title: A new approach to the side chain formation of 24-alkyl-22-hydroxy steroids: application to the preparation of early brassinolide biosynthetic precursors.
abstract: A new synthetic route to 22S-hydroxy-24R-methyl steroids has been developed and applied for the preparation of cathasterone, (22S)-hydroxycampesterol, and 6-deoxocathasterone, which are precursors in the early stages of the biosynthesis of brassinolide. The construction of the steroid side chain with the correct stereochemistry at C-24 is based on the use of Claisen rearrangement. The introduction of the 22-hydroxyl group has been achieved by epoxidation of the Δ(22)-double bond, nucleophilic opening of the intermediate mesyl epoxide with sodium sulfide, and desulfurization of the formed tetrahydrothiophenes with Raney nickel.
authors.affiliation: Institute of Bioorganic Chemistry, National Academy of Sciences of Belarus, Kuprevich Str., 5/2, 220141 Minsk, Belarus.
authors.forename: Alaksiej L
authors.initials: AL
authors.lastname: Hurski
authors.forename: Vladimir N
authors.initials: VN
authors.lastname: Zhabinskii
authors.forename: Vladimir A
authors.initials: VA
authors.lastname: Khripach
mesh_terms: D060406:Brassinosteroids / Q000737:chemistry*; D004852:Epoxy Compounds / Q000737:chemistry; D009682:Magnetic Resonance Spectroscopy; D013058:Mass Spectrometry; D013256:Steroids / Q000737:chemistry*; D013260:Steroids, Heterocyclic / Q000737:chemistry*
chemical_list: D060406:Brassinosteroids; D004852:Epoxy Compounds; D013256:Steroids; D013260:Steroids, Heterocyclic; C023623:brassinolide