THE METABOLISM OF R(+)- AND RS-PENTOBARBITAL

¹ Chemistry and Life Sciences Laboratory, Research Triangle Institute, Research Triangle Park, North Carolina

The urine from dogs which had received R(+)-pentobarbital sodium yielded two crystalline metabolites from fractions obtained by partition column chromatography. Mass spectroacopy, together with infrared, ultraviolet, proton nuclear magnetic resonance and optical rotatory dispersion spectroscopy, established the structures of the metabolities as 5-ethyl-5-[3’(R)-hydroxy-1’(R)-methylbutyl] and 5-ethyl-5-[3’(S)- hydroxy-1’(R)-methylbutyl] barbitunic acid. A comparable metabolic study with RS-pento- barbital yielded two crystalline metaboites similar to those obtained from R(+)-pento- barbital. One metaboite was found by optical rotatory dispersion to be derived from R(+)-pentobathital, while the other metabolite resulted from the metabolism of S(-)- pentobarbital.