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Racemic resolution of mandelic acid on polymers with chiral cavities. 3. Co-operative binding over phenylboronic acid groups andN-bases

Reactive Polymers
Publication Date
DOI: 10.1016/0923-1137(89)90083-3
  • Chemistry


Abstract The binding ability of a macroporous polymer-supported phenylboronic acid for mandelic acid increases markedly in the presence of various N-bases. Based on a correlation between the relative increase of binding ability and the base strength, the existence of co-operative binding of the types P7 and P9, through polymer-bound phenylboronic acid groups and freely interacting N-bases, could be deduced. A remarkable improvement of the efficiency for racemic resolution of d,l-mandelic acid on such polymers was achieved if both of the co-operating functionalities were introduced in a fixed stereochemical arrangement within the chiral polymeric cavities with a specific shape corresponding to the chemical structure of a template molecule, i.e. l-mandelic acid. Thus l-mandelic acid-1,2- O-(4-vinylphenyl)boronate ( 2) was copolymerized with a molar quantity of 4-vinylpyridine to highly crosslinked macroporous polymers ( P10). The resulting polymers, after removal of the template, exhibit separation factors of up to 1.29. The reason for specific binding is discussed and compared with that of polymers with chiral cavities of the type P1, prepared from 2 according to Scheme 1.

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