The complestatins as HIV-1 integrase inhibitors. Efficient isolation, structure elucidation, and inhibitory activities of isocomplestatin, chloropeptin I, new complestatins, A and B, and acid-hydrolysis products of chloropeptin I

From the screening of a microbial extract library, isocomplestatin (1), a n ew axial-chiral isomer of complestatin (2) which is a known rigid bicyclic hexapeptide, was identified as a potent natural product inhibitor of HIV-1 integrase, a unique enzyme responsible for viral replication. Isocomplestat in showed inhibitory activities (IC50) in coupled 3'-end processing/strand transfer (200 nM), strand transfer (4 muM), and HIV-1 replication (200 nM) in virus-infected cells. Attempted large-scale isolation of 1 by the litera ture method, used for the isolation of complestatin, led to lower yield and limited availability. We have developed several new, two-step, high-yieldi ng absorption/elution methods of isolation based on reverse-phase chromatog raphy at pH 8 that are applicable to scales from one gram to potential indu strial quantities. We have also discovered and determined the structure of two new congeners of 1, namely, complestatins A (4) and B (5), with almost equal HIV-1 integrase activity. They differ from 1 at C2' and C3' of the tr yptophan moiety (residue F). Selective acid hydrolysis of chloropeptin I (3 ), itself a known acid-catalyzed rearranged isomer of 1 and 2 (8'- vs 7'-su bstitution in tryptophan residue F, respectively), an isomer of complestati n, and isocomplestatin resulted in a number of fragments (6-10) with retent ion of most of the HIV-1 integrase activity. The structure-activity relatio nship as revealed by these compounds could possibly lead to the design of b etter inhibitors or understanding of the HIV-1 integrase target.