Synthesis of vinylic iodides for incorporation into the C17-C27 fragment of bryostatins |
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Authors: | Thomas Gregson Eric J. Thomas |
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Affiliation: | The School of Chemistry, The University of Manchester, Manchester, M13 9PL, UK |
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Abstract: | Vinylic iodides were identified as useful intermediates for the synthesis of the C17-C27 fragment of the bryostatins with control of the geometry of the exocyclic methoxycarbonylmethylene group. Following literature precedent, the Piers (E)-stereoselective addition of tributyltin hydride to an alkynoate followed by ester reduction and tin-iodine exchange gave vinylic iodides that could be used to form the C20-C21 bond of the bryostatins. Chelation controlled addition of lithiated 3-silyloxypropynes to 2-alkoxyaldehydes followed by reductive iodination was used to prepare vinylic iodides that could be used in the complementary assembly of the C21-C22 bond of the bryostatins. Initial studies of the synthesis of intermediates for metathesis studies using metal catalysed reactions of a vinylic iodide for C21-C22 bond formation were complicated by cyclisation reactions. |
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Keywords: | Stereoselective synthesis Conjugate addition Vinylic iodides Chelation control Tin-iodine exchange |
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