Abstract
α-hydroxy ketones (HK) and 1,2-diols are important building blocks for fine chemical synthesis. Here, we describe the R-selective 2,3-butanediol dehydrogenase from B. clausii DSM 8716T (BcBDH) that belongs to the metal-dependent medium chain dehydrogenases/reductases family (MDR) and catalyzes the selective asymmetric reduction of prochiral 1,2-diketones to the corresponding HK and, in some cases, the reduction of the same to the corresponding 1,2-diols. Aliphatic diketones, like 2,3-pentanedione, 2,3-hexanedione, 5-methyl-2,3-hexanedione, 3,4-hexanedione and 2,3-heptanedione are well transformed. In addition, surprisingly alkyl phenyl dicarbonyls, like 2-hydroxy-1-phenylpropan-1-one and phenylglyoxal are accepted, whereas their derivatives with two phenyl groups are not substrates. Supplementation of Mn2+ (1 mM) increases BcBDH's activity in biotransformations. Furthermore, the biocatalytic reduction of 5-methyl-2,3-hexanedione to mainly 5-methyl-3-hydroxy-2-hexanone with only small amounts of 5-methyl-2-hydroxy-3-hexanone within an enzyme membrane reactor is demonstrated.
Highlights
The biocatalytic synthesis of enantiopure a-hydroxy ketones and vicinal diols is an intriguing eld, due to the broad application of these molecules, e.g. as avouring compounds, pheromones or as precursors for ne chemicals.[1,2,3,4] the development of efficient syntheses for enantiomerically enriched a-hydroxy ketones is an important research focus in the pharmaceutical industry
We describe the R-selective 2,3-butanediol dehydrogenase from B. clausii DSM 8716T (BcBDH) that belongs to the metal-dependent medium chain dehydrogenases/reductases family (MDR) and catalyzes the selective asymmetric reduction of prochiral 1,2-diketones to the corresponding hydroxy ketones (HK) and, in some cases, the reduction of the same to the corresponding 1,2-diols
The use of thiamine diphosphatedependent lyases (ThDP lyases) to catalyze the carboligation of aldehydes,[11,12,13] hydrolases and lipases produce a-hydroxy ketones through dynamic kinetic resolutions (DKRs)[14,15,16] and redox reactions catalyzed by oxidoreductases, either by means of free enzymes or by whole cell biotransformations gave a-hydroxy ketones and 1,2-diols.[17,18,19,20,21]
Summary
The biocatalytic synthesis of enantiopure a-hydroxy ketones and vicinal diols is an intriguing eld, due to the broad application of these molecules, e.g. as avouring compounds, pheromones or as precursors for ne chemicals.[1,2,3,4] the development of efficient syntheses for enantiomerically enriched a-hydroxy ketones is an important research focus in the pharmaceutical industry These compounds can be found in antidepressants and fungicides, in selective inhibitors of amyloid protein production (used in the treatment of Alzheimer's disease), in farnesyl transferase inhibitors (Kurasoin A and B), and in antitumor-antibiotics (Olivomycin A and Chromomycin A3 and Taxol).[5,6] Several chemical approaches, like the a-hydroxylation of carbonyl compounds such as alkenes and ketone enolates, the hydrolytic kinetic resolution of terminal epoxides, or the asymmetric dihydroxylation of ole ns are reported.[7,8,9,10] Besides the chemical synthesis, different biocatalytic routes were reported to efficiently produce ahydroxy ketones. The use of thiamine diphosphatedependent lyases (ThDP lyases) to catalyze the carboligation of aldehydes,[11,12,13] hydrolases and lipases produce a-hydroxy ketones through dynamic kinetic resolutions (DKRs)[14,15,16] and redox reactions catalyzed by oxidoreductases, either by means of free enzymes (applying a cofactor regeneration system) or by whole cell biotransformations gave a-hydroxy ketones and 1,2-diols.[17,18,19,20,21]
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