PTERIDINES .C. STRUCTURE AND NONENZYMATIC SYNTHESIS OF AURODROSOPTERIN

The nonenzymatic synthesis of aurodrosopterin (5) from -tetrahydro-4H- pyrimido-[4,5-b][1,4]diazepin-4-one (3) and 7,8-dihydrolumazine (4) at pH 3 (HCl) was performed. The identity of the synthesized compound wi th the natural eye pigment isolated from drosophila heads was confirme d by thin-layer chromatography on cellulose and by comparisons of the H-1-NMR and UV/VIS spectra. The nonenzymatic synthesis of a neodrosopt erin-like red pigment from 3 and 2,4-diamino-7,8-dihydropteridine was also carried out, but its identity could not be established. This pigm ent, called aminodrosopterin, has an absorption peak at 489 nm, which is very close to that of neodrosopterin.