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.