共查询到20条相似文献,搜索用时 62 毫秒
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Bernhard Krutler Christian Caderas Robert Konrat Michael Puchberger Christoph Kratky 《Helvetica chimica acta》1995,78(3):581-599
The four α,α,α, β,β,β,-hexamethyl α-hydrogen Coα, Coβ-dicyanocobyrinates 2b, d–f , with a free b-, d-, e-, and f-propionic-acid function, respectively, were prepared by partial hydrolysis of heptamethyl Coα, Coβ-dicyanocobyrinate (cobester; 1 ) in aqueous sulfuric acid. The cobester monoacids 2b, d–f were obtained as a ca. 1:1:1:1 mixture which was separated. The monoacids were purified by chromatography and isolated in crystalline form. The position of the free propionic-acid function was determined by an extensive analysis of 2b, d–f using 2D-NMR techniques; an analysis of the C,H-coupling network topology resulted in an alternative assignment strategy for cobyrinic-acid derivatives, based on pattern recognition. Additional information on the structure of the most polar of the four hexamethyl cobyrinates, of the b-isomer 2b , was also obtained in the solid state from a single-crystal X-ray analysis. Earlier structural assignments based on 1D-NMR spectra of the corresponding regioisomeric monoamides 3b, d–f (obtained from crystalline samples of the monoacids 2b, d–f ) were confirmed by the present investigations. 相似文献
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A concise and efficient synthesis of α,α′,β-trisubstituted β-lactones is presented. These novel lactones are easily obtained in five steps and will be dedicated to anionic ring opening polymerization. 相似文献
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Hermann Fuhrer Grety Rihs Ljubinka Lorenc Lidija Bondarenko Jaroslav Kalvoda Mihailo Lj. Mihailovi 《Helvetica chimica acta》1987,70(1):37-42
The thermolysis of the steroidal 5α,8β-peroxide 1 , under acidic conditions afforded in addition to the expected 5,10:8,9-diseco derivative 2 , the rearranged 5α,8β-epoxide 3 , the structure of which was determined by NMR spectroscopy and X-ray analysis. 相似文献
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