Synthesis of a 2,3-di-O-substituted heptose structure by regioselective 3-O-silylation of a 2-O-substituted heptose derivative

Article abstract of DOI:10.1002/ejoc.200300652

A 3,4-diol derivative of 2-O-benzyl (Bn) heptose (Hep), methyl 6,7-di-O-acetyl-2-O-benzyl-L-glycero-α-D-manno-heptopyranoside (3), was treated with both triethylsilyl (TES) and tert-butyldimethylsilyl (TBDMS) chlorides to regioselectively form the 3-O-sil

Full text of DOI:10.1002/ejoc.200300652

FULL PAPER
Synthesis of a 2,3-Di-O-substituted Heptose Structure by Regioselective
3-O-Silylation of a 2-O-Substituted Heptose Derivative
Kazuyuki Ishii,[a] Yasuaki Esumi,[b] Youhei Iwasaki,[a] and Ryohei Yamasaki*[a]
Keywords: Glycosylation / Lipooligosaccharide / Lipopolysaccharide / Oligosaccharides / Regioselective silylation
A 3,4-diol derivative of 2-O-benzyl (Bn) heptose (Hep),
methyl 6,7-di-O-acetyl-2-O-benzyl- -glycero-α- -manno-
heptopyranoside (3), was treated with both triethylsilyl (TES)
acceptor 16 with per-O-benzylated β-lactosyl trichloroaceti-
midate 17, we obtained the desired 2,3-branched tetrasac-
charide, α-Lac-(1Ǟ3)-[α-GlcN3-(1Ǟ2)]-Hep 18a. Hydrogena-
L
D
and tert-butyldimethylsilyl (TBDMS) chlorides to regioselec- tion of 18a, followed by N-acetylation, gave α-Lac-(1Ǟ3)-[α-
tively form the 3-O-silyl ethers 4 and 6, respectively. To ex- GlcNAc-(1Ǟ2)]-Hep 22. Thus, we synthesized the 2,3-di-
amine whether silylation of the 3,4-diol of a 2-O-substituted
disaccharide also gives the corresponding 3-O-silylated dis-
branched Hep by utilizing the 2-O-substituted Hep. This re-
gioselective O-3-silylation of the 2-O-substituted Hep pro-
accharide, we synthesized α-GlcN3-(1Ǟ2)-Hep 11a by coup- vides an intermediate that can be utilized for the synthesis
ling a Hep 2-OH acceptor 9 with a GlcN3 trichloroacetimid-
ate 10. As expected from the results obtained using the 2-O-
Bn Hep 3, treatment of α-GlcN3-(1Ǟ2)-Hep-3,4-diol 14 with
TESCl followed by acetylation gave only the 3-O-TES 15.
Compound 14 was converted into the 3-OH acceptor 16 by
silylation/acetylation — without isolating 15 — and sub-
of not only 2,3- and 3,4-dibranched Hep but also the 2,3,4-
tribranched Hep structures present in lipooligo- and lipo-
polysaccharides produced by pathogenic Gram-negative
bacteria.
( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
sequent acid hydrolysis. By coupling the disaccharide 3-OH Germany, 2004)
Introduction
tively. The 2,3-dibranched structure is expressed in not only
Haemophilus LOS[16,17] but also in Campylobacter LOS.[1]
Therefore, it is important to establish a synthetic method-
ology for obtaining this branched structure.
Pathogenic Gram-negative bacteria such as the Neisserial
and Haemophilus species produce glycolipid antigens called
lipooligosaccharides (LOS).[1] LOS, which consist of the
oligosaccharide[2Ϫ6] (OS) moiety and the lipid A, are con-
sidered as vaccine targets against those pathogenic
bacteria.[7Ϫ11] A carbohydrate epitope within LOS pro-
duced by a strain of Neisseria gonorrhoeae 15253[8,9,11,12] is
one of those targets, and we have been focusing our efforts
in constructing the OS of 15253 LOS.[11,13,14]
In a recent paper, we described the synthesis of α-lacto-
syl-(1Ǟ3)-Hep by glycosidating methyl 2-O-Bn-4,6-O-
benzylidene-7,8-dideoxy-manno-oct-7-enopyranoside with a
per-O-benzylated β-lactosyl trichloroacetimidate to obtain
the α-lactosylated product as a reference compound.[14] The
resulting trisaccharide cannot, however, be directly utilized
for the synthesis of the 2,3-dibranched structure because
selective removal of the benzyl protecting group of O-2 can-
not be accomplished under hydrogenolysis conditions with-
out affecting the per-O-benzylated lactose residue at O-3.
To utilize a 2-O-Bn Hep derivative, which is readily avail-
able from its mannose counterpart,[13] as a starting material
for the synthesis of the branched Hep structures, we exam-
ined the selective protection of the 3-OH group of the 2-O-
substituted Hep containing unprotected hydroxy groups at
both the C-3 and C-4 positions. We found that treating the
3-OH group of the 2-O-Bn-Hep-3,4-diol with silyl chlorides
gave the corresponding 3-O-silylated products in high
yields. Similarly, silylation of a 3,4-diol derivative of α-
GlcN3-(1Ǟ2)-Hep gave only the 3-O-silylated product. By
using this selective 3-O-silylation of the 3,4-diol, we synthe-
sized the desired 2,3-dibranched structure expressed in
15253 LOS.[12]
The OS of 15253 LOS[12] contains two dibranched hep-
tose (Hep) residues: 3,4- and 2,3-dibranched Hep. The syn-
thesis of the former structure is described in the preceding
paper;[15] this paper describes the construction of the latter.
The 2,3-dibranched Hep expressed in 15253 LOS is a tetra-
saccharide, and N-acetyl--glucosamine (GlcNAc) and lac-
tose (Lac) are α(1Ǟ2)- and α(1Ǟ3)-linked to Hep, respec-
[a]
Department of Biochemistry
University,
&
Biotechnology, Tottori
Koyama-Minami 4-101, Tottori City,
Tottori-Ken 680-8553, Japan
Fax: (internat.) ϩ 81-857-31-5347
E-mail: yamasaki@muses.tottori-u.ac.jp
[b]
The Institute of Physical and Chemical Research (RIKEN)
Wako-shi,
Saitama 351-0198, Japan
1214
 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
DOI: 10.1002/ejoc.200300652
Eur. J. Org. Chem. 2004, 1214Ϫ1227

Synthesis of a 2,3-Di-O-substituted Heptose Structure
FULL PAPER
The 3-O-TES ether of compound 5 was removed by treat-
ing it with 1% iodine (w/v) in methanol (MeOH)[22] at room
temperature to give the 3-OH product 8 in 88% yield.
Although de-O-silylation of the 3-O-TBDMS ether 7 did
not reach completion when using either I2/MeOH or tetra-
butylammonium fluoride (TBAF) buffered with acetic acid
(AcOH),[23] the TBDMS group was removed by treating 7
for 15 min in TFA/water (9:1, v/v)[24] to give 8 in 93% yield.
Compound 8 was also prepared from 3 in 91% yield by
sequentially carrying out the silylation, acetylation, and
subsequent hydrolysis steps without isolating 4 and 5. Thus,
we confirmed that silylation of the 3,4-diol of 2-O-Bn-Hep
3 proceeded regioselectively to give the 3-O-silylated com-
pound in high yields. We then examined whether a 3,4-diol
of α-GlcN3-(1Ǟ2)-Hep could be silylated regioselectively to
give the 3-O-protected product, a useful intermediate for
the synthesis of the 2,3-di-O-substituted Hep structure pre-
sent in 15253 LOS.[12]
Results and Discussion
The reactivity of the secondary hydroxy groups within
methyl α--mannoside towards silyl chlorides decreases in
the order 2-OH Ͼ 3-OH ϾϾ 4-OH, i.e., the 4-OH group is
the least active of the three.[18Ϫ21] The inactivity of the 4-
OH group of the mannoside prompted us to utilize a 2-O-
substituted manno-heptopyranoside to accomplish regiose-
lective silylation of the 3-OH group. To examine the reactiv-
ity of the 3-OH group against TESCl and TBDMSCl, we
used methyl 6,7-di-O-acetyl-2-O-benzyl--glycero-α--
manno-heptopyranoside (3) as a substrate (Scheme 1).
Prior to silylation, we examined glycosylation conditions
for the synthesis of α-GlcN3-(1Ǟ2)-Hep by coupling a
Hep acceptor
9
with 6-O-acetyl-2-azido-3,4-di-O-
benzyl-2-deoxy-β--glucopyranosyl
trichloroacetimidate
(10)[25] (Scheme 2).
The acceptor 9 was obtained in 97% yield after hydro-
genolysis of 2 over 10% Pd/C, and its structure was con-
Scheme 1. a) Ac2O, DMAP, pyridine, quantitative; b) TFA/water
(9:1, v/v), 91%; c) TESCl, pyridine, 0 °C, 90% or TBDMSCl, imi-
dazole, DMF, 94%; d) Ac2O, pyridine, 93%; e) Ac2O, DMAP, pyri-
dine, 97%; f) 1% (w/v) I2 in MeOH for 5, 88%; TFA/water (9:1, v/
v) for 7, 93%; g) 1. TESCl, pyridine; 2. Ac2O, pyridine; 3. TFA/
water (9:1, v/v), 91%
This 3,4-diol 3 was prepared in 91% yield by acetylation
of (3ЈS,4ЈS)-methyl 2-O-benzyl-3,4-O-(2Ј,3Ј-dimethoxy-
butane-2Ј,3Ј-diyl)--glycero-α--manno-heptopyranoside
(1)[13] in acetic anhydride (Ac2O)/pyridine and subsequent
hydrolysis of
2 in trifluoroacetic acid (TFA)/water
(Scheme 1). Treatment of the 3,4-diol 3 with 2.2 molar
equiv. of TESCl in pyridine at 0 °C for 10 min, followed by
chromatographic purification, gave only the 3-O-TES ether
4 in 90% yield. Similarly, the 3-O-TBDMS ether 6 was ob-
tained in 94% yield by treating 3 with 2 molar equiv. of
TBDMSCl and imidazole in N,N-dimethylformamide
(DMF) for 4.5 h at room temperature. The locations of the
silyl groups of 4 and 6 were also confirmed by NMR spec-
troscopy of their corresponding 4-O-acetates 5 and 7 that
were obtained upon acetylation with Ac2O/pyridine; the
signals of the H-4 protons of both 4 and 6 were deshielded
after acetylation (Table 1), which confirmed that the 3-OH
group was silylated.
Scheme 2
Eur. J. Org. Chem. 2004, 1214Ϫ1227
www.eurjoc.org
 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
1215

K. Ishii, Y. Esumi, Y. Iwasaki, R. Yamasaki
FULL PAPER
1
Table 1. H NMR (500 MHz) data recorded in CDCl3 at 25 °C for compounds 2Ϫ9, 11a, 11b, and 14Ϫ16
Compound[a]
Residue
H-1
H-2
H-3
H-4
H-5
H-6a
H-6b
H-7a
H-7b
(3J1,2
)
(3J2,3
)
(3J3,4
)
(3J4,5
)
(3J5,6a
)
(3J5,6b
)
(2J6a,6b
)
(3J6,7a
)
(3J6,7b
)
(2J7a,7b
)
2
3
4.75
(1.0)
4.81
(1.5)
4.73
(1.5)
4.73
(1.5)
4.73
(1.5)
4.74
(1.5)
4.82
(1.5)
4.79
(1.0)
4.77
(1.5)
5.41
(4.0)
4.87
(1.0)
4.50
(8.5)
4.80
3.69
(2.8)
3.75
(3.0)
3.60
(3.0)
3.64
(2.5)
3.61
(3.0)
3.64
(2.5)
3.74
(3.5)
3.92
(3.0)
3.97
(3.0)
3.23
(10.5)
4.02
(2.5)
3.55
(9.3)
3.86
n.d.
3.49
(10.3)
3.83
(3.0)
3.28
(10.0)
3.85
4.70
(10.5)
3.84
(9.5)
3.93
(9.0)
4.07
(10.0)
3.94
(9.0)
4.05
(9.5)
3.84
(10.0)
4.01
(10.3)
4.08
(10.0)
4.12
(9.0)
4.07
(10.0)
3.42
(9.5)
3.87
(9.5)
3.88
(9.0)
4.11
(10.0)
4.09
4.19
(10.0)
3.55
(9.5)
3.70
(10.0)
5.43
(10.0)
3.69
(10.0)
5.45
(10.0)
5.09
(10.0)
4.06
(10.0)
4.30
(10.3)
3.55
(10.3)
4.13
(10.0)
3.59
(9.5)
3.53
(9.8)
3.54
(10.0)
5.46
(10.5)
3.55
3.92
(2.0)
3.67
(1.5)
3.65
(1.5)
3.84
(2.0)
3.65
(1.5)
3.86
(2.5)
3.89
(2.0)
3.95
(1.5)
3.92
(1.5)
3.95
(5.0)
3.92
(1.5)
3.40
(3.5)
3.66
(1.5)
4.05
(4.5)
3.82
n.d.
5.45
Ϫ
5.44
Ϫ
5.49
Ϫ
5.21
Ϫ
5.48
Ϫ
5.21
Ϫ
5.32
Ϫ
5.44
Ϫ
5.46
Ϫ
4.24
(2.0)
5.44
Ϫ
4.22
(2.5)
5.43
Ϫ
4.22
(2.5)
5.13
Ϫ
Ϫ
Ϫ
Ϫ
Ϫ
Ϫ
Ϫ
Ϫ
Ϫ
Ϫ
Ϫ
Ϫ
Ϫ
Ϫ
Ϫ
Ϫ
Ϫ
4.24
(6.5)
4.31
(5.5)
4.31
(5.5)
4.21
(5.5)
4.31
(6.0)
4.21
(7.5)
4.25
(5.5)
4.24
(7.0)
4.23
(6.5)
4.31
(6.5)
4.38
(7.5)
4.35
(7.5)
4.34
(7.5)
4.35
(7.0)
4.34
(5.5)
4.34
(8.0)
4.32
(6.5)
4.31
(6.5)
(11.0)
(11.0)
(10.0)
(11.0)
(11.0)
(11.0)
(11.5)
(11.0)
(12.0)
4
5
6
7
8
9
11a
Hep
Ϫ
Ϫ
4.31
(12.0)
Ϫ
GlcN3
Hep
11b
14
4.24
(7.0)
4.32
(6.5)
Ϫ
(11.0)
(11.5)
(11.0)
(11.0)
GlcN3
Hep
4.42
(12.0)
Ϫ
4.30
(6.0)
4.32
(7.5)
(Ͻ 1.0)
5.06
(3.5)
4.81
(1.0)
5.02
(3.5)
4.85
Ϫ
GlcN3
Hep
4.31
(12.3)
Ϫ
15
4.18
(7.5)
4.33
(6.0)
Ϫ
GlcN3
Hep
4.08
n.d.
3.88
(2.0)
4.15
(5.0)
4.30Ϫ4.24
n.d.
5.27
Ϫ
4.24
(9.0)
3.92
(10.0)
3.99
(10.0)
5.13
(10.0)
3.56
n.d.
Ϫ
Ϫ
4.32
(12.0)
16
4.24
(8.0)
4.32
(5.5)
(1.5)
5.02
(4.0)
(3.0)
3.56
(10.0)
GlcN3
(9.5)
(10.3)
(2.5)
[a]
1
The H NMR spectroscopic chemical shifts (ppm) were determined by analyzing 2D NMR spectroscopic data (DQF-COSY, HMQC
1
and HMBC) comparatively, and the J couplings (Hz) were obtained by analyzing either the DQF-COSY or 1D NMR spectra. The H
NMR spectroscopic chemical shifts of other protons are listed in the Exp. Sect. n.d.: not determined.
firmed by the downfield and upfield shifts of the signals formed, which explains the lower recovery of the unreacted
of the H-2 proton (Table 1) and the C-2 carbon (Table 2), acceptor 9. In contrast, glycosylations in Et2O (Entries 3
respectively, that occurred upon removal of the benzyl pro- and 4) gave much better yields of 11a and 11b (77Ϫ80%)
tecting group. Table 3 summarizes the results of glycosyl- than those in 1,4-dioxane, although the N-glycoside 12 and
ation of the acceptor 9 with 1.6 molar equiv. of the donor the 2-O-TMS ether 13 were also isolated; the best yield
10 in either 1,4-dioxane[14,26,27] or Et2O[27Ϫ29] when using (80%) was obtained with the reaction using 0.04 molar
trimethylsilyl trifluoromethanesulfonate (TMSOTf) as a equiv. of TMSOTf (Entry 3). The ratio, however, of 11a and
promoter; the isolated yields of the (1Ǟ2)-linked disacchar- 11b in Et2O was ca. 3:1, and the glycosylations in this sol-
ides 11a and 11b were in the range 29Ϫ80%. The acceptor vent were not stereospecific when compared with the results
9 was first treated with 10 in 1,4-dioxane using 0.04 molar that had been reported previously.[27Ϫ29] The conditions for
equiv. of TMSOTf, i.e., conditions used previously for 3-O- α-selective glycosylation in the synthesis of 11a could be op-
α-lactosylation of a manno-oct-7-enopyranoside deriva- timized by utilizing a glycosyl fluoride or thioglycoside as a
tive.[14] The combined yield, however, of the glycosides 11a donor or by examining whether the use of a donor carrying
and 11b was only 29%, and the β-N-glycoside 12 (16%) was an electron-withdrawing substituent at O-3 would affect the
also obtained (Entry 1). The use of 0.2 molar equiv. of outcome of the stereospecificity of the reaction, as has
TMSOTf increased the yield slightly (Entry 2), and, in ad- been observed with glycosylation using a GlcN3 trichloro-
dition to 12, the 2-O-trimethylsilyl (TMS) derivative 13 was acetimidate derivative.[30]
1216
 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
Eur. J. Org. Chem. 2004, 1214Ϫ1227

Synthesis of a 2,3-Di-O-substituted Heptose Structure
FULL PAPER
Table 2. 13C NMR (125 MHz) data recorded in CDCl3 at 25 °C
for compounds 2Ϫ9, 11a, 11b, and 14Ϫ16
Compound[a] Residue C-1
C-2 C-3 C-4 C-5 C-6 C-7
2
3
100.5 75.2 69.0 62.6 68.7 67.6 61.7
98.8 77.2 70.8 67.5 70.6 73.0 62.6
99.9 78.0 73.3 62.7 71.1 69.2 62.7
100.2 78.1 71.2 67.8 69.0 67.3 62.3
100.0 77.4 72.8 67.0 71.2 69.2 62.7
100.3 78.0 71.3 67.7 69.0 67.3 62.3
100.2 78.1 71.2 67.8 69.0 67.3 62.3
101.3 69.5 68.3 62.1 68.2 67.5 61.6
100.2 73.0 68.6 62.3 68.7 67.1 61.6
4
5
6
7
8
9
11a
Hep
GlcN3 98.3 63.3 79.1 79.1 69.4 62.8
Hep 99.4 74.7 67.6 62.2 68.8 67.4 61.6
GlcN3 100.0 66.2 83.2 76.8 73.1 62.5
Hep 99.7 79.2 70.8 67.7 70.4 69.1 62.5
GlcN3 99.5 64.1 80.7 77.9 69.8 62.7
Hep 99.3 78.1 70.1 67.5 68.9 67.2 62.1
GlcN3 99.9 63.5 79.5 77.9 69.5 62.9
Hep 99.5 80.4 69.9 67.9 68.2 67.2 62.7
GlcN3 99.7 64.3 81.0 77.8 70.0 62.2
11b
14
15
16
The 13C NMR spectroscopic chemical shifts (ppm) were deter-
mined by analyzing 2D NMR spectroscopic data (DQF-COSY,
HMQC and HMBC) comparatively. Only the data for the skeletal
carbon atoms are presented, and those for other carbon atoms are
listed in the Exp. Sect.
[a]
Scheme 3. a) TFA/water (9:1, v/v), 95%; b) 1. TESCl, pyridine, 0
°C Ǟ room temp.; 2. Ac2O, pyridine, 88%; c) TFA/water (9:1, v/v),
99%; d) 1. TESCl, pyridine, 0 °C Ǟ room temp.; 2. Ac2O, pyridine;
3. TFA/water (9:1, v/v), 88%
The structure of each disaccharide of 11a and 11b was
confirmed by 2D NMR spectroscopy in a similar manner
to that described previously[11,13Ϫ15] (Tables 1 and 2). The 3, demonstrate that the 3-OH group of the 2-O-substituted
anomeric configurations of the disaccharides were ident- Hep 3,4-diol is highly reactive toward silylation reagents
3
ified by the J1,2 values (4.0 and 8.5 Hz for the α- and β- when compared with the 4-OH group, as predicted from
anomers, respectively) and the value of the 13C-1 chemical the results of silylation of methyl α--mannoside;[18Ϫ21] the
shift of each GlcN3 residue. The downfield 13C-2 shift of reaction proceeded regioselectively to yield the 3-O-silylated
each Hep residue of 11a and 11b (Table 2), and the HMBC product in high yields. Regeneration of the 3-OH group was
experiment, also confirmed the GlcN3 linkage site.
accomplished by hydrolyzing 15 in 9:1 TFA/water at room
The α-GlcN3-(1Ǟ2)-Hep derivative 11a was hydrolyzed temperature, and the α-GlcN3-(1Ǟ2)-Hep derivative bear-
in TFA/water (9:1) to remove the butane-2,3-diacetal ing a free 3-OH group (16) was obtained in 99% yield.
(BDA) unit to give the 3,4-diol 14 (95%), which was used Compound 16 was obtained in 88% yield from 14 by
for silylation (Scheme 3).
sequentially carrying out the silylation/acetylation and sub-
As expected from the results of silylation of 3, treatment sequent hydrolysis without isolating 15. Thus, we obtained
of 14 with 3 molar equiv. of TESCl in pyridine, followed by the 3-OH acceptor 16 that is suitable for the construction
acetylation with Ac2O/pyridine, gave the 3-O-TES ether 15 of the 2,3-di-O-substituted Hep structure present in 15253
in 88% yield. The signal of the Hep H-4 proton of 15 was LOS.[12]
shifted downfield (∆δ ϭ 1.93 ppm) relative to that of 14,
The 3-OH acceptor 16 was coupled with 1.9Ϫ2.5 molar
which confirmed the location of the silyl group (Table 1). equiv. of a donor, per-O-benzylated lactosyl trichloroace-
The results of silylation of 14, taken together with those of timidate 17,[14] at room temperature in 1,4-dioxane or Et2O
Table 3. Glycosylation of the acceptor 9 with the donor 10 (the acceptor 9 was treated with 1.6 molar equiv. of the donor 10 at room temp.)
Isolated yields (%)
Entry TMSOTf (equiv.)[a] Solvent α-(1Ǟ2) 11a[b] β-(1Ǟ2) 11b[b] Recovered 9[b] N-glycoside 12[c] 2-O-TMS 13[b] Ratio 11a:11b
1
2
3
4
0.04
0.2
0.04
0.2
dioxane 23
dioxane 26
6
7
22
21
63
48
11
4
16
5
8
Ϫ
14
Ϫ
3.8:1
3.7:1
2.6:1
2.7:1
Et2O
Et2O
58
56
9
14
[a]
[b]
The amounts of TMSOTf are based on the quantity of the donor.
The yields are expressed in reference to the quantity of the
[c]
acceptor 9. The yields are expressed in reference to the quantity of the donor 10.
Eur. J. Org. Chem. 2004, 1214Ϫ1227
www.eurjoc.org
 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
1217

K. Ishii, Y. Esumi, Y. Iwasaki, R. Yamasaki
FULL PAPER
using TMSOTf as a promoter (Scheme 4); the results are when 0.04 molar equiv. of TMSOTf was used. These results
summarized in Table 4. Glycosylation using 0.04 molar confirmed again that Et2O is a better solvent than 1,4-diox-
equiv. of TMSOTf in 1,4-dioxane (Entry 1 of Table 4), con- ane in the case of these glycosylations. Also, as Table 4 (En-
ditions employed in a previous study,[14] gave the expected tries 1Ϫ4) shows, the glycosylations in both solvents gave
3-O-lactosylated products 18a and 18b in only 30% yield. much better α-selectivity (α/β, 7Ϫ9:1) than those of 9 with
In contrast to the glycosylations using 9 as an acceptor, the 10 (Table 3).
use of 0.2 molar equiv. of TMSOTf in 1,4-dioxane (Entry
In addition to 16, we used the 3,4-diol 14 as an acceptor,
2) improved the yield (64%), and the β-N-glycosylated prod- expecting that formation of 3-O-substituted tetrasaccharide
uct 19 was also obtained. When Et2O was used as the sol- would be a dominant reaction pathway based on the results
vent (Entries 3 and 4), the tetrasaccharides 18a and 18b of both the silylation described above and the glycosylation
were obtained in 84Ϫ85% yields even though they were of a tetra-O-acetyl mannosyl trichloroacetimidate with 4,6-
purified by gel permeation chromatography (Sephadex LH- O-benzylidene mannoside reported in the preceding
20) and subsequent flash column chromatography, and the paper.[15] The yield, however, of the α-(1Ǟ4) tetrasacchar-
best yield (77%) of the desired α-glycoside 18a was obtained ide 21 exceeded that of the desired α-(1Ǟ3) tetrasaccharide
Scheme 4
Table 4. Glycosylation of the acceptors 14 and 16 with the donor 17 (reactions were carried out at room temp.)
Isolated yield (%)
Entry
Acceptor
TMSOTf (equiv.)[a]
Solvent
α-Linked
β-Linked
Recovered 16
N-Glycoside
Ratio
α:β
tetrasaccharides[b]
tetrasaccharide[b]
or 14[b]
19[c]
1[d]
2[f]
3[f]
4[f]
5[g]
16
16
16
16
14
0.04
0.2
0.04
0.2
dioxane
dioxane
Et2O
Et2O
dioxane
27
58
77
3
6
8
67
28
10
7
n.d.[e]
13
9.0:1
9.7:1
9.6:1
7.4:1
3.3:1
32
74
10
n.d.[e]
n.d.[e]
0.04
52[h]
16[i]
21
[a]
[b]
The amounts of TMSOTf are based on the quantity of the donor 17.
The yields are expressed in reference to the quantity of the
[c]
[d]
acceptor 16. The yields are expressed in reference to the quantity of the donor 17.
Treated with 1.9 molar equiv. of the donor 17.
[e]
[g]
[h]
n.d. ϭ not determined.[f] Treated with 2.5 molar equiv. of the donor 17. Treated with 1.7 molar equiv. of the donor 17. α-(1Ǟ3)-
[i]
Linked 20 and α-(1Ǟ4)-linked tetrasaccharide 21 were isolated in 24 and 28% yields, respectively.
presumably β-(1Ǟ3)- and β-(1Ǟ4)-linked.
A mixture of tetrasaccharides,
1218
 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
Eur. J. Org. Chem. 2004, 1214Ϫ1227

Synthesis of a 2,3-Di-O-substituted Heptose Structure
FULL PAPER
1
Table 5. H NMR (500 MHz) data recorded in CDCl3 at 25 °C for compounds 18a, 18b, and 20Ϫ23
Compound[a]
Residue
H-1
H-2
H-3
H-4
H-5
H-6a
H-6b
H-7a
H-7b
(3J1,2
)
(3J2,3
)
(3J3,4
)
(3J4,5
)
(3J5,6a
)
(3J5,6b
)
(2J6a,6b
)
(3J6,7a
)
(3J6,7a
)
(2J7a,7b
)
18a
Hep
GlcN3
Glc
4.82
4.11
(2.5)
3.00
(10.0)
3.40
(9.5)
3.82
(9.8)
4.03
n.d.
4.02
5.51
3.84
(2.0)
4.19
n.d.
4.26
(6.0)
3.35
n.d.
3.88
(2.0)
3.97
(5.0)
3.39
n.d.
3.32
n.d.
3.70
(1.5)
4.09
(5.0)
4.13
(1.5)
3.37
(5.0)
3.79
n.d.
4.05
n.d.
4.07
n.d.
3.31
(5.0)
3.85
(1.5)
4.17
n.d.
3.75
(5.0)
3.30
(5.0)
3.86
(1.5)
4.25
n.d.
3.84
(6.5)
3.87
(7.5)
5.09
Ϫ
Ϫ
Ϫ
4.16
(7.5)
4.31
(6.0)
(Ͻ 1.0)
5.02
(3.5)
4.89
(4.0)
4.30
(8.0)
4.80
(Ͻ 1.0)
5.12
(3.5)
4.50
(7.5)
4.43
(7.5)
4.78
(1.5)
4.93
(3.5)
4.93
(3.5)
4.31
(8.0)
4.74
(1.0)
5.31
(4.0)
5.04
(4.0)
4.33
(7.5)
4.86
(1.5)
4.86
(3.5)
4.92
(3.0)
4.26
(7.5)
4.90
(Ͻ 1.0)
5.13
(3.5)
5.10
(3.5)
4.47
(8.0)
(10.0)
4.10
(9.5)
3.97
(9.5)
3.40
(3.0)
4.19
(9.5)
3.94
(9.5)
3.57
(9.5)
3.40
(3.5)
3.81
(9.5)
3.99
(9.5)
4.02
(9.5)
3.38
(2.5)
3.79
(10.0)
4.08
(9.5)
3.87
(9.5)
3.28
(3.0)
4.24
(10.0)
3.80
(9.5)
3.27
(9.0)
3.35
(2.5)
4.05
(10.0)
5.30
(10.0)
5.24
(9.8)
4.95
(4.0)
(10.0)
3.41
(9.5)
3.69
(9.5)
3.87
n.d.
5.49
(10.0)
3.32
(9.8)
3.93
(9.5)
3.90
n.d.
3.96
(9.5)
3.39
(10.0)
3.81
(10.0)
3.89
n.d.
4.05
(10.0)
3.54
(8.5)
4.03
(9.8)
3.85
n.d.
5.48
(10.0)
3.62
(9.5)
3.79
(9.3)
3.86
n.d.
5.50
(10.0)
5.15
(9.5)
3.64
(10.0)
5.34
(1.0)
(10.5)
4.15
n.d.
3.72
n.d.
3.28
n.d.
5.24
Ϫ
4.28
n.d.
3.75
(10.3)
3.40
n.d.
Ϫ
Ϫ
4.25
(12.0)
Gal
18b
Hep
GlcN3
Glc
4.18
(7.0)
4.32
(5.5)
(11.0)
(11.0)
n.d.
2.66
(10.3)
3.37
(8.5)
3.75
(9.5)
3.92
(3.0)
2.94
(10.0)
3.48
(9.8)
3.80
(10.3)
3.98
n.d.
3.25
(10.5)
3.49
(10.0)
3.72
(10.0)
3.96
(4.0)
4.43
(9.5)
3.48
(9.5)
3.75
(9.8)
3.95
n.d.
4.18
(2.0)
3.74Ϫ3.80
n.d.
3.30
n.d.
5.47
Ϫ
4.15
(2.0)
3.68
(5.0)
3.36
(10.0)
5.18
Ϫ
4.25
(2.5)
3.79
n.d.
3.39
(7.5)
5.15
Ϫ
4.19
n.d.
3.56
n.d.
3.23
(8.0)
5.24
Ϫ
n.d.
3.46
n.d.
Ϫ
Gal
20
Hep
GlcN3
Glc
4.23
(7.5)
4.31
(6.0)
Ϫ
4.26
(12.0)
3.80
(10.3)
3.47
(11.5)
Ϫ
Gal
21
Hep
GlcN3
Glc
4.25Ϫ4.30
n.d.
Ϫ
n.d.
4.30
(12.0)
3.98
n.d.
3.49
(9.5)
Ϫ
Gal
22
Hep
GlcNAc
Glc
4.16
(6.5)
4.31
(5.5)
Ϫ
(11.0)
(11.5)
4.24
n.d.
3.72
(10.5)
3.39
(9.0)
Ϫ
Gal
23
Hep
GlcNAc
Glc
4.20
(7.5)
4.33
(5.5)
Ϫ
4.46
(10.0)
4.79
(10.3)
5.06
(10.8)
4.09
n.d.
4.12
n.d.
4.04
(6.5)
4.25
n.d.
4.33
(11.5)
4.12
(11.5)
Gal
[a]
1
The H NMR spectroscopic chemical shifts (ppm) were determined by analyzing 2D NMR spectroscopic data (DQF-COSY, HMQC
1
and HMBC) comparatively, and the J couplings (Hz) were obtained by analyzing either the DQF-COSY or 1D spectra. The H NMR
spectroscopic chemical shifts of other protons are listed in the Exp. Sect.; n.d.: not determined.
20, and a mixture of tetrasaccharides, presumably the β- of the perbenzylated lactose unit made the spectral assign-
1
(1Ǟ3) and β-(1Ǟ4)-linked products, was also obtained ment rather difficult, the H and 13C NMR spectroscopic
(Table 4, Entry 5). Since glycosylation using the 3,4-diol 14 chemical shifts of each tetrasaccharide were determined by
as an acceptor was not regioselective, we did not explore analyzing the corresponding DQF-COSY, HMQC, and
any further glycosylation conditions using 14 for the syn- HMBC NMR spectra comparatively and also by examining
thesis of the 2,3-dibranched structure.
the previous data[14] for the 3-O-lactosylated Hep (Tables 5
The structures of the tetrasaccharides 18a, 18b, 20, and and 6). As an example, parts of the HMQC (panels A and
21 were determined by 2D NMR spectroscopy in a similar B) and HMBC (panels C and D) NMR spectra of 18a are
manner to that described earlier. Although the introduction presented in Figure 1. The existence of the (1Ǟ3) linkage
Eur. J. Org. Chem. 2004, 1214Ϫ1227
www.eurjoc.org
 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
1219

K. Ishii, Y. Esumi, Y. Iwasaki, R. Yamasaki
FULL PAPER
Table 6. 13C NMR (125 MHz) data recorded in CDCl3 at 25 °C
for compounds 18a, 18b, and 20Ϫ23
peaks, Glc H-1/Hep C-3 and Hep H-3/Glc C-1; other cross-
relay peaks labeled in the panels C and D also confirmed
the structure of 18a. The J1,2 value of the Glc residue
3
Compound[a] Residue C-1 C-2 C-3 C-4 C-5 C-6 C-7
(Table 5) verified its anomeric configuration.
Finally, we investigated reaction conditions for the con-
version of the azide (N3) unit of the tetrasaccharide 18a
into an acetamide (NHAc) group (Table 7). Reductive N-
acetylation of 18a using thioacetic acid (AcSH)/pyridine[31]
was very sluggish: the acetamide 22 was obtained in 68%
yield after treatment of the mixture at 40 °C for 12 days.
Therefore, we examined two other methods to perform this
conversion: treatment with zinc powder/AcOH[32] or hydro-
genation over Lindlar catalyst[33] followed by N-acetylation.
Reduction with Zn was also slow (8 days at room tempera-
ture) and subsequent N-acetylation gave 22 in the same
yield as the reaction with AcSH/pyridine (Scheme 5). A se-
quence, however, of hydrogenation of 18a over Lindlar cata-
lyst, N-acetylation, and subsequent chromatographic purifi-
cation gave the desired compound 22 in 89% yield.[33] Thus,
we successfully constructed the 2,3-di-O-substituted Hep
structure, α-Lac-(1Ǟ3)-[α-GlcNAc-(1Ǟ2)]-Hep 22.
As described earlier, we accomplished selective 3-O-silyl-
ation of the Hep 3,4-diol and then regenerated the 3-OH
acceptor for the synthesis of the 2,3-dibranched Hep struc-
ture. Selective protection of the Hep 3-OH group has been
achieved by selective O-alkylation of a 2,3-diol using either
a phase-transfer method[34,35] or a tin intermediate.[10,34,35]
The drawback of the O-alkylation method is that the reac-
18a
18b
20
Hep
GlcN3
Glc
99.5 78.2 77.7 65.6 68.9 67.2 62.0
100.2 63.0 79.5 79.0 69.5 63.0
99.5 78.3 79.9 78.3 71.4 69.2
103.6 79.7 82.8 73.5 73.3 68.3
99.8 73.4 74.7 65.1 69.1 67.1 62.2
98.3 62.8 79.7 77.7 69.4 62.9
100.1 81.1 83.3 76.7 75.1 68.2
102.8 79.9 82.5 73.5 73.0 67.9
99.8 78.9 81.2 65.6 70.5 68.3 62.4
100.0 62.8 79.3 78.3 69.4 63.0
101.0 78.7 80.4 77.4 71.4 68.5
103.3 79.8 82.5 73.7 73.3 68.3
99.9 76.4 71.8 78.9 68.4 68.7 61.4
99.3 63.2 79.4 78.3 69.3 62.9
101.0 78.5 80.3 76.0 71.4 67.1
102.6 79.9 82.4 73.9 73.2 68.3
99.3 77.9 74.9 66.0 69.0 67.0 62.1
Gal
Hep
GlcN3
Glc
Gal
Hep
GlcN3
Glc
Gal
21
Hep
GlcN3
Glc
Gal
Hep
22
GlcNAc 98.0 52.7 81.7 77.4 70.0 63.0
Glc
Gal
Hep
99.9 78.7 80.1 77.6 71.6 68.3
103.5 79.7 82.6 73.4 73.1 68.2
99.3 77.2 75.6 65.4 69.1 66.7 62.0
23
GlcNAc 96.2 51.6 70.8 68.2 68.4 62.2
Glc
Gal
99.0 70.9 69.2 76.4 69.4 62.1
101.2 68.8 71.1 66.6 70.5 60.7
[a]
The 13C NMR spectroscopic chemical shifts (ppm) were deter-
mined by analyzing 2D NMR spectroscopic data (DQF-COSY,
HMQC and HMBC) comparatively. Only the data for the skeletal
carbon atoms are presented, and those for other carbon atoms are
listed in the Exp. Sect.
Figure 1. Partial HMQC (panels A and B) and HMBC (panels C and D) spectra of compound 18a in CDCl3 at 25 °C; only partial 13C/
1
1H cross-peaks (A and B) and cross-relay peaks (C and D) are labeled; both H (ω2) and 13C (ω1) signals due to the CH2-Ph unit are
not labeled; each Roman numeral in panels AϪD corresponds to that of 18a as shown in Scheme 4
1220
 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
Eur. J. Org. Chem. 2004, 1214Ϫ1227

Synthesis of a 2,3-Di-O-substituted Heptose Structure
FULL PAPER
versatility of the 3-O-silyl ether intermediate for the syn-
thesis of branched Hep structures, regioselective 3-O-silyl-
ation of the 2-O-substituted Hep has advantages over the
existing procedures[34Ϫ37] described above. Although we did
not examine silylation of a 2-O-substituted mannoside in
the present study, its regioselective 3-O-silylation could
possibly be accomplished in a similar manner; such O-3 si-
lylation would be useful also for the manipulation of the
secondary hydroxy groups of mannose.
Table 7. Conversion of azide 18a into acetamide 22
Experimental conditions
Yield (%)
Lindlar cat./H2 followed by N-acetylation
AcSH/pyridine at 40 °C for 12 days
Zn/AcOH followed by N-acetylation
89
68
68
Conclusions
In summary, we have found that the 3,4-diol derivatives
of both 2-O-Bn Hep and α-GlcN3-(1Ǟ2)-Hep can be silyl-
ated regioselectively to give the corresponding 3-O-pro-
tected products in high yields. By coupling the 3-OH ac-
ceptor generated from the 3-O-silylated α-GlcN3-(1Ǟ2)-
Hep with the per-O-benzylated lactosyl trichloroacetimid-
ate, we synthesized the 2,3-dibranched Hep structure, α-
Lac-(1Ǟ3)-[α-GlcN3-(1Ǟ2)]-Hep, in high yield and con-
verted its azide unit to an acetamide group by hydrogen-
ation and subsequent N-acetylation. Thus, we constructed
the 2,3-branched Hep, α-Lac-(1Ǟ3)-[α-GlcNAc-(1Ǟ2)]-
Hep, that is present in 15253 LOS.[12] The 3-O-silyl deriva-
tive of the 2-O-substituted Hep is a useful intermediate for
preparing the 2,3-dibranched compound and could also be
utilized for the synthesis of both 3,4-dibranched and 2,3,4-
tribranched structures.
Experimental Section
General: Optical rotations and melting points (uncorrected) were
measured using a HORIBA SEPA-200 polarimeter and a YANAG-
IMOTO micro melting point apparatus, respectively. Elemental
analyses were performed using a Vario El III apparatus (Elementar
Analysensysteme GmbH., Germany). High-resolution fast-atom
bombardment mass spectrometry (HR-FABMS) was performed as
described previously.[14] High-resolution electrospray-ionization
mass spectrometry (HR-ESIMS) was carried out in the positive-
ion mode using a JEOL JMS-T100LC spectrometer with methanol
as the mobile phase at a flow rate of 0.2 mL/min (internal standard:
sodium trifluoroacetate); samples were dissolved in methanol at a
concentration of ca. 1 µg/mL and 10 µL was injected. All NMR
spectra were recorded at 25 °C in CDCl3 using a JEOL JNM-ECP
500 MHz NMR spectrometer equipped with a Silicon Graphics O2
Scheme 5. a) See Table 7; b) 1. H2, Pd/C, MeOH/EtOH/AcOH
(2:1:0.1, v/v/v); 2. Ac2O, pyridine, 98%
tion is not highly regioselective and tends to give the 3-O-
alkyl ether in only moderate yields. Alternatively, the 3-OH
acceptor has been prepared by esterification of a 2,3-ortho-
ester and subsequent treatment with aqueous TFA.[36,37]
The yield of chloroacetylation[37] of the 2,3-orthoester, how-
ever, is not as high as that of acetylation,[36] which is a situ-
ation that may be a drawback for the synthesis of the 3,4-
di-O-substituted Hep. In addition, the 2,3-orthoester inter-
computer. Chemical shifts are reported in ppm relative to internal
1
tetramethylsilane (δH ϭ 0.00 ppm) for H NMR and CDCl3 (δC
ϭ
mediate may not be utilized directly for the synthesis of the 77.00 ppm) for 13C NMR spectra. 2D NMR spectroscopic data
(DQF-COSY, HMQC, and HMBC) were processed using a Delta
program (JEOL USA. Inc.) in a similar manner described pre-
viously.[13,14] Silica gel 60 (E. Merck) was used for flash column
(0.040Ϫ0.063 mm) and open column (0.063Ϫ0.200 mm) chroma-
tography. Silica gel 60 F254 (E. Merck) was used for thin-layer chro-
matography (TLC), and compounds were detected under UV light
or by spraying with 10% conc. sulfuric acid in methanol and then
heating the plates at 120 °C for 5 min. Glycosylation reactions were
carried out at room temp. under argon atmospheres using dry sol-
vents. The reaction mixtures were filtered through Celite and the
2,3-dibranched Hep structure. In contrast, both regioselec-
tive O-3-silylation and regeneration of the 3-OH group were
accomplished in high yields, and the 3-O-silyl ethers 4 and
6 can be employed directly for the synthesis of the 3,4-di-
O-substituted Hep. In addition, by using an appropriate si-
lyl ether that is stable under the conditions of hydro-
genolysis, the 2,3,4-tri-O-substituted Hep expressed in
Neisserial[38] and Campylobacter LOS[39] can be synthe-
sized from the 3-O-silyl intermediate. Therefore, in terms of
the ease and yields of protection and deprotection, and the filtrates were washed with water, dried with MgSO4, and concen-
Eur. J. Org. Chem. 2004, 1214Ϫ1227
www.eurjoc.org  2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim 1221

K. Ishii, Y. Esumi, Y. Iwasaki, R. Yamasaki
FULL PAPER
trated to a syrup in vacuo under 40 °C unless otherwise stated.
The following compounds were prepared according to literature
procedures: (3ЈS,4ЈS)-methyl 2-O-benzyl-3,4-O-(2Ј,3Ј-dimeth-
Table 2):
δ
ϭ
4.9 [Si(CH2CH3)3], 6.9 [Si(CH2CH3)3], 20.8
(COCH3), 20.9 (COCH3), 55.0 (OCH3), 72.5 (CH2-Ph), 127.5,
127.7 (2 C), 128.2 (2 C), 138.4 (aromatic C), 170.5 (COCH3), 171.7
oxybutane-2Ј,3Ј-diyl)--glycero-α--manno-heptopyranoside (1),[13] (COCH3) ppm. C25H40O9Si (512.67): calcd. C 58.57, H 7.86; found
6-O-acetyl-2-azido-3,4-di-O-benzyl-2-deoxy-β--glucopyranosyl
trichloroacetimidate [10; m.p. 105Ϫ106 °C (recrystallized from
Et2O/hexane), [α]2D6 ϭ ϩ4.0 (c ϭ 1.5, CHCl3) {ref.[25] (as a syrup)
[α]2D4 ϭ ϩ6.8 (c ϭ 1.5, CHCl3)}], and 2,3,4,6-tetra-O-benzyl-β--
galactopyranosyl-(1Ǟ4)-2,3,6-tri-O-benzyl-β--glucopyranosyl tri-
chloroacetimidate (17).[14]
C 58.31, H 7.64.
Methyl 4,6,7-Tri-O-acetyl-2-O-benzyl-3-O-triethylsilyl-L-glycero-α-
D-manno-heptopyranoside (5): A solution of compound 4 (157 mg,
0.306 mmol) in Ac2O/pyridine (1:2, v/v, 6 mL) was stirred for 19 h
at room temp. The mixture was concentrated to a residue that was
purified by flash column chromatography (hexane/EtOAc, 2:1) to
give the title compound 5 (166 mg, 97%) as a pale-yellow oil.
(2ЈS,3ЈS)-Methyl 6,7-Di-O-acetyl-2-O-benzyl-3,4-O-(2Ј,3Ј-dimeth-
oxybutane-2Ј,3Ј-diyl)-L-glycero-α-D-manno-heptopyranoside
(2): [α]2D4 ϭ ϩ5 (c ϭ 1.0, CHCl3). 1H NMR (500 MHz, CDCl3; data
Compound 1[13] (3.00 g, 7.00 mmol) was treated with Ac2O/pyri-
for the ring and the exocyclic protons are listed in Table 1): δ ϭ
0.54Ϫ0.65 [m, H, Si(CH2CH3)3], 0.93Ϫ0.96 [m, H,
dine (1:2, v/v, 30 mL) containing a catalytic amount of 4-dimeth-
6
9
ylaminopyridine (DMAP) at room temp. for 12 h. The mixture was Si(CH2CH3)3], 2.04 (s, 3 H, COCH3), 2.05 (s, 3 H, COCH3), 2.10
concentrated to a syrup that was purified by open column chroma-
tography (hexane/EtOAc, 2:1) to give the title compound 2 (3.59 g,
ca.100%) as a syrup. [α]2D5 ϭ ϩ130 (c ϭ 1.0, CHCl3). 1H NMR
(s, 3 H, COCH3), 3.32 (s, 3 H, OCH3), 4.68, 4.91 (d, 2J ϭ 12.0 Hz,
1 H each, CH2-Ph), 7.25Ϫ7.41 (m, 5 H, aromatic H) ppm. 13C
NMR (125 MHz, CDCl3; data for the skeletal carbon atoms are
(500 MHz, CDCl3; data for the ring and the exocyclic protons are listed in Table 2): δ ϭ 4.9 [Si(CH2CH3)3], 6.8 [Si(CH2CH3)3], 20.75
listed in Table 1): δ ϭ 1.28, 1.33 (s, 3 H each, BDA-CH3), 2.04 (s, (COCH3), 20.83 (COCH3), 21.1 (COCH3), 55.1 (OCH3), 73.6
3 H, COCH3), 2.09 (s, 3 H, COCH3), 3.17 (s, 3 H, OCH3), 3.27, (CH2-Ph), 127.5, 127.7 (2 C), 128.2 (2 C), 138.5 (aromatic C), 169.5
2
3.29 (s, 3 H each, BDA-OCH3), 4.69, 4.92 (d, J ϭ 12.0 Hz, 1 H
(COCH3), 170.6 (COCH3), 170.7 (COCH3) ppm. C27H42O10Si
each, CH2-Ph), 7.25Ϫ7.44 (m, 5 H, aromatic H) ppm. 13C NMR (554.70): calcd. C 58.46, H 7.63; found C 58.18, H, 7.39.
(125 MHz, CDCl3; data for the skeletal carbon atoms are listed in
Table 2): δ ϭ 17.81 (BDA-CH3), 17.84 (BDA-CH3), 20.8 (COCH3),
Methyl 6,7-Di-O-acetyl-2-O-benzyl-3-O-tert-butyldimethylsilyl-
glycero-α-D-manno-heptopyranoside (6): Compound 3 (1.24 g,
L-
20.9 (COCH3), 47.8 (BDA-OCH3), 48.0 (BDA-OCH3), 54.7
(OCH3), 72.9 (CH2-Ph), 99.8 (BDA-Cq), 100.0 (BDA-Cq), 127.4,
128.0 (2 C), 128.1 (2 C), 138.6 (aromatic C), 170.4 (COCH3), 170.5
(COCH3) ppm. HR-ESIMS: calcd. for C25H36O11Na [M ϩ Na]ϩ:
535.2155; found 535.2133.
3.12 mmol) was treated with TBDMSCl (939 mg, 6.23 mmol) in
DMF (20 mL) in the presence of imidazole (531 mg, 7.80 mmol)
for 4.5 h at room temp. The mixture was poured into water (80 mL)
and extracted with EtOAc (40 mL). The aqueous solution was ex-
tracted with EtOAc (2 ϫ 20 mL). The combined organic extracts
were washed with water (50 mL) and brine (50 mL), dried
Methyl 6,7-Di-O-acetyl-2-O-benzyl-L-glycero-α-D-manno-heptopyr-
anoside (3): Compound 2 (3.60 g, 7.02 mmol) was treated with (MgSO4), filtered, and concentrated. Open column chromatogra-
TFA/water (9:1, v/v, 30 mL) at room temp. for 20 min. The reaction
mixture was concentrated to a syrup using toluene as an azeotrope,
and purification by open column chromatography (hexane/EtOAc,
1:2 Ǟ 1:3 Ǟ 1:4) gave the title compound 3 (2.54 g, 91%) as a
phy of the residue (hexane/EtOAc, 1:2) gave the title compound 6
1
(1.50 g, 94%) as a syrup. [α]2D5 ϭ ϩ8 (c ϭ 1.0, CHCl3). H NMR
(500 MHz, CDCl3; data for the ring and the exocyclic protons are
listed in Table 1): δ ϭ 0.11, 0.12 [s, 3 H each, Si(CH3)2C(CH3)3],
syrup. [α]2D5 ϭ Ϫ10 (c ϭ 1.0, CHCl3). 1H NMR (500 MHz, CDCl3; 0.92 [s, 9 H, Si(CH3)2C(CH3)3], 2.05 (s, 3 H, COCH3), 2.14 (s, 3 H,
2
data for the ring and the exocyclic protons are listed in Table 1):
δ ϭ 2.07 (s, 3 H, COCH3), 2.17 (s, 3 H, COCH3), 2.46 (br. s, 1 H,
COCH3), 2.71 (br. s, 1 H, 4-OH), 4.66, 4.82 (d, J ϭ 12.0 Hz, 1 H
each, CH2-Ph), 7.25Ϫ7.36 (m, 5 H, aromatic H) ppm. 13C NMR
3-OH), 3.17 (br. s, 1 H, 4-OH), 3.34 (s, 3 H, OCH3), 4.62, 4.74 (d, (125 MHz, CDCl3; data for the skeletal carbon atoms are listed in
2J ϭ 12.0 Hz, 1 H each, CH2-Ph), 7.26Ϫ7.35 (m, 5 H, aromatic H) Table 2):
Ϫ4.6, Ϫ4.5 [Si(CH3)2C(CH3)3], 18.3
ppm. 13C NMR (125 MHz, CDCl3; data for the skeletal carbon
[Si(CH3)2C(CH3)3], 25.9 [Si(CH3)2C(CH3)3], 20.8 (COCH3), 20.9
atoms are listed in Table 2): δ ϭ 20.7 (COCH3), 20.9, (COCH3), (COCH3), 55.0 (OCH3), 73.4 (CH2-Ph), 127.5, 127.7 (2 C), 128.2
δ
ϭ
55.1 (OCH3), 73.0 (CH2-Ph), 127.7 (2 C), 127.9, 128.5 (2 C), 137.72
(aromatic C), 170.5 (COCH3), 172.0 (COCH3) ppm. HR-ESIMS:
calcd. for C19H26O9Na [M ϩ Na]ϩ: 421.1475; found 421.1480.
(2 C), 138.4 (aromatic C), 170.5 (COCH3), 171.8 (COCH3) ppm.
C25H40O9Si (512.67): calcd. C 58.57, H 7.86; found C 58.23, H
7.82.
Methyl 6,7-Di-O-acetyl-2-O-benzyl-3-O-triethylsilyl-
manno-heptopyranoside (4): TESCl (347 µL, 2.06 mmol) was added
slowly to a solution of compound 3 (412 mg, 1.03 mmol) in pyri-
L
-glycero-α-
D
-
Methyl 4,6,7-Tri-O-acetyl-2-O-benzyl-3-O-tert-butyldimethylsilyl-
glycero-α- -manno-heptopyranoside (7): Compound (145 mg,
0.283 mmol) was acetylated with Ac2O/pyridine (2:1, v/v, 3 mL)
L-
D
6
dine (3 mL) at 0 °C and then the reaction mixture was stirred for containing a catalytic amount of DMAP at room temp. for 22 h.
10 min at 0 °C. The reaction mixture was poured into ice-water
and extracted with EtOAc. The combined extracts were washed
with brine, dried (MgSO4), filtered, and concentrated. Purification
by flash column chromatography (hexane/EtOAc, 2:1) gave the title
compound 4 (482 mg, 90%) as an oil. [α]2D4 ϭ Ϫ40 (c ϭ 1.0, CHCl3).
1H NMR (500 MHz, CDCl3; data for the ring and the exocyclic
The reaction mixture was concentrated to a syrup that was purified
by flash column chromatography to give the title compound 7
1
(154 mg, 97%) as an oil. [α]2D4 ϭ ϩ10 (c ϭ 1.0, CHCl3). H NMR
(500 MHz, CDCl3; data for the ring and the exocyclic protons are
listed in Table 1): δ ϭ 0.07, 0.07 [s, 3 H each, Si(CH3)2C(CH3)3],
0.88 [s, 9 H, Si(CH3)2C(CH3)3], 2.04 (s, 6 H, 2 COCH3), 2.10 (s, 3
2
protons are listed in Table 1):
δ
ϭ
0.63Ϫ0.68 [m,
6
H,
H, COCH3), 3.32 (OCH3), 4.64, 4.93 (d, J ϭ 12.0 Hz, 1 H each,
Si(CH2CH3)3], 0.95Ϫ0.98 [m, 9 H, Si(CH2CH3)3], 2.05 (s, 3 H, CH2-Ph), 7.26Ϫ7.40 (m, 5 H, aromatic H) ppm. 13C NMR
3
COCH3), 2.14 (s, 3 H, COCH3), 2.72 (d, J4-OH,H-4 ϭ 3.5 Hz, 1 H, (125 MHz, CDCl3; data for the skeletal carbon atoms are listed in
4-OH), 3.31 (s, 3 H, OCH3), 4.68, 4.79 (d, 2J ϭ 12.0 Hz, 1 H each, Table 2):
δ
ϭ
Ϫ5.1, Ϫ4.3 [Si(CH3)2C(CH3)3], 17.9
[Si(CH3)2C(CH3)3], 25.6 [Si(CH3)2C(CH3)3], 20.75 (COCH3), 20.83
(125 MHz, CDCl3; data for the skeletal carbon atoms are listed in (COCH3), 21.1 (COCH3), 55.1 (OCH3), 73.7 (CH2-Ph), 127.5,
CH2-Ph), 7.25Ϫ7.37 (m, 5 H, aromatic H) ppm. 13C NMR
1222
 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
Eur. J. Org. Chem. 2004, 1214Ϫ1227

Synthesis of a 2,3-Di-O-substituted Heptose Structure
FULL PAPER
127.7 (2 C), 128.2 (2 C), 138.4 (aromatic C), 169.4 (COCH3), 170.6
CH3), 20.7 (COCH3), 21.0 (COCH3), 47.8, 48.1 (BDA-OCH3), 54.9
(COCH3), 170.7 (COCH3) ppm. C27H42O10Si (554.70): calcd. C (OCH3), 100.1, 100.5 (BDA-Cq), 170.8 (COCH3), 170.4 (COCH3)
58.46, H 7.63; found C 58.22, H 7.47.
ppm. HR-FABMS: calcd. for C18H30O11Na [M ϩ Na]ϩ: 445.1685;
found 445.1678.
Methyl 4,6,7-Tri-O-acetyl-2-O-benzyl-L-glycero-α-D-manno-hepto-
(2ЈS,3ЈS)-Methyl (6-O-Acetyl-2-azido-3,4-di-O-benzyl-2-deoxy-α-
pyranoside (8): (a) Compound 5 (89 mg, 0.160 mmol) was treated
with a solution of 1% (w/v) I2 in MeOH[22] (4 mL) at room temp.
for 50 min. The mixture was poured into an aqueous solution of
Na2S2O3 (10 mL) and then extracted with EtOAc (3 ϫ 10 mL).
Purification by flash column chromatography (hexane/EtOAc, 1:1)
gave the title compound 8 (63 mg, 88%) as a colorless syrup. Com-
pound 7 (24 mg, 0.043 mmol) was also treated with 1% (w/v) I2 in
MeOH (2 mL) at room temp. Even after 7 days, however, TLC
(hexane/EtOAc, 2:1) showed that de-O-silylation was incomplete.
No further attempts at optimizing this reaction or characterizing
the reaction products were carried out. (b) Compound 7 (114 mg,
0.206 mmol) was treated with TFA/water[24] (9:1, v/v, 5 mL) at
room temp. for 20 min. The mixture was concentrated to a residue,
using toluene as an azeotrope, that was purified by flash column
chromatography (hexane/EtOAc, 1:1) to give the title compound 8
(84 mg, 93%) as a colorless syrup. (c) Glacial acetic acid (143 µL,
2.50 mmol) and TBAF (1  in THF; 1.25 mL, 1.25 mmol)[23] were
and β-
D-glucopyranosyl)-(1Ǟ2)-6,7-di-O-acetyl-3,4-O-(2Ј,3Ј-dimeth-
oxybutane-2Ј,3Ј-diyl)-
L
-glycero-α- -manno-heptopyranosides
D
(11a,b): Glycosylation of 9 with 10: TMSOTf was added at room
temp. to a stirred mixture of the acceptor 9, the donor 10,[25] and
molecular sieves (AW-300, 0.5 g) in either 1,4-dioxane or Et2O
(10 mL). Although TLC monitoring (hexane/toluene/EtOAc, 3:2:2)
showed the complete consumption of the donor 10 after 10 min,
the mixture was stirred for 1 h and then the reaction was termin-
ated by the addition of triethylamine. The mixture was diluted with
EtOAc (30 mL) and filtered through Celite. The filtrate was washed
with water (30 mL) and the aqueous phase was extracted with
EtOAc (2 ϫ 10 mL). The combined organic extracts were washed
with water (30 mL), brine (30 mL), dried (MgSO4), filtered, and
concentrated. Flash column chromatography (hexane/toluene/
EtOAc, 3:2:2) of the residue gave the α-(1Ǟ2)-linked 11a, the β-
(1Ǟ2)-linked 11b, N-(6-O-acetyl-2-azido-3,4-di-O-benzyl-2-deoxyl-
β--glucopyranosyl)trichloroacetamide (12), (2ЈS,3ЈS)-methyl 6,7-
di-O-acetyl-3,4-O-(2Ј,3Ј-dimethoxybutane-2Ј,3Ј-diyl)-2-O-trimeth-
ylsilyl--glycero-α--manno-heptopyranoside (13), and the un-
reacted acceptor 9. Compound 11a, which co-eluted with both
trichloroacetamide [Cl3CC(ϭO)NH2] and the donor hydrolysate,
was purified as follows. Most of trichloroacetamide of the mixture
was removed after crystallization (CH2Cl2/hexane) and filtration,
and the donor hydrolysate was removed after acetylation (Ac2O/
pyridine) of the resulting mixture and subsequent flash column
chromatography (hexane/toluene/EtOAc, 3:2:2). The β-anomer 11b
was crystallized from EtOAc/hexane. Both the N-glycoside 12 and
the 2-O-trimethylsilylated acceptor 13 were re-purified by flash col-
umn chromatography (toluene/hexane/EtOAc, 6:2:1, and toluene/
EtOAc, 10:1, respectively). (a) Using 0.04 molar equiv. of TMSOTf
added sequentially to
a solution of compound 7 (139 mg,
0.250 mmol) in THF (2 mL). After stirring for 1 day at room temp.,
TBAF (1  in THF; 0.63 mL, 2.5 molar equiv.) was added. The
reaction was stopped by quenching with water after stirring for 10
days at room temp. The usual workup, followed by flash column
chromatography (toluene/acetone, 9:1), gave the title compound 8
(76 mg, 67%). (d) Compound 3 (301 mg, 0.756 mmol) was stirred
in pyridine (3 mL) containing TESCl (253 µL, 1.51 mmol) for
30 min at 0 °C. After performing the workup as described for 4,
the reaction mixture was acetylated with Ac2O/pyridine (1:2, v/v,
9 mL) at room temp. for 2 days. The mixture was concentrated by
coevaporation with toluene. The residue was treated with TFA/
water (9:1, v/v, 10 mL) for 15 min at room temp. and concentrated
as described in (b). Purification by flash column chromatography
(CH2Cl2/acetone, 14:1) gave the title compound 8 as a colorless
foam (304 mg, 91%).Compound 8: [α]2D4 ϭ Ϫ40 (c ϭ 1.0, CHCl3).
1H NMR (500 MHz, CDCl3; data for the ring and the exocyclic
protons are listed in Table 1): δ ϭ 2.05 (s, 3 H, COCH3), 2.07 (s, 3
in 1,4-dioxane: Glycosylation of the acceptor
9 (203 mg,
0.480 mmol) with the donor 10 (441 mg, 0.771 mmol) in 1,4-diox-
ane (10 mL) in the presence of TMSOTf (6 µL, 0.033 mmol) gave
11a (91 mg, 23%), 11b (23 mg, 6%), the N-glycoside 12 (71 mg,
16%: based on the donor), and the acceptor 9 (129 mg, 63%). (b)
Using 0.2 molar equiv. of TMSOTf in 1,4-dioxane: Glycosylation
of 9 (200 mg, 0.473 mmol) with 10 (433 mg, 0.758 mmol) in 1,4-
dioxane (10 mL) in the presence of TMSOTf (27 µL, 0.152 mmol)
gave 11a (104 mg, 26%), 11b (26 mg, 7%), the N-glycoside 12
(21 mg, 5%), the 2-O-trimethylsilylated acceptor 13 (33 mg, 14%),
and the acceptor 9 (97 mg, 48%). (c) Using 0.04 molar equiv. of
TMSOTf in Et2O: Glycosylation of 9 (208 mg, 0.492 mmol) with
10 (450 mg, 0.787 mmol) in Et2O (10 mL) in the presence of
TMSOTf (6 µL, 0.033 mmol) gave 11a (236 mg, 58%), 11b (89 mg,
3
H, COCH3), 2.11 (s, 3 H, COCH3), 2.27 (d, J3-OH,H-3 ϭ 11.0 Hz,
2
1 H, 3-OH), 3.34 (s, 3 H, OCH3), 4.58, 4.77 (d, J ϭ 12.0 Hz, 1 H
each, CH2-Ph), 7.26Ϫ7.37 (m, 5 H, aromatic H) ppm. 13C NMR
(125 MHz, CDCl3; data for the skeletal carbon atoms are listed in
Table 2): δ ϭ 20.7 (2 C, 2 COCH3), 20.9 (COCH3), 55.2 (OCH3),
73.0 (CH2-Ph), 127.8 (2 C), 128.1, 128.6 (2 C), 137.4 (aromatic C),
170.4 (COCH3), 170.5 (COCH3), 170.9 (COCH3) ppm. HR-ES-
IMS: calcd. for C21H28O10Na [M ϩ Na]ϩ: 463.1580; found
463.1562.
(2ЈS,3ЈS)-Methyl 6,7-Di-O-acetyl-3,4-O-(2Ј,3Ј-dimethoxybutane- 22%), the N-glycoside 12 (35 mg, 8%), and the acceptor 9 (23 mg,
2Ј,3Ј-diyl)-
L
-glycero-α-
D
-manno-heptopyranoside (9): Compound 2
11%). (d) Using 0.2 molar equiv. of TMSOTf in Et2O: Glycosyl-
ation of 9 (205 mg, 0.485 mmol) with 10 (445 mg, 0.778 mmol) in
Et2O (10 mL) in the presence of TMSOTf (28 µL, 0.156 mmol)
gave 11a (225 mg, 56%), 11b (84 mg, 21%), the N-glycoside 12
(40 mg, 9%), the 2-O-trimethylsilylated acceptor 13 (33 mg, 14%),
and the acceptor 9 (9 mg, 4%).
(1.10 g, 2.15 mmol) was dissolved in EtOAc (50 mL) and 10% Pd/
C (0.3 g) was added. The mixture was hydrogenated under atmos-
pheric pressure of hydrogen for 1 day and then filtered through
Celite. The filtrate was evaporated to a syrup that was purified by
open column chromatography (hexane/EtOAc, 2:1 Ǟ 1:2) to give
the title compound 9 (0.88 g, 97%) as a foam. [α]2D5 ϭ ϩ165 (c ϭ
1.0, CHCl3). 1H NMR (500 MHz, CDCl3; data for the ring and
the exocyclic protons are listed in Table 1): δ ϭ 1.27, 1.31 (s, 3 H
Compound 11a: [α]2D4 ϭ ϩ149 (c ϭ 1.0, CHCl3). 1H NMR
(500 MHz, CDCl3; data for the ring and the exocyclic protons are
listed in Table 1): δ ϭ 1.27, 1.29 (s, 3 H each, BDA-CH3), 2.05 (s,
each, BDA-CH3), 2.05 (s, 3 H, COCH3), 2.12 (s, 3 H, COCH3), 9 H, 2 COCH3), 2.05 (s, 3 H, COCH3), 3.13, 3.25 (s, 3 H each,
2
2.34 (br. s, 1 H, 2-OH), 3.15, 3.27 (s, 3 H each, BDA-OCH3), 3.35 BDA-OCH3), 3.33 (s, 3 H, OCH3), 4.58, 4.86 (d, J ϭ 11.0 Hz, 1
(s, 3 H, OCH3) ppm. 13C NMR (125 MHz, CDCl3; data for the H each, CH2-Ph), 4.87, 4.90 (d, 2J ϭ 11.0 Hz, 1 H each, CH2-
skeletal carbon atoms are listed in Table 2): δ ϭ 17.7, 17.8 (BDA-
Ph), 7.26Ϫ7.39 (m, 10 H, aromatic H) ppm. 13C NMR (125 MHz,
Eur. J. Org. Chem. 2004, 1214Ϫ1227
www.eurjoc.org
 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
1223

K. Ishii, Y. Esumi, Y. Iwasaki, R. Yamasaki
FULL PAPER
CDCl3; data for the skeletal carbon atoms are listed in Table 2):
CDCl3; data for the skeletal carbon atoms are listed in Table 2):
δ ϭ 17.6, 17.8 (BDA-CH3), 20.7 (COCH3), 20.8 (COCH3), 47.9,
δ ϭ 20.7 (COCH3), 20.8 (COCH3), 55.1 (OCH3), 75.3 (CH2-Ph),
48.0 (BDA-OCH3), 54.7 (OCH3), 75.1 (CH2-Ph), 75.2 (CH2-Ph), 75.6 (CH2-Ph), 128.5Ϫ128.6, 137.2, 137.3 (aromatic C), 170.4
99.9, 100.5 (BDA-Cq), 127.9Ϫ128.5, 137.5, 137.8 (aromatic C),
(COCH3), 170.5 (COCH3), 170.8 (COCH3) ppm. HR-FABMS:
170.38 (COCH3), 170.41 (COCH3), 170.6 (COCH3) ppm. FAB- calcd. for C34H43O14N3Na [M ϩ Na]ϩ: 740.2643; found 740.2659.
HRMS: calcd. for C40H53O16N3Na [M ϩ Na]ϩ 854.3324; found
854.3334.
Methyl (6-O-Acetyl-2-azido-3,4-di-O-benzyl-2-deoxy-α-
D-glucopyr-
anosyl)-(1Ǟ2)-4,6,7-tri-O-acetyl-3-O-triethylsilyl-
L
-glycero-α-D-
Compound 11b: M.p. 157Ϫ158°. [α]2D1 ϭ ϩ82 (c ϭ 1.0, CHCl3). 1H
NMR (500 MHz, CDCl3; data for the ring and the exocyclic pro-
tons are listed in Table 1): δ ϭ 1.25, 1.27 (s, 3 H each, BDA-CH3),
1.99 (s, 3 H, COCH3), 2.04 (s, 3 H, COCH3), 2.08 (s, 3 H, COCH3),
3.11, 3.26 (s, 3 H each, BDA-OCH3), 3.35 (s, 3 H, OCH3), 4.57,
4.84 (d, 2J ϭ 11.0 Hz, 1 H each, CH2-Ph), 4.81, 4.91 (d, 2J ϭ
11.0 Hz, 1 H each, CH2-Ph), 7.25Ϫ7.40 (m, 10 H, aromatic H)
ppm. 13C NMR (125 MHz, CDCl3; data for the skeletal carbon
atoms are listed in Table 2): δ ϭ 17.75, 17.84 (BDA-CH3), 20.70
(COCH3), 20.73 (COCH3), 20.8 (COCH3), 47.6, 48.0 (BDA-
OCH3), 54.9 (OCH3), 75.0 (CH2-Ph), 75.4 (CH2-Ph), 99.8, 100.2
(BDA-Cq), 128.0Ϫ128.5, 137.5, 137.8 (aromatic C), 170.3
(COCH3), 170.4 (COCH3), 170.5 (COCH3) ppm. FAB-HRMS:
calcd. for C40H53O16N3Na [M ϩ Na]ϩ 854.3324; found 854.3345.
manno-heptopyranoside (15): Compound 14 (563 mg, 0.784 mmol)
was dissolved in pyridine (10 mL) and cooled in an ice-water bath.
TESCl (392 µL, 2.34 mmol) was added at 0 °C. After stirring at 0
°C for 30 min, the mixture was warmed to room temp. and stirred
for 30 min. The reaction mixture was quenched with water and
then extracted with EtOAc. The combined extracts were washed
with water (20 mL), brine (20 mL), dried (MgSO4), and filtered.
The filtrate was concentrated to give an oil that was acetylated
with Ac2O/pyridine (1:2, v/v, 15 mL) at room temp. for 3 days. The
reaction mixture was concentrated to a syrup that was purified by
flash column chromatography (hexane/EtOAc, 2:1) to give the title
compound 15 (603 mg, 88%) as a syrup. [α]2D7 ϭ ϩ71 (c ϭ 1.0,
CHCl3). 1H NMR (500 MHz, CDCl3; data for the ring and the
exocyclic protons are listed in Table 1): δ ϭ 0.55Ϫ0.67 [m, 6 H,
Si(CH2CH3)3], 0.96 [m, 9 H, Si(CH2CH3)3], 2.01 (s, 3 H, COCH3),
2.04 (s, 3 H, COCH3), 2.04 (s, 3 H, COCH3), 2.05 (s, 3 H, COCH3),
N-Glycoside 12: [α]2D6 ϭ ϩ29 (c ϭ 1.0, CHCl3). 1H NMR
3
(500 MHz, CDCl3): δ ϭ 2.04 (s, 3 H, COCH3), 3.62 (t, J4,5
ϭ
3
8.5 Hz, 1 H, H-4), 3.66 (t, J3,4 ϭ 8.5 Hz, 1 H, H-3), 3.75 (dddd, 1
H, H-5), 3.92 (dd, 3J2,3 ϭ 9.5 Hz, 1 H, H-2), 4.28 (d, 3J5,6 ϭ 3.5 Hz,
2 H, H-6a and 6b), 4.59, 4.83 (d, 2J ϭ 11.0 Hz, 1 H each, CH2-
Ph), 4.89, 4.92 (d, 2J ϭ 11.0 Hz, 1 H each, CH2-Ph), 5.63 (dd,
3J1,2 ϭ 5.5 Hz, 1 H, H-1), 7.02 (d, JNH,H-1 ϭ 6.5 Hz, 1 H, NH
COCCl3), 7.28Ϫ7.38 (m, 10 H, aromatic H) ppm. 13C NMR
(125 MHz, CDCl3): δ ϭ 20.7 (COCH3), 61.7 (C-2), 62.3 (C-6), 70.8
(C-5), 75.2 (CH2-Ph), 75.7 (CH2-Ph), 76.97 (C-4), 77.02 (C-1), 81.1
(C-3), 92.0 (NHCOCCl3), 128.1 (2 C), 128.2 (2 C), 128.3, 128.4,
128.6 (2 C), 128.7 (2 C), 136.85, 136.89 (aromatic C), 161.8
(NHCOCCl3), 170.5 (COCH3) ppm. HR-ESIMS: calcd. for
C24H25Cl3NO6Na [M ϩ Na]ϩ: 593.0737, found 593.0749.
2
3.35 (s, 3 H, OCH3), 4.57, 4.87 (d, J ϭ 11.0 Hz, 1 H each, CH2-
Ph), 4.88, 4.93 (d, 2J ϭ 10.5 Hz, 1 H each, CH2-Ph), 7.26Ϫ7.40
(m, 10 H, aromatic H) ppm. 13C NMR (125 MHz, CDCl3; data for
the skeletal carbon atoms are listed in Table 2):
δ ϭ 4.8
[Si(CH2CH3)3], 6.6 [Si(CH2CH3)3], 20.6 (COCH3), 20.7 (COCH3),
20.8 (COCH3), 20.9 (COCH3), 55.2 (OCH3), 75.2 (CH2-Ph), 75.3
(CH2-Ph), 127.9Ϫ128.5, 137.4, 137.8 (aromatic C), 169.1 (COCH3),
170.5 (COCH3), 170.6 (COCH3), 170.7 (COCH3) ppm. HR-
FABMS: calcd. for C42H59O15N3SiNa [M ϩ Na]ϩ: 896.3613;
found 869.3625.
Methyl (6-O-Acetyl-2-azido-3,4-di-O-benzyl-2-deoxy-α-
anosyl)-(1Ǟ2)-4,6,7-tri-O-acetyl- -glycero-α-
D
-glucopyr-
2-O-Trimethylsilylated Acceptor 13: [α]2D6 ϭ ϩ115 (c ϭ 1.0, CHCl3).
1H NMR (500 MHz, CDCl3): δ ϭ 0.15 [s, 1 H, Si(CH3)3], 1.25,
1.28 (s, 3 H each, BDA-CH3), 2.04 (s, 3 H, COCH3), 2.13 (s, 3 H,
COCH3), 3.11, 3.26 (s, 3 H each, BDA-OCH3), 3.32 (s, 3 H,
OCH3), 3.89 (m, 3J2,3 ϭ 3.0 Hz, 1 H, H-2), 3.90 (dd, 3J3,4 ϭ 9.5 Hz,
L
D-manno-
heptopyranoside (16): Compound 15 (597 mg, 0.683 mmol) was hy-
drolyzed with TFA/water (9:1, v/v, 10 mL) at room temp. for 5 min.
The mixture was concentrated to a residue that was purified by
open column chromatography (EtOAc/hexane, 1:1) to give the title
compound 16 (512 mg, 99%) as a syrup. Alternatively, compound
16 was prepared as follows: Compound 14 (408 mg, 0.568 mmol)
was treated with TESCl (285 µL, 1.70 mmol) in pyridine (10 mL)
at 0 °C for 1 h and then acetylated in a similar manner described
for 15. Hydrolysis of the acetylated mixture in TFA/water (9:1, v/
v, 10 mL) for 5 min, and subsequent purification by flash column
chromatography (CH2Cl2/acetone, 14:1), gave 16 as a colorless
foam (381 mg, 88%). [α]2D5 ϭ ϩ13 (c ϭ 1.0, CHCl3). 1H NMR
(500 MHz, CDCl3; data for the ring and the exocyclic protons are
3
3
1 H, H-3), 3.92 (dd, J5,6 ϭ 2.0 Hz, 1 H, H-5), 4.00 (t, J4,5
ϭ
2
9.5 Hz, 1 H, H-4), 4.27 (dd, J7a,7b ϭ 11.0 Hz, 1 H, H-7a), 4.33
(dd, 1 H, H-7b), 4.67 (s, 1 H, H-1), 5.44 (ddd, 3J6,7a ϭ 8.0, 3J6,7b ϭ
7.0 Hz, 1 H, H-6) ppm. 13C NMR (125 MHz, CDCl3): δ ϭ 0.4
[Si(CH3)3], 17.7, 17.8 (BDA-CH3), 20.7 (COCH3), 20.9 (COCH3),
47.4, 47.9 (BDA-OCH3), 54.7 (OCH3), 61.6 (C-7), 62.0 (C-4), 67.7
(C-6), 68.2 (C-3), 68.8 (C-5), 70.4 (C-2), 99.6, 100.0 (BDA-Cq),
102.8 (C-1), 170.2 (COCH3), 170.4 (COCH3) ppm. HR-ESIMS:
calcd. for C21H38O11SiNa [M ϩ Na]ϩ: 517.2081; found 517.2064.
listed in Table 1): δ ϭ 2.00 (s, 3 H, COCH3), 2.05 (s, 3 H, COCH3),
Methyl (6-O-Acetyl-2-azido-3,4-di-O-benzyl-2-deoxy-α-
D-glucopyr-
3
2.06 (s, 3 H, COCH3), 2.10 (s, 3 H, COCH3), 2.94 (d, J3-OH,H-3
ϭ
anosyl)-(1Ǟ2)-6,7-di-O-acetyl- -glycero-α- -manno-hepto-
L
D
11.5 Hz, 1 H, 3-OH), 3.35 (s, 3 H, OCH3), 4.59, 4.87 (d, 2J ϭ
10.5 Hz, 1 H each, CH2-Ph), 4.91 (m, 2 H, CH2-Ph), 7.26Ϫ7.40
(m, 10 H, aromatic H) ppm. 13C NMR (125 MHz, CDCl3; data for
the skeletal carbon atoms are listed in Table 2): δ ϭ 20.5 (COCH3),
20.7 (COCH3), 20.8 (COCH3), 20.9 (COCH3), 55.2 (OCH3), 75.3
(CH2-Ph), 75.8 (CH2-Ph), 127.1Ϫ128.6, 137.2, 137.3 (aromatic C),
170.3 (COCH3), 170.5 (2 C, 2 COCH3), 170.8 (COCH3) ppm. HR-
FABMS: calcd. for C36H45N3O15Na [M ϩ Na]ϩ: 782.2748; found
782.2769.
pyranoside (14): Compound 11a (685 mg, 0.823 mmol) was treated
with TFA/water (9:1, v/v, 10 mL) at room temp. for 15 min. The
reaction mixture was co-evaporated with toluene to give an oil.
Purification of the oil by flash column chromatography (CH2Cl2/
acetone, 9:1 Ǟ 6:1) gave the title compound 14 (563 mg, 95%) as
a foam. [α]2D0 ϭ ϩ41 (c ϭ 1.0, CHCl3). 1H NMR (500 MHz, CDCl3;
data for the ring and the exocyclic protons are listed in Table 1):
δ ϭ 2.06 (s, 3 H, COCH3), 2.06 (s, 3 H, COCH3), 2.06 (s, 3 H,
3
COCH3), 2.91 (d, J3-OH,H-3 ϭ 8.0 Hz, 1 H, 3-OH), 3.13 (d,
3J4-OH,H-4 ϭ 3.5 Hz, 1 H, 4-OH), 3.34 (s, 3 H, OCH3), 4.58, 4.86 Methyl (2,3,4,6-Tetra-O-benzyl-β-
D-galactopyranosyl)-(1Ǟ4)-(2,3,6-
(d, 2J ϭ 11.0 Hz, 1 H each, CH2-Ph), 4.87 (m, 2 H, CH2-Ph),
7.26Ϫ7.38 (m, 10 H, aromatic H) ppm. 13C NMR (125 MHz, 3,4-di-O-benzyl-2-deoxy-α-
tri-O-benzyl-α- and β-D-glucopyranosyl)-(1Ǟ3)-[6-O-acetyl-2-azido-
D
-glucopyranosyl-(1Ǟ2)]-4,6,7-tri-O-
Eur. J. Org. Chem. 2004, 1214Ϫ1227
1224
 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org

Synthesis of a 2,3-Di-O-substituted Heptose Structure
FULL PAPER
acetyl-
L
-glycero-α-
D
-manno-heptopyranosides (18a,b): Glycosyl-
Table 5): δ ϭ 1.93 (s, 3 H, COCH3), 2.00 (s, 3 H, COCH3), 2.03 (s,
3 H, COCH3), 2.04 (s, 3 H, COCH3), 3.30 (s, 3 H, OCH3), 4.21,
ation of 16 with the per-O-benzylated lactosyl trichloroacetimidate
17: The acceptor 16 was treated with 17[14] in a similar manner 4.30 (d, 2J ϭ 12.0 Hz, 1 H each, CH2-Ph), 4.40, 4.46 (d, 2J ϭ
described for the synthesis of 11a. Although TLC monitoring of
12.0 Hz, 1 H each, CH2-Ph), 4.49, 4.79 (d, 2J ϭ 11.0 Hz, 1 H each,
CH2-Ph), 4.53, 4.94 (d, 2J ϭ 11.5 Hz, 1 H each, CH2-Ph), 4.63,
each glycosylation mixture showed no significant changes in the
pattern of the reaction products after 20 min, the mixture was 5.01 (d, 2J ϭ 10.5 Hz, 1 H each, CH2-Ph), 4.67, 4.72 (d, 2J ϭ
stirred for 0.5Ϫ6 h at room temp. The tetrasaccharides and disac-
charides of each glycosylation mixture were separated by gel per-
meation chromatography [Sephadex LH-20 (2.6 ϫ 80 cm, CHCl3/
MeOH, 1:1)]. Purification of a mixture containing the tetrasacchar-
ides by flash column chromatography (hexane/EtOAc, 1:1) gave α-
11.5 Hz, 1 H each, CH2-Ph), 4.67, 4.72 (d, 2J ϭ 11.5 Hz, 1 H each,
CH2-Ph), 4.78, 4.82 (d, 2J ϭ 11.5 Hz, 1 H each, CH2-Ph), 4.87,
4.93 (d, 2J ϭ 12.0 Hz, 1 H each, CH2-Ph), 7.02Ϫ7.39 (m, 45 H,
aromatic H) ppm. 13C NMR (125 MHz, CDCl3; data for the skel-
etal carbon atoms are listed in Table 6): δ ϭ 20.6 (COCH3), 20.70
(1Ǟ3)-linked 18a and β-(1Ǟ3) 18b. Similarly, flash column chro- (2 C, 2 COCH3), 20.74 (COCH3), 55.1 (OCH3), 72.5 (CH2-Ph),
matography (hexane/EtOAc, 6:1) of a mixture containing the disac-
charides gave the unreacted acceptor 16 and N-(2,3,4,6-terta-O-
benzyl-β--galactopyranosyl)-(1Ǟ4)-(2,3,6-tri-O-benzyl-β--
glucopyranosyl)trichloroacetamide (19). (a) Using 0.04 molar
equiv. of TMSOTf in 1,4-dioxane: Glycosylation of the acceptor 16
(145 mg, 0.19 mmol) with the donor 17 (403 mg, 0.36 mmol) in 1,4-
72.8 (CH2-Ph), 73.3 (CH2-Ph), 74.1 (CH2-Ph), 74.6 (CH2-Ph), 74.9
(CH2-Ph), 75.0 (2 C, 2 CH2-Ph), 75.1 (CH2-Ph), 126.6Ϫ128.4,
137.4, 137.8, 138.0, 138.2, 138.4, 138.6, 138.9, 139.0 (2 C) (aromatic
C), 169.4 (COCH3), 170.43 (COCH3), 170.46 (COCH3), 170.50
(COCH3) ppm. FAB-HRMS: calcd. for C97H107O25N3Na [M ϩ
Na]ϩ: 1736.7091; found 1736.7075. N-Glycoside 19: [α]2D5 ϭ ϩ32
dioxane (10 mL) in the presence of TMSOTf (0.14  in 1,4-dioxane, (c ϭ 1.0, CHCl3). 1H NMR (500 MHz, CDCl3): δ ϭ 3.37 (dd,
3J3
ϭ 3.0 Hz, 1 H, H-3II), 3.37 (m, J5
ϭ 5.0, J5
ϭ
II II
3
II II
3
II II
102 µL, 0.014 mmol) for 6 h at room temp. gave the α-linked com-
,4
,6
a
,6
b
pound 18a (87 mg, 27%), the β-linked compound 18b (9 mg, 3%), 6.5 Hz, 1 H, H-5II), 3.53 (dd, 2J6
ϭ 11.5 Hz, 1 H, H-6IIa),
II II
a,6
I
b
I
2
and the unchanged acceptor 16 (97 mg, 67%). (b) Using 0.2 molar
equiv. of TMSOTf in 1,4-dioxane: Glycosylation of 16 (121 mg,
3.55 (dd, 1 H, H-6IIb), 3.57 (dd, J6 a,6 b ϭ 11.0 Hz, 1 H, H-6Ia),
3
I
I
3
I I
3.65 (dddd, J5 ,6 a ϭ 2.5, J5 ,6 b ϭ 3.5 Hz, 1 H, H-5I), 3.73 (t,
I
I
II II
0.159 mmol) with 17 (443 mg, 0.396 mmol) in 1,4-dioxane (10 mL) 3J3 ,4 ϭ 7.0 Hz, 1 H, H-3I), 3.74 (dd, 3J2
ϭ 9.8 Hz, 1 H, H-
,3
3
I I
in the presence of TMSOTf (0.55  in 1,4-dioxane, 143 µL,
2II), 3.76 (dd, J2 ,3 ϭ 7.5 Hz, 1 H, H-2I), 3.79 (dd, 1 H, H-6Ib),
0.079 mmol) for 30 min at room temp. gave the α-linked compound 3.90 (d, 1 H, H-4II), 4.01 (dd, 3J4 ,5I ϭ 9.0 Hz, 1 H, H-4I), 4.29, 4.37
I
2
3
II II
18a (159 mg, 58%), the β-linked compound 18b (16 mg, 6%), the N-
glycoside 19 (56 mg, 13%: based on the donor), and the unreacted
(d, J ϭ 12.0 Hz, 1 H each, CH2-Ph), 4.36 (d, J1
ϭ 7.5 Hz, 1
,2
H, H-1II), 4.36, 4.53 (d, 2J ϭ 12.0 Hz, 1 H each, CH2-Ph), 4.51,
acceptor 16 (34 mg, 28%). (c) Using 0.04 molar equiv. of TMSOTf 4.71 (d, 2J ϭ 11.5 Hz, 1 H each, CH2-Ph), 4.56, 4.97 (d, 2J ϭ
in Et2O: Glycosylation of 16 (121 mg, 0.159 mmol) with 17 11.5 Hz, 1 H each, CH2-Ph), 4.64, 4.94 (d, 2J ϭ 11.0 Hz, 1 H each,
(443 mg, 0.396 mmol) in Et2O (6 mL) in the presence of TMSOTf
(0.14  in Et2O, 147 µL, 0.016 mmol) for 30 min at room temp. (d, J ϭ 11.0 Hz, 1 H each, CH2-Ph), 5.53 (dd, J1 ,2 ϭ 4.5 Hz, 1
CH2-Ph), 4.70, 4.71 (d, 2J ϭ 12.0 Hz, 1 H each, CH2-Ph), 4.73, 4.76
2
3
I I
3
I
gave the α-linked compound 18a (210 mg, 77%), the β-linked com-
H, H-1I), 7.14Ϫ7.35 (m, 35 H, aromatic H), 7.47 (d, JNH,H-1
ϭ
pound 18b (21 mg, 8%), the N-glycoside 19 (143 mg, 32%), and the 6.5 Hz, 1 H, NH COCCl3) ppm. 13C NMR (125 MHz, CDCl3):
unreacted acceptor 16 (12 mg, 10%). (d) Using 0.2 molar equiv. of
TMSOTf in Et2O: Glycosylation of 16 (459 mg, 0.604 mmol) with
δ ϭ 67.9 (C-6I), 68.3 (C-6II), 72.4 (C-5I), 72.7 (CH2-Ph), 73.0 (CH2-
Ph), 73.1 (C-5II), 73.2, 73.4 (CH2-Ph), 73.6 (C-4II), 74.5 (CH2-Ph),
17 (1.66 g, 1.49 mmol) in Et2O (15 mL) in the presence of TMSOTf 74.7 (CH2-Ph), 75.2 (CH2-Ph), 75.8 (C-2I), 76.5 (C-1I), 78.8 (C-3I),
(54 µL, 0.30 mmol) and molecular sieves (AW-300, 2.0 g) for 1 h at
room temp. gave the α-linked compound 18a (771 mg, 74%), the β-
linked compound 18b (103 mg, 10%), and the unreacted acceptor
16 (34 mg, 7%).
79.7 (C-2II), 82.4 (C-3II), 92.5 (NHCOCCl3), 103.2 (C-1II),
127.4Ϫ128.5, 137.0, 138.0, 138.1, 138.4, 138.5, 138.6, 138.9 (aro-
matic C), 161.9 (NHCOCCl3) ppm. HR-ESIMS: calcd. for
C63H64Cl3NO11Na [M ϩ Na]ϩ: 1138.3443; found 1138.3448.
Compound 18a: [α]2D3 ϭ ϩ30 (c ϭ 1.0, CHCl3). 1H NMR (500 MHz,
CDCl3; data for the ring and the exocyclic protons are listed in
Table 5): δ ϭ 1.73 (s, 3 H, COCH3), 1.98 (s, 3 H, COCH3), 2.04 (s,
Methyl (2,3,4,6-Tetra-O-benzyl-β-
tri-O-benzyl-α- -glucopyranosyl)-(1Ǟ3)- and (1Ǟ4)-[6-O-acetyl-2-
azido-3,4-di-O-benzyl-2-deoxy-α- -glucopyranosyl-(1Ǟ2)]-6,7-di-O-
acetyl- -glycero-α- -manno-heptopyranosides (20, 21): Glycosyl-
D-galactopyranosyl)-(1Ǟ4)-(2,3,6-
D
D
2
6 H, 2 COCH3), 3.28 (s, 3 H, OCH3), 4.15, 4.30 (d, J ϭ 12.0 Hz,
L
D
1 H each, CH2-Ph), 4.33, 4.41 (d, 2J ϭ 12.0 Hz, 1 H each, CH2-
ation of the acceptor 14 (103 mg, 0.144 mmol) with the donor 17
(267 mg, 0.239 mmol) in 1,4-dioxane (10 mL) in the presence of
molecular sieves (AW-300, 0.5 g) and TMSOTf (0.14  in 1,4-diox-
ane, 70 µL, 0.0096 mmol) for 2 h gave the α-(1Ǟ3)-linked tetrasac-
charide 20 (56 mg, 24%), the α-(1Ǟ4)-linked tetrasaccharide 21
(66 mg, 28%), and the unreacted acceptor 14 (21 mg, 21%). In ad-
dition to 20 and 21, a mixture of tetrasaccharides, presumably β-
(1Ǟ3)- and β-(1Ǟ4)-linked products (38 mg, 16%) was obtained,
but these products were not further characterized because of the
complexity of their 2D spectra.
2
Ph), 4.52, 4.96 (d, J ϭ 11.5 Hz, 1 H each, CH2-Ph), 4.55, 4.84 (d,
2J ϭ 10.5 Hz, 1 H each, CH2-Ph), 4.62, 5.08 (d, 2J ϭ 11.0 Hz, 1 H
each, CH2-Ph), 4.64, 4.76 (d, 2J ϭ 12.0 Hz, 1 H each, CH2-Ph),
2
4.67, 4.71 (d, 2J ϭ 12.0 Hz, 1 H each, CH2-Ph), 4.85, 4.93 (d, J ϭ
10.5 Hz, 1 H each, CH2-Ph), 4.87, 4.93 (d, 2J ϭ 11.0 Hz, 1 H each,
CH2-Ph), 7.05Ϫ7.36 (m, 45 H, aromatic H) ppm. 13C NMR
(125 MHz, CDCl3; data for the skeletal carbon atoms are listed in
Table 6): δ ϭ 20.5 (COCH3), 20.6 (COCH3), 20.7 (COCH3), 20.8
(COCH3), 55.2 (OCH3), 72.5 (CH2-Ph), 73.29 (CH2-Ph), 73.33
(CH2-Ph), 73.5 (CH2-Ph), 74.5 (CH2-Ph), 74.9 (CH2-Ph), 75.1 (2
C, 2 CH2-Ph), 75.2 (CH2-Ph), 125.2Ϫ129.0, 137.4, 137.7, 138.0,
138.3, 138.4. 138.7, 138.97, 139.01, 139.5 (aromatic C), 169.3
(COCH3), 170.42 (COCH3), 170.46 (COCH3), 170.52 (COCH3)
ppm. FAB-HRMS: calcd. for C97H107O25N3Na [M ϩ Na]ϩ
1736.7091; found 1736.7126.
The α-(1Ǟ3)-Linked Tetrasaccharide 20: [α]2D3 ϭ ϩ49 (c ϭ 1.0,
CHCl3). 1H NMR (500 MHz, CDCl3; data for the ring and the
exocyclic protons are listed in Table 5): δ ϭ 2.00 (s, 3 H, COCH3),
2.02 (s, 3 H, COCH3), 2.05 (s, 3 H, COCH3), 3.31 (s, 3 H, OCH3),
3
3.67 (d, J4-OH,H-4 ϭ 2.0 Hz, 1 H, 4-OH), 4.20, 4.36 (d, 2J ϭ
12.0 Hz, 1 H each, CH2-Ph), 4.33, 4.47 (d, 2J ϭ 12.0 Hz, 1 H each,
CH2-Ph), 4.53, 4.97 (d, 2J ϭ 11.5 Hz, 1 H each, CH2-Ph), 4.68,
4.71 (d, 2J ϭ 11.5 Hz, 1 H each, CH2-Ph), 4.68, 4.84 (d, 2J ϭ
Compound 18b: [α]2D3 ϭ ϩ33 (c ϭ 1.0, CHCl3). 1H NMR (500 MHz,
CDCl3; data for the ring and the exocyclic protons are listed in
Eur. J. Org. Chem. 2004, 1214Ϫ1227
www.eurjoc.org
 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
1225

K. Ishii, Y. Esumi, Y. Iwasaki, R. Yamasaki
FULL PAPER
11.0 Hz, 1 H each, CH2-Ph), 4.69, 5.14 (d, 2J ϭ 11.5 Hz, 1 H each,
CH2-Ph), 4.82, 4.89 (d, 2J ϭ 11.0 Hz, 1 H each, CH2-Ph), 4.84,
4.87 (d, 2J ϭ 12.5 Hz, 1 H each, CH2-Ph), 7.10Ϫ7.37 (m, 45 H,
4.82 (d, 2J ϭ 10.5 Hz, 1 H each, CH2-Ph), 4.58, 5.06 (d, 2J ϭ
11.0 Hz, 1 H each, CH2-Ph), 4.63, 4.72 (d, 2J ϭ 12.0 Hz, 1 H each,
CH2-Ph), 4.66, 4.78 (d, 2J ϭ 11.0 Hz, 1 H each, CH2-Ph), 4.68,
aromatic H) ppm. 13C NMR (125 MHz, CDCl3; data for the skel- 4.71 (d, 2J ϭ 12.0 Hz, 1 H each, CH2-Ph), 4.76, 4.85 (d, 2J ϭ
3
etal carbon atoms are listed in Table 6): δ ϭ 20.7 (3 C, 3 COCH3),
11.0 Hz, 1 H each, CH2-Ph), 6.32 (d, JNH,H ϭ 4.0 Hz, 1 H,
55.0 (OCH3), 72.5 (CH2-Ph), 73.3 (CH2-Ph), 73.4 (CH2-Ph), 74.1 NHAc), 7.09Ϫ7.34 (m, 45 H, aromatic H) ppm. 13C NMR
(CH2-Ph), 74.6 (CH2-Ph), 74.92 (CH2-Ph), 74.93 (CH2-Ph), 75.2 (125 MHz, CDCl3; data for the skeletal carbon atoms are listed in
(CH2-Ph), 75.4 (CH2-Ph), 126.9Ϫ128.5, 137.3, 137.6, 137.7, 138.0,
Table 6): δ ϭ 20.6 (COCH3), 20.7 (COCH3), 20.8 (COCH3), 23.4
138.2, 138.5, 139.0 (2 C), 139.4 (aromatic C), 170.5 (2 C, 2 (COCH3), 55.2 (OCH3), 72.4 (CH2-Ph), 73.1 (CH2-Ph), 73.3 (CH2-
COCH3), 170.5 (COCH3) ppm. FAB-HRMS: calcd. for
C95H105O24N3Na [M ϩ Na]ϩ: 1694.6986; found 1694.6976.
The α-(1Ǟ4)-Linked Tetrasaccharide 21: [α]2D3 ϭ ϩ78 (c ϭ 1.0,
CHCl3). 1H NMR (500 MHz, CDCl3; data for the ring and the
exocyclic protons are listed in Table 5): δ ϭ 1.79 (s, 3 H, COCH3),
Ph), 73.9 (CH2-Ph), 74.6 (CH2-Ph), 74.9 (CH2-Ph), 75.0 (CH2-Ph),
75.1 (CH2-Ph), 75.3 (CH2-Ph), 126.9Ϫ128.5, 137.7, 137.9, 138.0,
138.1, 138.2, 138.4, 138.90, 138.93, 139.1 (aromatic C), 169.7
(COCH3), 170.35 (COCH3), 170.44 (COCH3), 170.61 (COCH3),
170.64 (COCH3) ppm. HR-FABMS: calcd. for C95H105O24N3Na
1.98 (s, 3 H, COCH3), 2.05 (s, 3 H, COCH3), 3.31 (s, 3 H, OCH3), [M ϩ Na]ϩ: 1694.6986; found 1694.6960.
3
3.67 (d, J3-OH,H-3 ϭ 2.0 Hz, 1 H, 3-OH), 4.23, 4.39 (d, 2J ϭ
12.0 Hz, 1 H each, CH2-Ph), 4.36, 4.62 (d, 2J ϭ 12.0 Hz, 1 H each,
CH2-Ph), 4.53, 4.96 (d, 2J ϭ 11.5 Hz, 1 H each, CH2-Ph), 4.58,
4.88 (d, 2J ϭ 11.0 Hz, 1 H each, CH2-Ph), 4.65, 4.68 (d, 2J ϭ
12.0 Hz, 1 H each, CH2-Ph), 4.65, 5.14 (d, 2J ϭ 11.0 Hz, 1 H each,
CH2-Ph), 4.71, 4.84 (d, 2J ϭ 11.0 Hz, 1 H each, CH2-Ph), 4.74,
4.87 (d, 2J ϭ 11.5 Hz, 1 H each, CH2-Ph), 4.90, 4.88 (d, 2J ϭ
11.0 Hz, 1 H each, CH2-Ph), 7.12Ϫ7.41 (m, 45 H, aromatic H)
ppm. 13C NMR (125 MHz, CDCl3; data for the skeletal carbon
atoms are listed in Table 6): δ ϭ 20.5 (COCH3), 20.7 (COCH3),
20.8 (COCH3), 54.9 (OCH3), 72.7 (CH2-Ph), 73.1 (CH2-Ph), 73.4
(CH2-Ph), 74.57 (CH2-Ph), 74.61 (CH2-Ph), 75.2Ϫ75.3 (4 C, 4
CH2-Ph), 127.0Ϫ128.6, 137.1, 137.3, 137.7, 138.25, 138.30, 138.6,
138.8, 139.1, 139.2 (aromatic C), 169.9 (COCH3), 170.2 (COCH3),
170.5 (COCH3) ppm. HR-FABMS: calcd. for C95H105O24N3Na [M
ϩ Na]ϩ: 1694.6986; found 1694.6960.
Methyl (2,3,4,6-Tetra-O-acetyl-β-
tri-O-acetyl-α- -glucopyranosyl)-(1Ǟ3)-[2-acetamide-3,4,6-tri-O-
acetyl-2-deoxy-α- -glucopyranosyl-(1Ǟ3)]-4,6,7-tri-O-acetyl-
glycero-α- -manno-heptopyranoside (23): Compound 22 (692 mg,
D-galactopyranosyl)-(1Ǟ4)-(2,3,6-
D
D
L-
D
0.400 mmol) was dissolved in EtOH/CH2Cl2 (4:1, v/v, 20 mL) and
stirred with activated charcoal overnight. The mixture was filtered
through Celite, and the filtrate was concentrated. The residue was
dissolved in MeOH/EtOAc/AcOH (2:1:0.1, v/v/v, 15 mL) and Pd/
C (10%, 500 mg) was added. The mixture was hydrogenated (0.9
MPa) with vigorous stirring for 1.5 h. The mixture was filtered
through Celite and the filtrate was concentrated to a residue. Acety-
lation of the residue with Ac2O/pyridine (1:2, v/v, 12 mL) overnight
at room temp., and subsequent flash column chromatography
(EtOAc/hexane, 9:1), gave the title compound 23 (509 mg, 98%).
1
[α]2D4 ϭ ϩ45 (c ϭ 1.0, CHCl3). H NMR (500 MHz, CDCl3; data
for the ring and the exocyclic protons are listed in Table 5): δ ϭ
1.96 (s, 3 H, COCH3), 1.99 (s, 3 H, COCH3), 2.01 (s, 3 H, COCH3),
2.02 (s, 3 H, COCH3), 2.03 (s, 3 H, COCH3), 2.06 (s, 6 H, 2
COCH3), 2.09 (s, 3 H, COCH3), 2.10 (s, 3 H, COCH3), 2.11 (s, 3
Methyl (2,3,4,6-Tetra-O-benzyl-β-
tri-O-benzyl-α- -glucopyranosyl)-(1Ǟ3)-[2-acetamide-6-O-acetyl-
3,4-di-O-benzyl-2-deoxy-α- -glucopyranosyl-(1Ǟ2)]-4,6,7-tri-O-
acetyl- -glycero-α-
catalyst:[33] A mixture of compound 18a (771 mg, 0.450 mmol) and 3 H, COCH3), 3.37 (s, 3 H, OCH3) 6.15 (d, JNH,H ϭ 4.5 Hz, 1 H,
D-galactopyranosyl)-(1Ǟ4)-(2,3,6-
D
D
L
D-manno-heptopyranoside (22): (a) Using Lindlar H, COCH3), 2.13 (s, 3 H, COCH3), 2.15 (s, 3 H, COCH3), 2.19 (s,
3
the catalyst [Pd (5%) on calcium carbonate; 2.0 g] in EtOAc
(40 mL) was stirred vigorously for 3 days under an atmospheric
pressure of hydrogen. The mixture was filtered through Celite and
the filtrate was concentrated to dryness. The residue was dissolved
in MeOH/Ac2O (7:3, v/v, 20 mL) and stirred at room temp. for 1 h.
The mixture was concentrated to a residue that was purified by
flash column chromatography (hexane/EtOAc, 3:2 Ǟ 1:1) to give
the title compound 22 (692 mg, 89%) as a foam. (b) Using AcSH/
pyridine:[31] Compound 18a (87 mg, 0.051 mmol) was treated with
AcSH (2 mL) and pyridine (1 mL) at 40 °C for 12 days. The AcSH
was evaporated under a stream of nitrogen and the residue was
purified by flash column chromatography (hexane/toluene/EtOAc,
1:1:1) to give the title compound 22 (59 mg, 68%) as a colorless
foam. (c) Zinc/AcOH:[32] A mixture of compound 18a (52 mg,
0.030 mmol), glacial acetic acid (0.4 mL), and zinc powder
(400 mg) was stirred in CH2Cl2 (5 mL) for 8 days at room temp.
After filtering the mixture through Celite, the filtrate was treated
with Ac2O/MeOH (3:7, v/v, 5 mL) at room temp. for 1 h. The mix-
ture was concentrated to a residue that was purified by flash col-
umn chromatography (hexane/EtOAc, 3:2 Ǟ 1:1) to give the title
compound 22 (36 mg, 68%). Compound 22: [α]2D3 ϭ ϩ36 (c ϭ 1.0,
CHCl3). 1H NMR (500 MHz, CDCl3; data for the ring and the
exocyclic protons are listed in Table 5): δ ϭ 1.84 (s, 3 H, COCH3),
1.91 (s, 3 H, COCH3), 1.97 (s, 3 H, COCH3), 2.01 (s, 3 H, COCH3),
2.04 (s, 3 H, COCH3), 3.26 (s, 3 H, OCH3), 4.16, 4.28 (d, 2J ϭ
12.0 Hz, 1 H each, CH2-Ph), 4.16, 4.29 (d, 2J ϭ 11.5 Hz, 1 H each,
CH2-Ph), 4.50, 4.95 (d, 2J ϭ 11.5 Hz, 1 H each, CH2-Ph), 4.54,
NHAc) ppm. 13C NMR (125 MHz, CDCl3; data for the skeletal
carbon atoms are listed in Table 6): δ ϭ 20.4Ϫ22.6 (COCH3), 55.3
(OCH3), 169.08 (COCH3), 169.11 (COCH3), 169.2 (COCH3), 169.8
(COCH3), 169.95 (COCH3), 170.00 (COCH3), 170.19 (COCH3),
170.23 (COCH3), 170.40 (COCH3), 170.42 (COCH3), 170.45
(COCH3), 170.55 (COCH3), 170.64 (COCH3) ppm. HR-FABMS:
calcd. for C54H76NO35 [M ϩ H]ϩ: 1298.4198; found 1298.4186.
Acknowledgments
This work was supported by Grants-in-Aid for Scientific Research
(10306022 and 14360207) from the Ministry of Education of Japan.
[1]
A. Preston, R. E. Mandrell, B. W. Gibson, M. A. Apicella,
Crit. Rev. Microbiol. 1996, 22, 139Ϫ180.
R. Yamasaki, B. E. Bacon, W. Nasholds, H. Schneider, J. M.
[2]
Griffiss, Biochemistry 1991, 30, 10566Ϫ10575.
C. M. John, J. M. Griffiss, M. A. Apicella, R. E. Mandrell, B.
[3]
W. Gibson, J. Biol. Chem. 1991, 266, 19303Ϫ19311.
[4]
D. E. Kerwood, H. Schneider, R. Yamasaki, Biochemistry 1992,
31, 12760Ϫ12768.
A. Gamian, M. Beurret, F. Michon, J. R. Brisson, H. J. Jen-
[5]
nings, J. Biol. Chem. 1992, 267, 922Ϫ925.
N. J. Phillips, M. A. Apicella, J. M. Griffiss, B. W. Gibson,
[6]
Biochemistry 1992, 31, 4515Ϫ4526.
A. F. M. Verheul, H. Snippe, J. T. Poolman, Microbiol. Rev.
[7]
1993, 57, 34Ϫ49.
1226
 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
Eur. J. Org. Chem. 2004, 1214Ϫ1227

Synthesis of a 2,3-Di-O-substituted Heptose Structure
FULL PAPER
M. J. Robins, V. Samano, M. D. Johnson, J. Org. Chem. 1990,
55, 410Ϫ412.
[8]
[24]
[25]
[26]
[27]
[28]
S. Gulati, D. P. McQuillen, J. Sharon, P. A. Rice, J. Infect. Dis.
1996, 174, 1238Ϫ1248.
S. Gulati, D. P. McQuillen, R. E. Mandrell, D. B. Jani, P. A.
[9]
S. Ogawa, M. Ashiura, C. Uchida, Carbohydr. Res. 1998, 307,
Rice, J. Infect. Dis. 1996, 174, 1223Ϫ1237.
83Ϫ95.
[10]
C. Bernlind, S. Oscarson, J. Org. Chem. 1998, 63, 7780Ϫ7788.
A. Demchenko, T. Stauch, G. J. Boons, Synlett 1997, 7,
818Ϫ820.
A. V. Demchenko, E. Rousson, G. J. Boons, Tetrahedron Lett.
1999, 40, 6523Ϫ6526.
B. Wegmann, R. R. Schmidt, J. Carbohydr. Chem. 1987, 6,
357Ϫ375.
H. Lönn, J. Carbohydr. Chem. 1987, 6, 301Ϫ306.
H. A. Orgueira, A. Bartolozzi, P. Schell, R. Litjens, E. R. Pal-
macci, P. H. Seeberger, Chem. Eur. J. 2003, 9, 140Ϫ169.
Y. Nakahara, H. Iijima, T. Ogawa, Carbohydr. Lett. 1994, 1,
99Ϫ106.
A. Ishii, H. Hojo, A. Kobayashi, K. Nakamura, Y. Nakahara,
Y. Ito, Tetrahedron 2000, 56, 6235Ϫ6243.
J. Tamura, K. W. Neumann, T. Ogawa, Liebigs Ann. 1996, 8,
1239Ϫ1257.
N. C. R. van Straten, N. Kriek, C. M. Timmers, S. C. M.
Wigchert, G. A. van der Marel, J. H. van Boom, J. Carbohydr.
Chem. 1997, 16, 947Ϫ966.
B. Grzeszczyk, A. Zamojski, Carbohydr. Res. 1994, 262,
49Ϫ57.
P. J. Garegg, S. Oscarson, M. Szönyi, Carbohydr. Res. 1990,
[11]
R. Yamasaki, H. Koshino, S. Kurono, Y. Nishinaka, D. P.
McQuillen, A. Kume, S. Gulati, P. A. Rice, J. Biol. Chem. 1999,
274, 36550Ϫ36558.
R. Yamasaki, D. E. Kerwood, H. Schneider, K. P. Quinn, J. M.
[12]
Griffiss, R. E. Mandrell, J. Biol. Chem. 1994, 269,
[29]
[30]
30345Ϫ30351.
[13]
R. Yamasaki, A. Takajo, H. Kubo, T. Matsui, K. Ishii, M.
Yoshida, J. Carbohydr. Chem. 2001, 20, 171Ϫ180.
[14]
[31]
[32]
[33]
[34]
K. Ishii, H. Kubo, R. Yamasaki, Carbohydr. Res. 2002, 337,
11Ϫ20.
[15]
H. Kubo, K. Ishii, H. Koshino, K. Toubetto, K. Naruchi, R.
Yamasaki, Eur. J. Org. Chem. 2004, 1202Ϫ1213, preceding
paper.
[16]
N. J. Phillips, M. A. Apicella, J. M. Griffiss, B. W. Gibson,
Biochemistry 1993, 32, 2003Ϫ2012.
S. P. Gaucher, M. T. Cancilla, N. J. Philips, B. W. Gibson, J. A.
[17]
Leary, Biochemistry 2000, 39, 12406Ϫ12414.
[18]
[35]
[36]
[37]
[38]
E. Mark, E. Zbiral, H. Brandstetter, Monatsh. Chem. 1980,
111, 289Ϫ307.
[19]
T. Halmos, R. Montserret, J. Filippi, K. Antonakis, Carbohydr.
Res. 1987, 170, 57Ϫ69.
205, 125Ϫ132.
[20]
´
´
M. S. Arias Perez, M. J. Santos, Tetrahedron 1996, 52,
P. J. Garegg, S. Oscarson, H. Ritzen, M. Szönyi, Carbohydr.
10785Ϫ10798.
Res. 1992, 228, 121Ϫ128.
[21]
[22]
[23]
´
´
M. S. Arias Perez, M. S. Lopez, M. J. Santos, J. Chem. Soc.,
Perkin Trans. 2 2002, 1549Ϫ1552.
A. R. Vaino, W. A. Szarek, Chem. Commun. 1996, 21,
2351Ϫ2352.
A. D. Cox, J. C. Wright, M. A. J. Gidney, S. Lacelle, J. S.
Plested, A. Martin, E. R. Moxon, J. C. Richards, Eur. J. Bi-
ochem. 2003, 270, 1759Ϫ1766.
G. O. Aspinall, M. A. Monteiro, H. P. Pang, L. A. Kurjanczyk,
J. L. Penner, Carbohydr. Res. 1995, 279, 227Ϫ244.
Received October 14, 2003
[39]
A. B. Smith, G. R. Ott, J. Am. Chem. Soc. 1996, 118,
13095Ϫ13096.
Eur. J. Org. Chem. 2004, 1214Ϫ1227
www.eurjoc.org
 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
1227