| 摘要 |
5835P/1200A 17608 TITLE OF THE INVENTION: IMPROVED PROCESS FOR PREPARING ACHPA A process for preparing (3S,4S)-N-.alpha.-BOC)-4-amino-5-cyclohexyl-3-hydroxypentanoic acid ethyl ester comprising (a) reacting the N-.alpha.-BOC-amino-3-hexahydrophenyl propionic acid with 1,1carbonyldiimidazole, to form an acylimidazol-activated derivative of said acid; (b) coupling said acylimidazoleactivated derivative with the magnesium salt of malonic acid monoethylester to afford the .beta.-ketoester; (c) reducing said .beta.-ketoester using sodium cyanoborohydride in tetrahydrofuran and glacial acetic acid to produce a mixture of (3S,4S)-(N.alpha.-BOC)-4-amino-5-cyclohexyl-3-hydroxypentanoic acid ethyl ester and (3B,4S)-(N.alpha.-BOC)-4-amino-5-cyclohexyl-3-hydroxypentanoic acid ethyl ester; (d) crystallizing off the (3R,4S) compound and purifying the remaining product to afford optically-pure (3S,4S)-(N.alpha.-BOC)-4-amino-5-cyclohexyl-3-hydroxypentanoic acid. |
