INTERMEDIATES IN THE BROWNING REACTION OF TRIOSE REDUCTONE WITH GUANINE, GUANOSINE OR GUANYLIC ACID

The intermediates in the browning reaction of triose reductone (I) with guanine, guanosine, 2'(3')- or 5'-guanylic acid were isolated. The reaction of I with guanine in 4 N HCl at 65°C for about 1 hr produced only a brown tricyclic compound, 1, N2-(2-hydroxypropenylidene)- guanine or 7-hydroxy-10-oxo-9,10-dihydropyrimido[1,2-a]purine (III) with the analogous structure to natural occurring Y bases, whereas that at room temperature yielded a labile light yellow intermediate, N2-(3-oxo-2-hydroxypropenyl)guanine (II) with the enaminol structure as a mixture with III. The ratio of II to III was about 1:1. The isolation of II in pure form was difficult because of its instability. On the other hand, the reaction of I with guanosine, 2'(3')- or 5'-guanylic acid in 4 N HCl at room temperature gave the reductive intermediate with the same enaminol structure as II, N2-(3-oxo-2-hydroxypropenyl)guanosine (IV), N2-(3-oxo-2-hydroxypropenyl)2'(3')-guanylic acid (V) or N2-(3-oxo-2-hydroxypropenyl)5'-guanylic acid (VI), respectively. © 1979 Taylor & Francis Group, LLC.