A convenient synthesis of toxoflavins and toxoflavin 4-oxides, which consists of the nitrosative cyclization of the aldehyde hydrazones of 3-methyl-6-(1-methylhydrazino) uracil, is described. Both toxoflavins and toxoflavin 4-oxides gave the corresponding 1-demethyltoxoflavins (8-demethylfervenulins) by treatment with nucleophiles such as dimethylformamide, dimethylacetamide and acetic acid. The preparation of some 4, 8-dihydrotoxoflavin derivatives is described.