Synthesis and Plant Growth-Inhibiting Activity of Pyridine derivatives

A number of 3-pyridyl-2-propenoic acid derivatives, pyridines possessing a γ-butyrolactone ring and related compounds were synthesized and evaluated for their activity by using a lettuce seedling test. Most of the pyridine derivatives inhibited the growth of lettuce seedlings at concentrations ranging from 10 to 100 ppm. In the pyridine analogs of cinnamic acid, the 4-pyridine analog is more active than the 2- and 3-isomers. Of the 3-(4-pyridyl)propenoic acid derivatives examined, the N, N-diethyl-3-(4-pyridyl)-2-propenamide 3c-3 was the most active, which caused more than 90% inhibition of the hypocotyl and root growth at 50 ppm. Pyridine analogs with a 1,4-butanediol showed activity comparable to that of pyridyl γ-butyrolactone compounds, suggesting that the presence of the γ-butyrolactone was dispensable for the activity.