6-N-Cyclopropyl-9-[(1R,4S)-4-[[(1,1-dimethylethyl)oxy]- methyl]cyclopent-2-en-1-yl]-9H-purine-2,6-diamine; Abacavir t-Butyl Ether; 6-(Cyclopropylamino)-9-[(1R,4S)-4-[[(1,1-dimethylethyl)oxy]methyl]cyclopent-2-enyl]-9H-purine-2-amine; 6-N-Cyclopropyl-9-[(1R,4S)-4-[[(1,1-dimethylethyl)oxy]- methyl]cyclopent-2-en-1-yl]-9H-purine-2,6-diamine;O-t-Butyl Derivative Abacavir; 9-((1R,4S)-4-(tert-Butoxymethyl)cyclopent-2-en-1-yl)-N6-cyclopropyl-9H-purine-2,6-diamine; 9-((1S,3R)-3-(tert-butoxymethyl)cyclopentyl)-N6-cyclopropyl-9H-purine-2,6-diamine