Enantioselective Total Syntheses of Manginoids A and C and Guignardones A and C.

An enantioselective synthetic approach for preparing manginoids and guignardones, two types of biogenetically related meroterpenoids, is reported. This bioinspired and divergent synthesis employs an oxidative 1,3-dicarbonyl radical-initiated cyclization and cyclodehydration of the common precursor to forge the central ring of the manginoids and guignardones, respectively, at a late stage. Key synthetic steps include silica-gel-promoted semipinacol rearrangement to form the 6-oxabicyclo[3.2.1]octane skeleton and the Suzuki-Miyaura reaction of vinyl bromide to achieve fragment coupling. This synthesis protocol enables the asymmetric syntheses of four fungal meroterpenoids from commercially available materials.