A Pd2L4 coordination cage with improved solubility properties was prepared and used to bind n-octyl glycosides, showing a preference for the all equatorial n-octyl glucoside.
Galectins are a galactoside specific subclass of carbohydrate binding proteins (lectins) involved in various cellular activities, certain cancers, infections, inflammations, and many other biological processes. The molecular basis for the selectivity of galectins is well‐documented and revolves around appropriate interaction complementarity: an aromatic residue for C−H⋅⋅⋅π interactions and polar residues for (charge assisted) hydrogen bonds with the axial hydroxyl group of a galactoside. However, no synthetic mimics are currently available. We now report on the design and synthesis of the first galectin mimic (6), and show that it has a higher than 65‐fold preference for n‐octyl‐β‐galactoside (8) over n‐octyl‐β‐glucoside (7) in CD2Cl2 containing 5 % [D6]DMSO (with Ka≥4500 M−1 for 6:8). Molecular modeling informed by nOe studies reveal a high degree of interaction complementarity between 6 and galactoside 8, which is very similar to the interaction complementarity found in natural galectins.
Designing compounds for the selective molecular recognition of carbohydrates is a challenging task for supramolecular chemists. Macrocyclic compounds that incorporate isophtalamide or bisurea spacers linking two aromatic moieties have proven effective for the selective recognition of all‐equatorial carbohydrates. Here, we explore the molecular recognition properties of an octa‐urea [Pd2L4]4+ cage complex (4). It was found that small anions like NO3− and BF4− bind inside 4 and inhibit binding of n‐octyl glycosides. When the large non‐coordinating anion ‘BArF’ was used, 4 showed excellent selectivity towards n‐octyl‐α‐D‐Mannoside with binding in the order of Ka≈16 M−1 versus non‐measurable affinities for other glycosides including n‐octyl‐β‐D‐Glucoside (in CH3CN/H2O 91 : 9).
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