Recent Research Developments

Index of Recent Research News
August 17th, 2005
Hoye and Ryba Describe a Desymmetrization Strategy for the Synthesis of a (+)-Peloruside A Fragment

    "Divergent Kinetic Control of Classical vs. Ozonolytic Lactonization: Mechanism-based Diastereoselection," Hoye, T. R.; Ryba, T. D. J. Am. Chem. Soc. 2005, 127, 8256-8257.

    Abstract: A strategy has been developed in which mechanistically distinct lactonization reactions are used to prepare diastereomeric d-lactones relevant to the C1-C9 fragment of (+)-peloruside A. Depending upon which of two reaction types is used, the central (C5) hydroxyl group can be directed to differentiate the C1 vs. C9 termini of pseudosymmetric substrates to provide diastereomeric lactones (3-trans vs. 3-cis). Thus, the 5-hydroxy-1,9-diester substrate 1 (an azelaic ester) cyclizes under classical (acid- or base-catalyzed) lactonization conditions to give a predominance of the 3-cis diastereomer, whereas the 5-hydroxy-1,10-diene congener 2 provides the opposite sense of diastereoselectivity when subjected to ozonolytic lactonization (O3, MeOH, NaOH, at -78 C). Thus, this underutilized oxidative transformation is mechanistically orthogonal to the classical reaction.

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