Syntheses of Several Compounds Related to Helminthosporol and their Plant Growth-regulating Activities

Several compounds related to helminthosporol (I), a natural plant-growth promoter, were prepared from I and their plant-growth regulating activities were examined together with those of the derivatives reported in the previous paper, using rice and lettuce seedlings. Among the compounds tested, helminthosporic acid (III) exhibited marked elongation effect to the shoot growth of rice and lettuce seedlings, whereas the effect of I was specific to the former. Results of the biological test are reported in details.