Catalytic Asymmetric Total Synthesis of Schibitubin G and Revision of Its Absolute Configuration

The first total syntheses of dibenzylbutane-type lignan shibitubin G, and of its enantiomer, were achieved from commercially available vanillin. A key catalytic asymmetric Michael addition reaction was used to introduce the C8′ chiral center of this natural product. The absolute configuration of natural schibitubin G was revised to 8′S based on the X-ray crystallographic analysis of 14, and by comparing optical rotations of both synthetic samples with that of natural schibitubin G.