Absolute configuration of a new mosquito repellent, (+)-eucamalol and the repellent activity of its epimer.

(+)-Eucamalol (1) and (-)-1-epi-eucamalol (2) were synthesized from (S)-(-)-perillaldehyde to determine the absolute configuration of 1, the structure of natural (+)-eucamalol being determined to be (1R,6R)-(+)-3-formyl-6-isopropyl-2-cyclohexen-1-ol. (+)-Eucamolol (1) and its 1-epimer (2) exhibited significant repellent activity against Aedes albopictus, and inhibited its feeding as well as DEET.