I. J. Talisman et al. / Carbohydrate Research 346 (2011) 883–890
889
Table 4
Glycosidation of 1a using in situ generated Ag–NHC complexesa
OAc
OAc
Ag2CO3
O
O
+
AcO
ArOH
AcO
AcO
IL, BTEACl, rt
AcO
OAr
OAc
Br
OAc
1b
3a-c
Entry
Acceptor
Product
Isolated yield (%)
a:b ratio
1
2
3
4-Nitrophenol
4-Cyanophenol
4-Methoxyphenol
3a
3b
3c
47/36b
35
37
ndc
b only
b only
a
BmIMꢀBF4 (1.0 g), BTEACl (2 equiv), and Ag2CO3 (2 equiv) were premixed at rt for 1 h followed by addition of ArOH (3 equiv) and 1a (0.24 mmol); the mixture was stirred
at rt for 3 h.
b
Isolated elimination product.
OAc
O
AcO
AcO
OAc
c
Not determined.
Table 5
1.1 Hz, 1H), 5.10 (dd, J = 10.5, 3.4 Hz, 1H), 4.99 (d, J = 8.0 Hz, 1H),
4.20 (ddd, J = 27.9, 11.3, 6.7 Hz, 2H), 4.04 (td, J = 6.9, 1.1 Hz, 1H),
2.30 (s, 3H), 2.18 (s, 3H), 2.07 (s, 3H), 2.06 (s, 3H), 2.01 (s, 3H).
13C NMR (101 MHz, CDCl3): d 170.48, 170.39, 170.26, 169.52,
155.07, 132.97, 130.12 (2C’s), 117.09 (2C’s), 100.24, 71.07, 71.01,
68.85, 67.04, 61.48, 20.87, 20.80, 20.79, 20.73. LC–MS (ESI-TOF):
[M+Na]+ calcd for C21H26O10+Na, m/z 461.1418; found, m/z
461.1405.
Recycling of BMImꢀBF4 from glycosidation of 1a with p-nitrophenola
No. of cycle
Isolated yield (%)
a:b ratio
0
1
2
82
80
78
b only
b only
b only
a
BmIMꢀBF4 (1.0 g), BTEACl (2 equiv), and Ag2CO3 (2 equiv) were premixed at rt
for 1 h followed by addition of 4-nitrophenol (3 equiv) and 1a (0.24 mmol); the
mixture was stirred at rt for 3 h.
4.4.3. Pyridin-2-yl 2,3,4,6-tetra-O-acetyl-b-D-galactopyranoside
4.4. General procedure for glycosidation of 1a with various
phenols in BMImꢀBF4 or BMIMꢀPF6
(2l)
1H NMR (400 MHz, CDCl3): d 8.17 (d, J = 3.8 Hz, 1H), 7.68–7.59
(m, 1H), 6.99 (dd, J = 6.6, 5.5 Hz, 1H), 6.82 (d, J = 8.3 Hz, 1H), 6.20
(d, J = 8.3 Hz, 1H), 5.51 (dd, J = 10.2, 8.5 Hz, 1H), 5.48 (d,
J = 3.1 Hz, 1H), 5.18 (dd, J = 10.4, 3.4 Hz, 1H), 4.20–4.12 (m, 3H),
2.18 (s, 3H), 2.02–2.01 (m, 6H), 1.98 (s, 3H). 13C NMR (101 MHz,
CDCl3): d 170.46, 170.40, 170.22, 169.65, 161.46, 146.87, 139.48,
118.97, 111.90, 94.00, 71.27, 71.23, 68.56, 67.13, 61.14, 20.83,
20.81, 20.78, 20.73. LC–MS (ESI-TOF): [M+Na]+ calcd for
Ag2CO3 (2 equiv) and BTEACl (2 equiv) were stirred in the RTIL
(1.5 g) at room temperature for 1 h followed by addition of phenol
(1.5 equiv). After 20 min at 25 °C, 1a (0.7 mmol) was added to the
reaction mixture. To check the progress of the reaction, a small ali-
quot of reaction mixture was taken out and diluted with CH2Cl2,
and this solution was used for TLC spotting. The TLC was per-
formed using an 40:60 EtOAc–hexanes solvent system as the mo-
bile phase. After completion of the reaction in approximately 3 h,
the reaction mixture was diluted with 1–2 mL of CH2Cl2 and loaded
onto a silica gel cartridge for product isolation by flash chromatog-
raphy using a gradient of EtOAc–hexanes (0–40% EtOAc). The de-
sired product was obtained as white foam, and the yields with
corresponding RTILs are given in Table 3.
C19H23NO10+Na, m/z 448.1214; found, m/z 448.1254.
4.4.4. 7-Hydroxy-4-oxo-2-phenyl-4H-chromen-3-yl 2,3,4,6-
tetra-O-acetyl-b- -galactopyranoside (2n)
D
1H NMR (400 MHz, CDCl3): d 8.10–8.04 (m, 3H), 7.98 (s, 1H),
7.46 (dd, J = 5.3, 1.9 Hz, 3H), 6.99–6.93 (m, 2H), 5.60 (d, J = 7.9 Hz,
1H), 5.39 (dd, J = 10.4, 7.9 Hz, 1H), 5.35 (d, J = 3.4 Hz, 1H), 5.07
(dd, J = 10.4, 3.4 Hz, 1H), 4.11 (ddd, J = 16.0, 13.9, 6.9 Hz, 1H),
3.84 (s, 3H), 2.12 (s, 6H), 1.99 (s, 3H), 1.90 (s, 3H). 13C NMR
4.4.1. p-Bromophenyl 2,3,4,6-tetra-O-acetyl-b-D-
galactopyranoside (2h)
(101 MHz, CDCl3): d 174.06, 170.56, 170.44, 170.32, 170.23,
1H NMR (400 MHz, CDCl3): d 7.40 (d, J = 8.8 Hz, 2H), 6.89 (d,
J = 8.8 Hz, 2H), 5.47 (dd, J = 8.6, 6.1 Hz, 1H), 5.45 (d, J = 3.5 Hz,
1H), 5.11 (dd, J = 10.4, 3.4 Hz, 1H), 5.00 (d, J = 7.9 Hz, 1H), 4.19
(ddd, J = 17.5, 11.3, 6.6 Hz, 2H), 4.05 (t, J = 6.7 Hz, 1H), 2.18 (s,
3H), 2.07 (s, 3H), 2.06 (s, 3H), 2.01 (s, 3H). 13C NMR (101 MHz,
CDCl3): d 170.43, 170.31, 170.20, 169.44, 156.05, 132.60 (2C’s),
118.90 (2C’s), 115.97, 99.76, 71.24, 70.86, 68.67, 66.93, 61.46,
20.84, 20.77, 20.69. LC–MS (ESI-TOF): [M+Na]+ calcd for
162.01, 157.43, 157.28, 136.10, 130.87, 130.82, 129.20 (2C’s),
128.18 (2C’s), 127.44, 117.60, 115.33, 102.97, 99.71, 71.01, 70.76,
69.42, 66.99, 60.91, 21.12, 20.74, 20.72, 20.68. LC–MS (ESI-TOF):
m/z [M+H]+ calcd for C29H28O13+H: 585.1603; found 585.1517.
LC–MS (ESI-TOF): [M+Na]+ calcd for C29H28O13+Na, m/z 607.1422;
found, m/z 607.1424.
4.4.5. 3-(2,3,4,6-Tetra-O-acetyl-b-D-galactopyranosyloxy)-4-oxo-
C20H23BrO10+Na, m/z 525.0367; found, m/z 525.0315.
2-phenyl-4H-chromen-7-yl 2,3,4,6-tetra-O-acetyl-b-D-
galactopyranoside (2o)
4.4.2. p-Tolyl 2,3,4,6-tetra-O-acetyl-b-
D
-galactopyranoside (2k)
1H NMR (400 MHz, CDCl3): d 8.17 (d, J = 8.9 Hz, 1H), 8.09–8.03
(m, 2H), 7.54–7.45 (m, 3H), 7.12 (d, J = 2.2 Hz, 1H), 7.06 (dd,
J = 8.9, 2.3 Hz, 1H), 5.66 (d, J = 7.9 Hz, 1H), 5.55 (dd, J = 10.5,
1H NMR (400 MHz, CDCl3): d 7.09 (dd, J = 8.7, 0.6 Hz, 2H), 6.90
(d, J = 8.6 Hz, 2H), 5.47 (dd, J = 9.8, 7.3 Hz, 1H), 5.45 (dd, J = 3.3,