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A combined experimental and computational mechanistic study of amide formation from thio acids and azides is described. The data support two distinct mechanistic pathways dependent on the electronic character of the azide component. Relatively electron-rich azides undergo bimolecular coupling with thiocarboxylates via an anion-accelerated [3+2]… (More)
Three closely related analogues of epoxomicin have been synthesized. Allene-derived spirodiepoxides were key intermediates. Spirodiepoxide formation and stereochemical dependence on solvent, oxidant, and allene structure were cataloged. The facial selectivity of the first epoxidation of 1,3-disubstituted and trisubstituted allenes was found to be >20:1 with… (More)
A formal synthesis of psymberin (irciniastatin A) is presented. Notable features of the synthesis include the chemo-, regio-, and stereoselective oxidation of a 1,3-disubstituted allene, a configuration-dependent spirodiepoxide opening, the efficient syntheses of functionalized trans-2,6-disubstituted pyrans, and the union of a highly functionalized… (More)
The first total synthesis of roquefortine C is achieved by implementation of a novel elimination strategy to construct the thermodynamically unstable E-dehydrohistidine moiety. Molecular modeling studies are presented which explain the instability of the roquefortine C structure compared to that of isoroquefortine C.
A new amide synthesis strategy based on a fundamental mechanistic revision of the reaction of thio acids and organic azides is presented. The data demonstrate that amines are not formed as intermediates in this reaction. Alternative mechanisms proceeding through a thiatriazoline intermediate are suggested. The reaction has been applied to the preparation of… (More)
Isoroquefortine E and phenylahistin were synthesized using the Horner-Wadsworth-Emmons reaction as the key step to build the dehydroamino acid moiety. The syntheses provide materials for the biological studies of the roquefortine-phenylahistin molecules.
Enzymes involved in the mammalian microsomal metabolism of drugs are, in numerous cases, inhibited by compounds bearing an imidazolyl scaffold. However, the inhibition potency is highly dependent upon the accessibility of the imidazolyl nitrogen lone pair. In order to highlight some structural parameters of inhibitors that control this phenomenon, a series… (More)