Chapter 6 - Synthetic Aspects of Brassinosteroids

Abstract The isolation of brassinolide in 1979 opened a new era in research on phytohormones. To date, more than 70 related compounds called as brassinosteroids (BS) have been found in natural sources. Extensive studies of BS revealed their multiple physiological properties ranging from enhancing effects on yield and quality of crops, significant role in stress protection of plants, to antiviral, antifungal, and antiproliferative properties in animal systems. Taking into account their vanishingly small content in plants, chemical synthesis is the only source of BS both for scientific and practical purposes. A wide range of chemical problems has been solved since BS studies started. Some compounds of this series have found a practical application and became commercially available. Current investigations of BS are greatly focused on understanding the molecular and cellular basis of their effects both in plants and in animals. In this respect, the role of chemists working with BS has changed from the solution of purely synthetic problems to meeting the needs of other scientists engaged in BS studies. Although different aspects of BS research have been reviewed repeatedly during the recent period, there were practically no publications summarizing the results of chemical efforts for a period longer than 10 years. The present review will cover the developments that have taken place in the BS synthesis since the publication of the monograph (Khripach V.A., Zhabinskii V.N., de Groot A. Brassinosteroids. A New Class of Plant Hormones . San Diego, CA: Academic Press; 1999), where early synthetic works on BS had been summarized. The main attention will be paid to the synthesis of BS analogs and derivatives for biochemical and immunoanalytical studies as well as stereoselective approaches to brassinolide.