Dihydropyrans have been prepared by the cyclisation of easily accessible propargyl vinyl ethers with (TFP)AuCl/AgBF(4) as a catalyst in high yields. These compounds undergo acid-catalysed rearrangement into cyclopentenone derivatives.

Two synthetic strategies from achiral precutsors especially useful for sugars requiring unusual functional groups, deoxy and branched sugars, as well as partially 0protected sugars, are outlined. One strategy employs inversetype hetero-Diels-Alder reaction with highly functionalized 1-oxa-1,3-dienes. Their reaction with electron rich heterodienophiles (enol ethers, etc.) and subsequent diastere...

We studied the mechanism of the lidocaine-induced shape change in human erythrocytes. Immunohistochemical analysis of erythrocytes using spectrin-specific antibodies revealed aggregation of fluorescence in lidocaine-treated cells, while the fluorescence was distributed diffusely in untreated cells. The intracellular pH in lidocaine-treated erythrocytes was examined by flow cytometry of the cell...

The validity of the chromane helicity rule correlating the sense of twist within the dihydropyran ring with the CD sign of the (1)Lb band observed at ca. 290 nm in their electronic circular dichroism (ECD) spectra is examined using a set of natural (S)-trolox derivatives. To investigate both the scope and the limitations of the rule a combination of ECD spectroscopy, especially the temperature ...

This computational study deals with the mechanism of spontaneous initiation in thermal polymerization of alkyl acrylates (e.g., methyl, ethyl, and n-butyl acrylate). The mechanism is presently still unknown. Density-functional theory (DFT) and Møller-Plesset (MP2) calculations are used to explore the Flory and Mayo mechanisms of self-initiation in methyl acrylate. On the singlet surface, a low-...

[reaction: see text] Spinosyn G was isolated in the late 1980s as a minor component from the broth of our potent, fermentation-derived insecticide spinosad. Its structure was then tentatively identified as 5' '-epispinosyn A (3) on the basis of (1)H and (13)C NMR data, but the 4' '-epi compound 4 could not be conclusively ruled out with the data available. Described herein are unambiguous synth...