Abstract
1. A new premercapturic acid metabolite of bromobenzene was isolated from the urine of β-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-premer-capturic 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 rearrangement.
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.