Novel stereoconvergent transformation of 1,2a-disubstituted 1,2,2a,8b-tetrahydro-3H-benzo[b]cyclobuta[d]pyran-3-ones to 1,3-disubstituted 1,2,4a,9b-tetrahydrodibenzofuran-4-ols and its application to the second-generation synthesis of (±)-linderol A

Abstract

1,2a-Disubstituted 1,2,2a,8b-tetrahydro-3H-benzo[b]cyclobuta[d]pyran-3-ones (10) bearing an electron-withdrawing group at the 2a-position were treated with two equivalents of dimethylsulfoxonium methylide to give r-1,t-4a,t-9b-1,3-disubstituted 1,2,4a,9b-tetrahydrodibenzofuran-4-ols (11) stereoconvergently regardless of the stereochemistry of the 1-position on the benzocyclobutapyran ring. This methodology was applied to the second-generation synthesis of (±)-linderol A (12), a melanin biosynthesis inhibitory natural product.