New Three-Step Syntheses of Racemic and Optically Active Ipsdienol from Myrcene.

Abstract
2-Methyl-6-methylene-3,7-octatriene-2-ol (6), which is readily available from photooxidation of myrcene, was transformed into racemic and optically active ipsdienol [pheromone of Ips typographus, a pest in conifer forests]. Treatment of the trienol 6 with perchloric acid in acetic acid yielded ipsdienyl acetate, which on hydrolysis gave racemic ipsdienol in 83% overall yield. Oxidation of the trienol 6 with pyridinium chlorochromate in the presence of pyridine hydrochloride furnished 2-methyl-6-methylene-2,7-octadien-4-one in 43% yield. Reduction of this ketone with lithium aluminium hydride partially decomposed by 1 molar equivalent each of ethanol and either (R)-(+)- or (S)-(-)-2,2''-dihydroxy-1,1''-binaphthyl gave (R)-(-)- or (S)-(+)-ipsdienol (2'' or 2", respectively) in 70% yield and 60 -65% ee [enantiomeric excess].