(1S,4R)-4-Amino-2-cyclopentene-1-methanol (-)-Dibenzoyl-L-tartaric Acid is an intermediate in synthesizing ent-Abacavir (Abacavir EP Impurity A) (A105015), an enatiomer of Abacavir (A105000). Abacavir is a carbocyclic 2′-deoxyguanosine nucleoside reverse transcriptase inhibitor and an anti-HIV drug used to treat HIV infection (1). Intracellular enzymes convert Abacavir to its active form, carbovir-triphosphate (CBV-TP), which then selectively inhibits HIV reverse transcriptase by incorporating into viral DNA (2). Abacavir is metabolized in the liver by uridine diphosphate glucuronyltransferase and alcohol dehydrogenase resulting in inactive glucuronide and carboxylate metabolites, respectively.