Synthesis of asymmetrical methyl‐branched chiral ketones from the corresponding homologous wax esters. A new synthesis of the insect pheromone lardolure and of 9‐norlardolure

The insect pheromone (2 R 4 R 6 R ,8 R )‐4,6,8‐trimethyl‐2‐undecyl formate (lardolure, 7c ) and (2 R ,4 R ,6 R ,8 R )‐4,6,8‐trimethyl‐2‐decyl formate (9‐norlardolure, 7b ) have been synthesized from the corresponding homologous chiral methyl‐branched esters 1b and 1c , which have been obtained from the preengland wax of the domestic goose Anser a. f. domesticus. The intermediate (4 R ,6 R ,8 R )‐4,6,8‐trimethyl‐2‐undecanone ( 4c ) and (4 R ,6 R ,8 R )‐4,6,8‐trimethyl‐2‐decanone ( 4b ), the (2 R )‐alcohols 5c and 5b , as well as some analogous compounds, have been characterized. 9‐Norlardolure ( 7b ) shows a weak pheromone activity.