The present invention relates to the production of a product compound having a structure according to Formulae IA and/or IB: wherein n is 0 or 1; R1 is hydrogen or hydroxy; R2 is hydrogen; or, when n is 0, R1 and R2 taken together form a second bond between the carbon atoms bearing R1 and R2, provided that when n is 1, R1 and R2 are each hydrogen; R3 is —COOH or —COOR4; R4 is an alkyl or aryl moiety; A, B, and D are the substituents of their rings, each of which may be different or the same, and are selected from the group consisting of hydrogen, halogens, alkyl, hydroxy, and alkoxy. This process involves incubating a starting compound having a structure according to Formulae IIA and/or IIB: wherein R3 is —CH3 and R1, R2, A, B, and D are defined above in the presence of a microorganism under conditions effective to produce the product compound. The microorganism can be from the genus Streptomyces, Stemphylium, Gliocladium, Bacillus, Botrytis, Cyathus, Rhizopus, Pycniodosphora, Pseudomonas, Helicostylum, Aspergillus, Mucor, Gelasinospora, Rhodotorula, Candida, Mycobacterium, or Penicilluc. Alternatively, the microorganism can be Cunninghamella baineri.