Reinvestigation of the alkylation of pyroglutamate ester urethanes

被引：23

作者：

Charrier, JD ^{[1
]}

Duffy, JES ^{[1
]}

Hitchcock, PB ^{[1
]}

Young, DW ^{[1
]}

机构：

[1] Univ Sussex, CPES, Sussex Ctr Biomol Design & Drug Dev, Brighton BN1 9QJ, E Sussex, England

来源：

TETRAHEDRON LETTERS | 1998年 / 39卷 / 15期

基金：

英国生物技术与生命科学研究理事会; 英国工程与自然科学研究理事会;

关键词：

D O I：

10.1016/S0040-4039(98)00174-9

中图分类号：

O62 [有机化学];

学科分类号：

070303 ; 081704 ;

摘要：

Previous studies by several groups on the alkylation of pyroglutamic acid derivatives have led to a consensus that the stereoselectivity of alkylation at C-4 is invariably trans to the ester group at C-2. We have now discovered that this generalisation is not invariably correct and that, although for S(N)1-type electrophiles stereoselectivity is in fact trans, S(N)2-type electrophiles can give the thermodynamically less stable cis products with high diastereoselectivity. Use of the bulky proton source 2,6-di-tert-butylphenol to quench these reactions yields cis isomers as the only products in good yield thus making direct alkylation of pyroglutamic add derivatives a useful starting point for the synthesis of homochiral target compounds. (C) 1998 Elsevier Science Ltd. All rights reserved.

引用

页码：2199 / 2202

页数：4

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