A Scaleable Synthesis of Methyl 3-Amino-5-(4-fluorobenzyl)-2-pyridinecarboxylate

Integrase Inhibitor Prodrugs: Approaches to Enhancing the Anti-HIV Activity of β-Diketo Acids

HIV integrase, encoded at the 3'-end of the HIV pol gene, is essential for HIV replication. This enzyme catalyzes the incorporation of HIV DNA into human DNA, which represents the point of "no-return" in HIV infection. Integrase is a significant target in anti-HIV drug discovery. This review article focuses largely on the design of integrase inhibitors that are β-diketo acids constructed on pyridinone scaffolds. Methodologies for synthesis of these compounds are discussed. Integrase inhibition data for the strand transfer (ST) step are compared with in vitro anti-HIV data. The review also examines the issue of the lack of correlation between the ST enzymology data and anti-HIV assay results. Because this disconnect appeared to be a problem associated with permeability, prodrugs of these inhibitors were designed and synthesized. Prodrugs dramatically improved the anti-HIV activity data. For example, for compound, 96, the anti-HIV activity (EC50) improved from 500 nM for this diketo acid to 9 nM for its prodrug 116. In addition, there was excellent correlation between the IC50 and IC90 ST enzymology data for 96 (6 nM and 97 nM, respectively) and the EC50 and EC90 anti-HIV data for its prodrug 116 (9 nM and 94 nM, respectively). Finally, it was confirmed that the prodrug 116 was rapidly hydrolyzed in cells to the active compound 96.

Approaches to the synthesis of a novel, anti-HIV active integrase inhibitor

The novel HIV-1 integrase inhibitor 1, discovered in our laboratory, exhibits potent anti-HIV activity against a diverse set of HIV-1 isolates and also against HIV-2 and SIV. In addition, this compound displays low cellular cytotoxicity and possesses a favorable in vitro drug interaction profile with respect to isozymes of cytochrome P450 (CYP) and uridine 5'-diphospho-glucuronosyltransferase (UGT). However, the total synthesis of this significant HIV integrase inhibitor has not been reported. This contribution describes an optimized, reproducible, multi-step, synthetic route to inhibitor 1. The yield for the separate steps averaged about 80%. The methodologies utilized in the synthesis were, among others, a palladium-catalyzed cross-coupling reaction, a crossed-Claisen condensation, and a hydrazino amide synthesis step. Successful alternative synthetic methodologies for some of the steps are also described.

Naphthyridinone (NTD) integrase inhibitors: N1 protio and methyl combination substituent effects with C3 amide groups

Substituent effects of a series of N1 protio and methyl naphthyridinone HIV-1 integrase strand-transfer inhibitors has been explored. The effects of combinations of the N1 substituent and C3 amide groups was extensively studied to compare enzyme inhibition, antiviral activity and protein binding effects on potency. The impact of substitution on ligand efficiency was considered and several compounds were advanced into in vivo pharmacokinetic studies ultimately leading to the clinical candidate GSK364735.

Discovery of a Potent HIV Integrase Inhibitor that Leads to a Prodrug with Significant anti-HIV Activity

Worldwide research efforts in drug discovery involving HIV integrase have produced only one compound, raltegravir, that has been approved for clinical use in HIV/AIDS. As resistance, toxicity and drug-drug interactions are recurring issues with all classes of anti-HIV drugs, the discovery of novel integrase inhibitors remains a significant scientific challenge. We have designed a lead HIV-1 strand transfer (ST) inhibitor (IC(50) 70 nM), strategically assembled on a pyridinone scaffold. A focused structure-activity investigation of this parent compound led to a significantly more potent ST inhibitor, 2 (IC(50) 6 ± 3 nM). Compound 2 exhibits good stability in pooled human liver microsomes. It also displays a notably favorable profile with respect to key human cytochrome P450 (CYP) isozymes and human UDP glucuronosyl transferases (UGTs). The prodrug of inhibitor 2, i.e., compound 10, was found to possess remarkable anti-HIV-1 activity in cell culture (EC(50) 9 ± 4 nM, CC(50) 135 ± 7 μM, therapeutic index = 15,000).

On the mechanism of the palladium-catalyzed tert-butylhydroperoxide-mediated Wacker-type oxidation of alkenes using quinoline-2-oxazoline ligands

The mechanism of the tert-butylhydroperoxide-mediated, Pd(Quinox)-catalyzed Wacker-type oxidation was investigated to evaluate the hypothesis that a selective catalyst-controlled oxidation could be achieved by rendering the palladium coordinatively saturated using a bidentate amine ligand. The unique role of the Quinox ligand framework was probed via systematic ligand modifications. The modified ligands were evaluated through quantitative Hammett analysis, which supports a "push-pull" relationship between the electronically asymmetric quinoline and oxazoline ligand modules.

Synthesis and antiviral activity of 7-benzyl-4-hydroxy-1,5-naphthyridin-2(1H)-one HIV integrase inhibitors

The medicinal chemistry and structure-activity relationships for a novel series of 7-benzyl-4-hydroxy-1,5-naphthyridin-2(1H)-one HIV-integrase inhibitors are disclosed. Substituent effects were evaluated at the N-1, C-3, and 7-benzyl positions of the naphthyridinone ring system. Low nanomolar IC(50) values were achieved in an HIV-integrase strand transfer assay with both carboxylic ester and carboxamide groups at C-3. More importantly, several carboxamide congeners showed potent antiviral activity in cellular assays. A 7-benzyl substituent was found to be critical for potent enzyme inhibition, and an N-(2-methoxyethyl)carboxamide moiety at C-3 significantly reduced plasma protein binding effects in vitro. Pharmacokinetic data in rats for one carboxamide analogue demonstrated oral bioavailability and reasonable in vivo clearance.

Palladium- and nickel-catalyzed cross-couplings of unsaturated halides bearing relatively acidic protons with organozinc reagents

A wide range of polyfunctional aryl, heteroaryl, alkyl, and benzylic zinc reagents were coupled with unsaturated aryl halides bearing an acidic NH or OH proton, using Pd(OAc)2 (1 mol %) and S-Phos (2 mol %) as catalyst without the need of protecting groups. A similar nickel-catalyzed reaction is described. The relative kinetic basicity of organozinc compounds as well as their stability toward acidic protons is also described.