Abstract
The selective recognition of caffeine in water among structurally related xanthines and purine or pyrimidine bases was achieved by a simple tweezer-shaped receptor featuring sulfonate hydrosolubilizing groups. The remarkable affinity for caffeine, among the highest reported thus far in the literature and larger than that shown by adenosine receptors of all subtypes, stems from a synergistic combination of hydrogen bonding, CH−π, and π-stacking interactions.
Highlights
The effective molecular recognition of biologically relevant targets by biomimetic receptors through noncovalent interactions in physiological media represents a main challenge for supramolecular chemists due to the strong competition from water molecules.[1]
To achieve caffeine recognition in aqueous media, we developed the water-soluble analogue of receptor 1 (2, Scheme 1) featuring sulfonate groups on the diaminocarbazole unit
Receptor 2 was prepared in six steps with a 16% overall yield from 1,8diacetamidocarbazole 3 (Scheme 1)
Summary
The effective molecular recognition of biologically relevant targets by biomimetic receptors through noncovalent interactions in physiological media represents a main challenge for supramolecular chemists due to the strong competition from water molecules.[1] Purine bases are among the most studied biological guests because of their pervasive occurrence as constituents of nucleotides and their key role in many metabolic and signaling processes.[2] Among purine alkaloids, caffeine is the most widely consumed psychostimulant drug in the world and, in addition to its central stimulant effects, exerts various beneficial pharmacological activities as a competitive inhibitor of adenosine receptors.[3] Caffeine plays multiple roles as a drug for its antibronchospastic properties and is used as an analgesic adjuvant for pain treatment.[4] Other attractive effects of caffeine have been observed in the prevention of neurodegenerative diseases and cancer immunotherapy.[5] The use of artificial receptors that effectively recognize caffeine in water can find a wide range of applications in biomedical, technological, and analytical fields.[6,7]. Despite the excellent binding properties of receptor 1 in organic media,[10] at present the receptor cannot be leveraged in an aqueous or physiological environment where most useful applications concerning caffeine can be envisaged, from biomedical devices to analytical applications
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