Side chain hydroxylation of aromatic compounds by fungi.: 1. Products and stereochemistry

The fungus Mortierellaisabellina can convert ethylbenzene and a number of para-substituted derivatives to the corresponding optically active 1-phenylethanols with enantiomeric excesses between 5 and 40% and chemical yields up to 45%. 2-Ethylnaphthalene, 2-ethylthiophene, and n-propylbenzene were similarly converted, as were the bicyclic compounds indane and tetralin. In most cases, the R absolute configuration of product predominated. The fungi Cunninghamellaechinulata var. elegans and Helminthosporium species are also capable of performing some of these transformations. M. isabellina and C. elegans also produce 2-phenylethanols as products in some cases. The highest enantiomeric excesses during benzylic hydroxylation were obtained with Helminthosporium and are attributable, at least in part, to further stereoselective oxidation of the alcohol. Cross induction experiments with M. isabellina indicate that the same enzyme may be responsible for the benzylic hydroxylation of ethylbenzene, 2-ethylthiophene, and 2-ethylnaphthalene.