Abstract

After oral administration of racemic (RS) phensuximide (1) to dogs, compounds found in urine (with approximate yields as percentage of dose) were: unchanged 1, trace amounts; α-phenylsuccinimide (2),1.3%; levo-2-phenylsuccinamic acid (8), 14%; N-methyl-α-(p-hydroxyphenyl)succinimide (9), 5% (isolable only after treatment of urine with β-glucuronidase). After administration of RS-α-phenylsuccinimide (2), the compounds found in urine were: unchanged 2, 8%; levo-8, 23%. No α-(p-lmydroxyphenyl) succinimide, free or conjugated, was found as a metabolic product of either 1 or 2. No 3-phenylsuccinamic acid (4) was produced from either 1 or 2. 2-Phenylsuccinamic acid as isolated from urine of dogs receiving either 1 or 2 is essentially the optically pure levo form which was shown to have the R-configuration. The same absolute configuration of R(—)-2-phenylsuccinamic acid and of R(—)-phenylhydantoic acid, previously found to be a metabolic product of the RS-forms of 5-phenylhydantoin and its 3-methyl and 3-ethyl derivatives, suggests that the same enzyme may be responsible for these stereospecific reactions of opening of the succinimide and hydantoin rings.