Computer-assisted structure-activity correlations of halodideoxynucleoside analogs as potential anti-HIV drugs

Synthesis and Antiviral Evaluation of Novel 6′(α)-Methyl-Branched Carbovir Analogues

A new stereoselective synthesis of 6'-branched Carbovir analogues was accomplished in this study. The introduction of a methyl group in the requisite 6'(alpha)-position was carried out using an ester enolate alkylation (LHMDS, CH3I). The desired cyclopentenol 7 was synthesized via a Felkin-Anh-controlled Grignard addition and ring-closing metathesis using second-generation Grubbs' catalyst. The natural bases (adenine, cytosine) were efficiently coupled using a Pd(0) catalyst. When the synthesized compounds were examined for their activity against several viruses such as the HIV-1, HSV-1, HSV-2, and HCMV, the adenine analogue 12 exhibited moderate antiviral activity against the HCMV.

QSAR studies of antiviral agents using molecular similarity analysis and structure-activity maps

Quantitative structure-activity relationships (QSAR) were developed for nucleoside analogs with anti-HIV activity. These compounds were investigated to determine the correlation of structure and toxicity/activity using molecular similarity analysis and structure-activity maps. A multiple-formula approach was used to perform quantitative molecular similarity analysis (QMSA) and QSAR study. Molecular descriptors such as number of atoms and bonds of a molecule (NAB), maximum common substructure (MaCS), and molecular similarity index (MSI) were used in our structure-activity relationship study. The MaCS of two molecules is defined as the substructure with the greatest NAB value common to both molecules. The MSI of two molecules X and Y is defined as MSI(X,Y) = [MaCS(X,Y)/NAB(X)] x [MaCS(X,Y)/NAB(Y)]. MaCS and MSI quantify the similarity between two molecular structures. Structure-activity maps (structure-toxicity map and structure-antiviral map) and QMSA were used to determine the site and type of modification for reduced toxicity and improved activity of new compounds.

Synthesis and antiviral evaluation of hydantoin analogues of AZT

3'-Azidonucleosides 4 have been synthesized by condensation of silylated (Z)-5-ethylidenehydantoin and (Z)-5-benzylidenehydantoin with methyl 3-azido-5-O-tert-butyldiphenylsilyl-2,3-dideoxy-D-erythro-pento furanoside (3). The nucleosides 4 were deblocked on treatment with tetrabutylammonium fluoride. The ethylidene group isomerized from Z to E configuration during the nucleoside synthesis. The new nucleosides did not show any appreciable activities against HIV-1 or HSV-1.

Identification of a pharmacophore for nucleoside analog inhibitors directed at HIV-1 reverse transcriptase

An 'active analog' approach to receptor mapping was used to identify a pharmacophore for a set of thymidine nucleoside analog inhibitors of HIV-1 reverse transcriptase. The preliminary results indicate that the O2, O4', and O5' atoms are capable of adopting a unique pharmacophoric pattern which may be the key to their recognition by reverse transcriptase.

Empirical and rational approaches for development of inhibitors of the human immunodeficiency virus--HIV-1

The human immunodeficiency virus, HIV-1, is generally accepted to be responsible for AIDS. It is imperative that all approaches, empirical and rational, be taken for development of a drug for therapy of this disease. These approaches are discussed, with emphasis on the direction being pursued in our laboratory. Empirically, we found 3'-deoxy-2',3'-didehydrothymidine, a compound first synthesized for potential anticancer activity by J. Horwitz in the 1960s, to be a potent inhibitor of HIV-1. It is now in Phase II/III clinical trials. We have also synthesized several 2,5'-anhydro pyrimidine nucleoside analogs, which have interesting chemical and biological properties. We have evaluated a natural product, gossypol and synthesized various derivatives for anti-HIV-1 activity, but none were appreciably more inhibitory than the parent compound. More recently, we have taken the rational approach and synthesized a boron-modified tetrapeptide, Ac-Thr-Leu-Asn-boro-Phe, which corresponds to the COOH-terminal of the Phe-Pro scissle bond of the gag/pol gene polyprotein product. Potent inhibition of the HIV-1 encoded protease was observed. These approaches and findings will be discussed.

Synthesis and anti-HIV activity of 5-alkoxymethyl-3'-azido-2',3- dideoxyuridines

Methyl 3-azido-5-O-tert-butyldiphenylsilyl-2,3-dideoxy-D-erythro-furanosi de (3) was coupled with silylated 5-hydroxymethyluracil (1a) and its C1-C6 alkyl ethers 1b-g to give the corresponding protected nucleosides 4a-g which were deprotected with Bu4NF to afford 3-azido nucleosides 5a-g and 6a-g. The alpha-anomers 6f,g show moderate activity against HIV. No significant activity against HSV-1 was found for the compounds 5 and 6.

Antiviral therapy in human immunodeficiency virus infections. Current status (Part II)

Part I of this article reviewed the targets against which anti-HIV drugs can be directed, problems in assessing active compounds (e.g. resistance development and use of surrogate end-points). and nucleoside analogues effective against HIV reverse transcriptase. Intensive research is currently being undertaken in laboratories and hospitals to design and evaluate new inhibitors of HIV. In this work, combining different drugs is one important approach, both to decrease toxicity and to offset the rate of resistance development, which seems to be a major problem associated with therapy directed against the ever-changing HIV. Therapeutic vaccines and immunomodulators are other modalities being actively evaluated against HIV and AIDS, although this effort has not yet yielded any licensed treatment. It appears likely that new antiviral drugs and immunotherapies will be forthcoming during the next 5 years, that they will be used in a variety of combinations, and that the treatment options available for opportunistic infections will increase. These developments should improve the survival and the quality of life of patients with HIV infection.