Poly (vinyl alcohol)-graft-Poly (ethylene glycol) Supported Hydroxyproline: Synthesis and Application in the Enantioselective Aldol Condensation

摘要

L-Proline has served as catalyst in Michael additions, Robinson annulations and aldol condensations among other reactions [1]. Although the chemistry of this amino acid in solution is being intensively investigated, only a limited number of heterogeneous proline-based catalysts have thus far been reported [2-4]. Hydroxyproline is an attractive building block for proline-like catalysts, because immobilization via the hydroxy group leaves the amine and carboxylate functions available for catalysis. Poly (vinyl alcohol)-graft poly (ethylene glycol) (PVA-g-PEG) resins have recently been introduced by our laboratory in solid-phase synthesis [5], supported TEMPO catalysis and in on bead HR-MAS ~1H NMR spectral analysis [6]. Herein we report the preparation of a hydroxyl-proline-based catalyst on PVA-g-PEG resin and its exploration in the asymmetric aldol reaction.