The hexahydrofurofuranyloxy group was evaluated as a conformationally constrained Pt ligand for symmetry-based HIV protease inhibitors. A number of compounds showed nM level activity against HIV in MT4 cells and lower protein binding than the licensed protease inhibitor ritonavir. However, replacement of 5-thiazole of ritonavir with a furofuran caused a reduction of the bioavailability in vivo. Copyright (C) 1996 Elsevier Science Ltd