Phenylalanine anilide

Fig. 6-2. Preparation of MIPs using L-phenylalanine anilide (L-PA) as template. The L-PA model system.

The isotherms for the two enantiomers of phenylalanine anilide were measured at 40, 50, 60 and 70 C, and the data fitted to each of the models given in Equations (1-3) [42]. The isotherms obtained by fitting the data to the Langmuir equation were of a quality inferior to the other two. Fittings of the data to the Freundlich and to the bi-Langmuir equations were both good. A comparison of the residuals revealed that the different isotherms of d-PA were best fitted to a bi-Langmuir model, while the... 

Scheme 15.3 Noncovalent imprinting of L-phenylalanine anilide in a methacrylic acid (MAA)/ethylene glycol dimethylcrylate (EGDMA) polymer matrix. Adapted from Sellergren et al. (1998). Copyright 1988 American Chemical Society.

MIP assays can also be utilized in synthetic organic applications. For example, MIP-based assays have been used to measure the chiral purity of samples in organic solvents. An L-phenylalanine anilide (l-PAA) imprinted polymer was utilized as a recognition element to measure the enantiomeric excess (ee) of PAA samples (Chen and Shimizu 2002). The MIP displays greater capacity for l-PAA versus d-PAA samples of similar concentration, and this difference was used to estimate enantiomeric excess. The enantiomeric excess of an unknown solution was determined by comparing the UV absorbance of the PAA remaining in solution after equilibration against a calibration curve. This MIP assay was demonstrated to be rapid and accurate with a standard error of +5% ee. 

Chen YB, Kele M, Sajonz P, Sellergren B, Guiochon G. Influence of thermal annealing on the thermodynamic and mass transfer kinetic properties of D- and L-phenylalanine anilide on imprinted polymeric stationary phases. Anal Chem 1999 71 928-938. 

Only a few attempts were reported concerning the arrangement of MIP particles between two porous membranes, or their deposition on a single membrane. For example, Lehmann et al. used MIP nanoparticles with diameters between 50 nm and 300 nm imprinted with boc-L-phenylalanin-anilide obtained by miniemulsion polymerisation the selective rebinding properties as well as the hydrodynamic properties of the nanoparticles stacked between two polyamide membranes were studied [254]. 

Petkov, Christova, and Stoineva (11) have reported a study on the hydrolysis of N-acetyl-l.-phenylalanine anilide derivatives with o-chymotrypsin N-methylated anilides 34 (R CHj) were found to be unreactive under the conditions used for the hydrolysis of N—H anilides 34 (R=H). These authors have explained their results in a manner analogous to that described above, i,e. no hydrolysis takes place because steric hindrance caused by the N-methyl group prevents the formation of a tetrahedral intermediate in the N-methyl anilide derivatives. 

Conventionally, MlPs are obtained by bulk co-polymerization from a mixture consisting of a functional monomer, cross-linker, chiral template, and a porogenic solvent mixture. Nowadays, imprinting via non-covalent template binding is preferred over the covalent mode and involves three major steps (see Fig. 9.9). (i) Functional monomers (e.g. methacrylic acid, MAA) and a cross-linker (e.g. ethyleneglycol dimethacrylate, EDMA) assemble around the enantiomeric print molecule, e.g. (S)-phenylalanine anilide (1), driven by non-covalent intermolecular interactions, e.g. ionic interactions, hydrogen bonding, dipole-dipole interaction. Tr-rt-interaction. (ii) By thermally or photochemi-... 

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