Synthesis and cytokinin activity of (R)-(+)- and (S)-(−)-dihydrozeatins and their ribosides

Abstract

Abstract (R)-(+)- and (S)-(−)-dihydrozeatins [(R)-(+)- and (S)-(−)-6-(4-hydroxy-3-methylbutylamino)purines, 1a and 1b ] and their ribosides {(−)-6-[(R)-4-hydroxy-3-methylbutylamino]- and (−)-6-[(S)-4-hydroxy-3-methyl-butylamino]-9-β- D -ribofuranosylpurines, 3a and 3b } were synthesized and tested for their cytokinin activity by four bioassay systems, the growth of tobacco callus, the seed germination of lettuce, the fr. wt increase of excised radish cotyledons and the retardation of chlorophyll degradation in radish cotyledons. In tobacco callus bioassay, 1a was more active than 1b . The ribosides 3a and 3b were not less active than their corresponding aglycones 1a and 1b . In other bioassays used the activity followed the order: 1a > 3a > 1b > 3b . In tobacco callus bioassay and lettuce seed germination, trans -zeatin [6-(4-hydroxy-3-methylbut- trans -2-enylamino)purine] showed stronger cytokinin activity than 1 a .