Programmed Enzyme-Mimic Hydrolysis of a Choline Carbonate by a Metal-Free 2‑Amino­benz­imidazole-Based Cavitand

The hydrolysis of a choline carbonate through a metal-free, enzyme-like mechanism has been achieved using a 2-amino­benz­imid­azole-based deep cavitand as catalyst. The supramolecular catalysis involves three steps: host–guest binding, carbamoylation and enzyme-like hydrolysis. Interestingly the rate-determining step proceeds through a programmed hydrolysis of carba­moyl­choline-cavitand intermediate that may be driven by water molecules surrounding the benzimidazole walls of the cavity

Hydrogen Bonded Squaramide-Based Foldable Module Induces Both β- and α‑Turns in Hairpin Structures of α‑Peptides in Water

A novel tertiary squaramido-based reverse-turn module SQ is reported, and its conformational properties are evaluated. This module is easily incorporated into a α-peptide sequence by conventional solid-phase peptide synthesis. The structure characterization of the hybrid squaramido-peptide <b>4</b> is described, showing that the turn segment induces the formation of hairpin structures in water through the formation of both αSQ- and βSQ-turns

Cell Uptake and Localization Studies of Squaramide Based Fluorescent Probes

Cell internalization is a major issue in drug design. Although squaramide-based compounds are receiving much attention because of their interesting bioactivity, cell uptake and trafficking within cells of this type of compounds are still unknown. In order to monitor the cell internalization process of cyclosquaramide compounds we have prepared two fluorescent probes by covalently linking a fluorescent dye (BODIPY derivative or fluorescein) to a noncytotoxic cyclosquaramide framework. These two probes (C2-BDP and C2-FITC) rapidly internalize across live cell membranes through endocytic receptor-mediated mechanisms. Due to its higher fluorescence and photochemical stability, C2-BDP is a superior dye than C2-FITC. C2-BDP remains sequestered in late endosomes allowing their fast and selective imaging in various live cell types. Cyclosquaramide–cell membrane interactions facilitate cell uptake and have been investigated by binding studies in solution as well as in live cells. Cyclosquaramide <b>1</b> (C2-BDP) can be used as a highly fluorescent probe for the rapid and selective imaging of late endosomes in live cells