Effect of further substitutions at 5-, 6-, 7-, or 8-position of 3-[3-(4-methoxyphenyl)-1-hydroxyprop-2-yl]coumarin on phytotoxicity.

Derivatives of the coumarin ring in ()-3-[3-(4-methoxyphenyl)-1-hydroxyprop-2-yl]coumarin , which is a lignan structure, were synthesized to clarify their structure-phytotoxicity relationships. The growth-inhibitory activity of the 8-OCH derivative (IC=228 µM) was more potent against the roots of lettuce seedlings than the compound without substituents . As for the roots of Italian ryegrass seedlings, the presence of the methoxy group at the 7- or 8-position was extremely effective for inhibiting growth (7-OCH : IC=121 µM, 8-OCH : 56.7 µM). Methyl derivatives at the 5- or 8-position showed activity levels similar to those of the compound without substituents (5-CH : IC=214 µM, 8-CH : IC=225 µM). The activities of OH- and F-derivatives were not observed or were lower.