Oxolane Ammonium Salts (Muscarine-Like)-Synthesis and Microbiological Activity.

Commercially available 2-deoxy-D-ribose was used to synthesize the appropriate oxolane derivative-(2R,3S)-2-(hydroxymethyl)oxolan-3-ol-by reduction and dehydration/cyclization in an acidic aqueous solution. Its monotosyl derivative, as a result of the quaternization reaction, allowed us to obtain eight new muscarine-type derivatives containing a quaternary nitrogen atom and a hydroxyl group linked to the oxolane ring. Their structure was fully confirmed by the results of NMR, MS and IR analyses. The crystal structure of the pyridinium derivative showed a high similarity of the conformation of the oxolane ring to previously published crystal structures of muscarine. Two reference strains of Gram-negative bacteria (Escherichia coli ATCC 25922 and Pseudomonas aeruginosa ATCC 27853), two reference strains of Gram-positive staphylococci (Staphylococcus aureus ATCC 25923 and Staphylococcus aureus ATCC 29213) and four reference strains of pathogenic yeasts of the genus Candida spp. (Candida albicans SC5314, Candida glabrata DSM 11226, Candida krusei DSM 6128 and Candida parapsilosis DSM 5784) were selected for the evaluation of the antimicrobial potential of the synthesized compounds. The derivative containing the longest (decyl) chain attached to the quaternary nitrogen atom turned out to be the most active.

Hydrazinolysis Products of Selected Sugar Lactones-Crystal Structure and Microbiological Activity.

Commercially available lactones, as well as those synthesized by us, turned out to be good substrates for the synthesis of sugar hydrazides. The exception was L-ascorbic acid, whose hydrazinolysis led to the formation of a hydrazinium salt, not the hydrazide as expected. The structure of all compounds was confirmed by NMR and X-ray analyses. The lower durability of hydrazinium L-ascorbate was additionally confirmed by thermogravimetric tests. All products were tested for biological activity against Gram-negative bacteria strains Escherichia coli ATCC 25922 and Pseudomonas aeruginosa ATCC 27853 and against Gram-positive Staphylococcus aureus ATCC 25923 and Staphylococcus aureus ATCC 29213. Their antifungal activity against Candida albicans SC5314, Candida glabrata DSM 11226 SM 11226, Candida krusei DSM 6128, and Candida parapsilosis DSM 5784 was also tested. The most interesting results of microbiological activity were obtained for D-gluconic acid hydrazide and hydrazinium L-ascorbate. The results of the latter encourage more extensive testing.

NMR and MD Analysis of the Bonding Interaction of Vancomycin with Muramyl Pentapeptide.

The article describes an NMR spectroscopy study of interactions between vancomycin and a muramyl pentapeptide in two complexes: vancomycin and a native muramyl pentapeptide ended with D-alanine (MPP-D-Ala), and vancomycin and a modified muramyl pentapeptide ended with D-serine (MPP-D-Ser). The measurements were made in a 9:1 mixture of H2O and D2O. The obtained results confirmed the presence of hydrogen bonds previously described in the literature. At the same time, thanks to the pentapeptide model used, we were able to prove the presence of two more hydrogen bonds formed by the side chain amino group of L-lysine and oxygen atoms from the vancomycin carboxyl and amide groups. This type of interaction has not been described before. The existence of these hydrogen bonds was confirmed by the 1H NMR and molecular modeling. The formation of these bonds incurs additional through-space interactions, visible in the NOESY spectrum, between the protons of the L-lysine amino group and a vancomycin-facing hydrogen atom in the benzylic position. The presence of such interactions was also confirmed by molecular dynamics trajectory analysis.

Different Schiff Bases-Structure, Importance and Classification.

Schiff bases are a vast group of compounds characterized by the presence of a double bond linking carbon and nitrogen atoms, the versatility of which is generated in the many ways to combine a variety of alkyl or aryl substituents. Compounds of this type are both found in nature and synthesized in the laboratory. For years, Schiff bases have been greatly inspiring to many chemists and biochemists. In this article, we attempt to present a new take on this group of compounds, underlining of the importance of various types of Schiff bases. Among the different types of compounds that can be classified as Schiff bases, we chose hydrazides, dihydrazides, hydrazones and mixed derivatives such as hydrazide-hydrazones. For these compounds, we presented the elements of their structure that allow them to be classified as Schiff bases. While hydrazones are typical examples of Schiff bases, including hydrazides among them may be surprising for some. In their case, this is possible due to the amide-iminol tautomerism. The carbon-nitrogen double bond present in the iminol tautomer is a typical element found in Schiff bases. In addition to the characteristics of the structure of these selected derivatives, and sometimes their classification, we presented selected literature items which, in our opinion, represent their importance in various fields well.

The Quaternization Reaction of 5-O-Sulfonates of Methyl 2,3-o-Isopropylidene-ß-D-Ribofuranoside With Selected Heterocyclic and Aliphatic Amines.

The synthesis of N-((methyl 5-deoxy-2,3-O-isopropylidene-ß-D-ribofuranoside)-5-yl)ammonium salts are presented. To determine the effect of the nucleophile type and outgoing group on the quaternization reaction, selected aliphatic and heterocyclic aromatic amines reacted with: methyl 2,3-O-isopropylidene-5-O-tosyl-ß-D-ribofuranoside or methyl 2,3-O-isopropylidene-5-O-mesyl-ß-D-ribofuranoside or methyl 2,3-O-isopropylidene-5-O-triflyl-ß-D-ribofuranoside were performed on a micro scale. High-resolution 1H- and 13C-NMR spectral data for all new compounds were recorded. Additionally, the single-crystal X-ray diffraction analysis for methyl 2,3-O-isopropylidene-5-O-mesyl-ß-D-ribofuranoside and selected in silico interaction models are reported.

Synthesis, Antimicrobial and Mutagenic Activity of a New Class of d-Xylopyranosides.

Eight N-[2-(2',3',4'-tri-O-acetyl-α/ß-d-xylopyranosyloxy)ethyl]ammonium bromides, a new class of d-xylopyranosides containing a quaternary ammonium aglycone, were obtained. Their complete structure was confirmed using NMR spectroscopy (1H, 13C, COSY and HSQC) and high-resolution mass spectrometry (HRMS). An antimicrobial activity against fungi (Candida albicans, Candida glabrata) and bacteria (Staphylococcus aureus, Escherichia coli) and a mutagenic Ames test with Salmonella typhimurium TA 98 strain were performed for the obtained compounds. The greatest activity against the tested microorganisms was shown by glycosides with the longest (octyl) hydrocarbon chain in ammonium salt. None of the tested compounds exhibited mutagenic activity in the Ames test.

Glycosylation of allyl 2-acetamido-4,6-O-benzylidene-2-deoxy-alpha-D-glucopyranoside with bulky substituted glycosyl donors.

Glycosylation of allyl 2-acetamido-4,6-O-benzylidene-2-deoxy-alpha-D-glucopyranoside with bulky substituted glycosyl donors leads to the formation of derivatives of the disaccharide alpha-D-Glc-(1-->3)-d-GlcNAc with different yields.

Vitamin C metabolomic mapping in the lens with 6-deoxy-6-fluoro-ascorbic acid and high-resolution 19F-NMR spectroscopy.

PURPOSE: Metabolomics, or metabolic profiling, is an emerging discipline geared to providing information on a large number of metabolites, as a complement to genomics and proteomics. In the current study, a fluorine-labeled derivative of ascorbic acid (F-ASA), a major antioxidant- and UV-trapping molecule in the aqueous humor and the lens, was used to investigate the extent to which the lens accumulates potentially toxic degradation products of vitamin C. METHODS: Human lens epithelial cells (HLE-B3) and rat lenses were exposed to hyperglycemic or oxidative stress in vitro or in vivo and probed for accumulation of F-ASA, fluoro-dehydroascorbate (F-DHA), fluoro-2,3-diketogulonate (F-DKG), and their degradation products in protein-free extracts, by proton-decoupled 750-MHz (19)F-nuclear magnetic resonance (NMR) spectroscopy. RESULTS: F-ASA and F-DHA were taken up into HLE B-3 cells by an Na(+)-dependent transporter. Their uptake was unexpectedly only slightly affected by hyperglycemia in vitro, unless glutathione was severely depleted. Glycemic stress catalyzed oxidation of F-ASA into a single novel F-compound at -212.4 ppm, whereas F-DHA and F-DKG were the major degradation products observed after GSH depletion. In contrast, F-ASA uptake was markedly suppressed in diabetic cataractous rat lenses, which accumulated both the F-DHA and the -212.4-ppm compound. In an unexpected finding, the latter formed only from F-ASA and not F-DHA or F-DKG, suggesting a novel pathway of in vivo F-ASA degradation. Both the cells and the intact rat and human lenses were permeable to several advanced F-ASA and F-DHA degradation products, except F-DKG. The unknown compound at -212.4 ppm was the only F-ASA degradation product that spontaneously formed in rabbit aqueous humor upon incubation with F-ASA. CONCLUSIONS: These studies suggest the existence of a novel ascorbic-acid-degradation pathway in the lens and aqueous humor that is influenced by the nature of the oxidant stress. Under similar culture conditions, intact lenses are more prone to hyperglycemia-mediated oxidant stress than are lens epithelial cells, but both are permeable to various F-ASA degradation products, the structure and biological roles of which remain to be established.

Vitamin C metabolomic mapping in experimental diabetes with 6-deoxy-6-fluoro-ascorbic acid and high resolution 19F-nuclear magnetic resonance spectroscopy.

Metabolomic mapping is an emerging discipline geared at providing information on a large number of metabolites as a complement to genomics and proteomics. Here we have probed ascorbic acid homeostasis and degradation in diabetes using 6-deoxy-6-fluoro ascorbic acid (F-ASA) and 750 MHz (19)F-nuclear magnetic resonance (NMR) spectroscopy with proton decoupling In vitro, Cu(2+)-mediated degradation of F-ASA revealed the formation of 4 major stable degradation products at 24 hours. However, when normal or diabetics rats were injected with F-ASA intraperitoneally (IP) for 4 days, up to 20 fluorine-labeled compounds were observed in the urine. Their composition resembled, in part, metal catalyzed degradation of F-ASA and was not explained by spontaneous degradation in the urine. Diabetes led to a dramatic increase in urinary F-ASA loss and a relative decrease in most other urinary F-compounds. Diabetes tilted F-ASA homeostasis toward oxidation in liver (P <.01), kidney (P <.01), spleen (P <.01), and plasma (P <.01), but tended to decrease oxidation in brain, adrenal glands, and heart. Surprisingly, however, besides the major oxidation product fluoro-dehydroascorbic acid (F-DHA), no F-ASA advanced catabolites were detected in tissues at 5 micromol/L sensitivity. These findings not only confirm the key role of the kidney in diabetes-mediated loss of ascorbic acid, but demonstrate that only selected tissues are prone to increased oxidation in diabetes. While the structure of most degradation products needs to be established, the method illustrates the power of high resolution (19)F-NMR spectroscopy for the mapping of complex metabolomic pathways in disease states.

The Transformation Mechanism of 3,4,6-Tri-O-acetyl-1,5-anhydro-2-deoxy-D-arabino-hex-1-enitol in Water.

Heating of 3,4,6-tri-O-acetyl-1,5-anhydro-2-deoxy-D-arabino-hex-1-enitol (per-O-acetyl-D-glucal) in water leads to a mixture of unsaturated compounds with cyclic as well as open-chain structures. The mixture obtained was analyzed by the CGC method. The experimental findings were employed to model the mechanism of the transformation studied. In addition, AM1 calculations were carried out in order to describe the elementary processes suggested. Full geometry optimizations performed for species found in the mixture made it possible to evaluate the thermodynamic characteristics of particular reactions. Next, the calculations for transition states afforded appropriate kinetic barriers. All computations were carried out for a gaseous phase as well as an aqueous solution. Both experimental and theoretical results conform well with the mechanism proposed.

Synthesis of cis-(1-->3)-glycosides of allyl 2-acetamido-4,6-O-benzylidene-2-deoxy-alpha-D-glucopyranoside.

Syntheses of allyl 2,3,4-tri-O-benzyl-alpha-D-gluco- and D-galactopyranosyluronate-(1-->3)-2-acetamido-4,6-O-benzylidene-2-deoxy-alpha-D-glucopyranoside via oxidation of the hydroxymethyl group of allyl 2,3,4-tri-O-benzyl-alpha-D-gluco- and D-galactopyranosyl-(1-->3)-2-acetamido-4,6-O-benzylidene-2-deoxy-alpha-D-glucopyranoside under Jones conditions are described. Structures of the title compounds were confirmed by (1)H and (13)C NMR spectroscopy.

Side products of glycosidation with selected 2-acetamido-2-deoxy-D-glucopyranosides.

Allyl 2-acetamido-4,6-O-benzylidene-2-deoxy-3-O-formyl-alpha-D-glucopyranoside, N-acetyl-2,3,4-tri-O-acetyl-L-fucopyranosylamine and products of O-acetyl group migration were found as side products during glycosidation of selected 2-acetamido-2-deoxy-D-glucopyranosides.

The solvent-free thermal dehydration of hexitols on zeolites.

Dehydration of galactitol, D-glucitol and D-mannitol at high temperature in the presence of molecular sieves without solvent under an argon atmosphere is described. Cyclodehydration products with retention or inversion of the configuration at asymmetric carbon atoms, were observed. Reaction of galactitol yielded racemic 1,4-anhydrogalactitol in a first step and then racemic 1,4:3,6-dianhydroiditol. Complete analytical separations of exhaustively O-acetylated reaction products were achieved by GC and structures were assigned using co-injection with standards.

Molecular modeling of Gram-positive bacteria peptidoglycan layer, selected glycopeptide antibiotics and vancomycin derivatives modified with sugar moieties.

Proper understanding of the mechanisms of binding to Gram-positive bacteria cell wall layers-especially to the peptidoglycan (PG) layer, seems to be crucial for proper development of new drug candidates which are effective against these bacteria. In this work we have constructed two different models of the Gram-positive bacteria PG layer: the layered and the scaffold models. PG conformational changes during geometry optimization, models relaxation, and molecular dynamics were described and discussed. We have found that the border surface of both PG layer models differs from the surface located away from the edge of models and the chains formed by disaccharide units prefer helix-like conformation. This curling of PG chains significantly affects the shape of antibiotic-accessible surface and the process is thus crucial for new drug development. Glycopeptide antibiotics effective against Gram-positive bacteria, such as vancomycin and its semisynthetic derivatives-oritavancin and telavancin, bind to d-alanyl-d-alanine stem termini on the peptidoglycan precursors of the cell wall. This binding inhibits cross-linking between the peptides and subsequently prevents cell wall synthesis. In this study some of the aspects of conformational freedom of vancomycin and restrictions from the modifications of vancomycin structure introduced into oritavancin and telavancin and five other vancomycin derivatives (with addition of 2-acetamido-2-deoxy-ß-d-galactopyranosylamine, 2-acetamido-2-deoxy-ß-d-glucopyranosylamine, 1-amine-1-deoxy-d-glucitol, 2-amino-2-deoxy-d-galactitol, or 2-amino-2-deoxy-d-glucitol to the C-terminal amino acid group in the vancomycin) are presented and discussed. The resulting molecular dynamics trajectories, root mean square deviation changes of aglycon and saccharide moieties as well as a comparative study of possible interactions with cyclic and chain forms of modified groups have been carried out, measured, and analyzed. Energetically advantageous conformations show close similarity to the structures known from the experimental data, but the diversity of others suggest very high conformational freedom of all modeled antibiotics and vancomycin derivatives. Alditol derivatives move closer to the peptidoglycan chain more easily but they also form intramolecular interactions more frequently than their homologous cyclic forms. One of the proposed derivatives seems to be a promising agent which is efficient in treatment of infections caused by Gram-positive bacteria.

Structure and properties of the exopolysaccharides produced by Pseudomonas mutabilis T6 and P. mutabilis ATCC 31014.

This paper presents a study on the purification, primary structure, and rheological properties of exopolysaccharides isolated from cultures of Pseudomonas mutabilis T6 and P. mutabilis ATCC 31014. Both polymers are exopolysaccharides of D-mannose. The mannan isolated from P. mutabilis T6 contains on average about 5% of residual ß-D-glucose, in contrast to the mannan from P. mutabilis ATCC 31014, which contained only trace amounts of residual ß-D-glucose (less than 1%). Based on the (13)C NMR spectra, all of the remaining carbohydrates in the exopolysaccharides occur in the form of pyranose rings. All of the mannose residues have the α configuration at the anomeric carbon atom while the glucose adopts the ß configuration. The reaction of both polysaccharide hydrolysates with an optically active alcohol indicates that all of the sugar residues have the D configuration. We found that the main chain of the exopolysaccharide is composed of mannose residues connected through α-(1→6) linkages, of which a large number are substituted on O2 with D-mannose and the remaining are substituted with di- to pentasaccharide fragments. The rheological properties of the exopolysaccharide isolated from P. mutabilis T6 show that its viscosity is over 30 times greater than that of P. mutabilis ATCC 31014.