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Ab initio calculations show a cyclic resonance stabilization of ~20 kcal/mol for the 6-pi electron oxetenyl anion. The 4-pi electron cation is destabilized by ~50 kcal/mol.  相似文献   

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Two steroids, 3-oxo-chol-4-ene-24-oic acid (2) andi ts unsaturated analog 4 have been isolated from the dorid nudibranch Aldisasanguineacooperi, and the acid 2 has been shown to have antifeedant properties.  相似文献   

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Four novel fusicoccane diterpenoids, fusicoplagins A, B, C, and D, have been isolated from the liverwort Plagiochilaacanthophylla subsp. japonica and the structures determined by spectroscopic methods, chemical transformations, and X-ray crystallographic analysis.  相似文献   

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The structures of alkaloid-A and -B were established via X-ray crystallography of the former as its HI salt, and its chemical conversion to the latter.  相似文献   

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All four isomers of substituted 3-alkylthio-4-hydroxybutenes have been synthesised: both the geometry of the double bond and the relative stereochemistry of the two chiral centres are controlled.  相似文献   

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Head space analysis, GLC retention time data, and solution calorimetry are used to determine the effect of medium on the thermodynamic parameters for the equilibrium (1) ? (2). It is shown that changes in ΔG° and ΔH° can be evaluated for the transfer of the equilibrium from a series of solvents to the gaseous phase which is used as the reference medium.  相似文献   

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The structure of phaseolotoxin, a toxin produced by cultured Pseudomonassyringae pv. phaseolicola, the causal agent of halo blight disease in bean plants is revised to 3. The structure of octicidin, isolated from leaves of bean plants infected with pv. phaseolicola. has been determined to be 4, a protease degradation product of 3 which is formed in the plant.  相似文献   

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