Asymmetric Synthesis of Substituted Azetidine Type α- and β-Amino Acids

A versatile asymmetric synthesis of 3-substituted azetidine-2-carboxylic acids and 2-substituted azetidine-3-carboxylic acids via 1,3-amino alcohols with excellent stereoselectivities (de ÷ 96%, ee ÷ 96%) is reported. The high asymmetric inductions were achieved employing the SAMP/RAMP-hydrazone methodology. A phenyl moiety was used as a synthetic equivalent of the carboxylic acid function. In addition, the amino acids prepared were tested as organocatalysts in an asymmetric aldol reaction.