Convenient synthesis and cytokinin activity of β-substituted 4-styrylpyridines, the simplest cytokinin analogs with a moderate cell division-promoting activity

Article abstract of DOI:10.1021/jf9502313

Designed synthesis of Z- and E-isomers of β-substituted 4-styrylpyridines as cytokinin analogs was conveniently achieved by nucleophilic and electrophilic addition of ethanol, methyl mercaptan, and hydrogen halides (HCl, HBr, and HI) to 4-(phenylethynyl)pyridine prepared by palladium-catalyzed coupling. They easily underwent E-Z photoisomerization under monochromatic UV light or sunlight. A tobacco callus assay revealed that the Z-isomers were more active than their E-isomers and that the Z-ethoxy derivative, which showed the highest activity among the β-substituted 4-styrylpyridines, was one-fifth as potent as kinetin. The Z-ethoxy derivative also promoted betacyanin biosynthesis of Amaranthus seedlings at 4-100 μM.