A new route to enantiopure β-aryl-substituted β-amino acids and 4-aryl-substituted β-lactams through lipase-catalyzed enantioselective ring cleavage of β-lactams

A simple and efficient direct enzymatic method was developed for the synthesis of 4-aryi-substituted beta-lactams and the corresponding beta-amino acid enantiomers through the CAL-B (lipase B from Candida antarctica)-catalyzed enantioselective (E > 200) ring cleavage of the corresponding racemic beta-lactams with 1 equiv. of H2O in i-Pr2O at 60 degrees C. The product (R)-beta-amino acids (ee >= 98%, yields >= 42%) and unreacted (S)-beta-lactams (ee >= 95%, yields >= 41%) could be easily separated. The ring opening of enantiomeric beta-lactams with 18% HCl afforded the corresponding enantiopure beta-amino acid hydrochlorides (ee >= 99%).