PROCHIRAL RECOGNITION IN THE REACTION OF 3-SUBSTITUTED GLUTARIC ANHYDRIDES WITH CHIRAL SECONDARY ALCOHOLS

The scope of a previously-reported process for the desymmetrization 3-substituted glutaric anhydrides has been investigated. Thus, prochiral anhydrides 5-9 react with 1-(1'-naphthyl)ethanol (2) to give glutaric acid half-esters, which are esterified by treatment with diazomethane to obtain the corresponding diesters 16-20. The degree of prochiral recognition is inversely related to the steric bulk of the stereodifferentiating group, with the series TBDMSO, Me, Et, Ph, i-Pr, and t-Bu giving ratios of 40:1, 16:1, 14:1, 8:1, 7:1, and 1:3, respectively. The absolute sense of the prochiral recognition was established by conversion of two of the diesters, 16a and 18a, into 3-substituted valerolactones (22a, 22c) of known absolute configuration.