The syntheses of (2R,3S)-2-tert-butyldiphenylsilyloxymethylpyrrolidin-3-ol (TBDPS-protected CYB-3) (21) and its C(3) epimer (25) have been achieved in 9 and 8 steps respectively from D-serine. However, chiral HPLC analysis of the key β-hydroxy ester intermediates in these syntheses (17 and 18) revealed that appreciable levels of racemisation had occurred in the aldol and Claisen condensation reactions used in this synthetic sequence.
(2R,3S)-2-叔丁基二苯基
硅氧基甲基
吡咯烷-3-醇(T
BDPS保护的CYB-3)(21)及其C(3)差向异构体(25)的合成从D开始分别经过9步和8步完成-
丝氨酸。然而,对这些合成中关键 β-羟基酯中间体(17 和 18)的手性 HPLC 分析表明,在该合成序列中使用的羟醛和克莱森缩合反应中发生了明显
水平的外消旋化。