Tandem reactions that proceed with a single metal catalyst precursor offer novel opportunities for developing efficient new reaction sequences. In this regard, reaction conditions have been identified that allows for a tandem ring-closing metathesis-olefin isomerization sequence catalyzed by a common ruthenium precursor. Specifically, the tandem process generates cyclic enol ethers from a variety of readily available acyclic dienes in a single reaction vessel using Grubbs' ruthenium alkylidene.

A convergent diastereo- and enantioselective total synthesis of anti-HIV agent chloropeptin I is reported. Important features of the total synthesis include: (1) the use of Ti-catalyzed cyanide addition to imines to prepare a requisite amino acid moiety, (2) the discovery of the positive effect of MeOH in the Cu-mediated biaryl ether formation to afford one of the two macrocyclic peptide moieties, and (3) the discovery of the positive influence of collidine in the diastereoselective Pd-mediated cross-coupling to result in efficient formation of another macrocycle within this medicinally important molecule. This key step is performed in the presence of four unprotected phenols, two of which reside on dichlorophenylglycines.

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Two important pathogens of developing countries, Mycobacteium leprae, the etiologic agent of leprosy, and Leishmania donovani, the protozoal parasite that causes kalaazar, persist in the human host primarily in mononuclear phagocytes. The mechanims by which they survive in these otherwise highly cytocidal cells are presently unknown. Since the best understood cytocidal mechanism of these cells is the oxygen-dependent system that provides lethal oxidants including the superoxide anion (O-), hydrogen peroxide (H2O2

Reliable, selective and environmentally friendly chemical transformations are crucial to the development of new therapeutics and the design of novel materials. Chiral catalysts that can be easily prepared and used to obtain organic molecules of high enantiomeric purity are critical to modern chemical synthesis. The development of protecting groups that shield reactive functionalities has also proved indispensable in the preparation of complex biologically active molecules. Here we present a chiral catalyst that promotes the enantioselective protection of a secondary alcohol as one of the most commonly used protected forms of an alcohol: a silyl ether. The catalyst is a small, simple molecule that can be prepared in three steps from commercial materials without the need for rigorously controlled conditions. Enantioselective silylations are performed with commercial silyl chlorides and produce yields of up to 96 per cent at an enantiomeric ratio of up to 98:2. Chiral catalysts for selective formation of commonly used protecting groups such as silyl ethers should significantly enhance the ability of chemical synthesis to deliver, in a more practical and efficient manner, important organic molecules.