Metabolism of 2,3-, 2,4-, 2,5-, 2,6-, 3,4-and 3, 5-dichloro-l-nitrobenzenes by Mucor javanicus and metabolites of 2,4-dichloro-l-nitrobenzene (2,4-DCNB) by seven fungi were investigated. The dichloronitrobenzenes were reduced predominantly to the corresponding benzenamines by M., javanicus. In addition to the benzenamine derivatives, minor metabolites in which an ortho-chlorine atom was substituted with a methylthio group were detected in the medium of M. javanicus administered 2,3-and 2,4-DCNB. More or less amounts of 2,4-dichlorobenzenam.ine and 4-chloro-2-methylthio-l-nitrobenzene were detected as metabolites of 2,4-DCNB also in the media of 1V7. griseo-cyanus, M. hiemalis, M. praini and Aspergillus flavus. * Microbial Metabolism of Chlorinated Nitrobenzenes (Part 2). Part 1, see Ref. 1). ** To whom reprint requests should be addressed.

A new metabolic pathway of dichloronitrobenzenes (DCNB) through a glutathione conjugate in Mucor javanicus was established by using a radio-labeled substrate.In the fungal metabolism of 2, 4-DCNB (1) (and probably of 2, 3-DCNB as well), the substrate was initially transformed into a corresponding benzenamine (12) or a glutathione conjugate (2), and the latter was further metabolized into methylthio-, methylsulfinyl-or methylsulfonyl-substituted monochloronitrobenzene (5, 8 or 9), or similarly substituted monochlorobenzenamines (6, 10, 11) via a cysteine conjugate (3) and a corresponding benzenethiol (4). The former (3) was found to be temporarily N-acetylated in the fungus and reversively deacetylated.An unstable metabolic intermediate (4) was successfully trapped by reaction with an alkylthiosulfinate and identified unambiguously.

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Formation of a 2, 4-dichloro-l-nitrobenzene glutathione conjugate [S-(5-chloro-2-nitrophenyl)glutathione, 2] was confirmed in the cell-free system of Mucor javanicus which metabolizes 2, 3-and 2, 4-dichloro-l-nitrobenzenes into the corresponding chloro-methylthio-nitrobenzenes or chloro-methylthiobenzenamines. Further metabolisms of 2, the corresponding cysteine conjugate (3) and 5-chloro-2-nitrobenzenethiol (4) were investigated. Oxidation products (S-oxides and S-dioxides) of the formerly identified methylthio-containing metabolites were isolated from the growing cultures of the fungus administered 2. S-(5-Chloro-2-nitrophenyl)cysteine (3) and N-acetyl-S-(5-chloro-2-nitrophenyl)cysteine (7) were newly identified as metabolites of 2 in the resting cell system of the fungus.