3,7-Dihydro-purine-2,6-dione derivatives (also known as substituted xanthines) constitute an important class of pharmacologically active compounds with well-known activities as phosphodiesterase inhibitors, cystic fibrosis transmembrane conductance regulator (CFTR) chloride channel activators, and adenosine receptor antagonists. [ 1 1. (a) Dorfman , LJ ; Jarvik , ME Comparative stimulant and diuretic actions of caffeine and theobromine in man . Clin. Pharmacol. Ther. ...