Concise enantio- and diastereoselective synthesis of α-hydroxy-α-methyl-β-amino acids

Reported here is an efficient procedure for enantio- and diastereoselective synthesis of pure β-amino acids that display a tert-hydroxyl functionality in the α-position. Key steps include a catalytic asymmetric aldol reaction and a modified Curtius rearrangement to form oxazolidinone intermediates, which are chemoselectively opened to furnish N-protected α-hydroxy-α-methyl-β-amino acids. A modified work-up procedure of the aldol reaction allows for recovery of up to 90% of bisoxazolinyl ligands from the catalysts.