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

Methyl 2-(5,5-dimethyl-1,3,2-dioxa-borinan-2-yl)-4-nitro-benzoate

The six-membered boronate ester ring of the title compound, C₁₃H₁₆BNO₆, adopts an envelope conformation with the C atom bearing the dimethyl substituents at the flap. The O—B—C—C torsion angles between the boronate group and the benzene ring are 72.5 (2) and 81.0 (2)°. The 4-nitro­benzoate unit adopts a slightly twisted conformation, with dihedral angles between the benzene ring and the nitrate and methyl ester groups of 17.5 (2) and 14.4 (3)°, respectively. In the crystal, inversion-related pairs of mol­ecules show weak π–π stacking inter­actions [centroid–centroid distance = 4.0585 (9) Å and inter­planar spacing = 3.6254 (7) Å].

Facile analysis and sequencing of linear and branched peptide boronic acids by MALDI mass spectrometry

Interest in peptides incorporating boronic acid moieties is increasing due to their potential as therapeutics/diagnostics for a variety of diseases such as cancer. The utility of peptide boronic acids may be expanded with access to vast libraries that can be deconvoluted rapidly and economically. Unfortunately, current detection protocols using mass spectrometry are laborious and confounded by boronic acid trimerization, which requires time-consuming analysis of dehydration products. These issues are exacerbated when the peptide sequence is unknown, as with de novo sequencing, and especially when multiple boronic acid moieties are present. Thus, a rapid, reliable, and simple method for peptide identification is of utmost importance. Herein, we report the identification and sequencing of linear and branched peptide boronic acids containing up to five boronic acid groups by matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS). Protocols for preparation of pinacol boronic esters were adapted for efficient MALDI analysis of peptides. Additionally, a novel peptide boronic acid detection strategy was developed in which 2,5-dihydroxybenzoic acid (DHB) served as both matrix and derivatizing agent in a convenient, in situ, on-plate esterification. Finally, we demonstrate that DHB-modified peptide boronic acids from a single bead can be analyzed by MALDI-MSMS analysis, validating our approach for the identification and sequencing of branched peptide boronic acid libraries.

The schiff base of gossypol with 3,6,9,12,15,18,21,24-octaoxa-pentacosylamine complexes and monovalent cations studied by electrospray ionization-mass spectrometry,1H nuclear magnetic resonance, Fourier transform infrared, as well as PM5 semiempirical methods

A Schiff base of gossypol with 3,6,9,12,15,18,21,24-octaoxa-pentacosylamine (GSOB) forms stable complexes with monovalent cations. This process of complex formation was studied by electrospray ionization-mass spectrometry, (1)H-NMR and Fourier transform infrared spectroscopy as well as by the PM5 semiempirical method. It was found that GSOB forms 1:6 complexes with Li(+) and Na(+), and 1:4 complexes with K(+) as well as 1:2 complexes with Rb(+) or Cs(+) cations and exists in all these complexes in the enamine-enamine tautomeric form. Moreover, within these complexes only Li(+) cations can fluctuate between the oxygen atoms of the octaoxaalkyl chains. The interactions of Li(+) cations with hydroxyl groups of the gossypol part is also possible. All other cations are much more localized. In the complex of GSOB with protons, a 1:2 stoichiometry is realized. The two protons are localized on the N atoms of the Schiff base, and the complex exists in the imine-imine tautomeric form. The structures of the complexes are calculated by PM5 semiempirical methods and discussed.

Impact of Stavudine Phenotype and Thymidine Analogues Mutations on Viral Response to Stavudine plus Lamivudine in Altis 2 Anrs Trial

Objective

Stavudine-based antiretroviral combinations are less effective in zidovudine-experienced patients than in naive subjects and recently, mutations have been described to be associated to the use of both stavudine and zidovudine. In the ALTIS 2 trial, it was shown that a combination of stavudine and lamivudine is less effective in zidovudine-experienced patients than in naive patients. We conducted a retrospective genotypic and phenotypic resistance study (expressed as stavudine phenotypic index, calculated by dividing the inhibitory concentrations 50% [IC50] by the mean value of the sensitive viruses) to evaluate the factors associated with decrease in plasma HIV-1 RNA.

Design

Associations with continuous variables were studied using non-parametric Spearman correlation coefficients. Associations with categorical variables were studied using non-parametric Mann–Whitney tests. Multivariate stepwise regression analyses were used to determine independent prognostic factors of the virological response.

Results

At baseline, most of the subjects harboured zidovudine-associated mutations in plasma and peripheral blood mononuclear cells. Zidovudine and stavudine IC50 and IC90 were strongly associated with response. It appears that a cut-off of stavudine phenotypic index of 1.8-fold of IC50, much lower than the usually used value, could be clinically significant for response to stavudine. In the multivariate analysis, the stepwise model with the higher multiple correlation coefficient ( R2=0.742) included the presence of a 215 Y/F mutation, the number of previously used nucleoside analogues and a resistant stavudine phenotype.

Conclusion

These results argue for a phenotypic and genotypic cross resistance between stavudine and zidovudine. Modest increases of IC50 and IC90 for stavudine had an important impact on the virological response during the trial and plead for a new definition of the threshold value for stavudine phenotypic index.

Mitochondrial toxicity of antiviral drugs

Long-term treatment with antiviral nucleoside analogue drugs, such as AZT, can give rise to delayed and at times severe mitochondrial toxicity. Although these toxic effects are manifest in many tissues, a common disease mechanism can explain the diverse clinical events. A better understanding of these disorders will shed light on genetic mitochondrial diseases and lead to the design of safer and more effective antiviral drugs.