Heterocyclic studies. Part IV. The action of hydroxylamine on 4-hydroxypteridine and its methyl derivatives

Abstract

Hydroxylamine reacted with 4-hydroxypteridine, and its 2- or 6-methyl derivative (I), (II), or (III) to give the corresponding 3-hydroxypteridin-4(3H)-one (VII), (VIII), or (IX) by pyrimidine ring cleavage and recyclisation. 4,5-Diamino-6-hydroxypyrimidine (XIII; R = H) or its 2-methyl derivative (XIII; R = Me) was formed simultaneously by a competing pyrazine ring cleavage. The 3-hydroxypteridine derivatives (VII)—(IX) underwent further reactions with hydroxylamine to yield, ultimately, 5,6-diamino-3-hydroxypyrimidin-4(3H)-one (XIV) or its 2-methyl derivative (XV). Each pyrazine ring cleavage also gave the dioxime of glyoxal or pyruvaldehyde. 3-Hydroximinomethylamino-6-methylpyrazine-2-carboxylic acid (XXIV) was obtained as a by-product from the reaction of hydroxylamine with 4-hydroxy-6-methylpteridine (III). 4-Hydroxy-7-methyl-, 6-, 7-dimethyl- and -2,7-dimethylpteridine (IV)—(VI) gave only the corresponding 3-hydroxypteridin-4(3H)-ones (X)—(XII) which were not degraded by hydroxylamine under the reaction conditions. Spectral data and pK_a values are tabulated.