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Two new sterols, stigmasta-5,7,22,25-tetraene-3 beta -ol (1) and stigmasta-5,7,14,22,25-pentaene-3 beta -ol (2), have been characterized along with ergosterol and 7-dehydrostigmasterol in the nonsaponifiable fraction of the total lipids extracted from trophozoites of Acanthamoeba culbertsoni strain A-1 (virulent strain). However, these sterols were found to… (More)
In the developing world, multi-drug resistant malaria caused by the parasite Plasmodium falciparum is an epidemic that claims the lives of 1-3 million people per year. Artemisinin, a naturally occurring small molecule that has seen little resistance from malarial parasites, is a valuable weapon in the fight against this disease. Several easily accessible… (More)
The distortion/interaction model has been used to explain and predict reactivity in a variety of reactions where more common explanations, such as steric and electronic factors, do not suffice. This model has also provided new fundamental insight into regioselectivity trends in reactions of unsymmetrical arynes, which in turn has fueled advances in aryne… (More)
The pyridine heterocycle continues to play a vital role in the development of human medicines. More than 100 currently marketed drugs contain this privileged unit, which remains highly sought after synthetically. We report an efficient means to access di- and trisubstituted pyridines in an efficient and highly controlled manner using transient 3,4-pyridyne… (More)
The nickel-catalyzed amination of aryl O-sulfamates and chlorides using the green solvent 2-methyl-THF is reported. This methodology employs the commercially available and air-stable precatalyst NiCl2(DME), is broad in scope, and provides access to aryl amines in synthetically useful yields. The utility of this methodology is underscored by examples of… (More)
A mild heterogeneous, ligand-free protocol for Sonogashira and Heck couplings has been developed and used to access several biologically important deoxynucleoside derivatives in a facile manner.
We report the enantiospecific total synthesis of (+)-tubingensin A. Our synthesis features an aryne cyclization to efficiently introduce the vicinal quaternary stereocenters of the natural product and proceeds in only nine steps (longest linear sequence) from known compounds.
We report the strategic use of cyclohexyne and the more elusive intermediate, cyclopentyne, as a tool for the synthesis of new heterocyclic compounds. Experimental and computational studies of a 3-substituted cyclohexyne are also described. The observed regioselectivities are explained by the distortion/interaction model.
Due to a production error, in section 6 in the sentence that reads " First, it lowered cost based on the replacement of Wilkinson's catalyst with a more efficient rhenium catalyst " , " rhenium " should be " ruthenium ". The Royal Society of Chemistry apologises for these errors and any consequent inconvenience to authors and readers.
A simple method for the preparation of aryl methyl ketones is reported. The transformation involves the Pd-catalyzed coupling of an acyl anion equivalent, acetyltrimethylsilane, with aryl bromides to afford the corresponding acetylated arenes in synthetically useful yields. The methodology is tolerant of heterocycles and provides a new method for arene… (More)