Biocatalytic Reduction ofβ,δ-Diketo Esters: A Highly Stereoselective Approach to All Four Stereoisomers of a Chlorinatedβ,δ-Dihydroxy Hexanoate
作者:Michael Wolberg、Werner Hummel、Michael Müller
DOI:10.1002/1521-3765(20011105)7:21<4562::aid-chem4562>3.0.co;2-4
日期:2001.11.5
A stereoselective chemoenzymatic synthesis of all four stereoisomers of tert-butyl 6-chloro-3,5-dihydroxy-hexanoate (6a) is presented. The key step of the sequence is a highly regio- and enantioselective single-site reduction of tert-butyl 6-chloro-3,5-dioxohexanoate (1a) by two enantiocomplementary biocatalysts. Alcohol dehydrogenase from Lactobacillus brevis (recLBADH) afforded a 72% yield of enantiopure
提出了6-氯-3,5-二羟基己酸叔丁酯(6a)的所有四个立体异构体的立体选择性化学酶法合成。该序列的关键步骤是通过两种对映体互补的生物催化剂对6-氯-3,5-二氧己酸叔丁基酯(1a)进行高度区域和对映选择性的单中心还原。来自短乳杆菌的乙醇脱氢酶(recLBADH)得到对映纯的叔丁基(S)-6-氯-5-羟基-3-氧代己酸叔丁酯[(S)-2a],产率为72%。对映体(R)-2a是通过在两相系统中通过Baker酵母还原法以90-94%ee制备的(50%收率)。两种生物转化均以克为单位进行。如此获得的对映体δ-羟基-β-酮酯2a的β-酮基通过顺-和反选择性硼氢化物的还原而被还原。还原方法的置换产生了结晶目标化合物6a的全部四个立体异构体(≥99.3%ee,dr>≥205:1),这是一种通用的1,3-二醇结构单元。如在光度测定法中测定的那样,recLBADH接受各种β,δ-二酮酯。同时将3,5-二氧己酸叔丁酯(1b)和3