An Efficient Total Synthesis of (2E,4E,7R)-Farnesa-2,4,10-triene from (R)-(+)-Citronellal

(2E,4E,7R)-farnesa-2,4,10-triene(Caparratriene) ( 1 ), a novel sesquiterpene hydrocarbon with significant growth inhibitory activity against CEM leukemia cells, was first synthesized from (R)-(+)-citronellal ( 2 ) by employing titanium-induced intermolecular carbonyl-coupling as the key step. The absolute configuration of (+)-Caparratriene was determined to be 7R.