Stereoselective Formation of β-O-4 Structures Mimicking Softwood Lignin Biosynthesis: Effects of Solvent and the Structures of Quinone Methide Lignin Models
作者:Xuhai Zhu、Takuya Akiyama、Tomoya Yokoyama、Yuji Matsumoto
DOI:10.1021/acs.jafc.9b01968
日期:2019.6.26
guaiacyl (G) β-O-4 structures in plant cell walls. Water addition occurred in 3-methoxy-substituted QMs (G-type QMs) with half-lives (t1/2) between 13 and 15 min, at pH 7, in 50% water solution (dioxane–water, 1:1). The rate increased as the water concentration increased to 99% (t1/2, 1.2–1.4 min). Similar solvent effects were observed for more reactive nonsubstituted QMs (H-type QMs with t1/2 of <1 min)
在木质素生物合成过程中,对甲基苯醌(QM)会作为中间体形成。QM通过亲核体在其侧链的α位上的进攻而进行芳构化,从而在生长的聚合物中生成酚羟基,并在侧链中形成立体异构体形式。一系列β-O-4-芳基醚QM与水在25°C下反应,以复制植物细胞壁中对羟基苯基(H)和愈创木脂基(G)β-O-4结构的形成。在pH值为7的50%水溶液(二恶烷-水,1:1)中,在3-甲氧基取代的QM(G型QM)中,半衰期(t 1/2)在13至15分钟之间发生加水。 。随着水浓度增加到99%(t 1/2,1.2–1.4分钟)。对于更具反应性的未取代QM(t 1/2 <1分钟的H型QM),观察到了相似的溶剂作用。因此,在每种溶剂条件下,H型QM的t 1/2比G型QM的t 1/2短。在增加水浓度,在变化赤/苏四个二聚体β-O-4产物的比率增加。有趣的是,在50%的水溶液中观察到的pH值对立构偏爱的影响很小,并且随着水浓度增加到