s-Triazolo(3,4-I)purine derivatives

摘要

There are disclosed s-triazolo[3,4-i]purine derivatives represented by formula: <IMAGE> wherein Y-Z represents <IMAGE> R4 represents hydrogen, alkyl, substituted or unsubstituted aromatic heterocyclic group or substituted or unsubstituted aryl; and X2 represents oxygen, sulfur or NH; each of R1 and R2 independently represents hydrogen, alkyl, cycloalkyl, aralkyl or substituted or unsubstituted aryl; R3 represents alkyl, cycloalkyl, aralkyl or substituted or unsubstituted aryl; X1 represents oxygen or sulfur; and represents a single bond or a double bond or pharmaceutically acceptable salts thereof.