6-Substituted Indanoyl Isoleucine Conjugates Mimic the Biological Activity of Coronatine

The 6-substituted indanoyl isoleucine conjugates of type 12 are potent elicitors of plant secondary metabolism and tendril coiling. The 6-substituted indanoyl carboxylic acid is available in four steps from 1,2,3,4-tetrahydronaphthalene (6). Key steps of the synthesis involve double acylation of 6 followed by oxidative cleavage and intramolecular Friedel−Crafts acylation of the resulting dicarboxylic acid 10. The conjugate with isoleucine (12) triggers volatile biosynthesis in the Lima bean at 10 µM and coiling of the touch-sensitive tendrils of Bryonia dioica at 20 µM.