The triphosphate of beta-D-4'-C-ethynyl-2',3'-dideoxycytidine is the preferred enantiomer substrate for HIV reverse transcriptase.

The enantioselective synthesis of the beta-d (1) enantiomer of 4'-C-ethynyl-2',3'-dideoxycytidine confirms an earlier stereochemical assignment that was strictly based on the ability of HIV reverse transcriptase and its M184V mutant to discriminate between the d- and l-configuration of nucleoside 5'-triphosphates.