Mikrobiologische Umwandlung von bicyclischen Monoterpenen durch Absidia orchidis (VUILL.) HAGEM. 2. Teil. Hydroxylierung von Fenchon und Isofenchon. 18. Mitteilung über Reaktionen mit Mikroorganismen [1]

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Abstract
(+)‐Fenchone (3a) was transformed to 6‐exo‐hydroxy‐fenchone (6β‐hydroxy‐1, 3, 3‐trimethyl‐nor‐bornan‐2‐one) (1a) and to 5‐exo‐hydroxy‐fenchone 5β‐hydroxy‐1, 3, 3‐trimethyl‐nor‐bornan‐2‐one (4a) by the mycelium of Absidia orchidis (Vuill.) Hagem. The structure of the two products was proven by a detailed analysis of the NMR. spectra of the corresponding acetyl derivatives 2a and 5a respectively, and by CrO3‐oxidation. 1a yielded the β‐diketone 6a, and 4a the diketone 8a. Whereas 8a was stable to alkali 6a was cleaved to the cyclopentane carboxylic acids 7 and 9. — Incubation of (—)‐fenchone (3b) yielded the enantiomeric hydroxylation products 1b and 4b in the same ratio. ‐ (—)‐Isofenchone (11a) was transformed by Absidia orchidis into the two epimers 6‐endo‐hydroxy‐isofenchone (6β‐hydroxy‐1, 5, 5‐trimethyl‐nor‐bornan‐2‐one) (12a) and 6‐exo‐hydroxy‐isofenchone (6β‐hydroxy‐1, 5, 5‐trimethyl‐nor‐bornan‐2‐one) (10a.) CrO3‐oxidation of both 10a and 12a gave the same β‐diketone 6a. ‐ (+)‐Isofenchone gave the corresponding enantiomeric hydroxy derivatives 10b and 12b on incubation with Absidia orchidis.