Stereoselective synthesis of α-amino acids where the α-carbon of the amino acid is incorporated into a five-, six-or seven-membered ring is described. The stereoselective control results from stepwise bisalkenylation of (R)-2, 5-dihydro-3, 6-dimethoxy-2- isopropylpyrazine. Ring closing metathesis was effected by ruthenium (II)-catalysis. The spiro-cycloalkene intermediates were further transformed into 1-aminocycloalkene-1- ...
