A total synthesis of the monocyclic sesquiterpene elemol has been accomplished in seven steps and 16.7% overall yield. The key new carbon-carbon bonds were formed by the [2 + 2] photochemical cycloaddition reaction between 2,2,6-trimethyl-4H-1,3-dioxin-4-one and α-terpineol, a reaction that occurred with essentially complete regioselectivity (head/head) and good alkene face selectivity (3.35/1). The 35-38% enantiomeric purity of the starting (-)-α-terpineol was translated into optically active elemol predominating in the unnatural (+) enantiomer (ee = 31-40%). © 1985, American Chemical Society. All rights reserved.