Streamlined, Asymmetric Synthesis of 8,4'-Oxyneolignans

Highly direct, modular syntheses of several natural 8,4¢-oxyneolignans [(-)-1, (+)-1, (-)-2, and (-)-3] and some related variants [(-)-26, (+)-26, (+)-27, and (-)-28] are reported. Utilizing (S)- or (R)-methyl lactate as the chiral sources, two complementary syn- or anti-oriented routes were designed, encompassing nine and five steps, which were carried out to deliver the targets in an enantiomerically pure form. The embodiment of the two independent aryl and aryloxy moieties onto the lactate frame was performed according to a diversity-oriented protocol from the common precursors, aldehydes 6 and ent-6 for the syn-oriented routes and mesyl esters 19 and ent-19 for the anti-oriented routes. These syntheses set the stage for the generation of a wide and diverse repertoire of 8,4¢-oxyneolignan compounds and the broad biological interrogation of its members.