Preparation of (+)-Catechin, (-)-Epicatechin, (-)-Catechin, and (+)-Epicatechin and Their 5,7,3',4'-Tetra-O-Benzyl Analogues
申请人:Romanczyk, JR. Leo J.
公开号:US20100048920A1
公开(公告)日:2010-02-25
Processes for preparing racemic mixtures of 5,7,3′,4′-tetra-O-benzyl-(±)-catechin and (±)-epicatechin involves (i) condensing 2-hydroxy-4,6-bis(benzyloxy)-acetophenone and 3,4-bis(benzyloxy)benzaldehyde, cyclizing the resulting compound, oxidizing the resulting compound; (ii) dihydroxylating (E)-3-(3′,4′-bis(benzyloxy)phenyl)prop-2-ene-1-ol and reducing the 1,2-diol; or (iii) coupling 3,5-bis(benzyloxy)phenol with (E)-3,5-bis(benzyloxy)-2-(3′,4′-bis(benzyloxy)phenyl)allyl)phenol and cyclizing the resulting chalcone.
A process for preparing the benzylated epimers of catechin and epicatechin involves seven steps. 3,4-Bis(benzyloxy)benzaldehyde is coupled with 2-hydroxy-4,6-benzyloxy-acetophenone to form a chalcone. The chalcone is selectively reduced to an alkene. The phenolic group of the alkene is protected. The protected alkene is asymetrically dihydroxylated. The resulting compound is deprotected, cyclized, and finally hydrolyzed.
Epimers resulting from these processes are chemically resolved or separated by chiral high pressure liquid chromatography.
Also disclosed is a method for preparing enantiomerically pure 5,7,3′,4′-tetra-O-benzyl-(+)-catechin from a racemic mixture using dibenzoyl-L-tartaric acid monomethyl ester.
Further, disclosed is an improved process for preparing dibenzoyl-L-tartaric acid monomethyl ester.
制备5,7,3′,4′-四-O-苄基-(±)-儿茶素和(±)-表儿茶素的外消旋混合物的过程包括:(i)缩合2-羟基-4,6-双(苄氧基)-乙酮和3,4-双(苄氧基)苯甲醛,环化生成化合物,氧化化合物;(ii)双羟基化(E)-3-(3′,4′-双(苄氧基)苯基)丙-2-烯-1-醇,还原1,2-二醇;或(iii)将3,5-双(苄氧基)苯酚与(E)-3,5-双(苄氧基)-2-(3′,4′-双(苄氧基)苯基)丙烯基)苯酚偶联,生成的查尔酮环化。制备儿茶素和表儿茶素的苄基异构体的过程包括七个步骤。3,4-双(苄氧基)苯甲醛与2-羟基-4,6-双(苄氧基)-乙酮偶联形成查尔酮。查尔酮被选择性还原为烯烃。烯烃的酚基被保护。保护的烯烃被不对称地二羟基化。生成的化合物被去保护,环化,最后水解。这些过程生成的异构体通过手性高压液相色谱进行化学分离。还公开了一种使用二苯乙酰-L-酒石酸单甲酯制备对映纯5,7,3′,4′-四-O-苄基-(+)-儿茶素的方法。此外,还公开了一种改进的制备二苯乙酰-L-酒石酸单甲酯的方法。