Small dipeptide-based HIV protease inhibitors containing the hydroxymethylcarbonyl isostere as an ideal transition-state mimic

The human immunodeficiency virus (HN) codes for an aspartic protease known to be essential for retroviral maturation and replication. HIV protease is formed from two identical 99 amino acid peptides. We synthesized [(NHCH2CH2 -S-CH2CO)(51-52), Ala(67,95)]HIV-1 protease using the thioether chemical li gation method and then prepared the [(NHCH2CH2-S-CH2CO)(51-52), Ala(67,95), Cys(98)]HIV-1 protease dimer analogue covalently linked by a disulfide bri dge. These HN-I protease analogues effectively cleaved the Tyr-Phe-type sub strate, but had weak affinity to the Tyr-Pro-type substrate. Consequently, the molecular recognition of the protease analogues differs from that of th e wild-type enzyme. Based on the substrate transition state, we designed an d synthesized a novel class of HIV protease inhibitors containing an unnatu ral amino acid, (2S, 3S)-3-amino-2-hydroxy-4-phenylbutyric acid, named allo phenylnorstatine, with a hydroxymethylcarbonyl (HMC) isostere. The stereoch emistry of the hydroxyl group was significant for the enzyme inhibition and the HMC group interacted excellently with the aspartic acid carboxyl group s of HIV protease active site in the essentially same hydrogen-bonding mode as the transition state. Small dipeptide-based HIV protease inhibitors con taining the HMC isostere were studied as advantageous compounds. Among them , a dipeptide-based HIV protease inhibitor, KNI-577, exhibited patent antiv iral activities, low cytotoxicity, and good pharmacokinetic properties. (C) 1999 John Wiley & Sons, Inc.