Identification of α-Santalenoic and Endo β-Bergamotenoic Acids as Moth Oviposition Stimulants from Wild Tomato Leaves

The presence of oviposition-stimulating phytochemicals in hexane extracts of whole leaves of wild tomato (Lycopersicon hirsutum) accession LA 1777 was indicated by oviposition preference assays with gravid female Heliothis zea (Boddie) moths. Three sesquiterpenes isolated from these extracts were identified as (+)-(E)-α-santalen-12-oic acid (la), (+)-(E)-endo-β-bergamoten-12-oic acid (2a), and (-)-CE)-endo-α--bergamoten-12-oic acid (3a). Structure assignments based primarily on ¹H and ¹³C NMR spectral interpretations were confirmed by conversion to the parent sesquiterpene hydrocarbons and subsequent comparisons with authentic endo-β-ber-gamotene and/or literature data. The identity of la was verified by comparison of its methyl ester (lb) with a sample synthesized from (+)-α-santalol (9). Quantitative assays demonstrated that the two major sesquiterpene acids, 1a and 2a; are the principal oviposition stimulants in the tomato leaf extracts and that the activity of 2a is about twice that of la.