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calculations were carried out for three exocyclic alkylidene carbenes. Cyclopentadienylvinyl carbene is predicted to be highly electrophilic while the cyclopropenylidenevinyl carbene may provide the first example of a nucleophilic alkylidene carbene. 相似文献
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Two steroids, 3-oxo-chol-4-ene-24-oic acid () andi ts unsaturated analog have been isolated from the dorid nudibranch , and the acid has been shown to have antifeedant properties. 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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Michael J. Cook Michael H. Abraham Luigi E. Xodo Raymond Cruz 《Tetrahedron letters》1981,22(31):2991-2994
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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Toshihiro Hashimoto Motoo Tori Zenei Taira Yoshinori Asakawa 《Tetrahedron letters》1985,26(52):6473-6476
Four novel fusicoccane diterpenoids, fusicoplagins A, B, C, and D, have been isolated from the liverwort subsp. and the structures determined by spectroscopic methods, chemical transformations, and X-ray crystallographic analysis. 相似文献
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Penelope W. Codding K.Ann Kerr M.H. Benn Alan J. Jones S.William Pelletier Naresh V. Mody 《Tetrahedron letters》1980,21(2):127-128
The structures of alkaloid- and - 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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A regular heteropolysaccharide built of tetrasaccharide repeating units is synthesised by means of regio- and stereospecific polycondensation of a tritylated cyanoethylidene derivative. The polysaccharide obtained is identical with the O-antigenic polysaccharides of serotypes 3b, 3c, and variant Y. It also represents the basic chain of O-antigenic polysaccharides of all serotypes of this bacterium. 相似文献
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The amino acid tyrosine has been shown to be the specific precursor of the isonitrile acid produced by (Bon.) Bain. aggr. 相似文献