[Nitrefazole, a 4-nitroimidazole derivative with a marked inhibitory effect on aldehyde dehydrogenase. Synthesis and structural assignment].

2-Methyl-4-nitro-1-(4-nitrophenyl)imidazole (nitrefazole) is a drug which causes a strong and long lasting inhibition of aldehyde dehydrogenase, an enzyme involved in the metabolism of alcohol. The synthesis of this compound as well as that of the isomeric 5-nitro analogue are described. It can be shown by means of detailed 1H- and 13C-NMR studies of both isomers and some other structurally related compounds that the nitro group in nitrefazole is in position 4 of the imidazole ring, whereas the other pharmacologically active nitroimidazoles like metronidazole are mainly substituted in position 5 (or in exceptional cases in position 2).