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

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

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(R)-3,7-Dimethyl-2-methylene-6-octenyl chlorideC11H19Cl[α]D20=-18.7 (c 1.56, CHCl3)Source of chirality: (R)-citronellal (97% ee)Absolute configuration: (R)

(2R,6R)-1-Chloro-6,10-dimethyl-5-methylene-9-undecen-2-olC14H25ClO[α]D20=-9.7 (c 1.21, CHCl3)Source of chirality: (R)-citronellal (97% ee) and (R)-epichlorohydrin (98% ee)Absolute configuration: (2R,6R)

(6R,1′S,4′R,5′R)-2-Methyl-6-(4′-hydroxybicyclo[3.1.0]hexyl)hept-2-eneC14H24O[α]D21=+11.7 (c 1.04, CHCl3)Source of chirality: (R)-citronellal (97% ee) and (R)-epichlorohydrin (98% ee)Absolute configuration: (6R,1′S,4′R,5′R)

(6R,1′S,5′R)-2-Methyl-6-(4′-oxobicyclo[3.1.0]hexyl)hept-2-eneC14H22O[α]D21=+23.5 (c 1.12, CHCl3)Source of chirality: (R)-citronellal (97% ee) and (R)-epichlorohydrin (98% ee)Absolute configuration: (6R,1′S,5′R)

(2Z,6R,1′S,5′S)-2-Methyl-6-(4′-Methylenebicyclo[3.1.0]hexyl)hept-2-en-l-olC15H24O[α]D22=-52.7 (c 1.14, hexane)Source of chirality: (R)-citronellal (97% ee) and (R)-epichlorohydrin (98% ee)Absolute configuration: (2Z,6R,1′S,5′R)