The structures of monensin A derivatives and its complexes with some monovalent cations studied by the AM1d, PM3 as well as PM5 semiempirical methods

FT-IR, 1H, 13C NMR, ESI-MS and semiempirical investigation of the structures of Monensin phenyl urethane complexes with the sodium cation

In this paper three forms of phenyl urethane of Monensin i.e. its acid form (H-MU) and its 1:1 complex with NaClO4 (H-MU-Na) and its sodium salt (Na-MU) were obtained and their structures were studied by FT-IR, (1)H and (13)C NMR, ESI MS and PM5 methods. The FT-IR data of Na-MU complexes demonstrate that the C=O urethane group is not engaged in the complexation of the sodium cation. However spectroscopic studies of H-MU-Na complex show that the structure in which this C=O urethane groups participate in the complexation is also present, but it is in the minority. The PM5 semiempirical calculations allow visualisation of all structures and determination of the hydrogen bond parameters.

Synthesis, FT-IR, ¹H, ¹³CNMR, ESI MS and PM5 studies of a new Mannich base of polyether antibiotic - Lasalocid acid and its complexes with Li⁺, Na⁺ and K⁺ cations

The polyether antibiotic Lasalocid acid has been converted to its Mannich base derivative by a chemoselective one-pot reaction with formaldehyde and morpholine through the decarboxylation process. Spectroscopic studies of the structure of this new derivative have shown that in this ortho-phenol Mannich base the O-H⋯N intarmolecular hydrogen bond is present. The compound forms complexes with Li(+), Na(+) and K(+) cations of exclusively 1:1 stoichiometry. The structures of these complexes have been studied and visualized by semi-empirical calculation based on results of spectrometric and spectroscopic investigation. It is demonstrated that in contrast to Lasalocid acid the novel Mannich type derivative forms preferential complexes with Li(+) cation.

Structure and antimicrobial properties of monensin A and its derivatives: summary of the achievements

In this paper structural and microbiological studies on the ionophorous antibiotic monensin A and its derivatives have been collected. Monensin A is an ionophore which selectively complexes and transports sodium cation across lipid membranes, and therefore it shows a variety of biological properties. This antibiotic is commonly used as coccidiostat and nonhormonal growth promoter. The paper focuses on both the latest and earlier achievements concerning monensin A antimicrobial activity. The activities of monensin derivatives, including modifications of hydroxyl groups and carboxyl group, are also presented.

Reinvestigation of the structure of monensin A phenylurethane sodium salt based on X-ray crystallographic and spectroscopic studies, and its activity against hospital strains of methicillin-resistant S. epidermidis and S. aureus

Monensin A phenylurethane sodium salt (MON-UR1-Na) crystals were studied by the X-ray, NMR, FT-IR and PM5 semi-empirical methods. The X-ray data show that the compound forms a pseudocyclic structure, stabilized by three intramolecular hydrogen bonds, and the sodium cation coordinated by five oxygen atoms in the hydrophilic sphere. The NMR and FT-IR data demonstrate that this pseudocyclic structure is also conserved in CH(2)Cl(2) solution. This structure of MON-UR1-Na is significantly different than the ones previously proposed by Westley et al. and Tanaka et al. The semi-empirical calculations of the MON-UR1-Na structures indicate that the one of the crystal is the most energetically favorable one. Other parameters, such as the size, chemical and biological nature of the urethane substituent, and especially the free carbonyl urethane group, may have a role in the biological activity of MON-UR1-Na. The in vitro microbiological tests provide evidence that MON-UR1-Na shows higher antibacterial activity against human pathogenic bacteria, including antibiotic-resistant Staphylococcus aureus and Staphylococcus epidermidis than the parent unmodified antibiotic-Monensin A.