Biocatalytic Aerobic Oxidation

Fuchs, M., Tauber, K., Sattler, J., Lechner, H., Pfeffer, J., Kroutil, W., and Faber, K. (2012) Amination of benzylic and cirmamic alcohols via a biocatalytic, aerobic, oxidation-transamination cascade. RSCAdv., 2, 6262-6265. 

New interesting developments regarding technical processes for the preparation of AA such as biocatalytic oxidation of PA and the two-stage cleavage of oleic acid using H2O2 and O2 as oxidants are reported later in the text. However, ozonolysis coupled with an aerobic oxidative work-up of intermediates is the most important industrial process at the present time [5, 7]. 

Schrittwieser JH, Resch V, Sattler JH, Lienhart W-D, Durch-schein K, Winkler A, Gruber K, Macheroux P, Kroutil W. Biocatalytic enantioselective oxidative C-C coupling by aerobic C-H activation. Angew. Chem. Int. Ed. 2011 50 1068-1071. 

The recent synthesis of (—)-tetracycline by Myers and co-workers incorporates a biocatalytic step in the first stage which oxidizes benzoic acid aerobically to an a,f)-dihydroxy derivative in the presence of a whole-cell mutant strain of Alcaligenes eutrophus. Figure 4.61 shows a reduced tree diagram for the synthesis and Table 4.28 summarizes the metrics parameters. 

A microbial contacting process for the oxidation of H2S was disclosed [22], in which a chemoautotrophic bacterium T. thiooxidants or T. ferroxidans) is used to remove sulfides from gaseous streams, at aerobic conditions and low pH. The low pH is preferred since the optimum pH for growth of the bacteria is below 4.0. and for the elimination of undesired contaminant bacterial strains. A contactor is employed, the flow of the sulfur-containing stream is contacted counter-currently with the biocatalytic aqueous solution. The sulfate is recovered from the aqueous solution, which contains the biocatalyst, as well. 

The berberine bridge enzyme (BBE) was employed for the first preparative oxidative biocatalytic C-C coupling (Scheme 8.71). Racemic N-methyl THIQs (rac-146) was enantioselectively converted by BBE in toluene/buffer co-solvent under aerobic conditions. The sp -sp C-H coupling products (S)-147, berbine derivatives, and unreacted (R)-146 were obtained with high ee, accomplishing highly efficient kinetic resolution. 

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