叙述了以(4R) 羟基 (S) 脯氨酸为原料进行的几种新型手性催化剂的简便合成方法. (4S) 苯氧基 (S) 脯氨酸 1a由N 乙氧羰基 (4R) 羟基 (S) 脯氨酸甲酯经Mitsunobu反应, C 4构型发生翻转, 水解后得到; (4R) 芳甲氧基 (S) 脯氨酸由N 叔丁氧羰基 (4R) 羟基 (S) 脯氨酸用ArCH2X醚化后脱去N 保护基得到, C 4构型不受影响.
R)-Hydroxy-(S)-proline was N-protected by reaction with di-tert-butyl pyrocarbonate to give N-Boc-(4R)-hydroxy-(S)-proline, which was treated with NaH in anhydrous tetrahydrofuran and followed by etherification with PhCH 2Br to form the N-Boc-(4R)-benzyloxy-(S)-proline, which, after removal of the protecting group with CF 3COOH gave the title compound. As an efficient catalyst for the direct asymmetryic aldol reaction the compound gave products in yield ranged from 58% to 77% with enantiomeric excess up to 88%.
