Anhydro-N-Carboxy-DL-β-Phenylalanine

Abstract

A. L. LEVY¹ has described the preparation of anhydro-N-carboxy-DL-β-phenylalanine (II, R=CH₂Ph) by the action of phosgene on DL-β-phenylalanine. Prior to this, Fuchs² described the preparation of anhydro-N-carboxy-N-phenyl- and N-p-tolyl-glycine by phosgenation of the parent acids in aqueous solution. Isatoic anhydride³, the analogous compound from anthranilic acid, has been similarly prepared. A modified method based on this reaction of Fuchs has been used recently by several workers in these laboratories. The process, which is fairly generally applicable and has been protected by a patent application⁴, consists of suspending the powdered α-amino-acid in a dry inert solvent, for example, dioxan or tetrahydrofuran, at 30°–40° and passing in gaseous phosgene with stirring until the acid is dissolved. Removal of solvent and excess phosgene by heating in vacuo at 40° then affords the anhydro-N-carboxy derivative (II), the intermediate N- substituted carbamyl chloride (I) being decomposed with the loss of hydrochloric acid during the treatment: