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Reproductive Biology; 12/2014
Available from: Monika Dymarska
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ABSTRACT: Biotransformation of ten α-haloacetophenones in the growing culture of the strain Rhodotorula rubra KCh 82 has been carried out. Nine of the substrates underwent an effective enantioselective reduction to the respective (R)-alcohols according to Prelog's rule, with the exception of 2-chloro-1,2-diphenylethan-1-one that was not transformed by this strain. The expected reduction proceeded without dehalogenation, leading to the respective (R)-halohydrins in high yields. The use of this biocatalyst yielded (R)-2-bromo-1-phenyl-ethan-1-ol (enantiomeric excess (ee) = 97%) and its derivatives: 4'-Bromo- (ee = 99%); 4'-Chloro- (ee > 99%); 4'-Methoxy- (ee = 96%); 3'-Methoxy- (ee = 93%); 2'-Methoxy- (ee = 98%). There were also obtained and characterized 2,4'-dichloro-, 2,2',4'-trichloro- and 2-chloro-4'-fluoro-phenyetan-1-ol with >99% of enantiomeric excesses.
International Journal of Molecular Sciences 12/2014; 15(12):22392-22404. DOI:10.3390/ijms151222392
Available from: Monika Siepka
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ABSTRACT: This research investigated stereochemistry of reduction of racemic flavanone and a concurrent competitive process of oxidation, taking place in cultures of live yeast strains. The results obtained gave us information about capability of tested biocatalysts for enantioselective (with respect to both substrate and product) reduction of flavanone and for enantioselective oxidation of the resulting cis- and trans-flavan-4-ols. As a result of our experiments we obtained (2S,4S)-cis-flavan-4-ol with 43% of conversion and 96% of enantiomeric excess, and (2R,4S)-trans-flavan-4-ol with 41% of conversion and ee > 99% in the culture of Rhodotorula rubra; (2S,4S)-cis-flavan-4-ol (43%, ee = 96%) along with (2R,4R)-cis-flavan-4-ol (44%, ee = 61%) in the culture of Zygosaccharomyces bailii KCh 907. Additionally, some of the tested strains demonstrated an excellent capability for enantioselective oxidation of (+/-)-cis-flavan-4-ol and (+/-)-trans-flavan-4-ol, obtained by chemical synthesis. A one-day biotransformation in the culture of Candida parapsilosis KCh 909 afforded (S)-flavanone (ee = 93%) as 49% of the reaction mixture and 49% of unreacted (2R,4R)-cis-flavan-4-ol with ee = 97%. Racemic trans-flavan-4-ol was effectively oxidized in the culture of Yarrowia lipolytica KCh 71 - after a three-day biotransformation the reaction mixture contained 52% of (R)-flavanone (ee = 85%) and 48% of (2R,45)-trans-flavan-4-ol with a high enantiomeric excess (ee = 93%).
Journal of Molecular Catalysis B Enzymatic 11/2014; 109. DOI:10.1016/j.molcatb.2014.08.006
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