Aleksandra Dąbrowska

The use of tri-O-acetyl-D-glucal and -D-galactal in the synthesis of 3-acetamido-2,3-dideoxyhexopyranoses and -hexopyranosides.

Addition of hydrazoic acid to alpha,beta-unsaturated aldehydes derived from tri-O-acetyl-D-glucal and -D-galactal gave 3-azido-2,3-dideoxyhexopyranoses. These were converted into 1,4,6-tri-O-acetyl-3-azido-2,3-dideoxyhexopyranoses as well as methyl and ethyl glycosides. Hydrogenation of the proamine group in 3-azido-2,3-dideoxy derivatives provided different 3-amino and 3-acetamido sugars. The configuration and conformation of all products were established on the basis of the 1H and 13 C NMR, IR and polarimetric data.

Synthesis, X-ray structure and high-resolution NMR spectroscopy of methyl 3-azido-2,3-dideoxy-α-d-arabino-hexopyranoside

The synthesis, crystal structure data and 1H and 13C NMR spectroscopy of methyl 3-azido-2,3-dideoxy-alpha-D-arabino-hexopyranoside (5b) is reported. This compound adopts the 4C1 conformation. Hydrogen-bonded molecules of 5b form helices around the crystallographic 4(1) axis.

Coordinate cis-[Cr(C2O4)(pm)(OH2)2]+ Cation as Molecular Biosensor of Pyruvate’s Protective Activity Against Hydrogen Peroxide Mediated Cytotoxity

In this paper instrumental methods of carbon dioxide (CO2) detection in biological material were compared. Using cis-[Cr(C2O4)(pm)(OH2)2]+ cation as a specific molecular biosensor and the stopped-flow technique the concentrations of CO2 released from the cell culture medium as one of final products of pyruvate decomposition caused by hydrogen peroxide were determined. To prove the usefulness of our method of CO2 assessment in the case of biological samples we investigated protective properties of exogenous pyruvate in cultured osteosarcoma 143B cells exposed to 1 mM hydrogen peroxide (H2O2) added directly to culture medium. Pyruvic acid is well known scavenger of H2O2 and, moreover, a molecule which is recognized as one of the major mediator of oxidative stress detected in many diseases and pathological situations like ischemia-reperfusion states. The pyruvates antioxidant activity is described as its rapid reaction with H2O2, which causes nonenzymatic decarboxylation of pyruvate and releases of CO2, water and acetate as final products. In this work for the first time we have correlated the concentration of CO2 dissolved in culture medium with pyruvates oxidant-scavenging abilities. Moreover, the kinetics of the reaction between aqueous solution of CO2 and coordinate ion, cis-[Cr(C2O4)(pm)(OH2)2]+ was analysed. The results obtained enabled determination of the number of steps of the reaction studied. Based on the kinetic equations, rate constants were determined for each step.

From Tri‐O‐Acetyl‐D‐Glucal to (2R,3R,5R)‐2,3‐Diazido‐5‐Hydroxycyclohexanone Oxime

Abstract Methyl 3‐azido‐2,3‐dideoxy‐α/β‐D‐arabino‐ and ‐α/β‐D‐ribo‐hexopyranosides were transformed into 6‐iodo analogues via p‐tolylsulfonyl compounds. Elimination of hydrogen iodide from 6‐iodo glycosides provided methyl 4‐O‐acetyl‐3‐azido‐2,3,6‐trideoxy‐α‐ and ‐β‐D‐threo‐hex‐5‐eno‐pyranosides or 3‐azido‐4‐O‐p‐tolylsulfonyl‐2,3,6‐trideoxy‐α‐D‐threo‐ and ‐β‐D‐erythro‐hex‐5‐eno‐pyranosides. Ferriers carbocyclization of 4‐O‐acetyl‐3‐azido‐2,3,6‐trideoxy‐α‐ and ‐β‐D‐threo‐hex‐5‐eno‐pyranosides gave (2S,3R,5R)‐2‐acetoxy‐3‐azido‐5‐hydroxycyclohexanone, which was converted into oxime. The 2‐OAc group in oxime was substituted by azide ion to yield (2R,3R,5R)‐2,3‐diazido‐5‐hydroxycyclohexanone oxime. The configuration and conformation of all products are widely discussed on the basis of the 1H and 13C NMR.

Synthesis, the crystal structure, and high-resolution NMR spectroscopy of methyl 4-O-acetyl-3-azido-2,3,6-trideoxy-6-iodo-α-d-arabino-hexopyranoside

Selective tosylation followed by acetylation of methyl 3-azido-2,3-dideoxy-alpha-D-arabino-hexopyranoside (1) in pyridine at room temperature affords a mixture of methyl 4-O-acetyl-3-azido-2,3-dideoxy-6-di-O-p-tolylsulfonyl-alpha-D-arabino-hexopyranoside (4) and methyl 3-azido-2,3-dideoxy-4,6-di-O-p-tolylsulfonyl-alpha-D-arabino-hexopyranoside (3). Compound 4 undergoes nucleophilic displacement with sodium iodide in acetic anhydride to give methyl 4-O-acetyl-3-azido-2,3,6-trideoxy-6-iodo-alpha-D-arabino-hexopyranoside (7), whose crystal structure and (1H) and (13)C NMR data are reported. This compound adopts the 4C(1) conformation.

Coordination mode and reactivity of nickel(II) with vitamin B6

This contribution presents a selection of results obtained using spectrophotometric and potentiometric titrations. For several reasons, the investigated equilibria present particular challenges to traditional analysis techniques. Equilibrium constants and UV–vis absorption spectra for different ligands in the complexation process of Ni(II) with pyridoxamine (pm), pyridoxal (pl) and pyridoxine are reported. The gradual and cumulative stability constants occurring in aqueous solution are presented for all complexes studied. Additionally, crystal-field parameters were calculated for two nickel(II) complexes synthesized, [Ni(pm)2]Cl2 and [Ni(pl)2]Cl2, respectively. The minimum inhibitory concentration and minimal bactericidal/fungicidal concentration values for Ni(II) complexes studied were obtained at 25 °C for 24–48 h. The activity data show that the complexes are more potent antimicrobials than the parent ligands. Graphical Abstract

Potassium trans-(bis(oxalato)diaquacobaltate(II)) tetrahydrate: synthesis, structure, potentiometric and thermal studies

The title compound, trans-K2[Co(C2O4)2(H2O)2]·4H2O, was synthesised, and characterised by elemental analysis. Acid dissociation constants for the complex were determined by potentiometric titration and calculated by STOICHIO program. The crystal structure of trans-K2[Co(C2O4)2(H2O)2]·4H2O was determined by X-ray diffraction studies. The asymmetric part of the unit cell contains one symmetric anion of oxalate and water molecule bound with Co(II) ion in crystallographic special position, one potassium cation and two molecules of water. Thermal properties of the complex were examined by thermogravimetric analysis (TGA). A decomposition mechanism is proposed on the basis of the results.

Stopped-Flow Spectrophotometric Study of the Kinetics and Mechanism of CO2 Uptake by cis-[Cr(C2O4)(BaraNH2)(OH2)2]+ Cation and the Acid-Catalyzed Decomposition of cis-[Cr(C2O4)(BaraNH2)OCO2]− Anion in Aqueous Solution

The kinetics of CO2 uptake by the cis-[Cr(C2O4)(BaraNH2)(OH2)2]+ complex cation and the acid hydrolysis of the cis-[Cr(C2O4)(BaraNH2)OCO2]− complex anion (where BaraNH2 denotes methyl 3-amino-2,3-dideoxy-β-D-arabino-hexopyranoside) were studied using the stopped-flow technique. The reactions under study were investigated in aqueous solution in the 288–308 K temperature range. In the case of the reaction between CO2 and cis-[Cr(C2O4)(BaraNH2)(OH2)2]+ cation variable pH values (6.82–8.91) and the constant ionic strength of solution (H+, Na+, ClO4− = 1.0) were used. Carbon dioxide was generated by the reaction between sodium pyruvate and hydrogen peroxide. The acid hydrolysis of cis-[Cr(C2O4)(BaraNH2)OCO2]− was investigated for varying concentrations of H+ ions (0.01–2.7 M). The obtained results enabled the determination of the number of steps of the studied reactions. Based on the kinetic equations, rate constants were determined for each step. Finally, mechanisms for both reactions were proposed and discussed. Based on the obtained results it was concluded that the carboxylation (CO2 uptake) reactions of cis-[Cr(C2O4)(BaraNH2)(OH2)2]+ and the decarboxylation (acid hydrolysis) of the cis-[Cr(C2O4)(BaraNH2)OCO2]−are the opposite of each other.

Spectrophotometric and AM1d studies of the equilibria between oxidovanadium(IV) and four isomers of n-propyl-3-azido-2,3-dideoxy-d-hexopyranosides in aqueous solution

Abstract Complex formation and stability constants for complexes between isomers of n-propyl-3-azido-2,3-dideoxy-d-hexopyranosides and oxidovanadium(IV) were determined in aqueous solution by the spectrophotometric method. Complexes of 1 : 2 metal-to-ligand stoichiometry were formed. The impact of the structures of the ligands on the complex formation was discussed. The energetically most favorable structures of the complexes were calculated and visualized by the AM1d method at the semi-empirical level of theory.

New N-substituted hydrazones, derivatives of uridyl aldehyde

ABSTRACT N-substituted isomeric hydrazones of uridyl aldehyde have been synthesized. The occurrence of the dominant E isomers with respect to the azomethine group was confirmed by means of NMR spectroscopy. Synthesized hydrazones feature an acetonide moiety as a protection of two hydroxyl groups on the ribose part. The attempt to remove the protecting group resulted in an azo-hydrazone tautomeric mixture. The described compounds may be valuable chiral ligands for metal chelation. Assessment of manganese(II) ion affinity to one selected hydrazone was performed.