Sulfonamide as amide isostere for fine-tuning the gelation properties of physical gels

One-Pot Synthesis of Sulfonamides from Unactivated Acids and Amines via Aromatic Decarboxylative Halosulfonylation

The coupling of carboxylic acids and amines to form amide linkages is the most commonly performed reaction in the pharmaceutical industry. Herein, we report a new strategy that merges these traditional amide coupling partners to generate sulfonamides, important amide bioisosteres. This method leverages copper ligand-to-metal charge transfer (LMCT) to convert aromatic acids to sulfonyl chlorides, followed by one-pot amination to form the corresponding sulfonamide. This process requires no prefunctionalization of the native acid or amine and extends to a diverse set of aryl, heteroaryl, and s-rich aliphatic substrates. Further, we extend this strategy to the synthesis of (hetero)aryl sulfonyl fluorides, which have found utility as "click" handles in chemical probes and programmable bifunctional reagents. Finally, we demonstrate the utility of these protocols in pharmaceutical analogue synthesis.

Metal Cation Triggered Peptide Hydrogels and Their Application in Food Freshness Monitoring and Dye Adsorption

Metal-ligand interactions have emerged as an important tool to trigger and modulate self-assembly, and to tune the properties of the final supramolecular materials. Herein, we report the metal-cation induced self-assembly of a pyrene-peptide conjugate to form hydrogels. The peptide has been rationally designed to favor the formation of β-sheet 1D assemblies and metal coordination through the Glu side chains. We studied in detail the self-assembly process in the presence of H+, Li+, Na+, K+, Ca2+, Ni2+, Cu2+, Zn2+, Cd2+, Co2+, Fe3+, and Cr3+ and found that the morphology and mechanical properties of the hydrogels are ion-dependent. Moreover, thanks to the presence of the metal, new applications could be explored. Cu2+ metallogels could be used for amine sensing and meat freshness monitoring, while Zn2+ metallogels showed good selectivity for cationic dye adsorption and separation.

Sulfur(VI) Fluoride Exchange (SuFEx)-Mediated Synthesis of the Chitosan-PEG Conjugate and Its Supramolecular Hydrogels for Protein Delivery

Supramolecular hydrogels are considered promising drug carriers in the tissue engineering field due to their versatile nature. Chitosan hydrogels without chemical cross-linkers have low cytotoxicity and good delivery capacity; however, they have lower mechanical properties for injectable hydrogel usage. In this study, we developed novel chitosan derivatives via click chemistry for fabricating supramolecular hydrogels with higher mechanical strength under mild conditions. The chitosan derivative was successfully synthesized by a sulfur fluoride exchange reaction, and the synthesized chitosan-mPEG/Pluronic-F127 (CS-mPEG/F127) interacted with α-cyclodextrin (α-CD) to form a supramolecular hydrogel via a host-guest reaction. The gelation dynamics, hydrogel properties, and bovine serum albumin (BSA) release could be modulated by the concentration ratio of chitosan-mPEG and F127. This supramolecular hydrogel is a promising protein releasing carrier candidate for long term regeneration therapy.

The pH- and salt-controlled self-assembly of [1]benzothieno[3,2-b][1]-benzothiophene–peptide conjugates in supramolecular hydrogels

Salt- and pH-triggered supramolecular hydrogels were obtained from a novel [1]benzothieno[3,2-b][1]benzothiophene (BTBT)-peptide hybrid.