The design of high-affinity synthetic host-guest complexes is of paramount importance because they are key elements in constructing unprecedented supramolecular assemblies, functional materials, molecular probes, artificial signal transduction events, and interfaces with the biological world. The present review article collects recent achievements in the design of 1 : 1 host-guest complexes with outstanding stabilities, i.e., exceeding 10 6 M À 1 . The relationships between the measured thermodynamic constants and the structural parameters of the interacting species are analyzed. The design features of high-affinity hosts are discussed in light of their binding properties. Different solvents and different types of noncovalent interactions are considered for the stabilization of the complexes. Finally, some hints are provided for the design of future synthetic receptors displaying high affinity and selectivity.
This is the first report of a single-step
synthesis of primary
benzyl alcohol containing different cross-azo compounds (14 examples)
by Cu(II) in the presence of a newly synthesized amino-ether heteroditopic
macrobicycle cage. Interestingly, even with extreme conditions, the
benzyl alcohol remains unoxidized by the Cu(II) catalyst due to the
protective etherial pocket of the cage.
A heteroditopic macrocycle is reported as an efficient organocatalytic nanoreactor for the synthesis of diversely functionalized pyrroloacridinones in aqueous medium. A library of compounds was synthesized in a one-step pathway utilizing 10 mol % of the nanoreactor following a sustainable methodology in water with high yields.
Polyamide-polyamine hybrid macrobicycle L is explored with respect to its ability to bind α,ω-dicarboxylate anions. Potentiometric studies of protonated L with the series of dianions from succinate (suc) through glutarate (glu), α-ketoglutarate (kglu), adipate (adi), pimelate (pim), suberate (sub), to azelate (aze) have shown adipate preference with association constant value of K = 4900 M in a HO/DMSO (50:50 v/v) binary solvent mixture. The binding constant increases from glu to adi and then continuously decreases with the length of the anion chain. Further, potentiometric studies suggest that hydrogen bonding between the guest anions and the amide/ammonium protons of the receptor also contributes to the stability of the associations along with electrostatic interactions. Negative-mode electrospray ionization of aqueous solutions of host-guest complexes shows clear evidence for the selective formation of 1:1 complexes. Single-crystal X-ray structures of complexes of the receptor with glutaric acid, α-ketoglutaric acid, adipic acid, pimelic acid, suberic acid, and azelaic acid assist to understand the observed binding preferences. The solid-state structures reveal a size/shape complementarity between the host and the dicarboxylate anions, which is nicely reflected in the solution state binding studies.
Selectivity of aryl iodo over ethynyl iodo toward the Suzuki cross coupling reaction is explored by utilizinga palladium complex of amino-ether heteroditopic macrobicycle. Subsequently,u nreacted ethynyl iodide undergoes ho-mocoupling reactioni nt he same catalytic atmosphere, therebyr epresenting ac ascade dual CÀCc oupling reaction. Furthermore, this approach is extended for novel one-pot synthesis of unsymmetrical 1,3-diynes.
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