Abstract:
Incubations of several polycyclic heteroaromatic compounds and two
polycyclic aromatic hydrocarbons with a series of common fungi have been
performed. The fungi Cunninghamella elegans ATCC 26269, Rhizopus
arrhizus ATCC 11145, and Mortierella isabellina NRRL 1757 were
studied in this regard. Of the aza heteroaromatics, only dibenzopyrrole
gave a ring hydroxylated product following the incubation with C.
elegans. From the thio heteroaromatics studied, dibenzothiophene was
metabolized by all the three fungi and thioxanthone by C. elegans and
M. isabellina giving sulfones and sulphoxides. Thiochromanone was
metabolized stereoselectively to the corresponding sulphoxide by C.
elegans. Methyl substituted thioxanthones on incubation with C.
elegans produced oxidative products, arising from S -oxidation and
hydroxylation at the methyl group. Of the cyclic ketones studied, only
fluorenone was reduced to hydroxyfluorene and this metabolism is
compared with that reported with cytochrome P-450 monooxygenases of
hepatic microsomes.
A series of para-substituted ethylbenzenes has been transformed
stereoselectively to the 1-phenylethanols by incubation with M.
isabellina. Comparisons of the enantiomeric purities obtained from
products with their respective para substituent of the same steric size
but different electronic properties indicate that the stereoselectivity
of hydroxylation at benzylic carbon may be susceptible to electron
donating or withdrawing factors in some cases, but that observation is not va lid in all the comparisons. The stereochemistry of the reaction
is discussed in terms of three possible steps, ethylbenzene ---)
1-phenylethanol ---) acetophenone ---) 1-phenylethanol. This
metabolic pathway could account for the inconsistencies observed in the
comparisons of optical purities and electronic character of para
substituents. Furthermore, formation of 2-phenylethanol (in some
cases), l-(p-acetylphenyl)ethanol from p-diethylbenzene, and
N-acetylation of p-ethylaniline was observed. n-Propylbenzene was also
converted to optically active 1-phenylpropanol.
Acetophenone, p-ethylacetophenone, and o(,~,~-trifluoroacetophenone
were transformed to 1-phenylethanol, l-(p-ethylphenyl)ethanol, and
1-phenyl-2,2,2-trifluoroethanol, respectively, with high chemical and
excellent optical yields.
The 13 C NMR spectra of several substrates and metabolic
products have been reported and assigned for the first time.
