On the Mechanism of the Unexpected Facile Formation of <i>m</i><i>eso</i>-Diacetate Products in Enzymatic Acetylation of Alkanediols
作者:Michaela Edin、Jan-E. Bäckvall
DOI:10.1021/jo026652i
日期:2003.3.1
the enzymatic resolution of dl/meso mixtures of 2,4-pentanediol and 2,5-hexanediol with Candida antarctica lipase B has been elucidated. It was found that the formation of meso-diacetate proceeds via different mechanisms for the two diols. Enzyme-catalyzed acylation of AcO-d(3) labeled (R)-monoacetates of meso-2,4-pentanediol and meso-2,5-hexanediol and analysis of the meso-diacetates obtained show
已经阐明了先前在2,4-戊二醇和2,5-己二醇的dl /内消旋混合物与南极假丝酵母脂肪酶B的酶促拆分中观察到的,容易形成的细二乙酸双乙酸酯的机理。已经发现,对于两种二醇而言,内消旋二乙酸酯的形成是通过不同的机理进行的。酶催化的meso-2,4-戊二醇和meso-2,5-己二醇的AcO-d(3)标记的(R)-单乙酸酯的酰化反应和获得的meso-diacetates的分析表明,前一种反应是通过分子内酰基进行的迁移,而后者通过醇的直接S-酰化发生。对于(R,S)-2,4-戊二醇的(R)单乙酸酯,分子内酰基迁移是快速的,因此抑制了外部酰基供体的直接S-酰化作用。对于己二醇单乙酸酯,通过实验确定(5R,2R)-和(5R,2S)-5-乙酰氧基-2-己醇之间的比率(伪E值)为k(R,R)/ k(R,S )= 25,比2-戊醇和2-辛醇的E值低约10-20倍。在初步实验中,证明了1,3-二醇衍生物中的