Indanoyl amino acid conjugates: Tunable elicitors of plant secondary metabolism

The unassuming nature of plants belies their viciously effective defensive strategies in the face of herbivore attack. Under the direction of, among others, octadecanoid hormones, plants respond by producing phytoalexins, bitter and toxic alkaloids, protease inhibitors, and even volatile compounds that call predatory insects to the herbivores. A rational design of 4-oxoindanoyl amino acid conjugates based on the phytotoxin, coronatine, as a structural guide resulted in a series of highly active compounds which turn on defensive systems in much the same way as octadecanoid hormones. The developments in the syntheses of indanoyl amino acid conjugates have created easy access to substantial amounts of a variety of such compounds. When these compounds were tested in biological systems, they showed abilities to induce defensive responses that surpassed octadecanoid hormones. In addition, small changes in the structures of these compounds resulted in large differences in the particular defensive systems that were activated. lndanoyl amino acid conjugates are promising tools in photoaffinity approaches towards the macromolecular targets of octadecanoids and their subcellular localization. Owing to the strong activation of plant defense or their efficient induction of fruit abscission which facilitates mechanical harvest, the compounds are promising candidates for future application in agriculture. (C) 2003 The Japan Chemical journal Forum and Wiley Periodicals, Inc.