Synthesis and absolute configuration of the male aggregation pheromone of the stink bug Erysarcoris lewisi (Distant), (2 Z,6 R,1′ S,5′ S)-2-methyl-6-(4′-methylenebicyclo[3.1.0]hexyl)hept-2-en-1-ol

Abstract

The structure including the absolute configuration of the male-produced aggregation pheromone of the stink bug Erysarcoris lewisi (Distant) was determined to be (2 Z,6 R,1′ S,5′ S)-2-methyl-6-(4′-methylenebicyclo[3.1.0]hexyl)hept-2-en-1-ol 1 by bioassay and comparison of the 1H NMR spectrum of the natural pheromone with those of (2 Z,6 R,1′ S,5′ S)- and (2 Z,6 R,1′ R,5′ R)-isomers. These two diastereomers were synthesized from the corresponding ketones (6 R,1′ S,5′ R)- and (6 R,1′ R,5′ S)- 2, which were prepared by lipase-catalyzed asymmetric acetylation of a mixture of (6 R,1′ S,4′ S,5′ R)- and (6 R,1′ R,4′ R,5′ S)-7′-norsesquisabinen-4′-ol 3. The absolute configuration of ketone 2 was assigned by its CD comparison with (1 R,5 S)-sabina ketone 4. An alternative synthesis of (2 Z,6 R,1′ S,5′ S)- 1 was achieved without recourse to enzyme by employing Hodgson’s diastereoselective intramolecular cyclopropanation as the key step.