Bicyclic guanidinium derivatives

Bicyclic guanidinium derivatives have also been incorporated into bis(guanidinium) receptors capable of recognising tetrahedral oxoanions, particularly polyphosphate residues of important biological molecules. The flexibility of receptor 4.31 allows the two guanidinium arms to swing into a mutually perpendicular arrangement in order to effectively complex polyphosphates even in water. 

Chiral bicyclic guanidinium receptors (e.g. 12-14, S,S-configuration shown) have been developed in our group from aminoacid precursors [16]. Improved synthetic procedures for such compounds were later reported by Schmidtchen [17] (who in 1980 presented a first type of achiral bicycloguanidinium hosts [18] that form complexes with several oxoanions [19]). Most derivatives are highly... 

The bicyclic guanidinium tetramer 43 was first reported as a possible binder for helical oligonucleotides. Initial studies with 43 and sulfate anions showed that the tetramer formed double-helical dimers around sulfate counterions [69]. Despite the initial proposal of using this receptor for membrane transport of oligonucleotides, all subsequent work on 43 has been conducted on helical peptides. For example, the binding of 43 with several synthetic peptides caused an increase in the helicity and helical stability of the peptides in 10% water/methanol [70]. The peptide containing four Asp derivatives showed the... 

Echavarren, A. Galan, A. Mendoza, J. Salmeron. A. Lehn, J.-M. Anion receptor molecules Synthesis of a chiral and functionalized binding subunit, a bicyclic guanidinium group derived from L- or D-asparagine. Helv. Chim. Acta 1988. 71 (4). 685-693. 

A breakthrough in guanidinium-based anion hosts came with the synthesis of the bicyclic derivative 4.28 by Schmidtchen in 1980. The presence of the hydrocarbon backbone reduces dramatically the solvation of the guanidinium moiety and increases its lipophilicity, resulting in complexes with p-nitrobenzoate guest, for example, with association constants of the order of 1.4 X 10 in chloroform. Interestingly, Ci symmetric chiral derivatives may be prepared starting from chiral amino acids via the procedure shown in Scheme 4.2. ... 

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