DIONCOPHYLLINE-A AS A GROWTH-RETARDING AGENT AGAINST THE HERBIVOROUS INSECT SPODOPTERA-LITTORALIS - STRUCTURE-ACTIVITY-RELATIONSHIPS

Dioncophylline A (1) represents a novel insecticidal agent, as documen ted by its enhanced growth-retarding effect on larvae of the polyphago us pest insect Spodoptera littoralis. Within the scope of the work des cribed here, the potential of this as yet most active naphthylisoquino line alkaloid was further elucidated by the preparation and testing of selected analogues. Investigation of a broad series of structurally m odified dioncophylline A analogues (2-20) revealed the free amine func tion to be essential for the growth inhibitory effect, whereas a modif ication of the OH function partially led to a distinct increase of act ivity. In particular, the 8-O-alkyl (especially 8-O-benzylated) deriva tives (14 and 15 as well as 16-19) displayed pronounced effects. In th e case of 8-O-(p-bromobenzyl)dioncophylline A (16), the activity of th e natural parent compound dioncophylline A (1) (EC50 = 277 mu g/g fres h wt of diet; concentration that inhibits larval growth by 50%) was ev en improved by a factor of >15 (EC50 = 15.6 mu g/g fresh wt).