Studies towards complex bridged alkaloids: regio- and stereocontrolled enolate chemistry of 2,5-diketopiperazines
作者:Mark Pichowicz、Nigel S. Simpkins、Alexander J. Blake、Claire Wilson
DOI:10.1016/j.tet.2008.02.020
日期:2008.4
N-protected diketopiperazines (DKPs) via enolate intermediates has been studied. The enolate reactions were highly diastereocontrolled, leading to enantiopure DKP products if chiral amino acid precursors were employed, and giving racemic products, starting with centrosymmetric DKPs, even when a chiral lithium amide base was used to generate the lithium enolate. With unsymmetrical DKPs derived from proline
已经研究了通过烯醇化物中间体取代对称的N-保护的二酮哌嗪(DKP)。烯醇盐的反应是高度非对映体控制的,如果使用手性氨基酸前体,则会产生对映体纯的DKP产物,即使使用手性锂酰胺碱生成烯醇酸锂,也可以从中心对称的DKPs开始生成外消旋产物。对于衍生自脯氨酸和丙氨酸,苯丙氨酸或缬氨酸的不对称DKP,烯醇取代发生在脯氨酸残基上,具有很高的区域选择性和立体选择性。这样就可以合成取代的DKP,该化合物可以通过阳离子过程环化,得到天然产物对乙酰氨基酚和Stephacid中存在的双环[2.2.2]二氮杂辛烷核心结构。