Lactones 41.† Synthesis and Microbial Hydroxylation of Unsaturated Terpenoid Lactones with p-Menthane Ring Systems
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.
Terpenoid lactones with the p‐menthane system as feeding deterrents to the lesser mealworm, Alphitobius diaperinus
The application of antifeedants, often in combination with other methods within integrated pest management (IPM) strategies, has proven to be a good way to control insect pests. Little is known about compounds that have antifeedant activity against the lesser mealworm, Alphitobius diaperinus Panzer (Coleoptera: Tenebrionidae). The antifeedant properties of optically pure isomers of pulegone and isopulegol and some enantiomeric pairs of bicyclic terpenoid lactones with the p‐menthane system, derived from these isomeric starting compounds, were studied in choice and no‐choice tests with the lesser mealworm. The original monoterpenes and γ‐spirolactones were weak feeding deterrents to larvae and adults of A. diaperinus. The δ‐hydroxy‐γ‐spirolactones showed significant activity against adults, but substituting the hydroxy group with a ketone group considerably reduced the deterrent activity of the resulting δ‐keto‐γ‐spirolactones. The bicyclic γ‐hydroxy‐δ‐lactones with condensed rings and with the (1S,6R,8R)‐(+) and (1R,6S,8S)‐(–) configuration of the chiral centres, and δ‐hydroxy‐γ‐lactone (1S,4S,6S)‐(+) were very strong antifeedants to both larvae and adults. The hydroxy groups and the configuration of the chiral centres of the molecules were very important features for determining the antifeedant activity of the lactones tested. Generally, the compounds studied were better antifeedants to adults than to larvae.
Alkylation of aralkyl bromides with tetra alkyl tin compounds in presence of (2,2′-bipyridine)fumaronitrile palladium(0)
(2,2′-bipyridine)fumaronitrile palladium(0) acts catalytically in the alkylation of benzylic halides with tetra alkyl tin even for an alkyl halide with hydrogen atoms on a sp3 carbon β to the leaving group.