The new halolactones and hydroxylactone with trimethylcyclohexene ring obtained through combined chemical and microbial processes

• New compounds: γ,δ-unsaturated ester, γ,δ-unsaturated acid, chloro-, bromo- and iodolactone were synthesized from the racemic (±) α-ionone.
• These halolactones were converted into the hydroxylactone by several fungal strains on the way of hydrolytic dehalogenation.
• The antimicrobial activity of hydroxylactone against bacteria, yeasts and fungi was reported.

The commercially available racemic (±) α-ionone was used as a substrate for the four-step chemical synthesis of three new γ-halolactones. During these processes known α-ionol and new compounds: γ,δ-unsaturated ester ((6E)-5-(2,6,6-trimethylcyclohex-2-en-1-yl)oct-6-en-3-one) (3) and γ,δ-unsaturated acid ((6E)-3-(2,6,6-trimethylcyclohex-2-en-1-yl)hex-4-enoic acid) (4), were obtained as intermediates. γ,δ-Unsaturated acid was used as a substrate for obtaining also new compounds: 5-(1-chloroethyl)-4-(2,6,6-trimethylcyclohex-2-en-1-yl)dihydrofuran-2(3H)-one (5), 5-(1-bromo)-4-(2,6,6-trimethylcyclohex-2-en-1-yl)dihydrofuran-2(3H)-one (6) and 5-(1-iodo)-4-(2,6,6-trimethylcyclohex-2-en-1-yl)dihydrofuran-2(3H)-one (7). At the last step these halolactones were converted into the hydroxylactone by microorganisms. Several fungal strains (Fusarium species, Syncephalastrum racemosum, Botrytis cinerea) were tested. Most of the selected microorganisms transformed these lactones by hydrolytic dehalogenation into a new 5-(1-hydroxyethyl)-4-(2,6,6-trimethylcyclohex-2-en-1-yl)dihydrofuran-2(3H)-one (8), mainly the (+) stereoisomer. The hydroxylactone obtained during biotransformation has been examined for its antimicrobial activity against bacteria, yeasts and fungi. It was found that this compound exhibits growth inhibition against some tested microorganisms. The structure of all the substrates and products was established on the basis of their spectral data.

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