Dipeptides from methionine and S-methylcysteine as chiral ligands for asymmetric Michael reactions

Dipeptides derived from methionine and S-methylcysteine 3a – d have been prepared and screened as chiral ligands in combination with 13 metal salts 4a – m towards the catalysis of an asymmetric Michael reaction of a β-keto ester 1 with methyl vinyl ketone 2 resulting in an optimal ee of 18% achieved with FeCl₃ · 6 H₂O 4c as the metal salt.