Practical Proline-catalyzed asymmetric Mannich reaction of aldehydes with N-Boc-imines.

This protocol describes a procedure for the synthesis of alpha, beta-branched-b-amino aldehydes via Proline-catalyzed asymmetric Mannich reaction of aldehydes with N-tert-butoxycarbonyl-imines. The crystalline beta-amino aldehydes are formed in good yields and extremely high levels of diastereo- and enantioselectivities without the need for chromatographic purification and are readily oxidized to the corresponding beta-amino acids. The protocol can be completed in approximately 14 h on small scales or up to 30 h on larger scales.