Asymmetric bioreduction of natural xenobiotic diketones by Brassica napus hairy roots

Enantioselective bioreduction of natural prochiral diketones and some chemical derivatives were mediated by Brassica napus hairy root cultures. The natural bioactive diketones 1-(5-acetyl-2-hydroxyphenyl)-3-methylbut-2-en-1-one (1) and 6-acetyl-2,2-dimethyl-2,3-dihydro-4H-chromen-4-one (2) were both transformed into 6-(1(S)-hydroxyethyl)-2,2-dimethyl-2,3-dihydro-4H-chromen-4-one (4) in high enantiomeric excesses (>97%) and with good biotransformation rates (>78%). The assignment of the absolute configuration of the new stereogenic center was established by 1H NMR using modified Mosher's method. Moreover, B. napus hairy roots showed the ability to perform glycosylation of phenolic-hydroxyl groups. The natural ketone 1-(5-acetyl-2-hydroxyphenyl)-3-methylbutan-1-one (3) was biotransformed into 4-acetyl-2-(3-methylbutanoil)-phenyl-O-β-d-glucopyranoside (5). Additionally, the acetate derivative 4-(acetyl-2-(3-methylbut-2-enoyl)-phenylacetate (6) was hydrolyzed in the culture media and transformed into 4. The O-methyl derivative 1-(5-acetyl-2-metoxyphenyl)-3-methylbut-2-en-1-one (7) was recovered untransformed.