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Prochiral ketones with cofactor

CRED catalyzed bioreduclion of prochiral ketones with cofactor reeqrcling. [Pg.150]

In an alternative approach, Nakayama and Schultz [25] have successfully achieved the enantiofacial reduction of prochiral ketones. By utilizing the phosphonate hapten 15 catalytic antibodies were elicited which catalyze a highly stereospecific reduction of ketone 16 with sodium cyanoborohydride as a cofactor (Scheme 4). The most active antibody, A5, was found to have a pH optimum at acidic pH, consequently the reductions were performed in aqueous buffer at pH 5.0. The reaction was followed for multiple turnovers (>25) without any decrease in activity or stereoselectivity highlighting the utility of this catalytic system. [Pg.1318]

For example, a ferredoxin hydrogenase (EC 1.12.7.2) has been isolated recently from the hyperthermophile Pyrococcus fUriosus [38]. The performance of this biocatalyst, which showed a remarkable stability under operative conditions, has been investigated for the NADPH regeneration in the reduction of prochiral ketones catalyzed by the thermophilic NADPH-dependent ADH from Thermoanaerohium sp. Total turnover numbers (TTNs mole product/mole consumed cofactor NADP" ") of 100 and 160 could be estimated in the reduction of acetophenone and (2S)-hydroxy-l-phenyl-propanone, respectively. As a side note, it should be mentioned that, although the activity of the P. furiosus hydrogenase increased exponentially with temperature up to its maximum above 80 °C, the reactions had to be performed at much lower temperature (40 °C) because of the thermal instability of NADPH. [Pg.29]

An alternative for the transformation of a racemate into one single enantiomer in >99% yield and with high enantiomeric excess is the stereoinversion. In the case of racemic alcohols, this approach relies on the formation of prochiral ketones through an enantioselective oxidation process and subsequent opposite stereoselective reduction of these prochiral intermediates (Scheme 4.12). Therefore, an ideal system to carry out this type of transformation is composed of a pair of (bio) catalysts with opposite enantiopreference and different cofactor selectivity to avoid undesired interferences. [Pg.101]

Ni, Y., et al.. Highly stereoselective reduction of prochiral ketones by a bacterial reductase coupled with cofactor regeneration. Org. Biomol. Chem., 2011. 9(15) 5463-5468. [Pg.455]

Recently, a cascade process for the simultaneous preparation of two enantiopure secondary alcohols by the same ADH was investigated [12]. In this work, a kinetic oxidative resolution of different secondary alcohols was coupled with the irreversible asymmetric reduction of selected prochiral activated ketones, that is, a-chloro ketones (Scheme 11.5a). The proposed strategy, named PIKAT (parallel intercoimected kinetic asymmetric transformations), represents an example of redox neutral (or self-sufficient) cascade, with no additional reducing or oxidizing reagents being required. Moreover, the reaction was catalyzed by a single enzyme in the presence of catalytic amounts of the cofactor. As the outcome of the cascade process is a mixture of two different enantioenriched products, substrates were properly selected on the basis of different physical properties. [Pg.289]


See other pages where Prochiral ketones with cofactor is mentioned: [Pg.83]    [Pg.21]    [Pg.204]    [Pg.99]    [Pg.53]    [Pg.259]    [Pg.109]    [Pg.879]    [Pg.105]    [Pg.73]    [Pg.83]    [Pg.184]   


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Cofactor

Prochiral

Prochiral ketones

Prochirality

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