Selective Preparation of β-Monoesters of Mercaptosuccinic Acid with Acid or Base Labile Sulfur Protecting Groups and Esters

Abstract

Sulfur protected mercaptosuccinic acid β-monoesters were prepared by two complimentary methods. Alkylation of enolates of hemithioacetal protected mercaptoacetic acid with t-butyl bromoacetate directly provides the base stable t-butyl esters 2a and 2b. Alternatively, protection of the α-carboxylate and thiol as an oxathiolone permits the preparation of the base labile S-acyl protected mercaptosuccinic acid esters 2c and 2d.