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Synthesis of (-)-6,7-Dideoxysqualestatin H5 by Carbonyl Ylide Cycloaddition-Rearrangement and Cross-electrophile
Younes Fegheh-Hassanpour1, Tanzeel Arif1, Herman O Sintim1
1Department of Chemistry, Chemistry Research Laboratory, University of Oxford , Mansfield Road, Oxford OX1 3TA, United Kingdom.
Abstract:
An asymmetric synthesis of (-)-6,7-dideoxysqualestatin H5 is reported. Key features of the synthesis include the following: (1) highly diastereoselective n-alkylation of a tartrate acetonide enolate and subsequent oxidation-hydrolysis to provide an asymmetric entry to a β-hydroxy-α-ketoester motif; (2) facilitation of Rh(II)-catalyzed cyclic carbonyl ylide formation-cycloaddition by co-generation of keto and diazo functionality through ozonolysis of an unsaturated hydrazone; and (3) stereoretentive Ni-catalyzed Csp3-Csp2 cross-electrophile coupling between tricarboxylate core and unsaturated side chain to complete the natural product.
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