Characterization and synthesis of waxes from homopterous insects

Abstract

Wax (mp 102–103 °C) taken from the cochineal insectDactylopius confusus was saponified to give 11-oxotriacontanoic acid (1) and 15-oxotetratriacontanol (3) in good yields. The structure of these hydrolysis products follows most directly from examination of the mass spectra of the corresponding methyl ester (2) and acetate (4). These spectra are dominated by McLafferty rearrangements initiated by the ketonic carbonyl groups, and resulting in preferential loss of the unfunctionalized hydrocarbon end of the long-chain esters. The structures are confirmed by synthesis of both hydrolysis products via reaction of di-n-nonadecyl cadmium with the appropriate acid chlorides and of the C₆₄ wax ester (5) itself by acid-catalyzed condensation of these moieties. Mass spectral examination of the cochineal wax previously characterized as 15-oxotetratriacontanyl 13-oxodotriacontanoate on the basis of purely chemical evidence confirms the assignment, and the Wooly Alder AphidProciphilus tessalatus is now found to produce the same C₆₆ keto-ester.