A facile and convenient solid-phase procedure for synthesizing nucleoside hydroxamic acids

Palladium and Copper Catalyzed Sonogashira cross Coupling an Excellent Methodology for C-C Bond Formation over 17 Years: A Review

Sonogashira coupling involves coupling of vinyl/aryl halides with terminal acetylenes catalyzed by transition metals, especially palladium and copper. This is a well known reaction in organic synthesis and plays a role in sp2-sp C-C bond formations. This cross coupling was used in synthesis of natural products, biologically active molecules, heterocycles, dendrimers, conjugated polymers and organic complexes. This review paper focuses on developments in the palladium and copper catalyzed Sonogashira cross coupling achieved in recent years concerning substrates, different catalyst systems and reaction conditions.

Polymer-assisted structural modification on nucleosides and nucleotides

Nucleosides and their analogues play important roles in biological research and clinical therapeutics. Polymer-assisted structural modifications of nucleosides and nucleotides enable parallel and rapid construction of nucleoside library. For some nucleosides, higher chemical selectivity and regioselectivity can be achieved using solid-phase synthesis when compared to classic solution-phase synthesis.

Discovery of novel hydroxamates as highly potent tumor necrosis factor-alpha converting enzyme inhibitors: Part I--discovery of two binding modes

Through a de novo design approach, hydroxamates derived from trans-cyclopropyl dicarboxylate were examined as potential TNF-alpha converting enzyme (TACE) inhibitors. Two distinctive series of inhibitors (A and B) were identified and shown to have different structure-activity relationship trends and selectivity profiles against other matrix metalloproteases despite their close structural similarities. X-ray crystallography of the inhibitors binding to the TACE enzyme demonstrates that each series derives its activity from the opposite enantiomer of the cyclopropyl scaffolds, which display almost superimposable hydroxamate groups that coordinate to the zinc at the catalytic site. Mode A inhibitors occupy the S1'-S3' binding pockets, whereas mode B resides in the nonprime binding sites.

Angeli−Rimini's Reaction on Solid Support: A New Approach to Hydroxamic Acids

Angeli-Rimini's reaction has been performed for the first time on solid phase. A convenient one-step procedure for the synthesis of hydroxamic acids starting from aldehydes and solid-supported N-hydroxybenzenesulfonamide is reported. The hydroxamates are isolated in good to high yields and purities by simple evaporation of the volatile solvents, after treatment of the crude reaction mixture with sequestering agents.

The discovery of a potent and selective lethal factor inhibitor for adjunct therapy of anthrax infection

A potent and selective anthrax LF inhibitor 40, (2R)-2-[(4-fluoro-3-methylphenyl)sulfonylamino]-N-hydroxy-2-(tetrahydro-2H-pyran-4-yl)acetamide, was identified through SAR study of a high throughput screen lead. It has an IC50 of 54 nM in the enzyme assay and an IC50 of 210 nM in the macrophage cytotoxicity assay. Compound 40 is also effective in vivo in several animal model studies.

Tracelessness Unmasked: A General Linker Nomenclature

Nowadays it is rare to find an issue of a major chemistry journal without at least one article on solid-phase synthesis. This is hardly surprising: the technique promises an end to arduous work-up procedures and the ability to facilitate the creation of vast libraries of compounds using combinatorial techniques. No longer is the technique only of interest to those involved in peptide synthesis: an enormous variety of product classes have now been prepared on and isolated from the solid phase. It is the "linker" which is the focus of this article. The linker's ultimate function is to release a product from the support into solution: it does this, without exception, with a chemical change to the product at the former linkage site. Some linkers, apparently, are "traceless". But what, in fact, is "tracelessness"? Twenty years ago, in a climate where cleavage of a linker resulted in formation of a polar carboxylic acid as the vestige of the support, the concept was attractive. Today the chemist is faced with a myriad of novel linkers which have the ability to release products bearing most major functionalities at the former linkage site and we will argue here that the term "traceless", although currently in widespread use, is meaningless. Instead, we propose a new categorization of linkers based on the functionality they release upon cleavage, and suggest a nomenclature to underpin this categorization. We anticipate that the article will also serve to highlight areas of linker technology in need of further research.

Studies on the synthetic compatibility of aryloxime linkers in the solid-phase synthesis of 3-aminobenzisoxazoles

Further exploration of the scope of our solid-phase method for the synthesis of 3-aminobenzisoxazoles (using the Kaiser oxime resin 1) is described. The effects of base, leaving group, and solvent on the nucleophilic aromatic substitution based resin-loading reaction are discussed. Representative aryloxime intermediates were subjected to a variety of acidic conditions commonly used in protecting group removal to establish the acid stability profile of this linker. Regioselectivity was evaluated with various di- and trifluorobenzonitriles, which gave single benzisoxazole products after loading and cyclorelease reactions. Substituent effects observed in the course of the acid stability and regioselectivity studies suggest that the nitrile plays a critical role in the oxime hydrolysis mechanism. Finally, to establish the compatibility of the aryloxime linker with a variety of useful on-resin synthetic transformations, functionalized substrates were loaded onto resin 1, and carbon-nitrogen, carbon-oxygen, and carbon-carbon bond-forming reactions were successfully executed.