Quantitative structure-activity relationship of cytokinin-active adenine and urea derivatives

A stereochemical model for cytokinin activity

“…They concluded that for the N6-substituted adenines, a maximum in cytokinin activity occurred for those molecules which have an N6-substituent width of 5.2 A. While the size and chemical nature of the N6-substituent are undoubtedly important in the binding of the cytokinins to their appropriate receptors, the hypothesis of Iwamura et al [21] cannot explain the difference in activity of the cis-and transisomers of zeatin because the side-chains of both isomers are similar in size and composition.…”

“…Iwamura et al [21] used an empirical relationship to correlate cytokinin activity to the size of the N6-substituent after accounting for differences in the electronic structure and hydrophobicity of the N6-substituent. They concluded that for the N6-substituted adenines, a maximum in cytokinin activity occurred for those molecules which have an N6-substituent width of 5.2 A.…”

4-Styrylpyrimidines as a new class of cytokinins.

“…Compound 23,being devoid of both such multiple bonds and an electron-donating 2-substituent, was found to be inactive. ll,14 and 21 were exposed to the tobacco callus assay. Since they gave almost the same maximumyields as that of BA, they were new cytokinins;^-substituted derivatives ll, 14 and 21 were significantly more active than parent compound 6 (Fig.…”

Quantitative Structure-Activity Relationships, Conformational Analyses and Computer Graphics Study of Triflumizole Analogs, Fungicidal <i>N</i>-(1-Imidazol-1-ylalkylidene)anilines

“…21) was selected to quantify the electronic effect of substituents on the benzene ring. For the steric properties of X, Y and Z, we examined various combinations of the STERIMOL parameters defined by Verloop et al, 22,23) and the modified indices developed by Iwamura et al [24][25][26] and Mitsutake et a1. 27) The indicator variables which take a value of 1.…”