Study On The Synthesis Of Propionyl Brassinolide

Propionyl brassinolide,developed by Tama Biochemical Co.,Ltd.of Japan,is one of the plant growth regulators which can not only promote the plant cell division,regulate plant growth and development,but also enhance the capability of cold resistance with combating drought and the salt-tolerance of crops.It can also applicable in the periods of plants.Propionyl brassinolide has the advantages of wide spectrum,good safety,high efficiency and long persistence.Therefore,propionyl brassinolide has broad market prospects and the study of synthesis of propionyl brassinolide is important.The relevant reported synthetic routes of propionyl brassinolide were reviewed according to literature and one of them was determined to study in this paper.The stigmasterol was used as the starting material followed by sulfonylation and hydrolysis reaction to obtain i-stigmasterol which then was oxidized with Jones chromic acid to give the intermediate C-6 ketone.The propionyl brassinolide was prepared by ring-opening rearrangement,dihydroxylation,dipropionylation,epoxidation and Baeyer-Villiger oxidation rearrangement reaction of C-6 ketone.The structures of resulting product and intermediates produced from the above reactions had been characterized by ¹H NMR,¹³C NMR,IR and MS.A comprehensive study of the reaction condition and synthetic process of propionyl brassinolide,including the reaction time,material ratio,temperature,the kind of solvent and post-treatment technology,etc.,was proceeded.The total yield of the first three steps was of 72.16%（based on stigmasterol）with the products of sulfonylation and hydrolysis reaction without purification.The yield of dihydroxylation has been increased by 8%（e.e.96%）by adding the chiral ligand.The reacting time of the Baeyer-Villiger oxidation rearrangement reaction was reduced from 2 weeks to 3 days by optimizing the reactive conditions.The suitable purification method for the crude target compound was established to ensure the content of product was more than 95%.The optimized synthesis process of propionyl brassinolide is mild,the operation is simple,and the yield is stable with the total yield of the target compound propionyl brassinolide was 10.94%（based on stigmasterol）.The result of our study can provide a reference for the synthesis of propionyl brassinolide.