Discrimination of chiral copper(ii) complexes upon binding of galactonoamidine ligands

Abstract

The coordination between N-p-methylbenzyl-d-galactonoamidine, a putative transition state analogue of the hydrolyis of glycosidic bonds, and symmetric and chiral binuclear copper(ii) complexes was characterized by spectroscopic titration, isothermal titration calorimetry, circular dichroism spectroscopy, and DFT calculations to elucidate the binding sites in the carbohydrate upon coordination to selected metal complexes. For the formation of metal complex-glyconoamidine assemblies, contributions of the amidine site and of the hydroxyl group at C-2 in the glycon of the amidine are noted. The chiral complexes S- and R-Cubpdbo are discriminated by a third binding site in the carbohydrate that leads to higher stability of complexes derived from S-Cubpdbo (4-5 kcal mol) compared to those formed from R-Cubpdbo.

Structure–Activity-Relationship Studies to Elucidate Sources of Antibacterial Activity of Modular Polyacrylate Microgels

“…The antimicrobial activity of the resulting gels is highest when N -4-methylbenzyl- d -galactonoamidine ( 3 , amidine) or mannose ( 4 ) is used to chelate the metal core during synthesis (Table , entries 1 and 2). , The activity decreases when ethylene glycol ( 5 , EG), galactose ( 6 ), and triethylene glycol ( 7 , TEG) are employed (Table , entries 3–5). The binding of compounds 3 – 7 as counter anions to the immobilized binuclear Cu­(II) centers decreases in the same order.…”

“…Following the previously developed synthetic strategy, 24 a diverse selection of counter anions (Chart 2) was employed to determine the resulting structure− activity relationship and streamline future microgel syntheses. The antimicrobial activity of the resulting gels is highest when N-4-methylbenzyl-D-galactonoamidine (3, amidine) or mannose (4) 23 is used to chelate the metal core during synthesis (Table 1, entries 1 and 2). 23,31 The activity decreases when ethylene glycol (5, EG), 27 galactose (6), 27 and triethylene glycol (7, TEG) are employed (Table 1, entries 3−5).…”

“…The microgel body is typically composed of ethylene glycol dimethacrylate ( 1 , EGDMA) cross-linker, butyl acrylate (BA) monomer, and a metal-coordinating ligand such as pentadentate VBbpdpo ( 2 ) (Chart ). , Then, copper­(II) acetate is added to the prepolymerization mixture to transform the ligand in situ into copper­(II) complexes, followed by addition of an excess of coordinating counter ions, such as mannose, to prevent the copper­(II) ions from interfering with the radical polymerization. − Ultrasheering of the monomer mixture in an aqueous buffer-surfactant system yields in the presence of stabilizing hydrophobes defined droplets, which are captured as particles by free-radical polymerization under UV light. , The resulting microgels are spherical particles with predefined hydrodynamic diameters between 150 and 280 nm (Figure ). , An optimal antimicrobial activity was observed for microgels with a cross-linking content of 60 mol % …”

Antimicrobial Activity of Microgels with an Immobilized Copper(II) Complex Linked to Cross-Linking and Composition

“…The monomer mixtures yield stabilized droplets after ultra-sheering in the presence of a hydrophobe in an aqueous buffer–surfactant solution. The subsequent polymerization captures these droplets without alteration of their size as micro- or nanogels. , The immobilized ligand is usually transformed in situ into a binuclear metal complex by addition of copper­(II) acetate prior to polymerization. ,, To prevent interference of the paramagnetic copper­(II) ions with the radical polymerization, mannose or other counterions are added to the pre-polymerization mixture in aqueous buffer–surfactant solutions . The procedure saturates the metal complex core during material synthesis and prevents metal ion leakage and interference with the polymerization reaction.…”

“…17,18 The immobilized ligand is usually transformed in situ into a binuclear metal complex by addition of copper(II) acetate prior to polymerization. 15,19,20 To prevent interference of the paramagnetic copper(II) ions with the radical polymerization, mannose or other counterions are added to the pre-polymerization mixture in aqueous buffer−surfactant solutions. 15 The procedure saturates the metal complex core during material synthesis and prevents metal ion leakage and interference with the polymerization reaction.…”