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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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N-Acyl derivatives of D,L-acosamine and D,L-ristosamine were synthesized with high stereo selectivity utilizing intramolecular Michael addition of γ- and δ-carbomoyloxy-α,β-unsaturated esters.  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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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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A stereOselective conversion of 1,8- and 1,5-diethoxy-9,10-anthraquinone to 1,8- and 1,5-diketo-trans-syn-trans-perhydroanthracenes by successive sodium borohydride, metal-ammonia, and catalytic reductions is described.  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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The instrument described is suitable for the investigation of the thermal behaviour of substances and reaction mixtures under production conformable conditions; this is made possible by the sophisticated design of the sample chamber: easy stirring of the samples, measuring under any gas atmosphere and while bubbling gas through the sample, choice of the sample container and visual observation during the measurement. The control device allows the choice of one of three operational modes: constant temperature, linear increase in temperature, and adiabatic control; this permits the application of the SEDEX apparatus for a variety of methods including dynamic scanning, isoperibolic measurements, and (quasi) adiabatic studies.  相似文献   

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Treatment of halo-F-methylphosphonium salts with potassium fluoride and halogen (I2, Br2, ICl, IBr) gives modest yields of halo-F-methanes. This method of preparation augments the classical Hunsdiecker approach to these materials.  相似文献   

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The nitration of p-cresol by nitric acid in aqueous sulphuric acid involves ~40% ipso-substitution at CMe. The 4-methyl-4-nitrocyclohexa-2,5-dien-1-one (I) formed undergoes an acid-catalysed rearrangement to 4-methyl-2-nitrophenol.  相似文献   

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