HYDROCARBONS 339 



CH3CH:CHC(CH3):CHCONH2 > HOOCCH:CHC(CH3):CHCONH2 



/3-Methylsorbamide /3-Methylmuconic acid 



monoamide 



The Conversion of /3-Methylsorbamide to the Corresponding Muconic Acid**' 



f . Transformation of Benzene to Phenylmercapturic Acid: The 

 formation of phenylmercapturic acid by the rabbit indicates another 

 possible route for the detoxication of benzene. Thiophenol, which is 

 probably a derivative of phenylmercapturic acid, was formed when the 

 urine of rabbits which had received benzene was treated with hydrochloric 

 acid. On the basis of this finding, Drummond and Finar^^^ postulated 

 the possible formation of phenylmercapturic acid, although they failed to 

 isolate this compound by the methods used. This would involve the 

 following reaction : 



SCH2CHCOOH 

 NHCOCH3 



Phenylmercapturic acid 



Witter'^^* reached the erroneous conclusion that the rabbit does not ex- 

 crete phenylmercapturic acid in the urine. This compound is also formed 

 from benzene, and is excreted by the rat. In spite of its ready decomposi- 

 tion, Zbarsky and Young^^^ succeeded in isolating it from the urine after 

 the administration of phenyl-L-cysteine ; in fact, as much as 38% of the 

 theoretical yield of the L-phenylmercapturic acid was isolated ^^^ after the 

 feeding of phenyl-L-cysteine. ^^^ Moreover, Zbarsky and Young"^ re- 

 corded experiments on rats in which 0.37% of the theoretical yield was 

 isolated from the urine of rats when benzene was fed in corn oil (to delay 

 absorption), while 0.11% of that expected was excreted when benzene was 

 given without a diluent. Although Williams^'" originally considered that 

 phenylmercapturic acid is only a minor metabolite of benzene, Parke and 

 Williams"^ were later able to prove that 1% of the benzene fed was ex- 

 creted as phenylmercapturic acid when the dose level was 0.5 g./kg., and 

 0.8% when the dose level was 1 g./kg. This figure corresponds to 2.2% 

 and 1.7%, respectively, of the benzene cataboHzed and excreted as mer- 

 capturic acid when this hydrocarbon was fed at the two levels. According 



"« R. F. Witter, Univ. Microfilms Ann Arbor, 6, No. 1, p. 21 (1945); cited by R. T. 

 Williams, Detoxication Mechanisms, Wiley, New York, 1949, p. 38. 

 "5 S. H. Zbarsky and L. Young, J. Biol. Chem., 151, 487-492 (1943). 

 "« S. H. Zbarsky and L. Young, J. Biol. Chem., 161, 211-215, 217-219 (1943). 

 "' D. V. Parke and R. T. Williams, Biochem. J., 48, 624-629 (1951). 



