5.21 (s, 1H), 5.31 (d, J = 1.6 Hz, 2H), 5.39 (s, 1H),
5.46–5.48 (m, 1H), 5.57–5.59 (m, 1H), 5.66 (s, 2H), 7.12–
7.52 (m, 43H), 7.98 (d, J = 7.5 Hz, 1H). 13C NMR (63 MHz,
CDCl3) δ: 28.3, 29.8, 38.3, 60.57, 63.5, 64.0, 67.4, 68.3,
68.8, 70.0, 72.4, 73.0, 74.1, 74.3, 74.9, 77.9, 78.7, 79.6,
79.1, 79.3, 98.3, 99.4, 99.7, 100.3, 101.2, 101.7, 118.6,
126.1, 126.2, 127.5, 127.6, 127.8, 128.1, 128.2, 128.3,
128.5, 128.8, 128.9, 129.0, 130.9, 132.2, 132.8, 137.6,
137.8, 138.4, 138.5, 139.1, 171.4, 171.8, 206.5. MALDI-
TOF calcd. for [M + Na]+: 1744.6778; found: 1744.6571.
Acknowledgement
This work was supported by a grant from the Korea Sci-
ence and Engineering Foundation through the Center for
Bioactive Molecular Hybrids (CBMH).
References
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␤-D-mannopyranosyl)-(1→3)-(4,6-O-benzylidene-2-
acetamido-2-deoxy-␣-D-glucopyranosyl)-(1→6)-3,4-di-O-
benzyl-2-O-pivaloyl-␣-D-mannopyranoside (1)
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A
solution of 28 (10 mg, 0.006 mmol) and
triphenylphosphine (9 mg, 0.035 mmol) in THF (1.5 mL)
and H2O (0.15 mL) was stirred at rt for 3 h. The reaction
mixture was diluted with EtOAc, and then washed with
brine, dried over MgSO4, and concentrated in vacuo. The
residue was dissolved in pyridine (1 mL) and acetic anhy-
dride (5 µL, 0.046 mmol) was added. After stirring at rt for
1 h, the reaction mixture was diluted with EtOAc. The re-
sulting solution was washed with aq. 1 N HCl, H2O, and
brine, subsequently, then dried over MgSO4, and concen-
trated in vacuo. The residue was purified by flash column
chromatography (hexane–EtOAc, 1:1) to afford compound 1
(6 mg, 58%) as a colorless oil. Rf 0.25 (hexane–EtOAc, 1:1,
v/v). [α]20 +0.1° (c 0.1, CHCl3). IR (CHCl3, film, cm–1):
3350, 292D3, 2853, 1721, 1658, 1602, 1454, 1371, 1259,
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1137, 1094, 1036, 748, 698. H NMR (500 MHz, CDCl3) δ:
1.19 (s, 9H), 1.79 (s, 3H), 2.11 (s, 3H), 2.62–2.64 (m, 4H),
2.98–3.00 (m, 1H), 3.09–3.11 (m, 2H), 3.20 (t, J = 9.5 Hz,
2H), 3.59 (d, J = 8.0 Hz, 1H), 3.70–3.76 (m, 2H), 3.82–3.89
(m, 4H), 3.92–4.05 (m, 4H), 4.08–4.23 (m, 6H), 4.41 (m,
1H), 4.47 (d, J = 5.5 Hz, 1H), 4.53–4.63 (m, 4H), 4.72–4.80
(m, 2H), 4.83–4.90 (m, 3H), 5.16 (s, 2H), 5.26–5.35 (m,
3H), 5.44 (s, 1H), 5.52 (s, 1H), 5.63 (s, 2H), 5.71 (s, 3H),
6.12 (d, J = 9.5 Hz, 1H), 7.12–7.52 (m, 43H), 7.93 (d, J =
7.5 Hz, 1H). 13C NMR (125 MHz, CDCl3) δ: 27.4, 29.8,
38.3, 42.3, 46.0, 53.2, 63.4, 63.5, 63.7, 67.2, 67.4, 67.6,
68.0, 68.1, 68.3, 68.4, 68.4, 68.7, 68.9, 68.8, 70.2, 71.1,
71.7, 72.6, 72.8, 73.6, 74.2, 74.6, 75.3, 78.7, 79.4, 97.8,
99.0, 99.3, 99.7, 100.1, 100.7, 101.7, 126.2, 127.5, 127.8,
128.1, 128.4, 128.8, 130.0, 130.6, 131.0, 132.7, 135.6,
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© 2006 NRC Canada