Montmorillonite Clay Catalysis I: An Efficient and Convenient Procedure for Preparation of 5(6)/5′(6′)-Unsaturated 3β-Disteryl Ethers
作者:Tongshuang Li、Huizhang Li、Juanli Guo、Tongshou Jin
DOI:10.1080/00397919608004562
日期:1996.7
Abstract In the presence of montmorillonite K 10, 5(6)-unsaturated sterols (1) were heated at refluxing temperature in dichloromethane to provide 5(6)/5′(6′)-unsaturated 3β,3′β-disteryl ethers (4) in 69–73% yield. The mechanism of the reaction was discussed.
作者:Nina I. Uvarova、Lyubov N. Atopkina、Georgi B. Elyakov
DOI:10.1016/s0008-6215(00)85361-6
日期:1980.8
Characterisation of non-polar dimers formed during thermo-oxidative degradation of β-sitosterol
作者:Ewa Sosińska、Roman Przybylski、Paul Hazendonk、Yuan Yuan Zhao、Jonathan M. Curtis
DOI:10.1016/j.foodchem.2013.01.053
日期:2013.8
Thermo-oxidative degradation of sterols at temperature typical for frying leads to the formation of oxidised derivatives, fragmented sterols and oligomers. Recent research on sterol oxidation focuses mainly on the oxysterol derivatives formation to the exclusion of compounds with high molecular mass. The aim of this work was to decipher the chemical structure of non-polar dimers formed during beta-sitosterol oxidation at 180 degrees C in the presence of oxygen. The dimer fraction was separated by size-exclusion chromatography (SEC) after pre-fractionation on silica gel. The chemical structure of the dimers was assessed by 1D and 2D NMR, IR, Raman and MS spectroscopies. NMR data confirmed that the predominant non-polar dimer formed during beta-sitosterol oxidative degradation has a configuration of 3 beta,3 beta'-disitosteryl ether. Data from IR and Raman spectroscopies further proved it chemical structure. Applied analytical techniques also confirmed presence of dimers with different configuration than disteryl ethers. (C) 2013 Elsevier Ltd. All rights reserved.