Asymmetrie Reduction of Synthetic Ketones by Marine Microorganisms

Three strains of bacteria reducing (trifluoroacetyl)ferrocene (3) to optically pure (R)-2,2,2-trifluoro-l-hydroxyethylferrocene (4) and one bacterial strain reducing 3 to (S)-4 of moderate optical purity were isolated from sea-water collected at the coastal areas in Ibaraki prefecture of Japan. The former three strains were identified as Micrococcus lylae, Micrococcus luteus, and Deleya marina and the latter as Bacillus licheniformis. These strains also asymmetrically reduced some other synthetic ketones, e.g., 2,2,2-trifluoroacetophenone (7) and phenyl trimethylsilyl ketone (9). Further screening of microorganisms capable of reducing 3 was done with bacteria isolated from sea-water of the deep sea (Okinawa trough, Japan trench, and Mariana trough) and of the pelagic areas (Indian Ocean and South China Sea). Most of these marine strains preferentially reduced 3 to (R)-4 similar to the coastal strains, but the frequency of finding very highly enantioselective strains (i.e., those forming 4 of > 90% e.e.) was remark­ ably high in several sites of the deep sea and pelagic areas as compared with the coast and terrestrial environment.