Ruthenium-catalyzed enyne metathesis in stereoselective preparation of cyclic 1-amino-1-carboxylic acids

Abstract

Abstract Stereoselective syntheses of α-amino acids are described. The α-carbon of the amino acid is incorporated into a five- or six-membered ring which is a conjugated diene with one exocyclic double bond. Enynes were intermediates for the metathesis cyclization reaction effected by ruthenium(II)-catalysis. The enyne substrates were available in stereochemically pure form by stepwise alkylations of the chiral auxiliary ( R )-2,5-dihydro-3,6-dimethoxy-2-isopropylpyrazine with bromo-alkenes and -alkynes.