Thermal Acid-Catalyzed Rearrangement of trans-Methyl Chrysanthemate to Lavandulyl Derivatives and Their Effect on Lettuce Seedling Growth

Acid-catalyzed rearrangement of trans-methyl chrysanthemate in aqueous sulfuric acid gave only lavandulyl methyl esters at room temperature and a mixture of unsaturated γ- and δ-lactones at 130 °C. Acid-catalyzed methanolysis afforded the methoxylavandulyl methyl ester and its isomer methyl 2,2-dimethyl-3-(2-methoxy-2-methylpropyl)cyclopropanecarboxylate. The starting material was obtained from a mixture of cis/trans-chrysanthemic acid by lactonizing the cis isomer to cis-dihydrochrysant-hemo-δ-lactone which was separated and then esterifying the trans chrysanthemic acid. It was found that the δ-lactone, certain lavandulyl methyl esters, and certain unsaturated γ- and δ-lactones displayed potent inhibitory effect on root elongation and lettuce seed germination at 10^-4and 10^-5M concentrations. The relation of structure and lettuce seedling growth inhibitory activity is discussed. Structural determination of the saturated δ-lactone was carried out by single-crystal X-ray diffraction analysis.