Design of gem-Difluoro-bis-Tetrahydrofuran as P2 Ligand for HIV-1 Protease Inhibitors to Improve Brain Penetration: Synthesis, X-ray Studies, and Biological Evaluation.
Ghosh, A.K., Yashchuk, S., Mizuno, A., Chakraborty, N., Agniswamy, J., Wang, Y.F., Aoki, M., Gomez, P.M., Amano, M., Weber, I.T., Mitsuya, H.(2015) ChemMedChem 10: 107-115
- PubMed: 25336073 
- DOI: https://doi.org/10.1002/cmdc.201402358
- Primary Citation of Related Structures:  
4U8W - PubMed Abstract: 
The structure-based design, synthesis, biological evaluation, and X-ray structural studies of fluorine-containing HIV-1 protease inhibitors are described. The synthesis of both enantiomers of the gem-difluoro-bis-THF ligands was carried out in a stereoselective manner using a Reformatskii-Claisen reaction as the key step. Optically active ligands were converted into protease inhibitors. Two of these inhibitors, (3R,3aS,6aS)-4,4-difluorohexahydrofuro[2,3-b]furan-3-yl(2S,3R)-3-hydroxy-4-((N-isobutyl-4-methoxyphenyl)sulfonamido)-1-phenylbutan-2-yl) carbamate (3) and (3R,3aS,6aS)-4,4-difluorohexahydrofuro[2,3-b]furan-3-yl(2S,3R)-3-hydroxy-4-((N-isobutyl-4-aminophenyl)sulfonamido)phenylbutan-2-yl) carbamate (4), exhibited HIV-1 protease inhibitory Ki values in the picomolar range. Both 3 and 4 showed very potent antiviral activity, with respective EC50 values of 0.8 and 3.1 nM against the laboratory strain HIV-1LAI . The two inhibitors exhibited better lipophilicity profiles than darunavir, and also showed much improved blood-brain barrier permeability in an in vitro model. A high-resolution X-ray structure of inhibitor 4 in complex with HIV-1 protease was determined, revealing that the fluorinated ligand makes extensive interactions with the S2 subsite of HIV-1 protease, including hydrogen bonding interactions with the protease backbone atoms. Moreover, both fluorine atoms on the bis-THF ligand formed strong interactions with the flap Gly 48 carbonyl oxygen atom.
Organizational Affiliation: 
Departments of Chemistry and Medicinal Chemistry, Purdue University, West Lafayette, IN 47907 (USA). akghosh@purdue.edu.