(±)-Vitrenal (1), a sesquiterpene aldehyde with a novel vitrane skeleton, was synthesized from a monoterpene piperitenone (2) by 12-step reactions in ca. 7% overall yield. 2-Formyl-isocarane, derived from 2 via (±)-isocaran-2-one was allylated stereospecifically and, after protection of the formyl group, the allyl chain was modified to a 4-methoxy-3-butenyl group. Acid treatment of the masked dialdehydic intermediate yielded 1 by concomitant deprotection and aldol condensation.