Whole cells reduction

S Rodriguez Giordano. Baker s yeast (3-keto ester reductions whole cell biocatalysts with improved stereoselectivity by recombinant DNA techniques. Ph.D. thesis, University of Florida, Gainesville, FL, 2000. 

Carnell et al. discovered that whole cells of Cunninghamella echinulata NRRL1384 were able to deracemize racemic N-(l-hydroxy-l-phenylethyl)benzamide (24) to produce the (R) enantiomer (Figure 5.17) [30]. The deracemization involves fast, highly (S)-selective oxidation, followed by slower, partially (R)-selective reduction of the ketone (25). Optimization by removing competing extracellular amidase/prote-ase activity resulted in 82% yield and 92% ee. 

O Water absorbing polymer Figure 8.26 Asymmetric reduction of ketones in CO2 by Geotrichum candidum immobilized whole cell [20], (a) Time course for the reduction of o-fluoroacetophenone (b) substrate specificity (c) apparatus for C. candidum-cata yzed reduction with semiflow process using scC02. 

Deracemization via the biocatalytic stereoinversion is usually achieved by employing whole cells. In the case of secondary alcohols, it is believed that microbial stereoinversion occurs by an oxidation-reduction sequence... 

Reduction of carbon-carbon double bond Microalgae easily reduce carbon-carbon double bonds in enone. Usually, the reduction of carbonyl group and carbon-carbon double bond proceeds concomitantly to afford the mixture of corresponding saturated ketone, saturated alcohol, and unsaturated alcohol because a whole cell of microalgae has two types of reductases to reduce carbonyl and olefinic groups. The use of isolated reductase, which reduces carbon-carbon double bond chemoselectively, can produce saturated ketones selectively. 

Prochiral aryl and dialkyl ketones are enantioselectively reduced to the corresponding alcohols using whole-cell bioconversions, or an Ir1 amino sulfide catalyst prepared in situ.695 Comparative studies show that the biocatalytic approach is the more suitable for enantioselective reduction of chloro-substituted ketones, whereas reduction of a,/ -unsaturated compounds is better achieved using the Ir1 catalyst. An important step in the total synthesis of brevetoxin B involves hydrogenation of an ester using [Ir(cod)(py) P(cy)3 ]PF6.696... 

Goldberg, K., Schroer, K., Luetz, S. and Liese, A. (2007) Biocatalytic ketone reduction - a powerful tool for the production of chiral alcohols - part II whole-cell reductions. Applied Microbiology and Biotechnology, 76, 249-255. 

Similarly, whole-cell Lactobacillus kefir DSM 20587, which possesses two alcohol dehydrogenases for both asymmetric reduction steps, was applied in the reduction of tert-butyl 6-chloro-3,5-dioxohexanoate for asymmetric synthesis of ft rf-butyl-(31 ,5S)-6-chloro-dihydroxyhexanoate (Figure 7.5), a chiral building block for the HMG-CoA reductase inhibitor [ 17]. A final product concentration of 120 him and a specific product capacity of 2.4 mmol per gram dry cell were achieved in an optimized fed-batch process. Ado 99% was obtained for (3R,5S)- and (3.S, 55)-te/ f-butyl-6-chloro-dihydroxyhexanoate with the space-time yield being 4.7 mmolL-1 h-1. 

Figure 7.5 Reduction of tert-butyl 6-chloro-3,5-dioxohexanoate by whole-cell Lactobacillus kefir DSM 20587...

Lactobacillus kefir was also employed as the whole-cell biocatalyst for the asymmetric reduction of ethyl 4-chloroacetoacetate to ethyl (.S )-4-chloro-3-hydroxybutanoate, the chiral... 

Figure 7.9 Reduction of a-chloro-3 -chloroacetophenone catalyzed by a whole-cell biocatalyst and the corresponding purified enzyme...

The reduction of several ketones, which were transformed by the wild-type lyophilized cells of Rhodococcus ruber DSM 44541 with moderate stereoselectivity, was reinvestigated employing lyophilized cells of Escherichia coli containing the overexpressed alcohol dehydrogenase (ADH- A ) from Rhodococcus ruber DSM 44541. The recombinant whole-cell biocatalyst significantly increased the activity and enantioselectivity [41]. For example, the enantiomeric excess of (R)-2-chloro-l-phenylethanol increased from 43 to >99%. This study clearly demonstrated the advantages of the recombinant whole cell biocatalysts over the wild-type whole cells. 

In summary, ketoreductases have emerged as valuable catalysts for asymmetric ketone reductions and are preparing to enter the mainstream of synthetic chemistry of chiral alcohols. These biocatalysts are used in three forms wild-type whole-cell microorganism, recombinant... 

Carballeira, J.D., Alvarez, E., Campillo,M,etal. (2004)DiplogelasinosporagrovesiilNll 171018, anew whole cell biocatalyst for the stereoselective reduction of ketones. Tetrahedron Asymmetry, 15 (6), 951-962. 

Groeger, H., Rollmann, C., Chamouleau, F. et al. (2007) Enantioselective reduction of 4-fluoroacetophenone at high substrate concentration using a tailor-made recombinant whole-cell catalyst. Advanced Synthesis and Catalysis, 349 (4-5), 709-712. 

Ernst, M., Kaup, B., Mueller, M. et al. (2005) Enantioselective reduction of carbonyl compounds by whole-cell biotransformation, combining a formate dehydrogenase and a (R)-specihc alcohol dehydrogenase. Applied Microbiology and Biotechnology, 66 (6), 629-634. 

Octonol is an intermediate for the production of several optically active pharmaceuticals, such as steroids and vitamins. The asymmetric reduction of 2-octanone to (5)-2-octonol by baker s yeast was inhibited severely by substrate and product concentration of 10 him and 6 mM respectively. Whole-cell biotransformation of 2-octanone in a water-ra-dodecane biphasic system yielded a high product concentration of 106him with 89% ee in 96h [37],... 

Engelking, H., Pfaller, R., Wich, G. and Weuster-Botz, D. (2006) Reaction engineering studies on /3-ketoester reductions with whole cells of recombinant Saccharomyces cerevisiae. Enzyme and Microbial Technology, 38, 536-544. 

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