Hamilton macrocyclic

Fig. 6.12 Macrocyclic Hamilton receptor for barbiturate guest molecules (left-hand side). A non-cyclic Hamilton host compound with...

Macrocyclic receptors often possess a higher degree of selectivity than acyclic systems. Hamilton and Choi have described the synthesis and anion binding properties of a family of cyclic triamides 10a and 10b [18]. These C3 symmetric receptors were found to be selective for oxo-anions such as tosy-late with association constants of 2.6 x 10 and 2.1 x 10 M obtained for compoimds 10a and 10b respectively in CDCl3/2% dimethylsulfoxide at 296 K. Hamilton also studied the binding ability of an acyclic analogue (11) and found significantly lower stability constants for the anion complexes formed. For example, in the case of nitrate, a stabiUty constant of 620 M was calculated for compound 11 whereas a stability constant of 4.6 x 10 M (K2 = 2.1 X 10 M ) was foxmd with compound 10a. 

Choi, K. Hamilton, A.D. Selective anion binding by a macrocycle wdth convergent hydrogen bonding functionality. J. Am. Chem. Soc. 2001. 123 (10), 2456-2457. 

Hamilton, A. D., A. Muehldoif, S. Chang, N. Pant, S. Goswami, and D. Van Engen - Nucleotide recognition by macrocyclic receptors 27... 

In 1995, Hamilton et al. described one of the first examples of a combinatorial approach to synthetic receptors using reversible coordination around a metal ion [20]. In the same year Harding et al. described the guest-induced amplification of a metallo-macrocycle 4 and metaUo-[2]catenane 5 from a mixture (Scheme 1.4) [20, 21]. Although not described as such, these examples employed the basic principles of DCC-template-stabilized selection of effective synthetic receptors from among an equihbrating library of potential receptors. 

Hamilton and coworkers synthesized bis-acylguanidi-nium salt 47 as a receptor for phosphodiesters." The binding constant with TBA diphenylphosphate was A a = 4.6 x 10" measured by UV-vis spectrometry in CH3CN. The bicyclic guanidinium has also been shown to bind phosphate anions. Macrocycle 48 was designed to bind... 

Andrew Hamilton (Princeton) reported [late submission] the recent synthesis and characterisation of a macrocycle (7), designed specifically to control the environment around a complexed metal in order to influence its catalytic properties. The macrocycle was synthesised from a bipyridyl unit and two valine residues. It was designed to provide (a) ligands capable of stabilising a range of metal oxidation states, (b) chiral groups which are close enough to influence the approach to the metal, (c) a cavity in order to effect substrate specificity and (d) sufficient stability to withstand oxidation. Complexation with a number of transition metals has been successful and preliminary studies on the Fe complex show that in the presence of iodosylbenzene in acetonitrile, it will epoxidise cyclooctene in 55% yield. 

Structures in which one or two of the methylene groups CH2 of every bridge have been replaced by carbonyl groups CO have been reported recently. Hamilton et al. have generated a set of macrocycles 100 from a solid phase synthesis of linear trimers of 5-aminoacyl-3-aminomethyl benzoates. These macrocycles are large area scaffolds useful in molecular recognition studies [68]. 

Hamilton, A. D. (19Sk)) Molecular Recognition by Macrocyclic Receptors in J.. L. Atwood (ed.). Inclusion Phenomena and Molecular Recognition, Plenum Press, New York, pp. 57-64. 

Hamilton, A. D.and Pant, N. (1988) Ditopic Binding of Guanine to a Macrocyclic Receptor J. Chem. Soc. Chem. Commun. 765. 

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