BIOMIMETIC TRANSAMINATION OF ALPHA-KETO PERFLUOROCARBOXYLIC ESTERS - AN EFFICIENT PREPARATIVE SYNTHESIS OF BETA,BETA,BETA-TRIFLUOROALANINE

An efficient large-scale preparative synthesis of biologically interes ting beta,beta,beta-trifluoroalanine through the biomimetic transamina tion of the ethyl trifluoropyruvate has been developed. The azomethine -azomethine isomerization of the N-(1-phenyl)ethylimine of ethyl trifl uoropyruvate to the N-(1-phenyl)ethylidene alanine ethyl ester, a key stage of the process, was found to occur under the mild reaction condi tions, in a triethylamine solution at rt. The proposed working mechani stic rationale accounting for the easiness of the isomerization and it s stereochemical outcome, involves unusual non-asymmetric [1,5]-proton shift transfer from the methine carbon to the enolate oxygen. (C) 199 7 Elsevier Science Ltd.