Asymmetrically substituted xanthines

摘要

Xanthine derivatives of formula <IMAGE> I wherein R1 is hydrogen, alkyl or alkynyl, R2 is different and is alkyl, alkynyl, phenyl-alkylene, phenyl alkenylene, cycloalkyl, inter alia, R3 is cycloalkyl, phenyl, norbornane, inter alia and R4 is hydrogen, methyl, benzyl, inter alia.