During a search for insect antifeeding substances from plant, we found that the benzene extracts of the leaves of m futokadzura Sieb. et Zucc. showed an sntifeeding activity against the larvae of Suodoutera litura F. An active principle has been isolated from the benzene extracts 1) end named piperenone. We wish to report here on the structure of piperenone. Piperenone (I) had m.p. 86-88', -1 2, Ml, -129' (c, 1.16, MeOH), C22H2806 (Mt 388), Smax2) 1687, 1642, 1596 and 1515 cm and 'max 232, 280 and 285(sh) nm (&, 16600, 3640 and 3240). The spectral data suggested that I had a substituted benzene and an u,e-unsaturated carbonyl group. That the substituted benzene was a veratryl function was indicated by the NMR spectrum 2) of I (a 3.85 and 3.87, each 3H, s and 6.8-6.9, 3H, overlap). This was confirmed by oxidation of I with potassium permsnganate affording veratric acid. In addition to the veratryl function, the NMR spectrum of I revealed the presence of a moiety CH3-FH-:H-(O)-(a 0.98, 3H, d, J='IHz; 2.90, IH, dq, J=ll, 7Hz and 4.12, lH, d, J=llHz), an isolated methylene group (5 2.63 and 3.29, W, ABq, J=17Hz) and two aliphatic methoxy groups (5 3.40 and 3.53, each 3H, s). The remaining six protons were interrelated by decoupling experiments, indicative of a moiety -CH=t-CH2-CH=CH2.