Synthesis of trehalose mimics by bismuth(III) triflate or bis(trifluoromethane)sulfonimide-catalyzed 1-C-methyl-d-hexopyranosylation

Article abstract of DOI:10.1016/j.tetasy.2006.11.008

We investigated the ketopyranosylation of 2,3,4,6-tetra-O-benzyl-1-C-methyl-d-hexopyranoses with the benzylated d-aldohexopyranoses in order to produce novel non-reducing disaccharides as trehalose mimics. It was found that 5 mol % of bismuth(III) triflat

Full text of DOI:10.1016/j.tetasy.2006.11.008

Tetrahedron: Asymmetry 17 (2006) 2914–2918
Synthesis of trehalose mimics by bismuth(III) triflate
or bis(trifluoromethane)sulfonimide-catalyzed
1-C-methyl-D-hexopyranosylation
Takashi Yamanoi,a,* Ryo Inoue,a,b Sho Matsuda,a Kaname Katsurayac and Keita Hamasakib
aThe Noguchi Institute, 1-8-1 Kaga, Itabashi-ku, Tokyo 173-0003, Japan
bDepartment of Applied Chemistry, Shibaura Institute of Technology, 3-7-5 Toyosu, Koto-ku, Tokyo 135-8548, Japan
cSchool of Home Economics, Wayo Women’s University, Chiba 272-8533, Japan
Received 19 September 2006; accepted 4 November 2006
Abstract—We investigated the ketopyranosylation of 2,3,4,6-tetra-O-benzyl-1-C-methyl-D-hexopyranoses with the benzylated D-aldo-
hexopyranoses in order to produce novel non-reducing disaccharides as trehalose mimics. It was found that 5 mol % of bismuth(III) tri-
flate or bis(trifluoromethane)sulfonimide efficiently catalyzed the ketopyranosylation that produced various non-reducing disaccharides.
Ó 2006 Elsevier Ltd. All rights reserved.
1. Introduction
to synthesize trehalose mimics into which 1-C-methyl-
D-hexopyranoses were incorporated. As a result of the
preliminary experiment, the fully benzylated a-D-gluco-
pyranosyl 1-C-methyl-a-D-glucopyranoside derivative
was successfully obtained in 47% yield by the reaction
of 2,3,4,6-tetra-O-benzyl-1-C-methyl-a-D-glucopyranose 1
with 2,3,4,6-tetra-O-benzyl-D-glucopyranose 2 in the pres-
ence of 5 mol % Tf2NH in CH3CN.3a,c
The 1-C-alkyl-sugars, which have alkyl groups at their ano-
meric carbon centers, are considered to be a novel class of
artificial ketoses, which replace naturally occurring aldoses.
Their glycosylated compounds, that is, 1-C-alkyl-glyco-
sides, are expected to show biological functions that are
different from those of natural compounds.1 Therefore,
considerable attention has been paid to efficient glycosida-
tion methods for synthesizing 1-C-alkyl-O-glycosides.2
We have also studied the synthesis of 1-C-alkyl-D-gluco-
pyranosides by Lewis acid- or Brønsted acid-catalyzed
O-glycosidation.3 Our investigation into the 1-C-alkyl-D-
glucopyranosylation showed that 5 mol % of Tf2NH was
an efficient activator for a dehydration–condensation
O-glycosidation using 1-C-alkyl-2,3,4,6-tetra-O-benzyl-D-
glucopyranoses as the ketosyl donors.3a,c
To the best of our knowledge, this was the first example of
synthesizing a non-reducing disaccharide into which a 1-C-
methyl-D-hexopyranose was incorporated. Interestingly,
the non-reducing disaccharide synthesized was obtained
as a single isomer and both of its glycosidic linkages were
a-configured. In addition, since trehalose is well known
for its various biological activities such as the suppressive
effect on osteoporosis progress,5 this reaction was expected
to have the potential for synthesizing various types of
trehalose mimics, which show novel useful functions.
Therefore, we made a further investigation into the glycos-
idation conditions of 1 with 2 and applied the reaction
to the synthesis of several non-reducing disaccharides
composed of a 2,3,4,6-tetra-O-benzyl–1-C-methyl-D-hexo-
pyranose and a benzylated D-aldohexopyranose. Our inves-
tigation included not only the stereoselectivity of the
glycosidation, but also a search for other effective activa-
tors of 1, because Tf2NH is a moisture-sensitive compound.
The detailed results are described below.
Another interesting finding was that the ketopyranosyl-
ation showed high a-stereoselectivity. This feature was
expected to be useful for synthesizing mimics of trehalose
(a-D-glucopyranosyl a-D-glucopyranoside), as this natural
non-reducing disaccharide is composed of two glucose mole-
cules linked with each other by an a-glucopyranosidic
linkage.4 Thus we attempted the dehydrative glycosidation
*
Corresponding author. Tel./fax: +81 3 5944 3213; e-mail: tyama@
noguchi.or.jp
0957-4166/$ - see front matter Ó 2006 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tetasy.2006.11.008

T. Yamanoi et al. / Tetrahedron: Asymmetry 17 (2006) 2914–2918
2915
BnO
O Me
BnO
BnO
BnO
BnO
α
BnO
BnO
1
Activator
BnO
O Me
BnO
O
O
1'
OBn
BnO
+
BnO
OBn
Solvent, 0 oC
BnO
OBn
OH
OH
O
1
2
OBn
α
3
Scheme 1.
2. Results and discussion
and Bi(OTf)3 were used as the activators. These results
are shown in Table 2. The reactions using 5 mol % of
Tf2NH in CH2Cl2 at 0 °C for 3 h successfully gave the cor-
responding disaccharides 7–9 in good yields of 64%, 90%,
and 83%, respectively (entries 3, 5, and 7). The reaction
using 4 gave benzyl 2,3,4,6-tetra–O-benzyl-1-C-methyl-a-
D-glucopyranoside 128 as a major by-product (Scheme 3).
The reactions using 5 mol % of Bi(OTf)3 as the activator
also afforded 7–9 in 75%, 84%, and 89%, respectively
(entries 4, 6, and 8).
We first investigated the glycosidation conditions of 1 with
2 using 5 mol % of Tf2NH to afford 3 in the presence of
Ca2SO4 (Scheme 1). These results are summarized in Table
1. Remarkably, the reaction in CH2Cl2 at 0 °C for 3 h
increased the yield of 3 up to 87% (entry 2). This was
due to the high solubility of 2 in CH2Cl2. Lewis acids,
which were expected to be resistant to water, ytterbium(III)
triflate (Yb(OTf)3), scandium(III) triflate (Sc(OTf)3), and
bismuth(III) triflate (Bi(OTf)3)6 were used. The reactions
using Sc(OTf)3 and Bi(OTf)3 in CH2Cl2 at 0 °C for 3 h gave
3 in high yields of 80% and 89%, respectively (entries 4 and
6). Bi(OTf)3 was an efficient activator for the 1-C-methyl-
glucopyranosylation,7 while bismuth(III) trichloride
(BiCl3) did not work at all (entry 7). This was attributable
to the weaker Lewis acidity of BiCl3. Compound 3 was pro-
duced as a single isomer under the stated reaction condi-
tions and both of its glycosidic linkages were determined
as being a by analysis of the NMR spectra (NOE interac-
tion of CH3 and H-2, and H-10 d 5.34 (d, J = 3.4 Hz)).
Compound 7 was obtained as a single isomer (entries 3
and 4), while 8 and 9 were formed in isomeric ratios of
78/22, 58/42 and of 87/13, 76/24, respectively (entries
5–8). The anomeric configurations of all the formed
ketopyranosidic linkages of 7–9 were a, which were also
determined by the observation of the NOE interactions
between the CH3 group and the H-2 of the 1-C-methyl-
D-glucopyranosyl rings. The high a-stereoselectivities
of the 1-C-methyl-D-glucopyranosylation corresponded
to our former results.3a–c As the measurement, from the
0
0
NMR, spectra of JC1 –H1 of 7 indicated 168 Hz, its
mannopyranosidic linkage was determined to be a.9 The
two anomeric protons of H-10 of 8 and 9 were observed
as doublet peaks at d 5.26 (J = 3.4 Hz, a) and d 4.61
(J = 6.9 Hz, b), and at d 5.36 (J = 1.4 Hz, a) and d 4.70
(J = 6.9 Hz, b), respectively.
Next we examined the synthesis of several non-reducing
disaccharides into which 1 was incorporated (Scheme 2).
As the acceptors for the 1-C-methyl-glucopyranosylation,
2,3,4,6-tetra-O-benzyl-D-mannopyranose 4, 2-azido-3,4,6-
tri-O-benzyl-2-deoxy-D-glucopyranose 5, and 2,3,4,6-tetra-
O-benzyl-D-galactopyranose 6 were utilized. Both Tf2NH
In order to investigate the relationship between the a/b-
anomer ratios of the acceptors and those of the aldopyra-
nosidic linkages of the products, we measured the a/b-ano-
mer ratios of the aldohexopyranoses 2, 4–6 in the CH2Cl2
solvent based on the NMR spectra. Compounds 2 and 4–
6 were dissolved in CD2Cl2 and the NMR spectra
measured about 30 min later showed that 2 and 4
contained the b-anomers of ca. 15–20%, and that 5 and 6
contained the b-anomers of ca. 40%. In spite of the pres-
ence of the b-anomers, the ketopyranosylations of 2 and
4 did not form the products having b-aldopyranosidic link-
ages at all. This suggested that the a-anomers of 2 and 4
predominantly worked as the reactive acceptors. The keto-
pyranosylations of 5 and 6 formed small amounts of 8 and
Table 1. Synthesis of trehalose mimic 3 by reaction of 1 with 2 under
several reaction conditions
Entrya
Activator
Solvent
Yield (%)
1
2
3
4
5
6
7
Tf2NH
Tf2NH
CH3CN
CH2Cl2
CH2Cl2
CH2Cl2
PhCH3
CH2Cl2
CH2Cl2
47
87
21
80
61
89
Trace
Yb(OTf)3
Sc(OTf)3
Sc(OTf)3
Bi(OTf)3
BiCl3
a Molar ratio: 1:2:activator = 1:0.67:0.05, reaction time: 3 h, reaction
temperature: 0 °C.
R1
O Me
BnO
R1
O Me
BnO
BnO
BnO
Activator
BnO
BnO
O
2 O
+
(BnO)
R
CH2Cl2, 0 oC
R2 OH
(OBn)
OH
2, 4-6
O
R1= H: R2= OBn; 1
R1= OBn: R2= H; 10
3, 7-9, 11
Scheme 2.

2916
T. Yamanoi et al. / Tetrahedron: Asymmetry 17 (2006) 2914–2918
Table 2. Synthesis of various trehalose mimics 3, 7–9, 11 by the reaction of 1 (or 10) with 2, 4–6
Entrya 1-C-Methylated donor Aldopyranose of
acceptor
Activator (5 mol %) Product
Yield (%) a/b Ratio of
aldopyranosidic linkageb
1
2
1
1
2
2
Tf2NH
3
3
87
89
a Only
Bi(OTf)3
a Only
BnO
BnO
O Me
BnO
BnO
BnO
OBn
O
BnO
3
4
5
6
7
8
1
1
1
1
1
1
Tf2NH
64
75
90
84
83
89
a Only
O
BnO
OBn
OBn
OH
4
O
α
OBn
BnO
7
4
Bi(OTf)3
Tf2NH
7
a Only
78/22
58/42
87/13
76/24
BnO
BnO
O Me
BnO
BnO
BnO
BnO
O
O
N3
BnO
OBn
OBn
N3
OH
5
O
OBn
α, β
8
5
Bi(OTf)3
Tf2NH
8
BnO
BnO
O Me
BnO
OBn
O
BnO
BnO
O
OBn
BnO
OBn
BnO
OH
6
O
BnO
α, β
OBn
9
6
Bi(OTf)3
9
BnO
BnO
OBn
O Me
α
BnO
BnO
OBn
BnO
O Me
9
2
2
Tf2NH
37
80
a Only
a Only
O
BnO
OBn
OBn
OH 10
OBn
O
α
OBn 11
10
10
Bi(OTf)3
11
a Molar ratio: donor:acceptor:activator = 1:0.67:0.05, solvent: CH2Cl2, reaction time: 3 h, reaction temperature: 0 °C.
b All the 1-C-methyl-hexopyranosidic linkages of 3, 7–9, and 11 were a.
reaction conditions (Scheme 2). The reaction using
5 mol % of Tf2NH gave the corresponding 11 in 37% yield
(entry 9). Both of its glycosidic linkages were a. The reac-
tion using 5 mol % of Bi(OTf)3 successfully increased the
yield of 11 to 80% (entry 10).
BnO
O Me
OBn
BnO
BnO
BnO
12
Scheme 3.
9 with b-aldopyranosidic linkages, which showed that their
b-anomers partly participated in the ketopyranosylations
though the a-anomers were preferentially used as the reac-
tive acceptors.
3. Conclusion
Several types of non-reducing disaccharides, into which 1-
C-methyl-a-D-hexopyranoses were incorporated, were syn-
thesized as the trehalose mimics. It was found that 5 mol %
of Bi(OTf)3 or Tf2NH effectively promoted the 1-C-methyl-
hexopyranosylations of the benzylated D-hexopyranoses to
afford the desired non-reducing disaccharides in excellent
Similarly, we investigated the synthesis of a non-reducing
disaccharide by the reaction of 2,3,4,6-tetra-O-benzyl-1-
C-methyl-a-D-mannopyranose 10 with 2 under similar

T. Yamanoi et al. / Tetrahedron: Asymmetry 17 (2006) 2914–2918
2917
yields. The stereoselectivities of the glycosidic linkages
during the ketopyranosylation were also clarified.
H-50), 5.24 (1H, d, J = 2.1 Hz, H-10); 13C NMR (CDCl3):
d 23.0 (CH3), 68.6 (C-6), 69.1 (C-60), 71.6 (C-50), 72.2 (C-
5), 75.23 (C-40 or C-20 or CH2Ph), 75.25 (C-40 or C-20 or
CH2Ph), 75.36 (C-40 or C-20 or CH2Ph), 75.37 (C-40 or
C-20 or CH2Ph), 78.2 (C-4), 79.7 (C-30), 82.9 (C-3), 84.6
(C-2), 90.7 (C-10), 101.2 (C-1, JC1–H1 = 168 Hz); HRMS
(ESI): m/z calcd for C69H72O11Na+: 1099.4967; found:
1099.5009.
4. Experimental
4.1. General
The NMR spectra were measured using an ECA-600
(JEOL) spectrometer at 600 MHz (1H), and 150 MHz
4.2.3. 2-Azido-3,4,6-tri-O-benzyl-2-deoxy-a and b-D-gluco-
pyranosyl 2,3,4,6-tetra-O-benzyl-1-C-methyl-a-D-glucopyr-
anoside 8. Colorless oil (a,b-mixture); a-form; H NMR
1
(13C). The H NMR chemical shifts are referenced to the
internal standard TMS (dH = 0.00). The 13C NMR chemi-
cal shifts are referenced to the solvent signal (dC = 77.0 for
the central line of CDCl3). The ESI-MS spectra were
recorded using a Mariner (Applied Biosystems) spectro-
meter. Optical rotations were recorded using a JASCO
DIP-360 digital polarimeter. All reactions were monitored
by thin-layer chromatography (TLC) using Merck silica gel
60 F254 precoated plates (0.25 mm).
1
(CDCl3): d 1.47 (3H, s, CH3), 5.26 (1H, d, J = 3.4 Hz, H-
10), 3.29 (1H, d, J = 9.6 Hz, H-2); 13C NMR (CDCl3): d
23.0 (CH3), 90.6 (C-10), 101.2 (C-1); b-form; 1H NMR
(CDCl3): d 1.49 (3H, s, CH3), 4.61 (1H, d, J = 6.9 Hz, H-
10), 3.30–3.39 (1H, m, H-2); 13C NMR (CDCl3): d 22.3
(CH3), 95.7 (C-10), 102.6 (C-1); HRMS (ESI): m/z calcd
for C62H65O10N3Na+: 1034.4562; found: 1034.4598 (a, b-
mixture).
4.2. General synthesis of 3 by the ketopyranosylation of 1
with 2
4.2.4. 2,3,4,6-Tetra-O-benzyl-a and b-D-galactopyranosyl
2,3,4,6-tetra-O-benzyl-1-C-methyl-a-D-glucopyranoside 9.
23
To a stirred solution of Bi(OTf)3 (4.4 mg, 0.0067 mmol)
and 2 (48.3 mg, 0.0893 mmol) in CH2Cl2 (3.5 mL) was
added 1 (79.3 mg, 0.134 mmol) at 0 °C in the presence of
Drierite (ca. 100 mg) under an Ar atmosphere. The result-
ing mixture was stirred for 3 h. The reaction was then
quenched by the addition of a satd NaHCO3 solution
(5 mL). The reaction mixture was extracted with ethyl ace-
tate, and the organic layer was washed with water and a
satd NaCl solution. After the organic layer was dried over
Na2SO4, the solvent was evaporated under reduced pres-
sure. The crude product was purified by preparative silica
gel TLC (ethyl acetate/hexane = 1/3) to give 3 as a color-
less oil (85.3 mg, 89%).
a-Form; Colorless oil; ½aꢀD ¼ þ74 (c 0.95, CHCl3); 1H
NMR (CDCl3): d 1.47 (3H, s, CH3), 3.26 (1H, d,
J = 9.6 Hz, H-2), 3.28–3.33 (2H, m, H-6), 3.47 (1H,
dd, J = 6.2 Hz, J = 9.6 Hz, H-60a) 3.55 (1H, dd, J =
7.6 Hz, J = 8.9 Hz, H-60b), 3.63 (1H, dd, J = 9.6 Hz,
J = 10.3 Hz, H-4), 3.93 (1H, dd, J = 8.9 Hz, J = 9.6 Hz,
H-3), 4.02 (1H, d, J = 0.7 Hz, H-30 or H-40), 4.06–4.07
(2H, m, H-20, H-30 or H-40), 4.31–4.33 (1H, m, H-5),
4.34–4.37 (1H, m, H-50), 5.36 (1H, d, J = 1.4 Hz, H-10);
13C NMR (CDCl3): d 22.8 (CH3), 68.4 (C-6), 69.0 (C-60),
69.2 (C-50), 70.9 (C-5), 74.9 (C-30 or C-40), 76.8 (C-20 or
C-30 or C-40), 78.4 (C-4), 78.6 (C-20 or C-30 or C-40), 83.0
(C-3), 85.1 (C-2), 90.9 (C-10), 100.8 (C-1); HRMS (ESI):
m/z calcd for C69H72O11Na+: 1099.4967; found:
23
4.2.1. 2,3,4,6-Tetra-O-benzyl-a-D-glucopyranosyl 2,3,4,6-
tetra-O-benzyl-1-C-methyl-a-D-glucopyranoside 3. Colorless
1099.4985. b-Form; colorless oil; ½aꢀD ¼ þ48 (c 0.70,
CHCl3); 1H NMR (CDCl3): d 1.45 (3H, s, CH3), 3.34
(1H, d, J = 9.6 Hz, H-2), 3.45–3.53 (4H, m, H-30 or H-40,
H-50, H-6a, H-6b), 3.60–3.66 (2H, m, H-60), 3.70 (1H, t,
J = 9.6 Hz, H-4), 3.80–3.84 (2H, m, H-20, H-30, or H-40),
4.19 (1H, t, J = 9.6 Hz, H-3), 4.32–4.37 (3H, m, CH2Ph,
H-5), 4.70 (1H, d, J = 6.9 Hz, H-10); 13C NMR (CDCl3):
d 22.4 (CH3), 68.6 (C-60), 69.0 (C-6), 72.1 (C-5), 73.6 (C-
50), 73.8 (C-20 or C-30 or C-40), 78.7 (C-4), 79.0 (C-20 or
C-30 or C-40), 82.4 (C-20 or C-30 or C-40), 82.9 (C-3), 84.5
(C-2), 97.6 (C-10), 102.3 (C-1); HRMS (ESI): m/z calcd
for C69H72O11Na+: 1099.4967; found: 1099.4975.
23
1
oil; ½aꢀD ¼ þ70 (c 2.0, CHCl3); H NMR (CDCl3): d 1.49
(3H, s, CH3), 3.29 (1H, d, J = 9.6 Hz, H-2), 3.33–3.39 (3H,
m, H-6a, H-6b, H-60a), 3.55–3.58 (1H, m, H-60b), 3.56
(1H, dd, J = 10.3 Hz, J = 3.4 Hz, H-20), 3.64 (1H, dd,
J = 9.6 Hz, J = 10.3 Hz H-4), 3.68 (1H, t, J = 9.6 Hz, H-
40), 4.03 (1H, t, J = 10.3 Hz, H-3), 4.05 (1H, t, J = 9.6 Hz,
H-30), 4.17–4.19 (1H, m, H-50), 4.29–4.28 (1H, m, H-5),
5.34 (1H, d, J = 3.4 Hz, H-10); 13C NMR (CDCl3): d 22.7
(CH3), 68.3 (C-60), 68.5 (C-6), 70.0 (C-50), 71.0 (C-5), 78.0
(C-40), 78.5 (C-4), 80.1 (C-20), 81.8 (C-3), 82.7 (C-30), 85.1
(C-20), 90.2 (C-10), 101.0 (C-1); HRMS (ESI): m/z calcd for
C69H72O11Na+: 1099.4967; found: 1099.5006.
4.2.5. 2,3,4,6-Tetra-O-benzyl-a-D-glucopyranosyl 2,3,4,6-
tetra-O-benzyl-1-C-methyl-a-D-mannopyranoside 11. Col-
23
1
4.2.2. 2,3,4,6-Tetra-O-benzyl-a-D-mannopyranosyl 2,3,4,6-
tetra-O-benzyl-1-C-methyl-a-D-glucopyranoside 7. Color-
orless oil; ½aꢀD ¼ þ57 (c 0.81, CHCl3); H NMR (CDCl3):
1H NMR (CDCl3): d 1.46 (3H, s, CH3), 3.50–3.51 (2H, m,
H-60), 3.54–3.58 (3H, m, H-6a, H-40, H-20), 3.66 (1H, t,
J = 9.6 Hz, H-4), 3.72 (1H, dd, J = 3.4 Hz, J = 10.3 Hz,
H-6b), 3.77–3.78 (1H, m, H-5), 3.89 (1H, dd, J = 8.9 Hz,
J = 9.6 Hz, H-30), 3.94 (1H, dd, J = 9.6 Hz, J = 10.3 Hz,
H-3), 4.16 (1H, dd, J = 2.1 Hz, J = 9.6 Hz, H-2), 4.18–
4.21 (1H, m, H-50), 5.42 (1H, d, J = 3.4 Hz, H-10); 13C
NMR (CDCl3): d 22.5 (CH3), 68.5 (C-6), 69.3 (C-60), 70.5
(C-5), 72.9 (C-50), 74.8 (C-3), 77.9 (C-4), 79.1 (C-20), 80.1
23
1
less oil; ½aꢀD ¼ þ59 (c 0.83, CHCl3); H NMR (CDCl3): d
1.46 (3H, s, CH3), 3.23 (1H, d, J = 9.6 Hz, H-2), 3.29–
3.31 (1H, m, H-5), 3.44 (1H, d, J = 10.3 Hz, H-6a), 3.52–
3.54 (2H, m, H-6b, H-20), 3.56 (1H, dd, J = 8.9 Hz,
J = 10.3 Hz, H-4), 3.61 (1H, d, J = 10.3 Hz, H-60a), 3.70–
3.72 (1H, m, H-60b), 3.74 (1H, dd, J = 8.9 Hz,
J = 10.3 Hz, H-3), 3.96 (1H, dd, J = 2.8 Hz, J = 10.3 Hz,
H-30), 4.00 (1H, t, J = 9.6 Hz, H-40), 4.07–4.10 (1H, m,

2918
T. Yamanoi et al. / Tetrahedron: Asymmetry 17 (2006) 2914–2918
(C-40), 80.7 (C-2), 81.8 (C-30), 89.9 (C-10), 102.0 (C-1);
HRMS (ESI): m/z calcd for C69H72O11Na+: 1099.4967;
found: 1099.4999.
Yamazaki, I.; Inoue, R.; Hamasaki, K.; Watanabe, M.
Heterocycles 2006, 68, 673–677; We also reported the Brønsted
acid-catalyzed intramolecular b-glycosidation of 1-C-alkyl-D-
hexopyranoses to form the anhydroketopyranoses: (d) Yama-
noi, T.; Matsumura, K.; Matsuda, S.; Oda, Y. Synlett 2005,
2973–2977.
Acknowledgments
4. Higashiyama, T. Pure Appl. Chem. 2002, 74, 1262–1269.
5. Nishizaki, Y.; Yoshizane, C.; Toshimori, Y.; Arai, N.;
Akamatsu, S.; Hanaya, T.; Arai, S.; Ikeda, M.; Kurimoto,
M. Nutrition Res. 2000, 20, 653–664.
6. Gaspard-Iloughmane, H.; Le Roux, C. Eur. J. Org. Chem.
2004, 2517–2532, Bi(OTf)3 was commercially available from
Sigma–Aldrich Chemical Co.
Financial support from a Grant-in Aid for Scientific Re-
search from the Japan Society for the Promotion of Science
(Grant No. 185501600002) is acknowledged.
References
7. Other glycosidation reports using Bi(OTf)3: (a) Adinolfi, M.;
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8. (a) Li, X. L.; Ohtake, H.; Takahashi, H.; Ikegami, S.
Tetrahedron 2001, 57, 4297–4309; (b) Yamanoi, T.; Oda, Y.
Heterocycles 2002, 57, 229–234.
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