Asymmetric reduction of tetralones and their methoxy derivatives by Fusarium culmorum

Whole cells of the fungus Fusarium culmorum were used to carry out the bioreduction of 1- and 2-tetralones and their derivatives with a methoxy group in the aromatic ring. The process led to the corresponding (S)-alcohols. The microbial reduction system exhibited moderate activity and low enantioselectivity against 1-tetralones, but high activity and moderate selectivity against 2-tetralones. Reduction of 1-tetralones was accompanied by oxidation of the resulting alcohols (re-oxidation), but this was not observed in transformations of 2-tetralones. The effects of parameters such as concentration of the medium, time of substrate addition to the culture and time of incubation on the conversion and optical purity of the alcohols have been investigated. A young culture of the microorganism obtained after growth for 24 h exhibited higher (S)-reduction activity than that observed with 72-h-old cells. Doubling the concentration of ingredients in the cultivation medium limited both the (R)-reductive activity of the biocatalyst and the oxidation of the (S)-alcohols for the 1-tetralol series. Under modified reaction conditions, the yield and enantiomeric excess of (S)-alcohols were improved to 93-100% and 58-9 9%, respectively.