Copper(II) mixed ligands complexes of hydroxamic acids with glycine, histamine and histidine

Abstract

Um estudo potenciométrico e espectrofotométrico de complexos mistos de Cu II , fisiologicamente interessantes, foi realizado envolvendo ácidos hidroxâmicos como ligantes primários (A) e ligantes secundários (B) representados por histamina ou pelos aminoácidos glicina e histidina. Todos são potencialmente capazes de formar quelatos com anéis de cinco ou seis membros. A constante de formação e o espectro de absorção no visível são calculados para cada uma das espécies identificadas, tanto binárias quanto ternárias. As estruturas mais prováveis das espécies mistas são propostas com base nas constantes de formação calculadas, na estabilização em relação às duas espécies binárias correspondentes, bem como nos espectros de absorção no visível. Ficou comprovado que os complexos de Cu-hidroxamato não favorecem significativamente a formação de complexos ternários com aminoácidos que possuem apenas os grupos amino e carboxilato; contudo, a formação de complexos ternários com a histidina é fortemente favorecida, devido à presença do grupo imidazol. A potentiometric and spectrophotometric study of physiologically interesting Cu II mixed ligand complexes has been performed involving hydroxamic acids as primary ligands (A) and secondary ligands (B) represented either by histamine or the aminoacids glycine and histidine. All are potentially able to form chelate complexes with either five or six membered rings. The formation constant and the visible absorption spectrum were calculated for each one of the identified species, both binary and mixed ones. The most probable structures of the mixed species are discussed based upon their formation constants, their stabilization with regard to the two binary species as well as their visible absorption. It was evidenced that Cu-hydroxamate complexes do not favour significantly mixed ligand complex formation with aminoacids having only the carboxylate and amino groups; however, these complexes are strongly formed with histidine, due to the presence of the imidazol group.

Introduction of two polyvinyl alcohol resins for efficient solid support Cu‐catalyzed N‐arylation of α‐aminoacids with aryl halides in aqueous media

“…According to the several reports in the literature for copper catalyzed N‐arylation of α‐amino acid and dropping the reaction yield in the presence of Cu(II) salts the following plausible mechanism can be suggested: first, a well‐known chelation of Cu ions (Scheme , intermediate A ) could be formed through the carboxyl and amino groups of α‐amino acid anchored on the surface of resin . The chelate A is then coordinated with a aryl halide to form the π‐complex B , based on π‐complex mechanism of Ullmann condensation .…”

Glycine hydroxamate inhibits tyrosinase activity and melanin contents through downregulating cAMP/PKA signaling pathways

“…However, GH showed noncompetitive inhibition of monophenolase activity, meaning that it could bind to TYR far from the catalytic sites and alter conformations to reduce TYR activities with or without l-tyrosine. On the other hand, GH has been reported to form complexes or metallacrowns with Cu (II) ions and to act as a powerful chelator for many metal ions (Fernandes et al 1997;Tegoni and Remelli 2012), which might contribute in part to its inhibitory activities against the Cu-containing TYR.…”

Apparent Molar Volumes and Refractive Indices of Hydroxamic Acid Solutions

“…Hydroxamic acids show activities in all sphere of life, viz, analytical [1,2], agriculture [3,4], biological [5,6], medicinal [7,8] and technical fields [9,10]. These are the products of some photochemical reactions [11] and occur in nature also [12].…”