作者:Edwin Vedejs、Chutima Kongkittingam
DOI:10.1021/jo0104882
日期:2001.11.1
A total synthesis of (-)-hemiasterlin has been accomplished in nine steps from 25(8) (>35% yield overall). An improved enantiocontrolled route to the tetramethyltryptophan subunit 32 was developed using an asymmetric Strecker synthesis (five steps, 50% yield from 25), and the dipeptide 22 was prepared in seven steps, 37% yield from valinol. The synthesis exploits the high reactivity of a Bts-protected
从(25)(8)开始,九步完成了(-)-半胱氨酸的总合成(总收率> 35%)。使用不对称的Strecker合成方法开发了改进的对四甲基色氨酸亚基32的对映体控制路线(五个步骤,从25收率获得50%的收率),并在七个步骤中制备了二肽22,从缬氨醇收得了37%的收率。该合成方法利用Bts保护的氨基酸氯化物在位阻氨基酸残基18和20难以肽偶联形成21(70%,重结晶)的困难肽中的高反应性,并且还使用N-Bts中间体生产高产率的N 14和31的甲基化。此外,Bts保护的N-酰基二碳酸二叔丁酯33与22进行了有效偶联,形成34(偶联步骤中97%;活化时79%;偶联顺序从32)。