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

(-)-(1S,2R,3R,4S)-1,2-Epoxy-1-methyl-4-(1-methylethyl)-cyclohex-3-yl acetat e has previously been identified as the active compound of Minthostachys to mentosa responsible for the insecticidal activity against Oncopeltus fascia tus. Its structure was initially assigned on the basis of spectral data. In order to confirm the structure and to define the stereochemistry, stereose lective synthesis of its enantiomer, (+)-(1R,2S,3S,3R)-1,2-epoxy-1-methyl-4 -(1-methylethyl)-cyclohex-3-yl acetate, starting from (R)-(-)piperitone, wa s carried out using a Sharpless reaction as the key step. The natural produ ct is dextro-rotatory while the synthetic product is levo-rotatory. Measure ments of insecticidal activities of the different steroisomers revealed tha t only the natural product is active. (C) 2001 Elsevier Science Ltd. All ri ghts reserved.