Abstract
Racemic [(±)-4-isopropyl-1-methyl-7-oxa-cis-bicyclo[4.3.0]non-4-en-8-one] and optically active δ,ε-unsaturated lactones [(-)-(1R,6R)-4-isopropyl-1-methyl-7-oxabicyclo[4.3.0]non-4-en-8-one and (+)-(1S,6S)-4-isopropyl-1-methyl-7-oxabicyclo[4.3.0]non-4-en-8-one)] with the p-menthane system were obtained and their odoriferous properties were evaluated. Biotransformations of the racemic lactone with three fungal strains: Absidia cylindrospora AM336, Absidia glauca AM177 and Syncephalastrum racemosum AM105, were carried out. Microbial transformations afforded hydroxylactones with the hydroxy group in the allylic position.
Highlights
Lactones with the p-menthane system constitute a large group of naturally occurring and synthetic compounds
As a continuation of our interest in the synthesis of odoriferous and biologically active lactones [10], here we present the synthesis of racemic and enantiomeric pairs of new, -unsaturated lactones with the p-menthane system
The terpenoid lactone (±)-2 was obtained in good yield (92%) by dehydrohalogenation of -iodo-γlactone (±)-1, which was synthesized from racemic trans-piperitol as described earlier (Scheme 1) [21]
Summary
Lactones with the p-menthane system constitute a large group of naturally occurring and synthetic compounds. The introduction of the hydroxy group into a molecule often leads to changes in its biological activity Examples of such dependence are well-documented in the literature, especially among monoterpenes, e.g., limonene and carveol, sabinene and sabinol, α-pinene and verbenol [12,13,14,15]. This information inspired us to check the influence of the hydroxy group in the lactones obtained on their odoriferous properties. The aforementioned fungal strains were applied to transform the racemic , -unsaturated lactone (±)-2
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