Clothianidin, a neonicotinoid insecticide, has been found by former Agro Division, Takeda Chemical Industries, Ltd. (Sumitomo Chemical Co., Ltd., at present) and codeveloped with Bayer CropScience. During the studies on neonicotinoid insecticides, nitenpyram (an open-chain nitromethylene derivative) was prepared first, showing a potent activity against Hemiptera and Thysanoptera pests, and its modification led to clothianidin (a nitroguanidine derivative). Clothianidin exhibits excellent control efficacies in small amounts for a wide variety of insect pests such as Hemiptera, Thysanoptera, Coleoptera, Lepidoptera, and Diptera for the long term, with excellent systemic action and by a variety of application methods. The structural features of clothianidin are a thiazole ring and an open-chain guanidine skeleton. The structure-activity relationships of guanidine derivatives and the synthetic studies of clothianidin are also discussed.

Nitroguanidine derivatives with thiazol‐5‐ylmethyl moieties were prepared and their insecticidal activities against homopterous pests were tested. New synthetic routes for 2‐chloro‐5‐chloromethylthiazole from 2,3‐dichloro‐1‐propene and for substituted nitroguanidines from S‐methyl‐N‐nitroisothiourea were established. Biological evaluation led to a novel insecticide (E)‐1‐(2‐chlorothiazol‐5‐ylmethyl)‐3‐methyl‐2‐nitroguani dine (TI‐435) which has a broad activity spectrum and is under development. ©1999 Society of Chemical Industry

We identified two phenylquinazoline compounds in a large-scale screening for cytokinin antagonists in yeast expressing the Arabidopsis cytokinin receptor cytokinin response 1/histidine kinase 4 (CRE1). After chemical modifications, we obtained compound S-4893, which non-competitively inhibited binding of the natural ligand 2-isopentenyladenine to CRE1. S-4893 antagonized cytokinin-induced activation of the Arabidopsis response regulator 5 promoter in Arabidopsis. Importantly, S-4893 had no detectable intrinsic cytokinin agonist activity in Arabidopsis or in the transformed yeast system. Cytokinin bioassay further demonstrated that S-4893 antagonized cytokinin-induced stimulation of callus formation and inhibition of root elongation. S-4893 also promoted seminal, crown and lateral root growth in rice, suggesting that S-4893 could potentially promote root growth in a variety of agronomically important plants. We believe S-4893 will be a useful tool in functional studies of cytokinin action in a wide range of plants and a lead compound for the development of useful root growth promoters in agriculture.