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Syntheses of crystalline benzo[c]furans 2 and 3 are described. 13C NMR spectra of these compounds have been studied and chemical shifts assigned. The data appear to support a previously advanced structural representation of such o-quinonoidal heterocycles as a 6ir-hetero-ring annelated at C-3 and C-4 to a noninteracting cts-butadiene fragment as in 14. The first experimental determination of the geometry of a benzo[c] furan has been accomplished by an X-ray crystallographic study of 2. The results show a planar molecule with carbon-carbon bonds alternating in length, in general agreement with several earlier calculations, but in even better agreement with the published geometry of furan. Diels-Alder reactions of 2 and 3 with common dienophiles provide good yields of "ortho" adducts as endo-exo mixtures.

A series of compounds containing a cyclopropyl ring adjacent to the position of oxidation during fungal biotransformation has been prepared and subjected to enzymic oxidation using Mortierellaisabellina or Rhizopusarrhizus. Carbon hydroxylation and sulfoxidation reactions were observed, but in neither case did opening of the cyclopropyl ring occur. Both these reactions were subject to inhibition by carbon monoxide but not by cyanide ion, properties characteristic of cytochrome P-450 dependent mono-oxygenase enzymes. Hydroxylation at a cyclopropyl C—H bond has been studied by the use of phenylcyclopropane and phenylthiirane as substrates for the mono-oxygenase of M. isabellina. The former was not oxidized, but the latter was converted to phenyl glyoxylic acid in moderate yield. Keywords: biotransformation, cyclopropanes, fungi, metabolism.

The title fungus hydroxylates testosterone (I) at C‐2β in 40‐60% yield.

The enzymic oxidation of a series of title compounds, e.g. (I), (III), (V), (VIII), leads to carbon hydroxylation and sulfoxidation reactions, but in neither case opening of the cyclopropyl ring occurs.