ABSTRACT: RABBIT LIVER

The preparation of four optical isomers of 3’-hydroxyhexobarbital [5-(3’-hydroxy-l ‘-cyclohexen-l ‘-yl)-l,5-dimethylbarbituric acid] is described. The absolute configuration of the four isomers were assigned as (3’S, 5R) and (3’R, 5R) for a- and fl-isomers from (A)-(-)-hexobarbital, and (3’R, 5S) and (3’S, 5S) for a- and fl-isomers from (S)-(+)-hexobarbital, respectively. Some of these isomeric 3’-hydroxyhexobarbitals, which are formed in the reaction of hexobar-bital with liver microsomal mono-oxygenase, are oxidized to 3’-oxohexobarbital (5-(3’-oxo-l ‘-cyclohexen-l ‘-yI)-l,5-dimethylbarbi-turic acid] by dehydrogenase localized in the soluble fraction of liver homogenates. Comparison of activities among the four isomers for 3-hydroxyhexobarbital dehydrogenase was made by use of en-zymes from guinea pig and rabbit liver. It became evident that either enzyme had a quite different activity towards each opitcal isomer, and the configuration of the 3’-position of hydroxyhexobarbital wa