New Bromo- and Iodo-Hydroxylactones with Two Methyl Groups Obtained by Biotransformation of Bicyclic Halolactones

Abstract

The subject of the research was to determine the ability of the filamentous fungi to biotransform bicyclic halolactones containing two methyl groups in their structure. By chemical synthesis three bicyclic halolactones with two methyl groups, one in the cyclohexane ring and one in the lactone ring, were obtained: 2-chloro-4,7-dimethyl-9-oxabicyclo[4.3.0]nonan-8-one, 2-bromo-4,7-dimethyl-9-oxabicyclo[4.3.0]nonan-8-one, and 2-iodo-4,7-dimethyl-9-oxabicyclo[4.3.0]nonan-8-one. These compounds were formed as mixtures of two diastereoisomers. The obtained halolactones (as mixture of two diastereoisomers) were subjected to screening biotransformation with the use of eight strains of filamentous fungi: Fusarium culmorum AM10, F. avenaceum AM12, F. semitectum AM20, F. solani AM203, Absidia coerulea AM93, A. cylindrospora AM336, Penicillium chermesinum AM113, P. frequentans AM351. Two of the substrates, 2-bromo-4,7-dimethyl-9-oxabicyclo[4.3.0]nonan-8-one and 2-iodo-4,7-dimethyl-9-oxabicyclo[4.3.0]nonan-8-one, were hydroxylated without removing the halogen atom from the molecule, giving 2-bromo-7-hydroxy-4,7-dimethyl-9-oxabicyclo[4.3.0]nonan-8-one, 2-bromo-5-hydroxy-4,7-dimethyl-9-oxabicyclo[4.3.0]nonan-8-one, and 2-iodo-7-hydroxy-4,7-dimethyl-9-oxabicyclo[4.3.0]nonan-8-one as products. The hydroxylation capacity was demonstrated by strains of Absidia cylindrospora AM336, Fusarium avenaceum AM12, and F. solani AM203. The structures of all lactones were determined on the basis spectroscopic data.