CONVENIENT SYNTHESIS AND CYTOKININ ACTIVITY OF BETA-SUBSTITUTED 4-STYRYLPYRIDINES, THE SIMPLEST CYTOKININ ANALOGS WITH A MODERATE CELL DIVISION-PROMOTING ACTIVITY

Designed synthesis of Z- and E-isomers of beta-substituted 4-styrylpyr idines 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 pa lladium-catalyzed coupling. They easily underwent E-Z photoisomerizati on under monochromatic UV light or sunlight. A tobacco callus assay re vealed that the Z-isomers were more active than their E-isomers and th at the Z-ethoxy derivative, which showed the highest activity among th e P-substituted 4-styrylpyridines, was one-fifth as potent as kinetin. The Z-ethoxy derivative also promoted betacyanin biosynthesis of Amar anthus seedlings at 4-100 mu M.