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Khripach VA, Zhabinskii VN, Parkhimovich KV, Gyliakevich OV: [Synthesis of brassinolide and its biosynthetic precursors using methyl-3-hydroxy-2-methylpropionate]. Bioorg Khim. 2009 Mar-Apr;35(2):260-9.
Formal synthesis of plant hormones that belong to the group of 24alpha-methylbrassinosteroids, including brassinolide and its biosynthetic precursors with one hydroxyl group in their side chain, was performed. Stereochemistry of a methyl group at the C24 atom was provided by the choice of the desired enanthiomer of methyl-3-hydroxy-2-methylpropionate and by the sequence of its conversions into the chiral intermediate that was necessary for the formation of the C23-C28 fragment of the side chain. The (22R,23R)-diol group was introduced by the Sharpless asymmetric dihydroxylation of the intermediate delta22-steroids, the products of consecutive reactions of attachment of a low-molecular sulfone to the steroid C22-aldehyde, acetylation, and reductive desulfurization of the intermediate beta-acetoxysulfones. Reduction of 22-acetoxy-23,25-disulfones was shown to proceed with the preservation of the functional group at atom C22. |
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