Artificial biomimetic receptor molecules.
NMR titrns. of alkyl ammonium chlorides have been performed with the simple phosphonate receptors in [D6] DMSO. The chem. induced shift of the a-CH-N+ was measured and the binding curves were analyzed by linear regression methods. The drastic increase in Ka values from monophosphonate to m- and p-diphosphonate was strongly indicative for the chelate effect resulting in double electrostatic attraction for the alkylammonium cation. Surprisingly, it was obsd. that the binding consts. increased again by one order of magnitude when various related amino alcs. were titrated. A basic structural motif for a receptor of amino alcs. has been found. Another feature of these hosts is remarkable. Secondary amines are complexed at least as strongly as their primary counterparts. Contrary to all artificial ammonium receptors known to date, the bisphosphonates can be expected to bind esp. well to adrenaline itself, as well as to the resp. b-blockers. A systematic study of the binding behavior of 1,n amino alcs. revealed that m-xylylene bisphosphonate is a selective host for 1,2- and 1,3-amino alcs.
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