61% |
With 1H-imidazole; dmap; In N,N-dimethyl-formamide; at 0℃; for 1h; |
Under Ar flow, anhydrous DMF (2 ml) solution of <strong>[17673-25-5]phorbol</strong> (364 mg, 1 mmol), imidazole (201 mg, 3 mmol) and N,N-dimethylaminopyridine (12 mg, 0.1 mmol) was cooled with ice, anhydrous DMF (2 ml) solution of t-butyldimethylsilyl chloride (166 mg, 1.1 mmol) was added, and stirred under cooling with ice for 1 hour. The reaction solution was subjected to directly silica gel chromatography (AcOEt), and the solvent of the fraction containing products was distilled off under a reduced pressure. The obtained residue was suspended in CH2Cl2-hexane (1:1) and after cooling, crystals separated out were filtered out with suction and dried to obtain 271 mg of colorless crystals. The filtrate was dried under a reduced pressure, and the resulting residue was subjected to silica gel chromatography (AcOEt) again to obtain 21 mg of colorless crystals (compound 1 in FIG. 3). In total, 292 mg (61%). Mp (melting point): 270-273 C. (decomposition). 1H-NMR (acetone-d6): 0.05 (3H, s), 0.06 (3H, s), 0.71 (1H, d, J=5.6 Hz), 0.88 (9H, s), 1.07 (3H, d, J=6.4 Hz), 1.16 (3H, s), 1.23 (3H, s), 1.69 (3H, dd, J=3.0, 1.3 Hz), 1.95-2.00 (1H, m), 2.46 (2H, s), 3.09-3.14 (2H, m), 3.24 (1H, bs), 3.51 (1H, br), 4.05 (2H, s), 4.09 (1H, br), 4.10 (1H, d, J=9.8 Hz), 4.65 (1H, s), 5.61 (1H, d, J=5.6 Hz), 7.58 (1H, s); 13C-NMR (acetone-d6): -5.14, 10.22, 15.53, 17.81, 18.78, 24.08, 26.22, 26.46, 37.15, 38.25, 40.12, 46.06, 58.23, 62.99, 68.64, 74.50, 78.79, 81.43, 130.31, 133.14, 140.90, 159.75, 208.49; IR (KBr) cm-1: 3315, 1675; Anal. Calcd for C26H42O6Si Calculated: C, 65.24; H, 8.84. Measured: C, 64.95; H, 8.69; [alpha]D25=+83.39 (c=0.85, MeOH). |