Unusual bridgehead hydroxylations via selenoxides: evidence for carbocations
作者:Robert M. Williams、Jen-Sen Dung
DOI:10.1016/s0040-4039(00)98459-4
日期:1985.1
Treatment of C-6-phenylselenyl bicyclo[4.2.2]piperazinediones with H2O2 affords the C-6-peroxy and C-6-hydroxy bicyclic piperazinediones and is rationalized on the basis of intermediate bridgehead carbocations.
用H 2 O 2处理C-6-苯基硒烯基双环[4.2.2]哌嗪二酮可得到C-6-过氧和C-6-羟基双环哌嗪二酮,并在中间桥头碳正离子的基础上合理化。
Studies on asymmetric synthesis of bicyclomycin precursors. A chemoenzymatic route to chiral 2,5-diketopiperazines and 2-oxa-bicyclo[4.2.2]decane-8,10-diones
A novel asymmetric route to bicyclomycin analogues, 2-oxa-bicyclo[4.2.2]decane-8,10-diones, is described. The key chiral synthons 3-(omega-hydroxyalkyl)-2,5-diketopiperazines 3a-c were obtained via enzymatic kinetic resolution of their respective acetates 2a-c using hydrolases (up to >98% ee, E > 200). The chiral 2,5-diketopiperazines were then transformed into their bicyclic derivatives in a stereospecific manner. Circular dichroism and NMR studies were performed to determine the absolute and relative configuration of the obtained products. The biocatalytic approach gave high stereoselectivities in comparison to the chiral pool synthesis from glutamic acid (58% ee) and thus demonstrated the ability of hydrolases to discriminate a remote stereocenter. (C) 2017 Elsevier Ltd. All rights reserved.