Amphiphilic polymer supports for the asymmetric hydrogenation of amino acid precursors in water

This paper describes the synthesis and characterization of a new class of amphiphilic, water-soluble diblock copolymers based on 2-oxazoline derivatives with pendent (2S,4S)-4-diphenylphosphino-2-(diphenylphosphinomethyl)pyrrolidine (PPM) units in the hydrophobic block. The synthetic strategy involves the preparation of a diblock copolymer precursor with ester functionalities in the side chain; which were converted into carboxylic acids in a polymer-analogous step and finally reacted with the PPM ligand. The structures of the copolymers were characterized by H-1 and P-31 NMR spectroscopy and GPC measurements. Subsequently, these polymers were successfully utilized as a polymeric support for the asymmetric hydrogenation of 1) (Z)-alpha-acetamido cinnamic acid and 2) methyl (Z)-alpha-acetamido cinnamate in water, showing 90% substrate conversion at 25degreesC within 20 minutes at atmospheric H-2 pressure (1 bar) for methyl (Z)-alpha-acetamido cinnamate.