Synthesis of Brassinolide Analogs with or without the Steroidal Side Chainf

Abstract

Four brassinolide analogs were synthesized starting from cholesterol, stigmasterol or pregnenolone. An analog possessing a hydroxyl group at C-17 instead of the steroidal side chain was only 0.001% as active as brassinolide upon lamina-inclination testing with rice seedlings, while other analogs were 1-2% as active as brassinolide. This indicates the indispensable role of the side chain for the plant growth-promoting activity of brassino-steroids.