Biotransformations of terpenes by fungi from Amazonian Citrus genus plants

The biotransformations of R,S-linalool (1), S-citronellal (2), and sabinene (3) with fungi isolated from the epicarp of fruits of Citrus genus of the Amazonian forest (i.e. Citrus limon, Citrus aurantifolia, Citrus aurantium, Citrus paradisiaca) are reported. The more active strains have been characterized and belong to the genus Penicillium and Fusarium. Various biotransformation products have been obtained depending on fungi and substrates. R,S-linalool (1) afforded the E- and Z-furanlinalool oxides (7) and (8) (39 and 37%, respectively) with Fusarium sp. (1D2), 6-methyl-5-hepten-2-one (4) (49%) with F. fujikuroi and 1-methyl-1-(4-methypentyl)-oxiranemethanol (6) (42%) with F. concentricum. S-citronellal (2) gave S-citronellol (12) (36-76%) and S-citronellic acid (11) (5-43%) with Fusarium species while diastereomeric p-menthan-3,8-diols (13) and (14) (20 and 50% yield, respectively) were obtained as main products with Penicillium paxilli. Finally, both Fusarium species and P. paxilli biotransformed sabinene (3) to give mainly 4-terpineol (19) (23-56%) and Z- and E-sabinene hydrates (17) (3-21%) and (18) (11-17%), respectively.