Synthesis of insect trail pheromones: The isomeric 3-butyl-5-methyloctahydroindolizines

The syntheses of the geometrical isomers of 3-butyl-5-methyloctahydroindolizine are described. These compounds, reported as trail pheromones of Pharaoh ants, Monomorium pharaonis (L.), cannot be distinguished from each other by physical data alone and assignments must therefore be based on unambiguous synthesis. Routes to these compounds via suitably constituted dialkylpiperidines and a sequence involving a dialkylpyrrole are described. Infrared and nmr spectral data are presented. These data are examined for their potential in conformaational analyses of these compounds.