Structure-activity relationship of new anti-tuberculosis agents derived from oxazoline and oxazole benzyl esters

During the syntheses and studies of natural iron chelators (mycobactins), we serendipitously discovered that a simple, small molecule, oxazoline-containing intermediate 3 displayed surprising anti-tuberculosis activity (MIC of 7.7 microM, average). Herein we report elaboration of SAR around this hit as well as the syntheses and evaluation of a hundred oxazoline- and oxazole-containing compounds derived from an efficient three step process: 1) formation of beta-hydroxy amides with serine or threonine; 2) cyclization to afford oxazolines; and 3) dehydration to give the corresponding oxazoles. A number of compounds prepared by this method were shown to possess impressive activity against Mycobacterium tuberculosis, extremely low toxicity and therefore high therapeutic indexes, as well as activity against even the more recalcitrant non-replicating form of M. tuberculosis. The uniqueness of their structures and their simplicity should allow them to be further optimized to meet ADME (absorption, distribution, metabolism, excretion) requirements. The syntheses of eight of the most potent in vitro compounds were scaled up and the compounds were tested in an in vivo mouse infection model to evaluate their efficacy before engaging upon more elaborate compound design and optimization.

A new benzyl ester and ergosterol derivatives from the fungus Gymnoascus reessii

A new benzyl ester, reessiate (1), anthraquinone, islandicin (2), ergosterol and seven ergosterol derivatives (3-9) were isolated from the fungus Gymnoascus reessii. All structures were identified by spectroscopic methods. This is the first report of their isolation from this fungus. Compounds 4-7 and 9 exhibited antimalarial activity against Plasmodium falciparum with IC50 values in the range of 3.3-4.5 μg/mL. In addition, 4 showed cytotoxicity against KB, MCF7 and NCI-H187 cancer cell lines. It was found that 4 has cytotoxic effect to MCF7 (IC50 = 7.9 μg/mL) lower than Doxorubicin (IC50 = 8.5 μg/mL).

An Efficient Metal-Free Oxidative Esterification and Amination of Benzyl C-H Bond

An esterification and amination of benzylic C-H bonds was developed by using 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) under metal- and iodide-free conditions. Both carboxylic acids and amines could be used as ideal coupling partners for the oxidative coupling reactions with various diarylmethanes. A close to equal amount of coupling reagents was enough to afford the product in good to high yields.

Design, Synthesis, Bioactivity, and Tentative Exploration of Action Mode for Benzyl Ester-Containing Derivatives

The active splicing strategy has witnessed improvement in bioactivity and antifungal spectra in pesticide discovery. Herein, a series of simple-structured molecules (Y1-Y53) containing chloro-substituted benzyl esters were designed using the above strategy. The structure-activity relationship (SAR) analysis demonstrated that the fatty acid fragment-structured esters were more effective than those containing an aromatic acid moiety or naphthenic acid part. Compounds Y36 and Y41, which featured a thiazole-4-acid moiety and trifluoromethyl aliphatic acid part, respectively, exhibited excellent in vivo curative activity (89.4%, 100 mg/L Y36) and in vitro fungicidal activity (EC50 = 0.708 mg/L, Y41) against Botrytis cinerea. Determination of antifungal spectra and analysis of scanning electron microscopy (SEM), membrane permeability, cell peroxidation, ergosterol content, oxalic acid pathways, and enzymatic assays were performed separately here. Compound Y41 is cost effective due to its simple structure and shows promise as a disease control candidate. In addition, Y41 might act on a novel target through a new pathway that disrupts the cell membrane integrity by inducing cell peroxidation.