AJUGATAKASIN-A AND AJUGATAKASIN-B, NEW DITERPENOIDS FROM AJUGA-DECUMBENS, AND FEEDING STIMULATIVE ACTIVITY OF RELATED NEOCLERODANE ANALOGS TOWARD THE TURNIP SAWFLY

Adults of the turnip sawfly, Athalia rosae ruficornis, are strongly at tracted to the leaves of Ajuga decumbens (Labiatae). Specific feeding stimulants of the sawfly were examined in the leaf surface extracts of A. decumbens. Among seven neoclerodane diterpenoids isolated from the extracts, two new analogs, ajugatakasins A and B, were characterized as 6 alpha,18-diacetoxy-1 beta,12-ditigloyloxy-4 alpha,17-epoxyneocler od-13-en-15,16-olide and its 1 beta,12-di-(2-methylbutanoyl)-oxy analo g, respectively. Among these analogs, clerodendrin D, a very minor con stituent which possesses a tetrahydrofurofuran moiety, was identified as the feeding stimulant for A. rosae ruficornis, while the other anal ogs with an alpha,beta-unsaturated gamma-lactone moiety were found to be completely inactive in the sawfly feeding test.