Table 1 Ceric ammonium nitrate-catalyzed O-glycosidation of tri-O-acetyl- or tri-O-benzoyl-D-glucala
Alcohol
R@OHb
Entry
Glucal Rb
Reaction time/h
Yieldc (%)
Anomeric ratiod a : b
a
Ac
Ac
3.0
3.5
90
92
7 : 1
7 : 1
b
c
d
e
Ac
Ac
Bz
4.0
2.5
7.0
87
89
80
8 : 2
9 : 1
10 : 1
f
Bz
Ac
Ac
6.0
3.0
3.5
80
92
81
8 : 2
8 : 2
g
h
14 : 1
i
Ac
3.0
90
14 : 1
j
Ac
Ac
4.0
2.5
82
90
8 : 2
8 : 2
k
l
Ac
4.5
87
12 : 1
m
n
Bz
Ac
Ac
Ac
8.0
4.5
3.0
4.0
87
85
90
85
8 : 2
7 : 2
8 : 2
7 : 2
o
p
q
Ac
3.0
90
10 : 1
r
s
Ac
Ac
4.5
5.0
80
78
14 : 1
10 : 1
Cholesterol
a All the products were characterized by 1H and 13C NMR and IR spectra. b Bn \ benzyl; Bz \ benzoyl; Bu \ n-butyl. c Isolated yields as
anomeric mixtures after puriÐcation. d The anomeric ratio was determined on the basis of the integrated ratios of the anomeric hydrogens in the
1H NMR spectra.
ammonium nitrate (0.5 mmol) in acetonitrile (15 ml) was
stirred under reÑux for the appropriate time (see Table 1).
After completion of the reaction as indicated by TLC, the
reaction mixture was quenched with water (10 ml) and
extracted with ethyl acetate (2 ] 15 ml). The combined layers
were dried over anhydrous Na SO , concentrated in vacuo
and puriÐed by column chromatography on silica gel (Merck,
100È200 mesh, ethyl acetateÈhexane 2 : 8) to a†ord pure 2,3-
unsaturated glycosides. Representative spectroscopic data are
given below.
(d, 1H, J \ 8.5, 1-H), 5.85 (dd, 2H, J \ 10.3 and 4.7 Hz, 2-H,
3-H). 13C NMR (proton decoupled, CDCl ): d 19.9, 20.6, 20.8,
3
62.7, 65.0, 66.7, 66.9, 69.3, 80.9, 94.4, 127.3, 129.2, 170.1, 170.6.
IR (KBr): l 3468, 3286, 2926, 2121, 1739, 1373, 1232, 1042,
907, 733 cm~1. b-isomer: liquid, 1H NMR (CDCl ): d 1.90 (s,
3
1H), 2.05 (s, 6H), 2.50 (m, 2H), 3.65 (m, 1H), 3.85 (m, 1H), 4.13
2
4
(m, 1H, 5-H), 4.20 (m, 2H, 6-H , 6-H ), 5.10 (br s, 1H, 4-H),
a
b
5.25 (d, 1H, J \ 8.5, 1-H), 5.95 (dd, 2H, J \ 10.3 and 4.7 Hz,
2-H, 3-H).
Entry n. a-isomer: liquid, 1H NMR (CDCl ): d 2.05 (s, 6H),
3
Entry i. a-isomer: liquid, 1H NMR (CDCl ): d 0.20 (m, 2H),
3.35 (s, 3H), 3.55 (t, 2H, J \ 6.8), 3.65 (m, 1H), 3.85 (m, 1H),
3
0.55 (m, 2H), 1.05 (m, 1H), 2.05 (s, 6H), 3.45 (m, 2H), 4.05 (m,
4.05 (m, 1H, 5-H), 4.20 (m, 2H, 6-H , 6-H ), 5.0 (br s, 1H, 4-H),
a
b
1H, 5-H), 4.15 (m, 2H, 6-H , 6-H ), 5.05 (br s, 1H, 4-H), 5.25
5.30 (d, 1H, J \ 8.5, 1-H), 5.85 (dd, 2H, J \ 10.7 and 5.0 Hz,
a
b
(d, 1H, J \ 8.50 Hz, 1-H), 5.85 (m, 2H, 2-H, 3-H). 13C NMR
2-H, 3-H). 13C NMR (proton decoupled, CDCl ): d 20.5, 20.7,
58.7, 62.8, 65.2, 66.8, 67.5, 71.6, 94.4, 127.6, 129.0, 130.2, 170.0,
3
(proton decoupled, CDCl ): d 2.9, 3.2, 10.4, 20.5, 20.7, 62.8,
65.1, 66.7, 72.5, 73.1, 93.6, 127.8, 128.8, 169.9, 170.3. IR (KBr):
3
172.2. IR (KBr): l 3469, 2929, 1741, 1373, 1234, 1047, 904, 735
l 3469, 3378, 3007, 2907, 2358, 1744, 1374, 1235, 1039, 907,
cm~1. b-isomer: liquid, 1H NMR (CDCl ): d 2.05 (s, 6H), 3.35
3
830 cm~1. b-isomer: liquid, 1H NMR (CDCl ): d 0.20 (m, 2H),
(s, 3H), 3.55 (t, 2H, J \ 6.8), 3.65 (m, 1H), 3.85 (m, 1H), 4.10
3
0.55 (m, 2H), 1.05 (m, 1H), 2.05 (s, 6H), 3.45 (m, 2H), 4.10 (m,
(m, 1H, 5-H), 4.25 (m, 2H, 6-H , 6-H ), 5.10 (br s, 1H, 4-H),
a
b
1H, 5-H), 4.20 (m, 2H, 6-H , 6-H ), 5.10 (br s, 1H, 4-H), 5.25
5.30 (d, 1H, J \ 8.5, 1-H), 5.95 (dd, 2H, J \ 10.7 and 5.0 Hz,
a
b
(d, 1H, J \ 8.50 Hz, 1-H), 5.90 (m, 2H, 2-H, 3-H).
2-H, 3-H).
Entry k. a-isomer: liquid, 1H NMR (CDCl ): d 1.90 (s, 1H),
Entry q. a-isomer: liquid, 1H NMR (CDCl ): d 1.75 (d, 3H,
3
3
2.05 (s, 6H), 2.50 (m, 2H), 3.65 (m, 1H), 3.85 (m, 1H), 4.10 (m,
J \ 6.8), 2.05 (s, 6H), 3.95 (m, 2H), 4.05 (m, 1H, 5-H), 4.15 (m,
1H, 5-H), 4.15 (m, 2H, 6-H , 6-H ), 5.00 (br s, 1H, 4-H), 5.25
2H, 6-H , 6-H ), 5.00 (br s, 1H, 4-H), 5.25 (d, 1H, J \ 8.5, 1-H),
a
b
a
b
New J. Chem., 2001, 25, 538È540
539