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Synthesis of (−)-6,7-Dideoxysqualestatin H5 by Carbonyl Ylide Cycloaddition–Rearrangement and Cross-electrophile Coupling

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posted on 2017-06-19, 23:03 authored by Younes Fegheh-Hassanpour, Tanzeel Arif, Herman O. Sintim, Hamad H. Al Mamari, David M. Hodgson
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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