Rapid Syntheses of Dehydrodiferulates via Biomimetic Radical Coupling Reactions of Ethyl Ferulate
Rapid Syntheses of Dehydrodiferulates via Biomimetic Radical Coupling Reactions of Ethyl Ferulate
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DOI：
10.1021/jf302140k
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发表时间：
2012-08-29
影响因子：
6.1
通讯作者：
Ralph, John
中科院分区：
文献类型：
--
作者：
Lu, Fachuang;Wei, Liping;Ralph, John
阿魏酸在草细胞壁中的脱氢二聚化提供了一种通向交联多糖链的途径，限制了反刍动物细菌对碳水化合物的消化率，并且通常影响草作为可再生生物资源的利用。分析植物细胞壁中的脱氢二阿魏酸（以下称为二阿魏酸）可用于评价植物细胞壁的生物活性。乳制品的质量;作为动物饲料的草料。因此，有相当多的...需要大量的二阿魏酸作为这种分析的标准。以阿魏酸乙酯为原料，以CuCl（OH）TMEDA为氧化剂或催化剂，通过仿生自由基偶联反应合成了二阿魏酸酯。虽然CuCl（OH）-TMEDA在乙腈中氧化阿魏酸乙酯产生由8-O-4-、8-5-、8-8-（环状和非环状）和5-5-偶联的二阿魏酸酯组成的混合物，但使用CuCl（OH）-TMEDA作为催化剂和氧气作为氧化剂的催化氧化导致此类二阿魏酸酯的更好的总产率。快速色谱分离允许分离8-8-和diferulates。8-5-二阿魏酸与8-O-4-二阿魏酸共洗脱，但通过结晶与其分离;在简单的四丁基铵之后，通过再色谱分离留在母液中的8-O-4-二阿魏酸。氟处理：44，.将8-5-二阿魏酸酯转化为另一种有用的二阿魏酸酯，8-5-（非环）。大阿魏酸。因此，迄今为止在植物细胞壁的碱性水解产物中发现的九种（5-5，8-O-4，8- 5- c，8 - 5-nc，8-5-dc，8 -8-c，8-8-nc，8-8-THF，4-O-5）二阿魏酸中的六种可以。要爽快。由CuCl（OH）-TMEDA催化的有氧氧化偶联反应合成。：和随后的皂化反应。
Dehydrodimerization of ferulates in grass cell walls provides a pathway toward cross-linking polysaccharide chains limiting the digestibility of carbohydrates by ruminant bacteria and in general affecting the utilization of grass as,a renewable bioresource. Analysis of dehydrodiferulates (henceforth termed diferulates) in plant cell walls is useful in the evaluation: of the. quality of dairy; forages as animal feeds. Therefore, there has been considerable.. demand for quantities of diferulates as standards for such analyses. Described here are syntheses of diferulates from ethyl ferulate via biomimetic radical coupling reactions using the copper(II)-tetramethylethylenediamine [CuCl(OH) TMEDA] complex as oxidant or catalyst. Although CuCl(OH)-TMEDA oxidation of ethyl ferulate in acetonitrile produced mixtures composed of 8-O-4-, 8-5-, 8-8- (cyclic and noncyclic), and 5-5-coupled diferulates, a catalyzed oxidation using CuCl(OH)-TMEDA as catalyst and oxygen as an oxidant resulted in better overall yields of such diferulates. Flash chromatographic fractionation allowed isolation of 8-8-;,and diferulates. 8-5-Diferulate coeluted with 8-O-4-diferulate but was separated from it via crystallization; the 8-O-4 diferulate left in the Mother solution was isolated by rechromatography following a simple tetrabutylammonium. fluoride treatment:44,. converted 8-5-diferulate to another useful diferulate, 8-5-(noncyclic). diferulate. Therefore, six of the nine (5-5, 8-O-4, 8-5- c, 8-5-nc, 8-5-dc, 8-8-c, 8-8-nc, 8-8-THF, 4-O-5) diferulic acids that have to date been found in the alkaline hydrolysates of plant cell Walls can. be readily. Synthesized by the CuCl(OH)-TMEDA catalyzed aerobic oxidative coupling reaction.: and subsequent saponification described here.