title: Synthesis of fatty acyl derivatives of 24-epibrassinolide.
abstract: A number of fatty acid (palmitic, myristic and lauric) esters (both 3α- and 3β-isomers) of epibrassinolide has been prepared as reference compounds for metabolic studies. Selective protection of the three of four hydroxyl groups of epibrassinolide was successively performed first as cyclic 22,23-methylboronates and then as 2α-benzyl ethers. α,β-Inversion of C-3 hydroxyl group was achieved through a consecutive oxidation-reduction reactions or by a nucleophilic substitution of the 3α-mesylates. Treatment of the 3α- and 3β-alcohols with palmitic, myristinic or lauric acid chlorides gave the corresponding esters. The hydrolysis of 22,23-methylboronates was performed after their transformation into 2-hydroxy-1,3,2-dioxaborolanes using a cation exchange column with DOWEX 50WX8 in NH4(+) form. Hydrogenolysis of the benzyl ethers catalyzed by palladium yielded the target compounds. This article is part of a Special Issue entitled "Synthesis and biological testing of steroid derivatives as inhibitors".
authors: Institute of Bioorganic Chemistry, National Academy of Sciences of Belarus, Kuprevich str., 5/2, 220141 Minsk, Belarus. Electronic address: khripach@iboch.bas-net.by.
authors: Vladimir A
authors: VA
authors: Khripach
authors: Vladimir N
authors: VN
authors: Zhabinskii
authors: Dmitrii V
authors: DV
authors: Tsavlovskii
mesh_terms: D060406:Brassinosteroids / Q000138:chemical synthesis* / Q000737:chemistry; D005227:Fatty Acids / Q000138:chemical synthesis* / Q000737:chemistry; D009682:Magnetic Resonance Spectroscopy; D013058:Mass Spectrometry; D010084:Oxidation-Reduction; D013260:Steroids, Heterocyclic / Q000138:chemical synthesis* / Q000737:chemistry
chemical_list: D060406:Brassinosteroids; D005227:Fatty Acids; D013260:Steroids, Heterocyclic; C023623:brassinolide
keywords: Brassinosteroids; Cyclic methylboronates; Epibrassinolide metabolites; Fatty acid esters