New brassinosteroid analogs having nitrogenated functionalities at C3 to provide more information about the brassinosteroid-receptor interaction

An efficient synthesis of different brassinosteroid derivatives with an azide or an amine function at C3 without any function at C2 and their biological activity evaluation in the rice lamina inclination test is described. The key step in the synthetic strategy involves a nucleophilic substitution by azide of an activated 3beta-OH followed by reduction to amine. The activity elicited by 7 and 9 having an azide group, in contrast with the residual ones elicited by their corresponding amines, suggests that the 3alpha-OH group of an active brassinosteroid could act as acceptor in the putative hydrogen bonding interaction with the receptor/s. (C) 2004 Elsevier Ltd. All rights reserved.