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.