Translation of a Polar Biogenesis Proposal into a Radical Synthetic Approach: Synthesis of Pleurocin A/Matsutakone and Pleurocin B.

A synthetic approach to recently reported and structurally unique 11(9→7) abeo-steroids pleurocin A/matsutakone (1) and pleurocin B (2) was developed by reconsidering the originally suggested polar transformations of their biogenesis. An intricate radical cyclization of a late stage intermediate followed by an oxidative quench was used instead and forged the abeo-framework, while the 9,11-seco-motif was obtained by conversion of ergosterol into a 9,11-secoenol ether employing a mercury-free desaturation of the Treibs type, an oxidative bond scission preluding a dioxa-[4+2]-cycloaddition of an aldehyde to an enone and a combined transacetalization/elimination followed by an ionic hydrogenation.