Intermediates in the Browning Reaction of Triose Reductone with Guanine, Guanosine or Guanylic Acid

Abstract

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′)-guanyIic acid (V) or N²-(3-oxo-2-hydroxypropenyl)5′-guanylic acid (VI), respectively.