brassinosteroids with very high specific activity is reported. A 3H-labeled 24-epicastasterone was isolated in high yield (40 mCi), radiochemical purity (>97%) and a specific activity up to 99 Ci mmol−1. The labeling strategy was designed to employ a radiolabeling step at the late stage of the synthetic sequence.
Regioselective oxyfunctionalization of brassinosteroids by methyl(trifluoromethyl)dioxirane: Synthesis of 25-hydroxy-brassinolide and 25-hydroxy-24-epibrassinolide by direct C-H insertion
作者:Brunhilde Voigt、Andrea Porzel、Dieter Golsch、Waldemar Adam、Günter Adam
DOI:10.1016/0040-4020(96)00587-x
日期:1996.8
The direct oxyfunctionalization of suitable brassinosteroid derivatives at position 25 using methyl(trifluoromethyl)dioxirane is reported. Whereas reaction with tetraacetyl brassinolide led after deprotection directly to the desired 25-hydroxy-brassinolide, in the (24R) series the 22,23-isopropylidenedioxy derivative has been shown to be a suitable precursor for the 25-hydroxylation leading to 25-