Process for making and isolating (r)-2-hydroxy-4- phenylbutyric acid and esters

Abstract From the Canadian patent

Disclosed herein is a novel compound (L)-menthyl, 2-oxo-4-phenylbutyrate, and an improved process for making and isolating a substantially pure compound of the structural formula:, wherein Y is hydrogen or (L)-menthyl the improvement which comprises:, a) stereoselectively reducing (L)-menthyl 2-oxo-4phenylbutyrate by contacting said compound with with S-Alpine borane, b) stereoselectively isolating (L)-menthyl-(R)-2hydroxy-4-phenylbutyrate by crystallization and, optionally hydrolyzing the so obtained ester; and further comprises optionally esterifying the so obtained acid by contacting said acid with a C1-C6 alkanol in the presence of acid.