A NEW ROUTE TO THE SYNTHESIS OF AMINO-ACIDS THROUGH THE MERCURY CYCLIZATION OF CHIRAL AMIDALS

By means of the mercury cyclization of the unsaturated amidals 3a-e, obtained from the reaction of 1,3,5-tris-[(S)-phenylethyl]hexahydrotriazine (1) and alpha,beta-unsaturated acyl chlorides, diastereomeric mixtures of imidazolidin-4-ones 5-8 and perihydropyrimidin-4-ones 9-10 have been synthesized and easily separated by flash chromatography. The subsequent hydrolysis under acid conditions of the separated heterocycles affords respectively D or L alpha- and beta-amino acids. The regiochemistry of the cyclization has been studied, depending on the substituents of the double bond. Furthermore the absolute configuration of the newly introduced stereogenic center has been attributed on the basis of the H-1 NMR spectra of the heterocycles.