The horse liver and pig liver esterase hydrolysis of racemic medium ring  lactones gives with excellent enantiomeric excess the S- (or R) lactones  and the corresponding R- (or S) hydroxy acids. This is the first general  method to obtain optically pure medium ring lactones. Application to  the preparation of (S)-(+)-Phoracantholide I is reported.
                                    马肝和猪肝
酯酶对外消旋中环内酯的
水解反应,以优异的对映体过量得到 S-(或 R)内酯和相应的 R-(或 S)羟基酸。这是获得光学纯中环内酯的第一个通用方法。报道了该方法在制备 (S)-(+)-Phoracantholide I 中的应用。