Molecularly imprinted polymeric adsorbents for byproduct removal

In this study, both diastereo- and enantioselective adsorbents for a dipeptide derivative were prepared using a molecular imprinting technique. The diastereo- and enantioisomers for the dipeptide derivative N-(benzyloxy-carbonyl)aspartylphenylalanine methyl ester (ZAPM), in addition to the alpha- and beta-isomers, were chosen as test compounds for the investigation of the imprinting effect. The close similarities between the structures of different isomers make it possible to interpret the roles of template structure on specific molecular recognition. A highly specific byproduct scavenger was prepared by simultaneously incorporating methacrylic acid and vinylpyridine as functional monomers. The binding selectivities of polymeric adsorbents for the alpha- and beta-isomers are shown to be greatly enhanced by introducing enantiocomplementarities into the polymer matrixes. An anti-beta-L,L-ZAPM polymer was applied in a solid-phase extraction protocol, for the purification of the product in the chemical synthesis of N-protected aspartame. Finally, polymer beads were also imprinted against beta-L,L-ZAPM using suspension polymerization performed in perfluorocarbon fluid. The imprinted polymer beads displayed the same binding characteristics as the imprinted bulk polymer and can be envisaged for the use of product purification in chromatographic mode.