Cytokinins: Synthesis and growth-promoting activity of 2-substituted compounds in the N⁶-isopentenyladenine and zeatin series

Fourteen compounds were tested for relative promotion of cell division and growth (cytokinin) activity in the tobacco bioassay. The results suggested that 2-substituted-N⁶-(hydroxy)isopentenylaminopurines were generally less active than their unsubstituted couterparts. Thus, a 2-OH substituent greatly lowered cytokinin activity in both the isopentenyl and hydroxyisopentenyl (zeatin) series, while 2-NH₂ and 2-SCH₃ groups had a lesser effect on activity and a 2-Cl substituent had a negligible effect. Mass spectra were determined for all of the 9-β-d-ribofuranosides and for a number of the purines as well; the fragmentation patterns were consistent and characteristic, providing a possible systematic approach to the identification of new 2-substituted-N⁶-(hydroxy)isopentenyladenines.