1SBG:
reference: An orally bioavailable HIV-1 protease inhibitor containing an imidazole-derived peptide bond replacement: crystallographic and pharmacokinetic analysis., Abdel-Meguid SS, Metcalf BW, Carr TJ, Demarsh P, DesJarlais RL, Fisher S, Green DW, Ivanoff L, Lambert DM, Murthy KH, et al., Biochemistry 1994 Oct 4;33(39):11671-7. PMID: 7918383

This OCA Structure page
uses Jmol, developed by the Jmol Development Team (documentation).