共查询到19条相似文献,搜索用时 109 毫秒
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木脂素是由两分子苯丙素聚合而形成的一类天然化合物,广泛存在于自然界中,其中大多数木脂素为游离的状态,小部分与糖结合成苷而存在于植物的木部和树脂中,所以称之为木脂素,而最近又在动物体内发现了有别于植物木脂素的哺乳动物木脂素[1].由于大部分木脂素具有很高的抗癌、抗肝炎、杀虫等生物活性,因此被广泛的应用于在医药、农业以及日化等方面,木脂素的合成一直是有机合成中的一个热点[2],而合成木脂素的偶联条件的选择是木脂素合成中起到关键性因素,文章就几种重要木脂素的合成方法中单体的氧化偶联方式进行简单的介绍. 相似文献
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1,4-苯并二氧六环类木脂素因其独特的杀虫、保肝、抗氧化、抗肿瘤等生理活性在农业及医药行业具有广阔的应用前景。目前1,4-苯并二氧六环合成方法主要包括生物偶联法、仿生偶联法及化学合成法,本文从合成工艺、对映选择性及反应机理等方面进行了系统性探讨。生物偶联法过程中的非酶催化步骤导致产物多为立体和区域选择性的异构体混合物;仿生偶联法通过选择不同的取代基和氧化偶联剂以较高的产率获得单一对映产物;化学合成法通过选择不同的催化剂、氧化偶联剂及合成路线实现了1,4-苯并二氧六环的高效合成,尤其是在过渡金属催化下,能够高选择性地合成1,4-苯并二氧六环,这类反应已开展深入研究。 相似文献
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从阿魏酸甲酯开始分7个步骤制得苯并呋喃新木脂素XH-14。在关键步骤中使用通过简单方法制备的纳米Ag2O以比普通Ag2O更高的转化率使阿魏酸甲酯仿生氧化偶联成其二聚物。 相似文献
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白腐菌木素过氧化物酶发酵条件及其酶液对稻草降解的研究 总被引:9,自引:0,他引:9
研究营养条件对白腐菌合成木素过氧化物酶(ligninperoxidase,LiP)的影响。在最适培养条件下,第6天获得7560U/L的酶活。利用LiP粗酶液在体外直接降解稻草,3天后Klason木素的降解率为8.7%,经红外光谱分析其降解产物,推断LiP粗酶液在体外降解稻草的反应主要是氧化反应。 相似文献
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文章通过Sonogashira偶联反应,将二茂铁基团引入特定化合物,考察了钯催化剂种类与用量,碱的种类,反应温度和溶剂等条件对反应性能的影响,结果表明,以Pd(PPh3)4为催化剂,用量为5 mol%时,在K2CO3作用下,该催化体系催化了一系列碘代芳烃和二茂铁乙炔的反应,高效率高产率得到一系列二茂铁类炔烃化合物。 相似文献
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Xian-quing Qiu Ning-bew Wong Kam-chung Tin Qi-ming Zhu 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》1996,65(4):303-308
A simple review is given to the recent work of the oxidative coupling of methane at low temperature. Emphasis is laid on the different systems of low-temperature catalysts under conventional CH4/O2 co-feed conditions, and on the investigations of low-temperature oxidative coupling of methane in the presence of steam in the feed. Other approaches, e.g. oxidative coupling of methane at elevated pressure and moderate temperature, preparing ethylene by oxidative coupling reaction of methane on laser-activated solid surface, are also included. 相似文献
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Using chlorophenols as probe compounds, we examined the occurrence of oxidative coupling during carbon nanotube adsorption of phenolic compounds in the presence of oxygen. The oxidative coupling was confirmed by the agreement of the dechlorination stoichiometries of various chlorophenols with the free-radical mechanism of oxidative coupling. The oxidative coupling reaction was first-order with respect to chlorophenols on carbon nanotubes and increased with the increase of pH. 相似文献
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Markus Dachtler Frans H. M. van de Put Frans v. Stijn Christiaan M. Beindorff Jan Fritsche 《European Journal of Lipid Science and Technology》2003,105(9):488-496
Sesame lignans were isolated by solvent extraction and subsequently purified by solvent crystallization from crude, unroasted sesame oil, and a sesame oil deodorizer distillate. In addition, an aliquot of the purified sesame oil extract was treated with camphorsulfonic acid to obtain a sesaminol‐enriched extract. The sesame lignan composition of the extracts was characterized by on‐line liquid chromatography nuclear magnetic resonance spectroscopy mass spectrometry coupling (LC‐NMR‐MS). The effect of the sesame oil extracts as well as pure sesame lignans and γ‐tocopherol on the oxidative stability of sunflower oil (lignan‐free) was studied by the Rancimat assay. The Rancimat assay revealed the following oxidative stability order: sesame oil extract < sesame oil deodorizer distillate < sunflower oil (no added sesame oil extracts) < sesamol < sesaminol‐enriched sesame oil extract. In addition, the radical‐scavenging capacity of these extracts was assessed by the Trolox® equivalent antioxidant capacity (TEAC) assay. The TEAC assay revealed a slightly different AOX activity order: sesamin < sesame oil extract < sesaminol‐enriched sesame oil extract < sesamol. In conclusion, the sesaminol‐enriched extract revealed strong antioxidant activity and is therefore suitable to increase the oxidative stability of edible oils high in polyunsaturated fatty acids. 相似文献
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Anne Neudörffer Maurice-Bernard Fleury Jean-Pierre Desvergne 《Electrochimica acta》2006,52(2):715-722
New insights into the electrochemical oxidative coupling of 4-hydroxycinnamate derivatives are delineated through the variation of the nature of the supporting electrolyte. In particular, replacement of a tetraethylammonium salt by a lithium salt markedly modified the outcome of the reaction, thus allowing the isolation of different coupling products. This effect could be ascribed to lithium ion-pairing phenomena, which affected both the starting materials and the bis-quinonemethide species generated during the oxidative coupling process. 相似文献
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Microkinetics of methane oxidative coupling 总被引:1,自引:0,他引:1