Petuniolides. Unusual ergostanoid lactones from Petunia species that inhibit insect development

Abstract

Four new compounds that strongly contribute to the resistance of Petunia parodii and P. integrifolia against feeding by larvae of the lepidopteran, Heliothis zea, were isolated from leaves of these plant species. These consist of the (22R,24R)-22,24,25-orthoacetates and orthopropionates derived from multiply functionalized ergostanoids in which the A-ring has lost one carbon and has been converted into a spirolactone. An epoxy group is present at position 6α,7α. Petuniolides A (11) and B (12) have a Δ⁹⁽¹¹⁾-12α-acetoxy group whereas petuniolides C (13) and D (14) possess the corresponding allylic ketone functionality. The molecular structures of (12) and (14) were determined by X-ray crystallography.