Different Ways to Lardolure Precursors: Application of Enzymatic Methods

Seven-membered lactones which possess alkyl or substituted alkyl groups in different positions are interesting pheromone precursors.[1] Such a compound is (-)-lardolure (1), the aggregation pheromone of the acarid mite, Lardoglyphus konoi,[2] which was prepared in a thirteen-step synthesis starting from the racemic lactone 2 by Mori et al.[3] The resolution of the hydroxycarboxylic acids (+)-5 and (–)-5 via the diastereomeric precursors 4a and 4b was the key reaction of this synthesis (scheme 1). The enzymatic Baeyer-Villiger oxidation of the ketone 6 (scheme 2) and the kinetic resolution of the racemic lactone 2 with an esterase (scheme 3) could be alternative ways for a shorter synthesis of the hydroxyacids (+)-5 and (–)-5, respectively.