Syntheses and Potato Tuber-inducing Activity of Coronafacic Acid Analogues

Coronafacic acid (1) is an acid component of coronatine, and has been isolated from several pathovars of Pseudomonas syringae. Syntheses of C 6 -non- and C 6 -alkyl-substituted analogues of 1 were accomplished via intramolecular 1,6-conjugate addition as the key step. Among them, 1 and four C 6 -alkyl-substituted analogues exhibited potato tuber-inducing activity, but the C 6 -non-substituted analogue did not. It was revealed that a certain length of the C 6 -alkyl group was necessary to exhibit activity.