Structure elucidation of the photolysis and hydrolysis products of tinidazole.

A labile intermediate in the photolytic rearrangement of the antibacterial drug tinidazole was isolated after photolysis of the drug in acetone. The intermediate was identified through structural studies as 1-[2-(ethylsulphonyl)ethyl]-2-methyl-4-hydroxyimino-5-oxo-im idazole. A second product was identified as N-[2-(ethylsulphonyl)ethyl]-5-methyl-1,2,4-oxadiazole-3-carboxa mid e. A different compound, N-[2-(ethylsulphonyl)ethyl]-oxamide, crystallized in an ethanolic solution of tinidazole exposed for four months on a sunny window sill. Tinidazole was hydrolyzed completely to 2-methyl-5(4)-nitroimidazole when refluxed in 0.1 M NaOH solution, and was converted to 4-nitro isomer when refluxed in water with a catalytic amount of base.