Effect of Cl-Substitution on Rooting- or Cytokinin-like Activity of Diphenylurea Derivatives

Twenty-eight Cl-substituted diphenylurea derivatives differing in either the number and the position of the substituents, or in the type of substitution, that is, symmetric or asymmetric, were synthesized. Their hypothetical enhancement of rooting activity was assayed using the mung bean shoot bioassay; their possible cytokinin-like activity was assesed using the betacyanin (so-called “amaranthin”) accumulation test and the tomato regeneration test. Seven Cl-substituted diphenylurea derivatives (2E, 4A, 4B, 4E, 4G, 6A, 6B) having two substituted phenyl rings showed the capacity to enhance adventitious root formation in mung bean shoots. Furthermore the presence of a halogen substituent was not sufficient to reach the adventitious rooting activaties shown by the N,N′-bis-(2,3-methylenedioxyphenylurea) and the N,N′-bis-(3,4-methylenedioxyphenylurea), two diphenylurea derivatives for which an interaction with auxin was the first reported in enhancing adventitious root formation. Seven compounds (1B, 3E, 3D, 4B, 4E, 4F, 6B) showed cytokinin-like activity and three of them (4B, 4E, 6B) also evidenced rooting activity, once more demonstrating the wide action spectrum of diphenylurea derivatives.