Stereospecific and Stereoselective Reactions. II. Preparation of Esters of N-Phthaloyl-a-amino Acid from Esters of a-Hydroxy Acid

Functional selectivity and stereospecificity of the intermolecular dehydration between alcohols and phthalimide (III) by means of diethyl azodicarboxylate (I) and triphenylphosphine (II) was examined. The reaction of allyl alcohol, 2-chloroethanol or (±)-ethyl lactate with I, II, and III led to the formation of corresponding N-alkylphthalimide. The reaction was further applied to the synthesis of esters of N-phthaloyl-a-amino acid. (S)-(-)-ethyl 2-hydroxy-3-phenylpropionate was converted into (R)-(+)-N-phthaloylphenylalanine ethyl ester with high stereospecificity.