S. Deng et al. / Carbohydrate Research 317 (1999) 53–62
57
H-3%, H-5%, H-3, H-26b), 1.24 (s, 9 H); 13C
NMR (75 MHz, CDCl3): l 177.69, 140.15,
136.78, 128.95, 128.04, 126.00, 121.56, 109.04,
101.49, 99.57, 80.70, 80.54, 79.06, 74.16, 72.43,
68.40, 66.59, 65.85, 61.87, 56.24, 49.84, 41.35,
40.02, 39.49, 38.64, 36.91, 36.62, 31.82, 31.58,
31.17, 30.02, 29.32, 28.54, 26.92, 20.58, 19.07,
16.87, 16.01, 14.25; FABMS (m/z): 749 [M+
1], 747, 663, 607, 397 (base). Anal. Calcd for
C45H64O9·H2O: C, 70.47; H, 8.67. Found: C,
70.52; H, 8.80. 7b: [h]2D1 −73.9° (c 0.57,
CHCl3); Rf 0.71 (4:1 petroleum ether–EtOAc);
1H NMR (300 MHz, CDCl3): l 7.40–7.20 (m,
5 H), 5.51 (s, 1 H, PhCH), 5.34 (m, 2 H, H-6,
H-3%), 5.03 (dd, 1 H, J1%,2% 7.9, J2%,3% 8.9, H-2%),
4.71 (d, 1 H, H-1%), 4.45–4.27 (m, 2 H, H-16,
H-6%a), 3.81 (t, 1 H, J6%a,6%b 10.3, J5%,6%b 10.1,
H-6%b), 3.71 (t, 1 H, J 9.3, H-4%), 3.56–3.34
(m, 4 H, H-5%, H-3, H-26a, H-26b), 1.18 (s, 9
H), 1.16 (s, 9 H); 13C NMR (75 MHz, CDCl3):
l 176.95, 176.25, 140.04, 136.73, 128.60,
127.88, 125.59, 121.62, 108.99, 100.80, 99.89,
80.54, 79.19, 78.53, 71.46, 71.13, 68.41, 66.57,
66.03, 61.89, 56.22, 49.82, 41.35, 40.02, 39.49,
38.64, 38.47, 36.89, 36.60, 31.82, 31.58, 31.17,
30.03, 29.30, 28.56, 26.97, 26.83, 20.58, 19.07,
16.87, 16.01, 14.26; FABMS (m/z): 833 [M+
1], 831, 662, 397 (base). Anal. Calcd for
C50H72O10: C, 72.08; H, 8.71. Found: C, 71.95;
H, 8.98.
Diosgenyl 4,6-O-benzylidene-i- -glucopyr-
D
anoside (6).—A solution of 5 (111 mg, 0.127
mmol) and NaOMe (catalytic) in CH2Cl2 (6
mL) and MeOH (6 mL) was stirred at 50 °C
overnight. The mixture was then neutralized
with Dowex-50 (H+ form), and filtered. The
filtrate was concentrated, and the resulting
residue was purified by column chromatogra-
phy to afford diol 6 (71 mg, 85%) [5b].
Diosgenyl 4,6-O-benzylidene-3-O-pi6aloyl-
i-
ylidene-2-O-pi6aloyl-i-
and diosgenyl 4,6-O-benzylidene-2,3-di-O-pi-
6aloyl-i- -glucopyranoside (7b).—To a solu-
D
-glucopyranoside (7), diosgenyl 4,6-O-benz-
D-glucopyranoside (7a),
D
tion of 6 (723 mg, 1.09 mmol) in pyridine (4
mL) was slowly added pivaloyl chloride (0.27
mL, 2.19 mmol) at room temperature. After
being stirred for 2 h, the mixture was
quenched with MeOH and concentrated.
Chromatography of the residue on a silica gel
column (6:1 to 4:1 petroleum ether–EtOAc)
gave 7 (511 mg, 64%) as a white foam, 7a (77
mg, 9.6%), 7b (41 mg, 4.7%) and recovered 6
(82 mg, 11.3%). 7: [h]2D2 −91.9° (c 0.48,
CHCl3); Rf 0.43 (4:1 petroleum ether–EtOAc);
1H NMR (300 MHz, CDCl3): l 7.50–7.30 (m,
5 H), 5.52 (s, 1 H, PhCH), 5.39 (d, 1 H, J 4.7,
H-6), 5.20 (t, 1 H, J2,3 J3,4 9.3, H-3%), 4.59 (d,
1 H, J1%,2% 7.7, H-1%), 4.40 (m, 1 H, H-16), 4.36
(dd, 1 H, J5%,6%a 4.7, J6%a,6%b 10.6, H-6%a), 3.80 (t,
1 H, J5%,6%b 10.2, H-6%b), 3.67 (t, 1 H, J4%,5%9.6,
H-4%), 3.60–3.30 (m, 5 H, H-2%, H-3, H-5%,
H-26a, H-26b), 1.23 (s, 9 H); 13C NMR (75
MHz, CDCl3): l 178.71, 140.26, 137.15,
129.00, 128.28, 126.01, 122.17, 109.38, 102.10,
101.23, 80.92, 79.53, 78.70, 73.71, 73.64, 68.83,
66.96, 66.54, 66.08, 62.25, 56.61, 50.21, 41.74,
40.39, 39.05, 37.30, 36.97, 32.20, 31.96, 31.53,
31.28, 30.42, 29.73, 28.93, 27.20, 20.98, 19.48,
17.25, 16.39, 16.25, 14.64; EIMS (m/z): 747,
397, 282, 253, 139 (base). HREIMS Calcd for
C45H63O9: 747.4472. Found: 747.4476 [M+ −
H]. 7a: [h]2D1 −84.1° (c 0.59, CHCl3); Rf 0.30
Diosgenyl 2-O-(2,3,4-tri-O-acetyl-h-
nopyranosyl) - 4,6 - O - benzylidene - 3 - O - pi6al-
oyl-i- -glucopyranoside (9).—To a suspen-
L
-rham-
D
sion of 8 (1.68 g, 3.87 mmol), 7 (833 mg, 1.13
,
mmol) and 4 A MS (2 g) in dry CH2Cl2 (10
mL) at −40 °C was added a solution of
BF3·OEt2 (0.55 mL, 0.1 M) in CH2Cl2. After
being stirred for 1 h, the reaction was
quenched with NEt3 (0.5 mL), filtered, and
concentrated. Chromatography of the residue
on a silica gel column (5:1 to 4:1 petroleum
ether–EtOAc) gave 9 (1.13 g, 100%) as a
white solid: [h]D22 −61.9° (c 1.41, CHCl3); Rf
1
1
(4:1 petroleum ether–EtOAc); H NMR (300
0.47 (4:1 petroleum ether–EtOAc); H NMR
MHz, CDCl3): l 7.50–7.20 (m, 5 H), 5.54 (s,
1 H, PhCH), 5.35 (d, 1 H, J 4.9, H-6), 4.86
(dd, 1 H, J1%,2% 8.0, J2%,3% 8.8, H-2%), 4.65 (d, 1 H,
H-1%), 4.41 (q, 1 H, J 7.5, H-16), 4.33 (dd, 1 H,
J5%,6%a 5.0, J6%a,6%b 10.5, H-6%), 3.87 (t, 1 H, J 11.8,
H-26a), 3.80 (t, 1 H, J5%,6%b 10.4, H-6%b), 3.60 (t,
1 H, J3%,4% J4%,5% 9.3, H-4%), 3.57–3.32 (m, 4 H,
(300 MHz, CDCl3): l 7.40–7.20 (m, 5 H),
5.44 (brs, 1 H, PhCH), 5.44–5.36 (m, 2 H,
H-6, H-3%%), 5.21 (dd, 1 H, J2%%,3%% 3.3, J3%%,4%%
9.9, H-3%%), 5.16 (dd, 1 H, J1%%,2%% 1.5, H-2%%), 5.03
(t, 1 H, J4%%,5%% 10.0, H-4%%), 4.90 (d, 1 H, H-1%%),
4.72 (d, 1 H, J1%,2% 7.7, H-1%), 4.48–4.30 (m, 2
H, H-5%%, H-16a), 3.80–3.30 (m, 7 H), 2.09,