An enantioselective enzymatic desymmetrization route to hexahydro-4H-furopyranol, a high-affinity ligand for HIV-1 protease inhibitors

Dehydration reactions in polyfunctional natural products

Here, we review methods for chemical dehydration of alcohols to alkenes and discuss the potential of late-stage functionalization by direct, site- and chemo-selective dehydration of complex molecular substrates.

A Photochemical Route to Optically Active Hexahydro-4H-furopyranol, a High-Affinity P2 Ligand for HIV-1 Protease Inhibitors

We describe here the syntheses of optically pure (3aS,4S,7aR)-hexahydro-4H-furo[2,3-b]pyran-4-ol and (3aR,4R,7aS)-hexahydro-4H-furo[2,3-b]pyran-4-ol. These stereochemically defined heterocycles are important high-affinity P2 ligands for a variety of highly potent HIV-1 protease inhibitors. The key steps involve an efficient Paternò-Büchi [2 + 2] photocycloaddition, catalytic hydrogenation, acid-catalyzed cyclization to form the racemic ligand alcohol, and an enzymatic resolution with immobilized Amano Lipase PS-30. Optically active ligands (-)-6 and (+)-6 were obtained with high enantiomeric purity. Enantiomer (-)-6 has been converted to potent HIV-1 protease inhibitor 3.

Nature Inspired Molecular Design: Stereoselective Synthesis of Bicyclic and Polycyclic Ethers for Potent HIV-1 Protease Inhibitors

We have developed a conceptually new generation of non-peptidic HIV-1 protease inhibitors incorporating novel structural templates inspired by nature. This has resulted in protease inhibitors with exceptional potency and excellent pharmacological and drug-resistance profiles. The design of a stereochemically defined bis-tetrahydrofuran (bis-THF) scaffold followed by modifications to promote hydrogen bonding interactions with the backbone atoms of HIV-1 protease led to darunavir, the first clinically approved drug for treatment of drug resistant HIV. Subsequent X-ray crystal structure-based design efforts led us to create a range of exceptionally potent inhibitors incorporating other intriguing molecular templates possessing fused ring polycyclic ethers with multiple stereocenters. These structural templates are critical to inhibitors' exceptional potency and drug-like properties. Herein, we will highlight the synthetic strategies that provided access to these complex scaffolds in a stereoselective and optically active form, enabling our medicinal chemistry and drug development efforts.