Tebuconazole derivatives are potent inhibitors of strigolactone biosynthesis

To find strigolactone (SL) biosynthesis inhibitors, we screened the azolecontaining chemicals that reduce the level of 2′-epi-5-deoxystrigol (epi-5DS) in rice. As a result of the screening, tebuconazole, a known fungicide targeting ergosterol biosynthesis, was selected as a potent SL biosynthesis inhibitor. A structure-activity relationship study of tebuconazole was carried out to discover more potent SL biosynthesis inhibitors. By evaluating the inhibitory activity on epi-5DS biosynthesis, we found that 2-(2-chlorophenyl)-4-(4-chlorophenyl)-1-(1H-1,2,4-triazol-1-yl) butan-2-ol (4b) and 4-(4-chlorophenyl)-2-(4-phenoxyphenyl)-1-(1H-1,2,4-triazol-1-yl)butan-2-ol (4e) showed potent ability to reduce epi-5DS biosynthesis.