338
Lin, Han, Chen, and Yuan
cerium(III) chloride heptahydrate (13 mg,
0.035 mmol) and acetic anhydride (0.13 mL,
1.3 mmol) were added, and then stirred at 40◦C
for 2 h. At the end of this period, the solution was
quenched with distilled water and extracted with
ethyl acetate. The organic phase was washed with
water for three times and dried over anhydrous
magnesium sulfate, and concentrated in vacuo to
obtain a white solid. Column chromatography of
the solid on silica gel with 25% petroleum ether
in ethyl acetate solution as an eluent gave the title
compound 3 171 mg in 82% yield. IR νmaks (KBr)
cm−1: 3443.8, 1738.5, 1716.9, 1650.3, 1452.4,
1372.1, 1241.3, 969.5, 714.9.1H NMR (CDCl3,
ppm): δ 1.15 (s, 3H), 1.63–1.71 (m, 1H), 1.75 (s,
3H), 1.81 (s, 3H), 1.96 (s, 3H), 1.90–2.03 (m,
2H), 2.13 (s, 3H), 2.19 (s, 3H), 2.28 (s, 3H),
2.39–2.50 (m, 1H), 2.51–2.62 (m, 1H), 2.89 (d,
J = 8.4 Hz, 1H), 4.16 (d, J = 8.52 Hz, 1H), 4.37
(d, J = 8.24 Hz, 1H), 4.45–4.48 (m, 1H), 4.45
(d, J = 10.99 Hz, 1H), 5.00 (d, J = 8.52 Hz, 1H),
5.74 (dd, J = 5.91, 2.06 Hz, 1H), 5.94 (t, J = 9.07,
7.69 Hz, 1H), 6.16 (d, J = 10.99 Hz, 1H), 7.47
(t, J = 7.55 Hz, 2H), 7.59 (t, J = 7.42 Hz, 1H),
8.06 (d, J = 7.14 Hz, 2H).13C NMR: δ 12.6, 14.6,
21.1, 21.2, 22.7, 26.5, 26.9, 31.2, 37.9, 38.0, 44.3,
44.6, 47.0, 69.0, 71.5, 73.8, 73.9, 76.6, 77.2,
81.9, 84.0, 128.5, 129.6, 133.4, 134.7, 136.9,
165.0, 169.2, 170.6, 170.7. ESI Full MS m/z:
638, 637 (M + Na)+. The colorless single crystal
was cultured from a mixture solution of methanol
and water (9:1.v/v) by slow evaporation at room
temperature.
Scheme 1.
methanol/water), and the reaction progress was
followed by TLC until completion. After care-
ful neutralization (saturated ammonium chloride)
and removal of the methanol, the residue was
extracted with ethyl acetate and purified by col-
umn chromatography on silica gel with ethyl ac-
etate/hexane 3/2 as an eluent to give 2 (186.0 mg,
65%).1H NMR (CDCl3, ppm): δ 1.21 (s, 3H),
1.64–1.69 (m, 1H), 1.77 (s, 3H), 1.80 (s, 3H), 1.86
(s, 3H), 1.92–1.96 (m, 2H), 2.18 (s, 3H), 2.27 (s,
3H), 2.42–2.48 (m, 1H), 2.51–2.58 (m, 1H), 2.89
(d, J = 5.83 Hz,1H), 3.16 (s, 1H), 3.65 (s, 1H),
4.16 (d, J = 8.40 Hz, 1H), 4.32–4.39 (m, 3H),
4.83 (d, J = 6.95 Hz, 1H), 4.92 (d, J = 10.31 Hz,
1H), 4.99 (d, J = 8.81 Hz, 1H), 5.76 (dd, J = 2.10,
5.89 Hz, 1H), 5.97 (t, J = 8.61, 8.87 Hz, 1H),
7.47 (t, J = 7.83 Hz, 2H), 7.59 (t, J = 7.42 Hz,
1H), 8.05 (dd, J = 7.79, 1.19 Hz, 2H);13C NMR
(CDCl3): δ 12.5, 14.8, 21.2, 22.8, 26.7, 26.9, 31.7,
38.0, 38.2, 44.1, 44.3, 47.4, 69.5, 71.2, 71.8, 74.3,
76.7, 78.9, 81.9, 84.0, 128.6, 129.8, 133.5, 135.2,
137.5, 165.1, 169.3, 170.7; ESI Full MS m/z: 573
(M + H)+, 555 (M + H-H2O)+, 495, 373, 331,
313, 295.
Crystal structure determination of 3
A summary of the crystallographic informa-
tion is given in Table 1, and selected bond dis-
tances and angles are listed in Tables 2 and 3, re-
spectively. The selected crystal was mounted on a
ENRAF-NONIUS CAD4 diffractometer. Diffrac-
tion data were measured at 20◦C using graphite
monochromated Mo Kα (λ = 0.071073 nm) radi-
ation. The structure was solved by direct methods
and refined by full-matrix least squares method
Synthesis of 7,9-dideacetyl-
1-deoxybaccatinVI (3)
In a solution of anhydrous 2 (195 mg,
0.34 mmol) in dry tetrahydrofuran (7 mL),
2
on Fobs by using the SHELXTL 97 software