Synthesis of 6,6′-Binaphthopyran-2-one Natural Products: Pigmentosin A, Talaroderxines A and B

Efficient and stereoselective syntheses of pigmentosin A, talaroderxine A, and its diastereomer talaroderxine B are reported. The binaphthyl ring system is assembled by vanadium-catalyzed phenolic coupling of tricyclic precursors. These key intermediates were prepared by Michael–Dieckmann annulation of a protected orsellinate ester, with the requisite pyranones accessed by a new variant of Ghosez’s sulfone-epoxide annulation. Preliminary biological experiments are reported for pigmentosin