Confocal microscopy with Zinquin, a fluorogenic Zn(2+)-specific indicator, was used for spatially and temporally resolved measurement of Zn2+ efflux from single pancreatic beta-cells. When cells were incubated in buffer containing Zinquin, application of insulin secretagogues evoked an increase in fluorescence around the surface of the cell, indicative of detection of Zn2+ efflux from the cell. The fluorescence increases corresponded spatially and temporally with measurements of exocytosis obtained simultaneously by amperometry. When images were taken at 266-ms intervals, the detection limit for Zn2+ was approximately 0.5 microM. With this image frequency, it was possible to observe bursts of fluorescence which were interpreted as fluctuations of Zn2+ level due to exocytosis. The average intensity of these fluorescence bursts corresponded to a Zn2+ concentration of approximately 7 microM. Since insulin is co-stored with Zn2+ in secretory vesicles, it was concluded that the Zn2+ efflux corresponded to exocytosis of insulin/Zn(2+)-containing granules from the beta-cell. Exocytosis sites identified by this technique were frequently localized to one portion of the cell, indicative of active areas of release.
Highly substituted carbocyclic seven-membered rings are frequently found in natural products and their synthesis represents a significant challenge to the synthetic chemist. Direct intramolecular cyclization of these systems often proves difficult and this fact has catalyzed the development of a variety of strategies based on a convergent intermolecular cycloaddition strategy. This concept article discusses the major cycloaddition approaches utilized to access these types of structures and primarily focuses on examples employed in the synthesis of natural products.
Volatiles emitted byAnastrepha suspensa andAnastrepha ludens males were trapped and compared by GC-MS. Both species emitted previously reported nine-carbon alcohols, (Z)-3-nonenol and (Z,Z)-3,6-nonadienol, and epimeric lactones, anastrephin and epianastrephin. A third isomeric lactone, the macrolide suspensolide, which was previously known only fromA. suspensa is reported here for the first time in the volatiles ofA. ludens. We also report that both species released different proportions of the same three sesquiterpene hydrocarbons:α-farnesene,β-bisabolene, andα-trans-bergamotene. Theβ-bisabolene was isolated in sufficient quantity fromA. suspensa volatiles to establish its absolute configuration as the (R)-(+)-enantiomer. Some plausible biosynthetic relationships of farnesol to the isoprenoid lactones and sesquiterpenes identified in this study are discussed. Finally, we report thatA. suspensa produces the monoterpene (Z)-β-ocimene whileA. ludens volatiles contained limonene.
THE literature provides many examples of thermal rearrangements of small-ring compounds to yield systems involving less bond-angle strain.' In the arylcyclopropene series these involve, in many cases, fairly complex pathways, and only formalized mechanisms have been suggested .l,2 Tetra-arylcyclopropenes have the advantage of no labile hydrogen atom, exhibit moderate thermal stability, and would be expected to yield only primary products from ring cleavage. We now report that 3-aryl-l,2,3-triphenylcyclopropenes (I) readily available by action of the appropriate aryl Grignard reagent on triphenylcyclopropenyl bromide, rearrange, either in a melt above 200" or in solution at somewhat lower temperatures, to 1,2,3-triarylindenes. The rearrangement also proceeds under acidic conditions at considerably lower temperature.8Molten tetraphenylcyclopropene (Ia)* rearranged at 235-240" in almost quantitative yield to 1,2,3-triphenylindene (IIa) The rearrangement exhibited first-order kinetics in diphenyl ether (88%)-quinoline (12%) (See Table), but was sensitive to traces of acid and oxygen.?7 Analysis was by n.m.r. integration, a t 120°, of the increasing 1-indenyl proton (T 4.93) against the aliphatic protons Erratic mm. Hg, and with less than 12% quinoSince (IIa), as well as most triarylindenes, fluoresces strongly in the visible the rearrangeof fluorene (7 6-28) used as an internal standard. kinetic behaviour was observed for tubes sealed a t pressures greater than line in the solvent mixture. ment can also be conveniently followed by fluorimetry.The average of 12 integrations was taken for each point.
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