Both enantiomers of secoisolariciresinol and enantiopure (-)-enterolactone
were synthesized through a highly stereoselective convergent synthesis.
An Evans diastereoselective alkylation followed by a substrate-induced
diastereoselective α-alkylation of the newly formed optically
active β-benzyl-γ-butyrolactone gave the β-β′ linkage
of the target skeleton. The (S,S)- and (R,R)-enantiomers of secoisolariciresinol
and (-)-enterolactone were obtained in 12-14% (11
steps) and 20% (7 steps) overall yield, respectively.
total synthesis - natural product - lactones - asymmetry - diastereoselective alkylation
