Stereoconservative and stereoselective syntheses of rare and non-naturalα-amino acids from (S)-aspartic acid and (S)-malic acid.

A new strategy for stereoconservative and stereoselective syntheses of several types of amino acids starting fromα-functional carboxylic acids employing hexafluoroacetone as protecting and activating reagent is described. Outstanding features of this new method are the mild reaction conditions and the high yields for introduction and cleavage of the protective group allowing sensitive functional groups in the side chain to survive. Furthermore, the new concept results in saving of synthetic steps.