Potent HIV-1 Protease Inhibitors: Stereoselective Synthesis of a Dipeptide Mimic.

The synthesis of a differentially protected dipeptide mimic 10 in enantiomerically pure form is described. The key step involves the epimerization of the C-2 center of the lactone 4, hydrolysis and protection of the resulting hydroxy acid, followed by Curtius rearrangement to introduce the urethane functionality. The scope and versatility of this isostere has been demonstrated by its conversion to potent HIV-1 protease inhibitors with nanomolar potencies.