JOURNAL OF MOLECULAR RECOGNITION, VOL. zyxwvuts 9. zyxwvuts 139-142 (1996) zyxwvut Inhibitors of HIV Protease: Unique Non-peptide Active Site Templates Bradley D. Tait*’, John Domagala’, Edmund L. Ellsworth’, Donna Ferguson’, Christopher Gajda’, Donald Hupe’, zyxwvut Elizabeth A. Lunney, and Peter J. Turnmino*. Department of Chemistry’, Biochemistry*. Biomolecular Structure and Drug Design’, Parke-Davis Pharmaceutical Research Division of the Warner-Lambert Company, 2800 Plymouth Road, Ann Arbor, Michigan 48106, USA New templates were designed and prepared which straddle the active site of HIV-1 protease. These templates were designed to be ‘flexible scaffolds’ upon which substituents could be appended to fill the pockets of HIV protease. The new templates prepared and analysed were 4-hydroxy-5H-furan-2-ones, 4-hydroxy-5,6-dihy- dropyrones, 3-hydroxy-cyclohex-2-enones, and 4-hydroxy-2(lH)-pyridinones, of which the 4-hydroxy- 5,6-dihydropyrones were found to be the most potent inhibitors of HIV-1 protease. zyxw Keywords: HIV protease; inhibitors; 4-hydroxy-SH-furan-2-one; tetronic acids; 4-hydroxy-5,6-dihydropyrone; 3-hydroxy-cyclohex-2-enone; 4-hydroxy-2( lH)-pyridinone. Introduction Acquired Immunodeficiency Syndrome (AIDS) was first defined in 1982 as the clinical manifestations of immunode- ficiency.The etiological agent of AIDS was later determined to be a retrovirus, human immunodeficiency virus (HIV), of the lentivirus subfamily (Wakefield et al., 1994). Character- ization of HIV has provided numerous potential antiviral approaches, one of which is inhibition of an aspartyl protease (Katz and Skalka, 1994). HIV protease is responsible for post-translational proc- essing of the precursor polyproteins zyxwvuts - Gag and GagPo1 (Redshaw, 1994) which is essential for maturation of the virus. The proteolytic activity of HIV protease cannot be provided by host cellular enzymes. It has been shown that HIV which lacks this protease or contains a mutant defective protease is non-infectious (Kohl et zyxwvuts al., 1988). The sum of these observations makes inhibition of HIV protease an attractive target for antiviral therapy. The majority of the HIV protease inhibitors reported are peptidic or peptidomimetic in nature (Meek, 1992; Thaisri- vongs, 1994). Peptidic compounds are known to possess pharmacological problems such as biliary excretion and low bioavailability. Due to these problems, the compounds currently under investigation in the clinic require substantial doses and, therefore, large quantities of drug. Supplies of these agents have been limited by synthetic problems associated with large compounds containing multiple chiral centers (Askin et zyxwvutsrqp al., 1994; Parkes et al., 1994; Vella, 1994). We have reported a series of nonpeptidic inhibitors of HIV protease, the 3,6-disubstituted-4-hydroxy-2-pyrones, which were identified by mass screening the Parke-Davis compound portfolio (Tummino et al., 1994; Vara Prasad et al., 1994). Limited optimization of the substituents has afforded potency enhancement from micromolar to nano- molar (Vara Prasad et al., 1995). Thaisrivongs and Author to whom correspondence should be addressed. co-workers have also reported on 3.6-disubstituted- 4-hydroxy-2-pyrones as inhibitors of HIV protease (Thaisrivongs et al., 1994). There is a need for small nonpeptide HIV protease inhibitors which are easy to synthesize and exhibit good bioavailability. We set out to design and synthesize new templates which would straddle the active site of HIV protease and act as a scaffold upon which to build. Experimental 4-Hydroxy-5-phenyl-SH-furan-2-one was purchased from Eastman-Kodak. The 4-hydroxy-5.6-dihydropyrone tem- plates were prepared according to the method of Groutas et al., (1985). The 4-hydroxy-2(lH)-pyridinone template was prepared by decarboxylation of methyl 6-phenyl-2,4-dioxo- piperidine-3-carboxylate (Ashton et al., 1989) according to the method of Toda et al., (1980). The 1,3-cyclohexadione templates were prepared as described by Werbel et al., (1992). The 3-position sulfur side chains were attached to the templates by reaction with the appropriate thiotosylate reagent (Harris and Dunbar, 1976) and triethylamine in absolute ethanol. Additional synthetic and characterization details for these compounds can be found in a Parke-Davis patent (WO 95 1401 1-A2). The compounds prepared were fully characterized by ‘H NMR, CHN(S), MS, IR. The compounds were assayed against HIV- 1 protease using the method described by Tummino et zy af., (1995). The reported IC,,s are averaged values from two runs. Results and Discussion In designing a new template we focused on knowledge obtained from X-ray co-crystal structures of HIV- 1 protease with a 4-hydroxy-coumarin (Lunney et al., 1994) and a 4-hydroxy-2-pyrone (Vara Prasad et al., 1994). These X-ray CCC 0952-3430/96/020139-04 0 1996 by John Wiley & Sons, Ltd. Accepted 23 October I995