Stereospecific production of double chiral compounds by novel enzymatic processes

手性化合物是生产医药、精细化学品等的重要中间体。由于具有较高的立体专一性和环境因素，生物催化合成手性化合物引起了人们的极大关注。另一方面，分子中含有两个不对称碳的双手性化合物对于合成许多有用的化合物也是重要的，如药物和农用化学品。将两个手性中心通过酶作用引入到有机化合物中的方法有很多，主要有两步法将双手性中心引入到前手性化合物酮异佛尔酮中，通过两个不同的酶反应生成(4R，6R)-放线醇。将黄原酶与左旋二酮还原酶结合，合成双手性化合物(4R，6R)-放线醇，用于合成玉米黄质、黄曲霉毒素等天然光学活性化合物。以共表达旧黄酶或左旋二酮还原酶基因和辅因子再生酶基因的大肠杆菌转化细胞为催化剂。100g/L的酮异佛尔酮通过两步反应几乎按化学计量和立体专一性转化为(4R，6R)-放线醇，麻黄碱也是一种有用的双手性化合物，d-ψ-异构体具有降充血或平喘的药理作用。我们发现红球红球菌产生一种新的依赖于NADP^+的氨基醇脱氢酶，该酶催化对应的氨基酮MAK的外消旋混合物中的L异构体不对称还原为d-ψ-麻黄碱。利用共表达AADH基因和辅因子再生酶基因的大肠杆菌转化细胞，通过全细胞反应生物催化转化外消旋麻黄素为d-ψ-麻黄碱。反应时间为24 h，d-ψ-麻黄碱的摩尔产率为89%。

Chiral compounds are useful intermediates for the production of pharmaceuticals, fine chemicals, and so on. Because of high stereospecificity and environmental aspects, biocatalytic production of chiral compounds has been attracting considerable attention. On the other hand, double chiral compounds, which have two asymmetric carbons in their molecules, are also important for the synthesis of many useful compounds, such as pharmaceuticals and agrochemicals. There are several ways to enzymatically introduce two chiral centers into organic compounds.Two-step introduction of double chiral centers into the prochiral compound, ketoisophorone, forming (4R,6R)-actinol through two separate enzyme reactions were performed. By combination of old yellow enzyme and levodione reductase, production of doubly chiral compound, (4R,6R)-actinol, which is a useful chiral intermediate for the synthesis of naturally-occurring optically active compounds, such as zeaxanthin and xanthoxin, was investigated. E.coli transformant cells co-expressing old yellow enzyme or levodione reductase gene with cofactor regeneration enzyme gene were used as the catalysts. 100 g/l of ketoisophorone was almost stoichiometrically and stereospecifically converted to (4R,6R)-actinol by two-step reaction Ephedrine is also one of the useful double chiral compounds, and d-ψ-isomer has pharmacological effects as a decongestant or antiasthmatic compound. We found that Rhodococcus erythropolis produces a novel NADP^+-dependent amino alcohol dehydrogenase (AADH), which catalyze the asymmetric reduction of l-isomer in the racemic mixture of the corresponding amino ketone, MAK, to d-ψ-ephedrine. Using E.coli transformant cells coexpressing the genes of AADH and cofactor regeneration enzyme, biocatalytic conversion of racemic MAK to d-ψ-ephedrine by whole cell reaction was performed. Cosequently, 178 mM of d-ψ-ephedrine was formed in 24 h reaction with a molar yield of 89%.