Molecular recognition in synthetic systems: I. Rigidified dendritic systems for imparting enantioselective molecular recognition to platinum-containing molecularly imprinted polymers, II. Using laser polarimetry to identify an enantioselective receptor for (-)-adenosine from a racemic dynamic combinatorial library.

摘要

The understanding of molecular recognition events is of great importance to current chemical research. This work documents two examples of molecular recognition in synthetic systems. Molecularly imprinted polymers containing platinum have been synthesized that can differentiate between enantiomers in a ligand exchange reaction. The use of laser polarimetry as a method to detect enantioselective interactions in a racemic dynamic combinatorial library is also described.; Platinum-containing molecularly imprinted polymers (MIPs) were synthesized by the covalent incorporation of polymerizable P2Pt((S )-BINOL) metallodendrimers constructed with a rigid phenyl benzoate ester linkage into a highly-porous and cross-linked methacrylate-based polymer. The enantioselectivity of the polymer with respect to BINOL ligand exchange reactions was studied and compared to similar polymers prepared from metallodendrimers containing a conformationally flexible phenyl benzyl ether linkage. The rigidity of the ester linkage resulted in higher enantioselectivities for a BINOL/Br 2BINOL ligand exchange reaction as compared to the ether linkage. The most selective polymer exchanged (+/-)-Br2BINOL for ( S)-BINOL at the platinum sites with an enantioselectivity of 82:18 which equals the highest observed for these polymers. At elevated temperatures preferential deactivation of the less hindered, and therefore less selective sites, is observed due to the thermolytic cleavage of the BINOL ligand. These polymers exhibit enantioselective molecular recognition for the imprinted enantiomer of BINOL through outer-sphere control by the polymer matrix.; The study of laser polarimetric detection for the analysis of dynamic combinatorial libraries comprised of racemic compounds was undertaken in an effort to identify enantioselective molecular recognition. An enantioselective receptor for the biologically important molecule (-)-adenosine was identified in this manner. This demonstrates a novel and efficient method for the study of enantioselective molecular recognition in synthetic systems. The use of deuterium-labeled species was developed as a method for identifying the stereochemistry of the receptor of interest by mass spectrometry. This method was also used to quantify the diastereomeric composition of a library component. This work proves that used together in this manner, laser polarimetry, dynamic combinatorial chemistry, and mass spectrometry are powerful strategies for the continued study of enantioselective molecular recognition.