Stereoconvergent Transformation of 1,2a-Disubstituted Benzo[<i>b</i>]cyclobuta[<i>d</i>]pyrans to 1,3-Disubstituted Tetrahydrodibenzofuran-4-ols and its Application to the Second-Generation Synthesis of (±)-Linderol A
2a-Disubstituted benzo[b]cyclobuta[d]pyrans, which were prepared by photochemical [2+2] cycloaddition between coumarins and alkenes, were treated with two equivalents of dimethyl-sulfoxonium methylide. 1,3-Disubstitutedtetrahydrodibenzofurans having r-1,t-4a,t-9b stereochemistry were obtained stereoconver-gently regardless of the stereochemistry of the 1-position in the cyclobutane derivatives. This methodology
1,2a-二取代的苯并[b]环丁并[d]吡喃是通过香豆素和烯烃之间的光化学[2+2]环加成反应制备的,用两当量的二甲基亚砜处理。1,3-二取代四氢二苯并呋喃具有 r-1,t-4a,t-9b 立体化学,无论环丁烷衍生物中 1-位的立体化学如何,均以立体收敛方式获得。该方法应用于 (')-linderol A 的第二代合成,这是一种抑制黑色素生物合成的活性天然产物。