Stereoselective synthesis of the C14-C23 fragment of biselyngbyolide A and B enabled by transition metal catalysis.

Transition met al catalysis has enabled the highly stereoselective and protecting group-free synthesis of the C14-C23 fragment of the apoptosis-inducing natural products biselyngbyolide A and B. A Pd-catalyzed Stille reaction between a vinyl stannane and a crotyl carbonate formed the skipped diene with complete control of the the trisubstituted bond and excellent control over the branched/linear products. A Cu-catalyzed Stahl oxidation was used to form the requisite aldehyde needed for a Ag-catalyzed asymmetric allylation. The latter provided the final fragment with excellent stereochemical control.