A Novel Synthesis of the Enantiomers of an Antihistamine Drug by Piperazine Formation from a Primary Amine

Abstract

An enantioselective synthesis of each enantiomer of the antihistamine drug 2(2-{4-[(4-chlorophenyl)phenylmethyl]-1-piperazinyl}ethoxy)acetic acid dihydrochloride (1) is described, involving the preparation of the benzhydrylpiperazine portion of the molecule from reaction of each enantiomer of 4-chlorobenzhydrylamine with N,N-bis(2-chloroethyl)-4-methylbenzenesulfonamide. A modification of standard toluenesulfonamide deprotection with hydrogen bromide in acetic acid was introduced, substituting 4-hydroxybenzoic acid for phenol.