HETEROCYCLIC STUDIES .7. ACTION OF METHOXYAMINE AND METHYLHYDRAZINES ON 4-HYDROXYPTERIDINE AND ITS METHYL DERIVATIVES

Unsymmetrical dimethylhydrazine reacted with 4-hydroxypteridine and its 2-methyl derivative to give mixtures of an aminopyrazine carboxamide (III; R2 = R3 = H), an aminopyrazine carbohyrazide (IVb; R2 = R3 = H), and 4,5-diamino-6-hydroxypyrimidine (IX; R1 = H or Me). The 6- and 7-methyl and 6,7- and 2,7-dimethyl derivatives of 4-hydroxypteridine gave analogous products except that no pyrimidine derivative was obtained in these cases. Methylhydrazine degraded 4-hydroxypteridines similarly. 4-Hydroxypteridine and its 2- and 6-methyl derivatives were cleaved by methoxyamine to yield 4,5-diamino-6-hydroxypyrimidines (IX; R1 = H or Me) and in two cases pyrazine derivatives (VIc; R2 = H or Me, R1 = R3 = H) which still contained all the carbon atoms of the original pteridines. 4-Hydroxy-7-methylpteridine and methoxyamine gave only the pyrazine derivative (VIc; R1 = R2 = H, R3 = Me) while 2,7- and 6,7-dimethyl-4-hydroxy-pteridine gave methyl aminopyrazine carbohydroxamates (IVc; R2 = H or Me, R3 = Me) under the more vigorous conditions necessary for their cleavage. 1H N.m.r. data for the products are recorded and possible mechanisms for pyrazine ring cleavage are suggested.