8-Mercapto-2-thiotheophylline

1,2,3,7,8,9-Hexahydro-1,3-dimethyl-2,8-dithioxo-6H-purin-6-one

3,7-Dihydro-1,3-dimethyl-8-mercapto-2-thioxo-1H-purin-6(2H)-one