5,6,7-Trimethylocta-2,5-dien-4-one (3) was suspected of being a trace component smelling of damascone in a crude complex reaction product. Although this trace component eventually turned out to be the constitutional isomer 2-methyl-3-isopropylhepta-2,5-dien-4-one (4), the title compound 3 was found to possess even superior fruity, rosy odor characteristics, reminiscent of apples, plums, raisins ... [Show full abstract] and other dried fruits, and these odor characteristics are, surprisingly, due mainly to its (5Z)-isomer. The synthesis of 3 commenced with the preparation of 1-ethoxyprop-1-yne (11) from 2-chloro-1,1-diethoxyethane (9). Borontrifluoride-catalyzed addition of methyl isopropyl ketone (10) to 11 provided ethyl 2,3,4-trimethylpent-2-enoate (8), which was transformed into the target molecule 3 by Grignard reaction with propen-1-ylmagnesium bromide and in situ enolization. Further derivatives 13−16 provide more insight into the structure−odor correlation of damascone-type odorants, and the use of 3 in perfumery is illustrated by a composition formula of a demonstration perfume.