BACTERIAL CONVERSION OF BICYCLIC MONOTERPENES BY ABSIDIA ORCHIDIS (VUILL) HAGEM .1. REDUCTION OF CAMPHORQUINONE AND ISOFENCHONEQUINONE .17.TION WITH MICROORGANISMS

(—)‐Camphorquinone (1a) was transformed to a mixture consisting of 3‐endo‐hydroxy‐camphor (2a) (40%), 3‐exo‐hydroxy‐camphor (3a) (30%) and 2‐endo‐hydroxy‐epicamphor (4a) (30%) by an aqueous suspension of the mycelium of Absidia orchidis (Vuill.) Hagem. The composition of the reduction products was determined by the NMR. spectra. Incubation of the enantiomeric (+)‐camphorquinone (1b) under the same condition yielded 3‐exohydroxy‐camphor (3b) as single product. Since both substrates form their products immediately and in the same ratio the possibility of a posterior isomerization of 3a yielding the ketols 2a and 4a can be ruled out. For comparison the course of the chemical reduction of camphorquinone (1) to the ketols (Zn in acetic acid, hydrogenation with Raney‐Ni as catalyst, NaBH4) was investigated. Camphor was not transformed by Absidia orchidis. (—)‐Isofenchonequinone (6a) yielded upon incubation with an aqueous suspension of the mycelium of Absidia orchidis exclusively 2‐endo‐hydroxy‐epi‐isofenchone (7a). The enantiomer diketone 6b gave the same result, i. e. the ketol 7b as the only transformation product. Also with isofenchonequinone the chemical reduction to the ketols by Zn in acetic acid, hydrogenation with Raney‐Ni as catalyst and NaBH4 was studied. Copyright © 1969 Verlag GmbH & Co. KGaA, Weinheim