反应详情

A mixture of 3 (2.60 g, 9.42 mmol) and 4,4-dimethoxy-2-methylbutan-2-ol (5.54 g, 37.7 mmol) were dissolved in anhydrous pyridine (6.5 mL). The mixture was refluxed under nitrogen for three days. After removal of the solvent in vacuo, the residue was dissolved in ethyl acetate. The ethyl acetate was washed several times with 1N HCl and brine. It was then dried over Na2SO4. The crude product obtained by evaporation in vacuo was purified by silica gel column chromatography, eluting with 25% ethyl acetate/hexane to afford 2.55 g of 4 in 78.6% yield, mp 96°-98° C. 1H-NMR (CDCl3) δ 1.05 (3H, t, J=7.3 Hz, CH3); 1.22 (3H, t, J=7.5 Hz, CH3); 1.53 (6H, s, 2 CH3); 1.75 (2H, m, CH2); 2.92 (2H, t, J=7.1 Hz, CH2); 3.35 (2H, q, J=7.1 Hz, CH2); 5.56 (1H, d, J=10.0 Hz, H3); 5.98 (1H, s, H9); 6.72 (1H, d, J=10.0 Hz, H4); MS (EI): 343 (5.7, M+1); 342 (22.5, M+); 327 (100, M-CH3); IR (KBr): 1728 (vs, C=O) cm-1; Anal. calcd. for C20H22O5 : C, 70.16; H, 6.48; Found: C, 70.45; H, 6.92.

1. temperatureThe mixture was refluxed under nitrogen for three days
2. customAfter removal of the solvent in vacuo
3. dissolutionthe residue was dissolved in ethyl acetate
4. washThe ethyl acetate was washed several times with 1N HCl and brine
5. dry with materialIt was then dried over Na2SO4
6. customThe crude product obtained by evaporation in vacuo
7. customwas purified by silica gel column chromatography
8. washeluting with 25% ethyl acetate/hexane