Biocatalytic Synthesis of Sugar-Containing Poly(acrylate)-Based Hydrogels

A chemoenzymatic approach has been developed to prepare monosaccharide-based poly-(acrylate)s. The lipase from Pseudomonas cepacia catalyzed the transesterification of a variety of monosaccharides with vinyl acrylate in pyridine to give the 6-acryloyl esters. The acrylate esters were polymerized in DMF with AIBN to give the poly(acrylate) products. Such a synthetic strategy has led to the synthesis of poly (methyl 6-acryloyl-α-galactoside) with M_w = 135 000 and M_n = 58 000 for a polydispersity of 2.3. The overall yield from methyl α-galactoside was 56%. The polymer was highly water soluble and soluble in polar organic solvents. Replacing the methyl aglycon with phenyl or 2-nitrophenyl moieties resulted in polymers with poor water solubilities and improved organic solvent solubilities. In the case of the phenyl aglycon the polymer was prepared in 40 % isolated yield from phenyl α-galactoside. The poly(phenyl 6-acryloyl-α-galactoside) had an M_w = 52 700 and an M_n = 28 900 for a polydispersity of 1.8. Addition of ethylene glycol dimethacrylate as a cross-linker during AIBN-catalyzed polymerization in DMF resulted in water-insoluble polymers that swelled in aqueous solution. In the presence of 0.3% cross-linker, a poly(methyl 6-acryloyl-α-galactoside-hema) copolymer swelled to contain 98% water and, hence, hold nearly 50-fold its weight in water. Such materials may be useful as biocompatible hydrogels for biomedical and membrane applications.