1. A new premercapturic
acid metabolite of
bromobenzene was isolated from the urine of
beta-naphthoflavone-induced rats; using 1H-n.m.r., FAB mass spectrometry and chemical degradation it was identified as S-(2-hydroxy-3-bromocyclohexa-3,5-dienyl)-N-acetylcysteine. 2. Two regioisomeric premercapturic
acids apparently derived from bromobenzene-3,4-oxide were isolated as an inseparable 1:1 mixture from the urine of
phenobarbital-induced rats and characterized by similar means. 3.
Acid dehydration of
bromobenzene 3,4- and 4,3-premercapturic
acids (mixture) afforded only p-bromophenylmercapturic
acid, whereas
acid dehydration of
3,2-premercapturic acid gave both o- and m-bromophenylmercapturic
acids. This implies a shift of sulphur in
acid dehydration of the 3,4- and 3,2- but not the 4,3-premercapturic
acids. 4. Base
dehydration of the 3,4- and
4,3-premercapturic acid mixture gave a mixture of p- and m-bromophenylmercapturic
acids, whereas base
dehydration of the
3,2-premercapturic acid gave only m-bromophenylmercapturic
acid. This indicates these premercapturic
acids dehydrate by direct elimination without rearrangment. 5. The
3,2-premercapturic acid was detected only in the urine of BNF-induced animals, whereas the 3,4- and 4,3-premercapturic
acids were detected in the urines of untreated as well as PB- and BNF-induced animals. 6. Together with earlier reports of the isolation of the 2,3-dihydrodiol, the isolation of the
3,2-premercapturic acid as a urinary metabolite of
bromobenzene implies that bromobenzene-2,3-oxide is a discrete metabolite of
bromobenzene and not merely a hypothetical intermediate.