STUDIES ON d- AND I-a-KETO-P-METHYLVALERIC ACIDS BY ALTON MEISTER

Although biochemical studies have been made of the cY-keto analogues of a number of a-amino acids, the cr-keto analogues of isoleucine have received relatively little attention. Two cY-keto analogues of this amino acid are possible, namely d-a-keto-p-methylvaleric acid, which has the same configuration at the P-carbon atom as L-isoleucine and n-alloisoleutine, and Z-a-keto-p-methylvaleric acid, which has the same configuration as L-alloisoleucine and n-isoleucine. It is evident that enolization of either keto acid would destroy the asymmetric center and that subsequent conversion to the keto form would yield a racemic product. In a previous communication from this laboratory (l), the preparation of optically active cY-keto-P-methylvaleric acids by enzymatic oxidation of the corresponding n-amino acid was briefly outlined. In the present report, the detailed procedure for the preparation of these keto acids as crystalline sodium salts is given, studies on the racemization of these compounds by alkali are described, and certain enzymatic properties are reported.