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 2oxazoline derivatives with pendent (2 S ,4 S )‐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 1 H and 31 P NMR spectroscopy and GPC measurements. Subsequently, these polymers were successfully utilized as a polymeric support for the asymmetric hydrogenation of 1) ( Z )‐ α ‐acetamido cinnamic acid and 2) methyl ( Z )‐ α ‐acetamido cinnamate in water, showing 90 % substrate conversion at 25 °C within 20 minutes at atmospheric H 2 pressure (1 bar) for methyl ( Z )‐ α ‐acetamido cinnamate.