Biotransformation of polycylic aromatic compounds by fungi and an investigation into the oxidation of alkylbenzenes by Mortierella isabellina NRRL 1757

摘要

Incubations of several polycyclic heteroaromatic compounds and twopolycyclic aromatic hydrocarbons with a series of common fungi have beenperformed. The fungi Cunninghamella elegans ATCC 26269, Rhizopusarrhizus ATCC 11145, and Mortierella isabellina NRRL 1757 werestudied in this regard. Of the aza heteroaromatics, only dibenzopyrrolegave a ring hydroxylated product following the incubation with C.elegans. From the thio heteroaromatics studied, dibenzothiophene wasmetabolized by all the three fungi and thioxanthone by C. elegans andM. isabellina giving sulfones and sulphoxides. Thiochromanone wasmetabolized stereoselectively to the corresponding sulphoxide by C.elegans. Methyl substituted thioxanthones on incubation with C.elegans produced oxidative products, arising from S -oxidation andhydroxylation at the methyl group. Of the cyclic ketones studied, onlyfluorenone was reduced to hydroxyfluorene and this metabolism iscompared with that reported with cytochrome P-450 monooxygenases ofhepatic microsomes.A series of para-substituted ethylbenzenes has been transformedstereoselectively to the 1-phenylethanols by incubation with M.isabellina. Comparisons of the enantiomeric purities obtained fromproducts with their respective para substituent of the same steric sizebut different electronic properties indicate that the stereoselectivityof hydroxylation at benzylic carbon may be susceptible to electrondonating or withdrawing factors in some cases, but that observation is not va lid in all the comparisons. The stereochemistry of the reactionis discussed in terms of three possible steps, ethylbenzene ---)1-phenylethanol ---) acetophenone ---) 1-phenylethanol. Thismetabolic pathway could account for the inconsistencies observed in thecomparisons of optical purities and electronic character of parasubstituents. Furthermore, formation of 2-phenylethanol (in somecases), l-(p-acetylphenyl)ethanol from p-diethylbenzene, andN-acetylation of p-ethylaniline was observed. n-Propylbenzene was alsoconverted to optically active 1-phenylpropanol.Acetophenone, p-ethylacetophenone, and o(,~,~-trifluoroacetophenonewere transformed to 1-phenylethanol, l-(p-ethylphenyl)ethanol, and1-phenyl-2,2,2-trifluoroethanol, respectively, with high chemical andexcellent optical yields.The 13 C NMR spectra of several substrates and metabolicproducts have been reported and assigned for the first time.