Department of Entomology, University of California, Riverside CA-92521, USA.
Short, efficient syntheses yielding products of very high isomeric purity have been developed for (10E,12E,14Z)-hexadeca-10,12,14-trienal 1 and the (10E,12E,14E)-isomer 2, the key pheromone components of the tobacco hornworm moth Manduca sexta. The penultimate EEZ-trienol, and aldehyde 1, were freed from isomeric impurities by selective reaction of the impurities with tetracyanoethylene. EEE-aldehyde 2 was prepared by Wittig reaction of (2E,4E)-hexa-2,4- dienyltriphenylphosphonium bromide with 10-acetoxydecanal, deprotection, selective crystallization of the EEE-trienol from the resulting mix of isomers, and oxidation. The yield of the EEE-trienol was increased further by iodine-catalyzed isomerization of the mix of isomers in the liquor, and further recrystallization.