O-t-Butylamino Abacavir is a by-product intermediate in synthesizing N6-Cyclopropyl-9-[(1R,4S)-4-[(1,1-dimethylethoxy)methyl]-2-cyclopenten-1-yl]-9H-purine-2,6-diamine (Abacavir EP Impurity F) (C989915), an impurity of Abacavir (A104990), a guanosine analog that inhibits reverse transcriptase (NRTI)?(1,2).