This invention relates to Trans cyclopentanyl purine analogs of the formula (1) ##STR1## wherein the substituent in the 3-position on the cyclopentanyl ring is in the Trans configuration relative to the bicyclic substituent,Y.sub.3, Y.sub.5 and Y.sub.9 are each nitrogen and Y.sub.7 and Y.sub.8 are a CH group,R is a hydrogen, a C.sub.1 -C.sub.7 alkyl acyl or aryl acyl,Q is NH.sub.2, halogen or hydrogen,Z is hydrogen, halogen, or NH.sub.2 ;or a pharmaceutically-acceptable salt thereof, and to their use as immunosuppressants.