Enantioselective total synthesis and structural assignment of callyspongiolide?

Organic & Biomolecular Chemistry Pub Date: 2016-10-20 DOI: 10.1039/C6OB02051H

Abstract

We have elucidated the complete absolute configuration of callyspongiolide and unambiguously assigned its stereochemistry at the C-21 center through synthesis. Four stereoisomers of callyspongiolide were synthesized in a convergent and enantioselective manner. A late-stage Sonogashira coupling forges the diene-ynic side chain. Other notable reactions are Yonemitsu's variation of Yamaguchi macrolactonization to cyclize an alkynic seco acid, highly trans-selective Julia–Kocienski olefination, CBS reduction to set the C-21 stereocenter, and methyl cuprate addition to an unsaturated pyranone to install the C-5 methyl center.

Graphical abstract: Enantioselective total synthesis and structural assignment of callyspongiolide
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