Diastereo‐ and Enantioselective Synthesis of Lignan Building Blocks by Tandem Michael Addition/Electrophilic Substitution of Lithiated α ‐Amino Nitriles to Furan‐2(5H)‐one.

Starting from chiral α-amino nitriles (S,S,R/S)-3, we prepared β-aroyl-γ-butyrolactones (S)-5 as well as 2,3-disubstituted γ -butyrolactones (S,S)- or (R,S,R)-6 in high yields and with high enantiomeric excesses by conjugate addition to butenolide, followed by protonation, α-alkylation or α-aldol addition, respectively. The introduction of one up to three stereogenic centers opens a flexible and highly efficient diastereo- and enantioselective route to 2,3-dibenzylated γ-butyrolactones 6, which proved to be important lignan building blocks.