1 290 6-methyl-3,9-dihydro-2h-purin-2-one 1.000 2 6MP 6-methylpurine 0.909 3 IGA 6-amino-3,7-dihydro-2h-purin-2-one 0.833 4 XAN Xanthine 0.833 5 8HX 8-hydroxy-3,9-dihydro-1h-purine-2,6-dione 0.769 6 8TX 8-thioxo-3,7,8,9-tetrahydro-1h-purine-2,6-dione 0.769 7 URC Uric acid 0.769 8 2BP 9h-purin-2-amine 0.750 9 ADE Adenine 0.750 10 BP1 6-bromo-7h-purine 0.750 11 ES4 6-chloro-9h-purine 0.750 12 HPA Hypoxanthine 0.750 13 PM6 9h-purine-6-thiol 0.750 14 37T Theobromine 0.714 15 MUA 9-methyl uric acid 0.714 16 TEP Theophylline 0.714