J. Pestic. Sci., 31(4), 405–408 (2006)

Chiral 3,3a,5,9b-tetrahydro-2H-furo[3,2-c][2]benzopyrans (TFBs) were synthesized and some of them were found to be herbicidally active against annual paddy weeds through intensive structure–activity relationship studies. These compounds were synthesized from D-glucose, which was used as a natural chiral source. This was the result of a series of studies based on the findings that certain benzyl ethers (e.g. cinmethylin) had herbicidal activity. Further investigation revealed that (2R,3S,3aS,9bR)-2-ethyl-3-(2-fluorobenzyloxy)6,7-methylenedioxy-3,3a,5,9b-tetrahydro-2H-furo[3,2c][2]benzopyran (MT-147) was the one of the most active compounds and seemed to have suitable herbicidal characteristics as a graminicide for paddy rice (Oryza sativa L.). Barnyardgrass (Echinochloa crus-galli L.) is one of the dominant annual weed species in paddy rice fields in Japan. Although preliminary tests indicated that MT-147 was a possible herbicidal agent to control barnyardgrass, detailed characterization of this compound has not been accomplished. It is useful to evaluate herbicidal activity under different conditions in order to understand herbicidal characteristics because herbicidal activity and phytotoxicity usually fluctuate depending on environmental and cultural factors. It is known that herbicidal activity and phytotoxicity usually change at the leaf stage of target plants, water depth and transplanting depth. In this study, the effect of several test conditions on the herbicidal activity of MT-147 was examined to clarify the characteristics of this compound. Herbicides registered for paddy rice in Japan are mostly combinations consisting of two to five active ingredients. It is important to examine the compatibility of certain herbicides with other compounds to develop effective combination products. During our preliminary investigation, bromobutide was found to increase the herbicidal activity for MT-147; therefore, the effects of this compound on the herbicidal activity of MT-147 are also reported here. J. Pestic. Sci., 31(4), 405–408 (2006) DOI: 10.1584/jpestics.G06-21