Structural and spectroscopic studies of the 1:1 complex of lasalocid acid with 1,5,7-triazabicyclo[4.4.0]dec-5-ene

Spectroscopic studies of the equilibrium between complexes of lasalocid acid with propargylamine and metal cations

The molecular structure of 1:1 complex formed between the naturally occurring polyether ionophore, called lasalocid acid (LAS) and propargylamine (PROP) is studied by X-ray, FT-IR, (1)H NMR, (13)C NMR and ESI-MS methods. The complex formed between deprotonated LAS acid and protonated PROP molecule is stabilized by intra- and inter-molecular hydrogen bonds. The protons of the protonated amine group are hydrogen bonded to etheric and hydroxyl oxygen atoms of the LAS anion. The similarity of the FT-IR spectra of the LAS-PROP complex in solid state and in solution demonstrated that the molecular structures of the complex in both states are comparable. It is shown that LAS in solution can form concurrent complexes with metal cations (M=Li(+), Na(+), K(+)) and amine existing in equilibrium. Analysis of the structures of lasalocid complexes is important for a better understanding of the antibacterial and anticancer properties of lasalocid acid.

Spectroscopic, crystallographic and theoretical studies of lasalocid complex with ammonia and benzylamine

A natural antibiotic--Lasalocid is able to form stable complexes with ammonia and organic amines. New complexes of lasalocid with benzylamine and ammonia were obtained in the crystal forms and studied using X-ray, FT-IR, (1)H NMR, (13)C NMR and DFT methods. These studies have shown that in both complexes the proton is transferred from the carboxylic group to the amine group with the formation of a pseudo-cyclic structure of lasalocid anion complexing the protonated amine or NH4(+) cation. The spectroscopic and DFT studies demonstrated that the structure of the complex formed between Lasalocid and benzylamine in the solid is also conserved in the solution and gas phase. In contrast, the structure of the complex formed between lasalocid and ammonium cation found in the solid state undergoes dissociation in chloroform solution accompanied with a change in the coordination form of the NH4(+) cation.

Structures and properties of naturally occurring polyether antibiotics

Polyether ionophores represent a large group of natural, biologically active substances produced by Streptomyces spp. They are lipid soluble and able to transport metal cations across cell membranes. Several of polyether ionophores are widely used as growth promoters in veterinary. Polyether antibiotics show a broad spectrum of bioactivity ranging from antibacterial, antifungal, antiparasitic, antiviral, and tumour cell cytotoxicity. Recently, it has been shown that some of these compounds are able to selectively kill cancer stem cells and multidrug-resistant cancer cells. Thus, they are recognized as new potential anticancer drugs. The biological activity of polyether ionophores is strictly connected with their molecular structure; therefore, the purpose of this paper is to present an overview of their formula, molecular structure, and properties.

X-ray crystallographic, FT-IR, and density functional theory studies of the salt formed between dipicrylamine and 1,5,7-triazabicyclo[4.4.0]dec-1-ene

The DPA-TBD (dipicrylamine-1,5,7-triazabicyclo[4.4.0]dec-1-ene) salt has been synthesized and characterized by FT-IR spectroscopy, X-ray single-crystal diffraction, and theoretical study. In the FT-IR spectrum of the crystalline DPA-TBD salt, an unexpected intense band at 1742 cm(-1) is present. The optimized geometry and the FT-IR spectra of the DPA salt were calculated at the B3LYP/6-31G+(d) level and give an explanation of the nature of this band as the ν(C═N═C) vibration. For comparison, the calculated IR spectra of the DPA anion, hydrogen-bonded DPA anion, and neutral DPA and TBD molecules as well as for the TBD cation are also shown. The presence of the free DPA anion in the gas phase was directly detected in the negative ion mode electrospray ionization MS spectra. The fragmentation of the DPA anion is also discussed.