反应详情

The foam containing (2) was heated at 95° with 90% aqueous acetic acid (500 ml) for 30 minutes. The mixture was cooled in ice and then poured into concentrated NH4OH (1 liter). This basic solution was extracted with three portions of chloroform, the organic extracts backwashed twice with dilute NH4OH, and the organic phase dried and evaporated to a thick syrup. The syrup was fractionated by filtration through a settled slurry of Silica Gel G (400 g), packed in a large sintered glass Buchner funnel using 30:1 methanol-chloroform as the suspending media and eluting solvent. Early fractions contained a mixture of (3a) and the corresponding B/C trans isomer (3b). Later fractions consisting mainly of (3a) were pooled and evaporated to give 94 g of a foam. The foam was crystallized from ethyl acetate to give 31 g (25%) of compound (3a). Recrystallization from ethyl acetate gave white needles of the hemi-ethyl acetate solvate of (3a), m.p. 183°-185.5°. NMR (CDCl3): δ 6.58 (2H), aromatic; 6.40 broad s (2H), H-8 and --OH; 4.30, d (1H), H-5α, J=15 Hz; 3.76, s (3H), CH3O; 2.40, s(3H), CH3N--; 1.60, m (3H), 7 CH3 --.

1. temperatureThe mixture was cooled in ice
2. extractionThis basic solution was extracted with three portions of chloroform
3. customthe organic phase dried
4. customevaporated to a thick syrup
5. filtrationThe syrup was fractionated by filtration through a settled slurry of Silica Gel G (400 g)
6. washeluting solvent
7. additiona mixture of (3a)
8. customevaporated