Abstract A new sesquiterpene ketone (C 15 H 22 O; 2, 4-dinitrophenylhydrazone, mp 227.5) was isolated from the essential oil of Cyperus scarosius R. Br. On hydrogenation it gave a dihydro compound, and on deoxidation it yielded the tricyclic hydrocarbon cyperene. The ketone was synthesized from cyperene by chromic acid oxidation. It is assigned structure I and named cyperenone in view of its relationship to cyperene.
