GC/FT-IR Analysis of Novel 4,6,9-Triene and 2,4,6,9-Tetraene Occurring in a Female Pheromone Gland of <i>Arctia plantaginis</i> (Erebidae: Arctiinae)

Abstract

Fifteen subspecies of the wood tiger moth, Arctia plantaginis (Lepidoptera: Erebidae: Arctiinae), have been recorded in the Northern Hemisphere. An analysis of crude pheromone extracts by GC equipped with an electroantennographic (EAG) detector showed four EAG-active components (Comps. I – IV ) that were commonly involved in the pheromone glands of two subspecies inhabiting Japan and Finland. Comp. I is a major component (>75%) and the others are minor components (3% - 15%). Their mass spectra, measured by GC/MS, revealed the chemical structures of C 21 unsaturated hydrocarbons as follows: 3,6,9-triene for Comp. I , 4,6,9-triene for Comp. II , 1,3,6,9-tetraene for Comp. III , and 2,4,6,9-tetraene for Comp. IV . Comps. I and III are known Type II pheromone compounds, and their retention times coincide with those of the authentic standards with all Z configurations. As a next step, the extract was analyzed by GC/FT-IR to determine the configuration of Comps. II and IV . Their IR spectra showed two characteristic C-H bending absorptions around 990 and 945 cm - 1 due to the conjugated dienyl moieties; thus, Z and E configurations were assigned to the double bonds at the 2- and 4-positions, respectively. Their Z double bonds at the 6- and 9-positions are indicated by no absorptions around 970 cm - 1 , due to the isolated double bonds with E configurations. Finally, the structures of Comps. II and IV were confirmed by synthesis using a double Wittig reaction. The synthetic (4 E ,6 Z ,9 Z )-4,6,9-triene and (2 Z ,4 E ,6 Z ,9 Z )-2,4,6,9-tetraene showed strong EAG activity, and their chemical data coincided well with those of the natural Comps. II and IV , indicating the correctness of the structure determination by GC/FT-IR analysis and its usefulness for Type II pheromone compounds.