1 28Y 3h-imidazo[2,1-B]purin-4(5h)-one 1.000 2 HPA Hypoxanthine 0.769 3 2ON 2-sulfanyl-1,9-dihydro-6h-purin-6-one 0.714 4 BOA 2-bromo-6-hydroxy-purine 0.714 5 GUN Guanine 0.714 6 K7L (4s)-imidazo[1,2-a]pyrimidine-5,7-diol 0.714 7 XAN Xanthine 0.714