Isolation, structural assignment and insecticidal activity of (1S,2R,3R,4S)1,2-epoxy-1-methyl-4-(1-methyl)cyclohex-3-yl acetate, a natural product from Minthostachys tomentosa

Abstract

[EN] (-)-(1S,2R,3R,4S)-1,2-Epoxy-1-methyl-4-(1-methylethyl)-cyclohex-3-yl acetate has previously been identified as the active compound of Minthostachys tomentosa responsible for the insecticidal activity against Oncopeltus fasciatus. Its structure was initially assigned on the basis of spectral data. In order to confirm the structure and to define the stereochemistry, stereoselective synthesis of its enantiomer, (+)-(1R,2S,3S,3R)-1,2-epoxy-1-methyl-4-(1-methylethyl)-cyclohex-3-yl acetate, starting from (R)-(-)piperitone, was carried out using a Sharpless reaction as the key step. The natural product is dextro-rotatory while the synthetic product is levo-rotatory. Measurements of insecticidal activities of the different steroisomers revealed that only the natural product is active.