2-Benzyl-3-hydroxybutanoic acid(1) was prepared starting with acetoacitic ester following benzylation, reduction using sodium dithionite and hydrolysis under alkaline condition. The inhibitory kinetic evaluation showed that 1(Ki =107mM) is potent than 2-benzyl-3-hydroxypropanoic acid(Ki =610mM) as inhibitor for carboxypeptidase A, suggesting that introducing of a methyl group at the b-position of a inhibitor with weak zinc ligating moiety such as hydroxyl group to improve potency of inhibitor to CPA is possible.