ThemethanolicextractfromaChineseendemicChrysanthemumplant,Dendranthemaindicumvar.aromaticum,wasfoundtoshowhighantifeedingactivityagainstPierisbrassicaeL.,andbybioassay-guidedseparation,theactivecomponent,B-ring-homo-tonghaosu,2-(2',4'-hexadiynylidene)-1,6-dioxaspiro-[4,5]-dec-3-ene(2)wasisolated.Itsstructurewaselucidatedbycomparingitsspectroscopicdatawiththoseof2reportedintheliteratures.FurthermorenewconvenienttotalsynthesismethodsofB-ring-homo-tonghaosuwerealsodevelopedtoconfirmitsstructureandmakeitsfurtherapplicationincropprotectionavailable.Inaddition,extensivecomparisonofspectroscopicdatashowedthatthestructureofcompound21reportedinliteratureshouldberevisedto2.
