Enantioselective noncovalent synthesis of hydrogen-bonded double-rosette assemblies

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Prins, Leonard J. and Verhage, Jeroen J. and Jong, Feike de and Timmerman, Peter and Reinhoudt, David N. (2002) Enantioselective noncovalent synthesis of hydrogen-bonded double-rosette assemblies. Chemistry: a European journal, 8 (10). pp. 2302-2313. ISSN 0947-6539

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Abstract:The noncovalent synthesis of enantiomerically pure hydrogen-bonded assemblies (M)- and (P)-13(CA)6 is described. These dynamic assemblies are of one single handedness (M or P), but do not contain any chiral components. They are prepared by using the chiral memory concept: the induction of supramolecular chirality is achieved through initial assembly with chiral barbiturates, which are subsequently replaced by achiral cyanurates. This exchange process occurs quantitatively and without loss of the M or P handedness of the assemblies. Racemization studies have been used to determine an activation energy for racemization of 105.9±6.4 kJ mol-1 and a half-life time to racemization of 4.5 days in benzene at 18 °C. Kinetic studies have provided strong evidence that the rate-determining step in the racemization process is the dissociation of the first dimelamine component 1 from the assembly 13(CA)6. In addition to this, it was found that the expelled chiral barbiturate (RBAR or SBAR) acts as a catalyst in the racemization process. Blocking the dissociation process of dimelamines 1 from assembly 13(CA)6 by covalent capture through a ring-closing metathesis (RCM) reaction produces an increase of more than two orders of magnitude in the half-life time to racemization.
Item Type:Article
Additional information:687
Copyright:© 2002 Wiley InterScience
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Link to this item:http://purl.utwente.nl/publications/37950
Official URL:http://dx.doi.org/10.1002/1521-3765(20020517)8:10<2302::AID-CHEM2302>3.0.CO;2-C
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