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