asymmetrically substituted xanthine derivatives having adenosine a 1 antagonistic activity . these are useful as pharmaceuticals . exemplary are : 3 - sulphonylethyl )- 8 -- 1 - n - propyl - xanthine ; 3 - sulphonylethyl )- 8 -- 1 - n - propyl - xanthine ; and , 3 -- 8 -- 1 - n - propyl - xanthine .