The discovery of allyltyrosine based tripeptides as selective inhibitors of the HIV-1 integrase strand-transfer reaction.

From library screening of synthetic antimicrobial peptides, an O-allyltyrosine-based tripeptide was identified to possess inhibitory activity against HIV-1 integrase (IN) exhibiting an IC50 value of 17.5 µM in a combination 3'-processing and strand transfer microtitre plate assay. The tripeptide was subjected to structure-activity relationship (SAR) studies with 28 peptides, incorporating an array of natural and non-natural amino acids. Resulting SAR analysis revealed the allyltyrosine residue was a key feature for IN inhibitory activity whilst incorporation of a lysine residue and extended hydrophilic chains bearing a terminal methyl ester was advantageous. Addition of hydrophobic aromatic moieties to the N-terminal of the scaffold afforded compounds with improved inhibitory activity. Consolidation of these functionalities lead to the development of the tripeptide 96 which specifically inhibited the IN strand-transfer reaction with an IC50 value of 2.5 µM.

Binaphthyl-anchored antibacterial tripeptide derivatives with hydrophobic C-terminal amino acid variations.

The facile synthesis of seven new dicationic tripeptide benzyl ester derivatives, with hydrophobic group variations in the C-terminal amino acid component, is described. Moderate to good activity was seen against Gram-positive bacteria in vitro. One cyclohexyl-substituted compound 2c was tested more widely and showed good potency (MIC values ranging from 2-4 µg/mL) against antibiotic-resistant strains of Staphylococcus aureus and Enterococci (VRE, VSE), and against Staphylococcus epidermidis.

Crystal structures of novel allosteric peptide inhibitors of HIV integrase identify new interactions at the LEDGF binding site.

An optimised method of solution cyclisation gave us access to a series of peptides including SLKIDNLD (2). We investigated the crystallographic complexes of the HIV integrase (HIV-IN) catalytic core domain with 13 of the peptides and identified multiple interactions at the binding site, including hydrogen bonds with residues Thr125 and Gln95, that have not previously been described as being accessible within the binding site. We show that the peptides inhibit the interaction of lens epithelium-derived growth factor (LEDGF) with HIV-IN in a proximity AlphaScreen assay and in an assay for the LEDGF enhancement of HIV-IN strand transfer. The interactions identified represent a potential framework for the development of new HIV-IN inhibitors.

Antiviral agents 3. Discovery of a novel small molecule non-nucleoside inhibitor of hepatitis B virus (HBV).

The discovery of a small molecule non-nucleoside inhibitor of Hepatitis B Virus is described. During our work on conocurvone derived naphthoquinone 'trimers' for the treatment of HIV, we discovered a potent inhibitor 9 of Hepatitis B Virus in an antiviral screen. During attempts to resynthesis 9 for proof of concept studies, we altered the synthesis in order to attempt to reduced side reactions and difficult to remove by-products. As a result we discovered a small molecule 19 that also was a potent inhibitor of HBV. Importantly, this small molecule inhibitor of Hepatitis B Virus is also an inhibitor of Hepatitis B Virus resistant to 3TC, a bench mark of nucleoside analogues active in the treatment of Hepatitis B Virus. The development of 19 as an agent to treat HBV infections is discussed.

Synthesis and antibacterial activity of some binaphthyl-supported macrocycles containing a cationic amino acid.

As part of a programme investigating antibacterial cyclic macrocycles containing a cationic amino acid with an internal aromatic hydrophobic scaffold, we previously reported a macrocycle anchored at the 3,3'-positions of a 1,1'-binaphthyl unit. This was prepared via key intermediates containing an internal allylglycine and an allyl-substituted binaphthyl unit for a subsequent ring-closing metathesis reaction. This paper presents some structure-activity relationship studies with additional macrocycles based on this lead compound against Staphylococcus aureus together with the antibacterial activity of two related acyclic compounds.

Discovery of potent HIV integrase inhibitors active against raltegravir resistant viruses.

A series of novel HIV integrase inhibitors active against rategravir resistant strains are reported. Initial SAR studies revealed that activities against wild-type virus were successfully maintained at single digit nanomolar level with a wide range of substitutions. However, inclusion of nitrogen-based cyclic substitutions was crucial for achieving potency against mutant viruses. Several compounds with excellent activities against wild-type virus as well as against the viruses with the mutations Q148H/G140S or N155H/E92Q were reported.

Design of a series of bicyclic HIV-1 integrase inhibitors. Part 2: azoles: effective metal chelators.

Synthesis of a diverse set of azoles and their utilizations as an amide isostere in the design of HIV integrase inhibitors is described. The Letter identified thiazole, oxazole, and imidazole as the most promising heterocycles. Initial SAR studies indicated that these novel series of integrase inhibitors are amenable to lead optimization. Several compounds with low nanomolar inhibitory potency are reported.

Studies on the structure-activity relationship of 1,3,3,4-tetra-substituted pyrrolidine embodied CCR5 receptor antagonists. Part 2: Discovery of highly potent anti-HIV agents.

Modification of 1,3,3,4-tetra-substituted pyrrolidine embodied CCR5 receptor antagonists revealed that introducing a fluoro group at the 3-position of the 3-phenyl group to reduce metabolism did not adversely affect the high potency against HIV infection, and that replacing the piperidine ring with a tropane ring could deliver the most potent anti-HIV agents. Stereochemistry of the substituted tropane ring is essential for maintaining the potent anti-HIV activity because only exo-isomers displayed subnanomolar whole cell activity.

Design of a series of bicyclic HIV-1 integrase inhibitors. Part 1: selection of the scaffold.

HIV integrase inhibitors based on a novel bicyclic pyrimidinone core is presented. Nine variations of the core scaffold are evaluated leading to optimization of the 6:6 core giving compound 48 with an EC(50) of 3 nM against wild type HIV infected T-cells.

Studies on the structure-activity relationship of 1,3,3,4-tetra-substituted pyrrolidine embodied CCR5 receptor antagonists. Part 1: Tuning the N-substituents.

A novel series of CCR5 antagonists has been identified, utilizing the lead, nifeviroc, which were further modified based on bioisosteric principles. Lead optimization was pursued by balancing potential toxicity and potency. Potent analogues with low toxic properties were successfully developed by formation of urea and amide bonds at the nitrogen at position 4- of the pyrrolidine ring.

Antiviral agents 2. Synthesis of trimeric naphthoquinone analogues of conocurvone and their antiviral evaluation against HIV.

The synthesis of a new series of conocurvone analogues is presented that explores the importance of the pyran rings of conocurvone, their degree of unsaturation as well as the role of alkoxy functionalities as pyran ring replacements, for the inhibition of the HIV-1 integrase (IN) enzyme. Difficulties in synthesising a trimeric naphthoquinone where the central quinone bears a peri-dihydropyran ring was attributed to distortion of the electrophilic dihaloquinone successfully utilised in the past. Increased electron density could also be a factor in reducing reactivity. The desired central dihydropyran bearing trimeric naphthoquinone was successfully synthesised by using a more reactive bromo-tosyloxyquinone intermediate. A maleimide derivative, where the central quinone between the pendant hydroxyquinones was replaced, was successfully synthesised and although it exhibited comparable enzyme inhibitory activity it had negligible HIV inhibitory cellular activity. Compounds were assessed for activity in both in vitro assays using purified recombinant HIV-1 IN and demonstrated superior or comparable activity to conocurvone derivatives previously reported.

Synthesis and antibacterial studies of binaphthyl-based tripeptoids. Part 2.

A compact synthesis of 15 new binaphthyl-based dicationic tripeptoids and one biphenyl based dicationic tripeptoid is described. Fourteen of these tripeptoids resulted from variation of the C-2' ether substituent of the binaphthyl unit. An O-iso-butyl ether binaphthyl derivative was found to be the most active against Staphylococcus aureus (MIC 1.95 µg/mL). The biphenyl analogue also showed good activity against S. aureus (MIC 1.95 µg/mL). These compounds, however, were less active against four vancomycin-resistant strains of enterococci (VRE) than some of our previously developed compounds that had an O-iso-pentyl ether substituent on the binaphthyl unit and a C-2 L-Leu moiety.

Synthesis and antibacterial studies of binaphthyl-based tripeptoids. Part 1.

An efficient synthesis of 29 new binaphthyl-based neutral, and mono- and di-cationic, peptoids is described. Some of these compounds had antibacterial activities with MIC values of 1.9-3.9microg/mL against Staphylococcus aureus. One peptoid had a MIC value of 6microg/mL against a methicillin-resistant strain of S. aureus (MRSA) and a MIC value of 2microg/mL against vancomycin-resistant strains of enterococci (VRE).

Binaphthyl scaffolded peptoids via ring-closing metathesis reactions and their anti-bacterial activities.

An efficient synthesis of four new acyclic and four new cyclic binaphthyl-based cationic peptoids is described. These compounds had anti-bacterial activities with MIC values of 4-62 microg/mL against Staphylococcus aureus.

A novel aspochalasin with HIV-1 integrase inhibitory activity from Aspergillus flavipes.

A novel aspochalasin, aspochalasin L (1), was isolated from the fermentation broth of a soil-derived fungal culture identified as Aspergillus flavipes (Deuteromycota). Structure elucidation of 1 was accomplished by detailed spectroscopic data analyses and by comparison with related cytochalasins. Aspochalasin L demonstrated activity against HIV integrase with an IC50 of 71.7microM.

Globoidnan A: a lignan from Eucalyptus globoidea inhibits HIV integrase.

An HTS campaign aimed at the identification of inhibitors of HIV integrase showed that the methanol extract from the buds of a Eucalyptus globoidea was active. Bioassay guided fractionation of this extract resulted in the purification and structural elucidation of the lignan, globoidnan A (1) as the only compound in the extract responsible for the inhibition of HIV integrase. The compound was found to inhibit the combined 3' processing and strand transfer activity of HIV integrase with an IC50=0.64 microM.

Small molecule inhibitors of the LEDGF site of human immunodeficiency virus integrase identified by fragment screening and structure based design.

A fragment-based screen against human immunodeficiency virus type 1 (HIV) integrase led to a number of compounds that bound to the lens epithelium derived growth factor (LEDGF) binding site of the integrase catalytic core domain. We determined the crystallographic structures of complexes of the HIV integrase catalytic core domain for 10 of these compounds and quantitated the binding by surface plasmon resonance. We demonstrate that the compounds inhibit the interaction of LEDGF with HIV integrase in a proximity AlphaScreen assay, an assay for the LEDGF enhancement of HIV integrase strand transfer and in a cell based assay. The compounds identified represent a potential framework for the development of a new series of HIV integrase inhibitors that do not bind to the catalytic site of the enzyme.

Synthesis and antibacterial activity of C2-symmetric binaphthyl scaffolded amino acid derivatives.

The synthesis of eleven novel antibacterial agents is reported. The structures are based on a C(2)-symmetric binaphthyl scaffold which holds two identical chains consisting of a short linker, a basic amino acid and a small hydrophobic side chain. Antibacterial activity is revealed for a number of derivatives down to an MIC of 2 µg/mL (2 µM) against Staphylococcus aureus--comparable to vancomycin, and an MIC of 31 µg/mL (31 µM) against some vancomycin-resistant enterococcal strains.