Pteridine studies. Part XLV. Addition of sodium hydrogen sulphite and other nucleophilic agents to pteridin-4-one and related compounds

Abstract

Although pteridin-4-one, unlike its 2- and 6-oxo-isomers, does not form stable adducts with weak nucleophiles such as water (and is less reactive than pteridin-7-one with the moderately strong nucleophile, acetylacetone), it reacts easily with more strongly nucleophilic reagents. Thus sodium hydrogen sulphite, in water at 25°, gives the isolable 2 : 1 adduct, disodium 3,4,5,6,7,8-hexahydro-4-oxopteridine-6,7-disulphonate (1b); and 5,5-dimethylcyclohexane-1,3-dione (dimedone), barbituric acid, and 2-thiobarbituric acid give similar 2 : 1 adducts. Addition of sodium hydrogen sulphite occurs across the 5,6- and 7,8-double bonds of pteridine-2,4-dione (lumazine) and 4-aminopteridine, and across the 7,8-double bond of 2-aminopteridine-4,6-dione (xanthopterin).