Biocatalytic desulfurization of arylsulfonates

A microbial strain, Klebsiella oxytoca KS3D, has been isolated which is capable of exploiting arylsulfonates as a sole source of sulfur during growth. The desulfurization catalyzed by intact K. oxytoca KS3D results in the conversion of arylsulfonates into the corresponding phenols. Even arylsulfonates carrying substituents which significantly alter steric and electronic characteristics are substrates. Only a single regioisomer is produced from substituted arylsulfonates. Based on the products formed from the biocatalytic desulfurizations and incorporation of isotopic oxygen in phenolic product when the desulfurization is run under 18O-enriched oxygen, hydrolysis mechanisms can be eliminated from consideration. Two reaction types which might mimic the chemistry occurring during microbial desulfurization of arylsulfonates were examined. The first reaction involved conversion of appropriately substituted arylsulfonates into phenols by single electron reduction followed by reaction of the radical anions with molecular oxygen. A second reaction using intramolecular reaction of arylsulfonates and arylsulfones with alkoxy radicals failed to achieve desulfurization. In addition to mechanistic evaluation, desulfurization of arylsulfonates catalyzed by K. oxytoca KS3D is examined from the perspective of its relevance to desulfurization of the organosulfur components of coal and its possible use for industrial manufacture of phenols.