The reaction of the carcinogenic electrophile N-acetoxy-4-acetylaminostilbene with methionine at neutral pH yielded β-methylmercapto-4-acetylaminostilbene as the major product and 3-methylmercapto-4-acetylaminostilbene as a minor product. Two other products were also formed. One of these had the apparent molecular weight (283) of a methylmercapto-4-acetylaminostilbene; it was not identical with 2-, 2′, 3′-, or 4′-methylmercapto-4-acetylaminostilbene. The second product had an apparent molecular weight of 301 and appeared to be a methylmercapto derivative. It was formed in larger amounts at slightly acidic pH's, and its yield was inversely related to that of β-methylmercapto-4-acetylaminostilbene. 3- and β-methylmercapto-4-acetylaminostilbene were also obtained on alkaline degradation of the liver protein from rats that had received i.p. injections of N-hydroxy-4-acetylaminostilbene. These data provide evidence that an ester of N-hydroxy-4-acetylaminostilbene or a derivative with similar electrophilic reactivity is formed from N-hydroxy-4-acetylaminostilbene in the rat liver.

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Supported at the University of Wisconsin by Grant CA-07175 of the National Cancer Institute, USPHS, and at The Fred Hutchinson Cancer Research Center by Grant CA-14500.

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