l -0-cis-Cinnamoyl-β-D-glucopyranose, an allelochemical isolated from Spiraea thunbergii, exhibits potent plant growth inhibitory activity. cis-Cinnamic acid is the essential portion structure of 1-0-cis-cinnamoyl-β-D-glucopyranose responsible for the growth inhibitory activity. cis-Cinnamic acid exhibited potent inhibitory activity against the elongation of lettuce roots, and the half maximal effective concentration (EC_<50>) of cis-cinnamic acid was 2.2 μM. In this project we adopted cis-cinnamic acid as a novel lead compound, and examined the structure-activity relationship of cis-cinnamic acid to develop the environmentally friendly agrochemical. Moreover, we synthesized the fluorescent probes of cis-cinnamic acid aiming at the clarification of the mechanism of the activity expression. At first, we synthesized 1-0-cis-cinnamoyl-β-D-glucopyranose by the Hanessian protocol, and the synthetic compound showed similar inhibitory activity (EC_<50> 6.4 μg/mL) with that of the natural product (EC_<50> 4.0 μg/rnL). Next, we synthesized the cis-cinnamic acid analogues, and evaluated the inhibitory activities on the elongation of lettuce roots. Some analogues were found to be more potent than cis-cinnamic acid. Moreover, we found that the analogues having an oxime ether substituent at the meta position on the aromatic ring maintained strong inhibitory activity even if a sterically bulky substituent was on the ether moiety. This result is very important for the probe design because the direct substitution on the aromatic ring with the bulky ether group resulted in loss of the activity. The synthesis of the fluorescent probes, in which the core cis-cinnamic acid was connected with a fluorescent group with the oxime linkage, was achieved, and some probes exhibited potent inhibitory activity comparable to cis-cinnamic acid.