反应详情

N-Hydroxysuccinimide (0.25 g, 2.2 mmol) and N,N′-dicyclohexyl carbodiimide (0.45, 2.2 mmol) was added to a solution of cyclohexylacetic acid 17 (0.45 g, 2 mmol) in THF (5 ml). The mixture was stirred for 18 h at room temperature and cooled in an ice bath. 25% aqueous NH4OH (2 ml) was added in one portion and the mixture was stirred at room temperature for 2 h. The precipitate was filtered off and washed with diethyl ether (30 ml). The organic phase of filtrate was separated and washed with 5% aqueous KHSO4 (10 ml) and brine. The extract was dried over MgSO4, filtered and evaporated. The residue was purified by flash chromatography on silica gel (light petroleum ether-ethyl acetate, 4:1 to 1:1) to give 18 (0.34 g, 76%) as a colorless solid with m.p. 44-46° C. 1H-NMR (CDCl3, TMS): 0.91 (6H, s, 3,5-CH3); 1.02 (6H, s, 3,5-CH3); 1.00-1.30 (4H, m, 4-CH2 and 2,6-CH); 1.85 (2H, d, 14 Hz, 2,6-CH); 2.13 (2H, s, CH2C═O); 5.18 and 5.19 (total 2H, both d, 18 and 11 Hz, ═CH2); 5.40 and 5.60 (total 2H, both br s, NH2) and 6.03 ppm (1H, dd, 18 and 11 Hz, ═CH).

1. temperaturecooled in an ice bath
2. stirringthe mixture was stirred at room temperature for 2 h
3. filtrationThe precipitate was filtered off
4. washwashed with diethyl ether (30 ml)
5. customThe organic phase of filtrate was separated
6. washwashed with 5% aqueous KHSO4 (10 ml) and brine
7. dry with materialThe extract was dried over MgSO4
8. filtrationfiltered
9. customevaporated
10. customThe residue was purified by flash chromatography on silica gel (light petroleum ether-ethyl acetate, 4:1 to 1:1)