Synthesis and activity of 3-oxo-α-ionone analogs as male attractants for the solanaceous fruit fly, Bactrocera latifrons (Diptera: Tephritidae).

Abstract

A series of 3-oxygenated α-ionone analogs have been developed as highly specific male lures for the solanaceous fruit fly Bactrocera latifrons, a pest of solanaceous fruits. We compared the attractant and phagostimulant activities of analogs with or without (i) unsaturations at the 4,5- and/or 7,8-positions and (ii) oxygen moieties at the 3- and/or 9-positions of the ionone molecule. Since naturally occurring vomifoliol (V2) was found to induce a highly potent phagostimulant activity in B. latifrons males, related analogs including dehydrovomifoliol (V1), 6-hydroxy-α-ionone (U1), and 6-hydroxy-α-ionol (U2) were synthesized to evaluate their attractant and phagostimulant activities. Synthetic V1, V2, U1, and U2 exhibited low attractant activity, but their phagostimulant activity was relatively high. Optical isomers of 3-oxo-7,8-dihydro-α-ionone (P3) and V1 were prepared to examine the stereochemical specificity of attractants. (+)-(6R)-P3 and (+)-(6S)-V1 exhibited the corresponding activities, while their respective antipodal enantiomers were found entirely inactive.