Abstract:
The 3-O-fatty acid ester derivatives (C-12-C-18) of two pentacyclic triterpenic acids, ursolic acid and oleanolic acid, were synthesized under mild esterification conditions in excellent yields (80-85%) and screened for their antifeedant activity, together with the parent acids, against the agricultural pest tobacco caterpillar larvae (Spodoptera litura F) in a no-choice laboratory study. The Urs-12-ene-28-carboxy-3beta- octadecanoate and olean-12-ene-28-carboxy-3beta-hexadecanoate were found to exhibit exceptionally potent antifeedant activities at 50 mug/cm(2) concentration, even after 48 h.