Synthesis of chiral 4-substituted 2-hydroxypent-4-enoic acid derivatives via diastereoselective ene reaction promoted by ZnBr2
作者:Piotr Kwiatkowski、Jacek Kwiatkowski、Jakub Majer、Janusz Jurczak
DOI:10.1016/j.tetasy.2007.01.007
日期:2007.2
The diastereoselective carbonyl-ene reaction of various 1,1-disubstituted olefins with the chiral derivatives of glyoxylic acid, with Oppolzer's sultam 1a and 8-phenylmenthol 1b auxiliaries, was studied. The reaction proceeds effectively under undemanding conditions in the presence of equimolar or catalytic amount of ZnBr2 in good yield and at 72-94% de. Diastereoselectivities are usually slightly better with 8-phenylmenthyl glyoxylate 1b, however, the use of hemiacetal la is preferred because the products are often crystalline. (c) 2007 Elsevier Ltd. All rights reserved.