Isourea and triazinone derivatives as related to their ability to stimulate rice seedling growth

TA 4-ethoxy-1-(p-tolyl)-s-triazine-2,6 (1H, 3H)-dione] wasprepared chemically by intramolecular cyclization of IU 2-ethyl-3-methoxycarbonyl-1-(p-tolylcarbamoyl)-isourea],which has been reported to be an effective GA-synergist. TAalone slightly stimulated the shoot growth of rice seedlings,and in combination with GA showed a distinctly synergistic effecton the growth of rice shoots. The results suggest that TA andIU are nearly equal in their physiological activity. From theresults of the rice seedling test of these two compounds andtheir analogs, structure-activity relationships of isoureaswere correlated with those of triazinones. The results of applicationof IU, at 100 mg/liter to rice seedlings followed by extractionand silica gel thin-layer chromatography, suggested that IUwas biologically converted into its closed-ring form, TA, whichis a stable and potent GA-synergist. Thus, isoureas like IUseem to be easily converted into their counterparts, triazinones,in rice tissues. ¹ This paper is Part III in the series "Plant growth-regulatingactivities of isourea derivatives and related compounds." ² Permanent address: Agricultural Chemicals Research Laboratories,Sankyo Co., Ltd., Hiro-machi, Shinagawa-ku, Tokyo 140, Japan. ³ Present address: Higashi-Osaka Junior College, Nishitsutsumigakuen,Higashi-Osaka 577, Japan. (Received February 21, 1977; )