Preparation and Absolute Configuration of (−)‐(E)‐α‐trans‐Bergamotenone

The synthesis, absolute configuration, and olfactive evaluation of (−)‐( E )‐α‐ trans ‐bergamotenone (= (−)‐(1′ S ,6′ R , E )‐5‐(2′,6′‐dimethylbicyclo[3.1.1]hept‐2′‐en‐6′‐yl)pent‐3‐en‐2‐one; (−)‐ 1 ), as well as its homologue (−)‐ 19 are reperted. The previously arbitrarily attributed absolute configuration of 1 and of (−)‐α‐ trans ‐bergamotene (= (−)‐(1 S ,6 R )‐2,6‐dimethyl‐6‐(4‐methylpent‐3‐enyl)bicyclo[3.1. 1]hept‐2‐ene; (−)‐ 2 ), together with those of the structurally related aldehydes (−)‐ 3a,b and alcohols (−)‐ 4a,b , have been rigorously assigned.