Dendritic Molecular Baskets for Selective Binding of Toxic Methotrexate

We describe the preparation, assembly, recognition characteristics, and bioactivity of dendritic basket 6^12-. This novel cavitand has a deep aromatic pocket with three (S)-glutamic acid dendrons at the rim to amplify water solubility and prevent self-association. ¹H NMR spectroscopy, calorimetry (ITC), and mass spectrometry (ESI-MS) measurements validate the formation of an inclusion complex between 6^12- and anticancer drug methotrexate (MTX^2-) in water (K_d=9.2 μM). To identify the docking pose, a comparison of computed (DFT and MM) and experimental ¹H NMR chemical shifts suggests that MTX^2- folds inside 6^12- (π⋅⋅⋅π), forming HBs with the peptidic dendrons while anchoring (C-H⋅⋅⋅π) to the aromatic pocket through its N-methyl group. In consequence, 6^12- selectively binds MTX^2- in competition with structurally similar folic acid and leucovorin (reversal poisoning agent). While the host is biocompatible (HEK293; IC₅₀>150 μM) and produces inclusion complex [MTX⊂6]^14- in cell media, it experiences limitation in pharmacokinetic sequestration of MTX^2- as dihydrofolate reductase's affinity to the drug is suggested to prevail over that of 6^12-. Nonetheless, considering the basket's biocompatibility, tunability, and chemoselectivity, it stands as the leading candidate in the pursuit of an effective abiotic antidote for methotrexate poisoning.