Microbiological hydroxylation. Part 23. Hydroxylations of fluoro-5α-androstanones by the fungi Calonectria decora, Rhizopus nigricans, and Aspergillus ochraceus

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Abstract
A series of monofluoro- and gem-difluoro-5α-androstanones and the parent ketones were incubated, under standard conditions, with the fungi named in the title. The results may be rationalised by comparing the positions of the fluorine atoms in the substrates with those of the favoured hydroxylation sites in the parent ketones. With few exceptions hydroxylation does not occur at, or adjacent to, the carbon to which a fluorine substituent is attached even though one of these centres is a favoured site (in the parent ketone). In such cases hydroxylation is usually diverted to an alternative position. Where the favoured site is more distant from the fluorine substituent(s) the behaviour of a fluoro-ketone resembles that of its parent. Hydroxylation of several fluoro-ketones by Aspergillus ochraceus gives the 11 α-hydroxy-derivatives cleanly and in yields which are satisfactory for preparative work.

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