Structure-Activity Relationship Studies and Development of s-Triazine and Carbamate Anticytokinins

Abstract

The importance of cytokinin antagonists for studies on the mode of action of cytokinins was postulated soon after the discovery of kinetin [16]. Earlier searches had also been made among purine analogues known as metabolic inhibitors. Reportedly examined were 2,6-diaminopurine, 6-mercaptopurine, and even puromycin [3]. Their inhibitory activity was, however, very weak and no specific antagonistic nature could be found. About a decade later anticytokinin activity of 7-substituted-3-methylpyrazolo[4,3-d]pyrimidines (1), a 9-deazaadenine was reported in the tobacco callus assay [5]. Anticytokinin activity has also been noted for 7-deazaadenine structures. The first ones prepared were 4-substituted 7-(β-D-ribofuranosyl)pyrrolo[2,3-d]pyrimidines (2) [7, 8], then 4-substituted-2-methylthio- (3) [19] and 4-substituted-2-methylpyrrolo[2,3-d]pyrimidines (4) [9]. Furthermore, by structural analogy with these compounds, 4-substituted-2-methylthiopyrido[2,3-d)pyrimidines (5), another series of anticytokinins having a fused 6–6 membered ring system have also been developed [10]. These compounds are listed in Fig. 1.