1 EXU 1,3,7-trimethyl-9h-purine-2,6,8-trione 1.000 2 CFF Caffeine 0.933 3 37T Theobromine 0.867 4 TEP Theophylline 0.867 5 E7R 1,3-dimethyl-7-propyl-purine-2,6-dione 0.824 6 209 8-amino-1,3-dimethyl-3,7-dihydropurine-2,6-dione 0.812 7 H33 8-chloro-1,3-dimethyl-3,7-dihydro-1h-purine-2,6-dione 0.812 8 8HX 8-hydroxy-3,9-dihydro-1h-purine-2,6-dione 0.800 9 URC Uric acid 0.800 10 7UM 3-methyl-7-propyl-purine-2,6-dione 0.765 11 MUA 9-methyl uric acid 0.750 12 X0T 7-[(2s)-2,3-dihydroxypropyl]-1,3-dimethyl-3,7-dihydro-1h-purine-2,6-dione 0.737 13 XAN Xanthine 0.733 14 IBM 3-isobutyl-1-methylxanthine 0.722 15 IUP 5-(hydro)peroxoisourate 0.706 16 7UH Doxofylline 0.700 17 M1D 4-(1,3-dimethyl-2,6-dioxo-1,2,3,6-tetrahydro-7h-purin-7-yl)butanoic acid 0.700 18 QOK 7-(2-methoxyethoxymethyl)-1,3-dimethyl-purine-2,6-dione 0.700