Asymmetric synthesis of(R)-5-(l,2,4-triazol-3-yl)cysteines by nucleophilic addition of triazolethiols to a Ni'complex with a chiral dehydroalanine Schiff base

摘要

An efficient method was developed for the asymmetric synthesis of(R)-S-( 1,2,4-triazol-3-yl)cysteines by the addition of 3,4-disubstituted l,2,4-triazole-5-thiols at the electrophilic C=C bond in a Ni~(II)complex of a Schiff base of dehydroalanine with(S)-N-(N-benzyl-prolyl)aminobenzophenone.The stereoselectivity of the formation of diastereomeric complexes with the(S,R)configuration under conditions of thermodynamic control of the nucleophilic addition exceeds 94%.Acid treatment of the reaction mixtures afforded enantiomerically pure(R)-5-hetarylcysteines(ee >98%).