X-ray structural analyses of two a,y-diketo esters and one a,y-diketo acid, which are amino acid antagonists, have shown them all to be present in the solid state in the a,ßunsaturated y-keto enolic form. The structures of the esters /3-acetyl-pyruvic acid methyl ester (1) and 2-oxo-cyclopentyl-glyoxylic acid ethyl ester (3) are stabilized by intramolecular O---H(-O) hydrogen bonds involving th...
