A new crystalline sesquiterpene ketone, Cl@i220, a.p. 480, (.a), + 39.9 (c, 3.1) (positive tetranitromethane test) has been isolated In a pure form (TIC and VFC) from the carbonyl fraction of the essential 011 obtained from the tubers of Cvnerus scariosus. We propose to name it as isopatchoulenone (I) because of its structural similarity to patchoulenone' (II). Infrared spectrum of lsopatchoulenone shows two bands of almost'equal intensity at 1663 and 1706 cm-l, which on the basis of its ultraviolet spectrum (&,a~. 243 w, a 14,235) are evidently due to the presence of a conjugated enone chromophore. Isopatchoulenone, however, did not form any semlcarbazone or a 2,4-dinitrophenylhydrazone. On catalytic hydrogenation @'t/acetic acid) it absorbs one mole of hydrogen to give the saturated, crystalline, dlhydroisopatchoulenone, Cl$-i24O, m.p. 74', (H), -28.4' (c, 3.31, which does not give any colcur + Communication No. 810 from the Natlonal Chemical Laboratory, Poona-8, India. 4053 W56 No.45 n.p. and mixed m.p. MOO. Oxidation of this orystalllne alaohol with Joner rragent giver a ketone, a.p. and mired m..p. ao, (a()D + 38O (0, 2.1), identloal ln all rorpectrl with the natural isopatcheulonone (I).