Abstract: The sulfonylurea herbicides have been characterized by broad-spectrum of weed control at ultra-low dosage of application, good crop selectivity and low mammalian toxicity. Because of its high herbicidal activity, phototoxicity of sulfonylurea herbicides residues to succeeding crops and weed resistance has become the very important factors affecting its further development in China. In order to search for more environmental-benign sulfonylurea herbicides and study their structure-activity relationship, on the basis of study on a new sulfonylurea herbicide N-[(4'-methyl) pyrimidin-2'-yl]-2-nitro-phenylsulfonyl urea, also called monosulf uron, under commercialization in China, 19 novel sulfonylurea compounds modified at the bridge of urea and 3 related aminopyrimidines were synthesized. The structures of all compounds synthesized were confirmed by elemental analysis and ¹H NMR. Preliminary herbicidal activity of the new sulfonylurea compounds derived from sulfonylurea bridge was determined by ALSscreening in vitro and pot bioassay experiment (in vivo). The results indicate that some compounds show good activities against ALS in vitro from Pisum sativum L. and Brassica napus L..

Key words: Sulf onylurea, Aminopyrimidine, Synthesis, Herbicidal activity