2-THIAZOLYL ALPHA-AMINO KETONES - A NEW CLASS OF REACTIVE INTERMEDIATES FOR THE STEREOCONTROLLED SYNTHESIS OF UNUSUAL AMINO-ACIDS

The thiazole-based one carbon homologation of four alpha-amino acids ( L-phenylalanine, L-leucine, L-threonine, and L-serine) to the correspo nding alpha-hydroxy beta-amino aldehydes and acids in both configurati ons at C(alpha), is described. The methodology involves the following key operations: (i) the conversion of an alpha-amino ester to a 2-thia zolyl alpha-amino ketone; (ii) the stereocontrolled reduction of a ket one carbonyl to either syn or anti alpha,beta-amino alcohols; (iii) th e aldehyde release from the thiazole ring; (iv) the oxidation of the a ldehyde to a carboxylic acid. The methodology was only partially appli ed to L-phenylglycine because of some limitations in operation (i).