Pteridine studies. Part XXXI. The covalent hydration and subsequent oxidation of 8-methyl derivatives of some amino- and hydroxypteridines

Abstract

Pteridine derivatives with a C-methyl substituent located at the site attacked by the hydroxyl group in the process of covalent hydration, are shown to undergo a facile demethylation when oxidised by potassium permanganate. Identification of the oxidation products (oxopteridines) by unambiguous syntheses served to establish the site of water addition in the original pteridines. Using this method, 2,8-dihydro-6,7,8-trimethyl-2-methyliminopteridine, 2,8-dihydro-6,7,8-trimethyl-2-oxopteridine, and a series of related compounds were shown to undergo transmolecular hydration at positions 1 and 7 (or 3 and 7) of the pteridine nucleus. The ultraviolet spectra of some unstable hydrated and anhydrous molecules are given, and these results are used to identify the stable hydrates of some heavily substituted pteridines which did not undergo oxidative dealkylation. The results of oxidation with other reagents, including xanthine oxidase, are reported.