Abstract: Twenty five clerodane diterpenoids were tested for antifeeding activities against fifth instar larvae of Ostrinia furnacalis (Guenee), and the structure-activity relationships were analyzed. Experimental results suggest that stereochemstry is importantfor antifeeding activity while the side chain at C₉ and acetyl group at C₁₈ exhibit certain effects, but a spiroepoxide structure at C₄ seems not important for the activity. The most potent antifeeding clerodane compound had an antifeeding ratio of 57.9% in choice test (250 μg/mL), and 43.2% in no-choice test (500 μg/mL).

Key words: clerodane diterpenoids, Ostrinia furnacalis (Guenee), antifeedant, strucu- ture activity relationship