Anna Kusakiewicz-Dawid

Bio: Anna Kusakiewicz-Dawid is an academic researcher from Opole University. The author has contributed to research in topics: Pyrazole & Hydrogen bond. The author has an hindex of 3, co-authored 7 publications receiving 33 citations.

The synthesis, structure and properties of N-acetylated derivatives of ethyl 3-amino-1H-pyrazole-4-carboxylate.

Abstract: Ethyl 3-amino-1H-pyrazole-4-carboxylate (1) was yielded through total synthesis and reacted with acetic anhydride to give the acetylated products 2-6. Compounds 1-6 were studied with HPLC, X-ray, FT-IR, (1)H-NMR, (13)C-NMR and MS. Acetylation was carried out in solvents of various polarity, namely; chloroform; dioxane; DMF; acetic anhydride, at room temperature and at boiling points; and in the presence and absence of DMAP. The acetylated products are mainly nitrogen atoms in the ring. The position of the ring proton in the solution was based on NOESY; multinuclear HMBC, HSQC spectra and calculations. For equivalent amounts (1-1.5 mol) of acetic anhydride at room temperature two products of monoacetylation are produced in the ring: 2 and 3, ca. 2 : 1 and at the same time only small amount of the third product of monoacetylated, 5 in DMF, as well the product diacetylated, 4. The greatest amount of the product 4 is produced during the reaction with chloroform. However, in this solvent and in dioxane no product 5 is produced. Compound 2 is, largely, formed in dimethylformamide, in the presence DMAP, 0.2 eq. In the presence of this catalytic base, for the first hour, there is a mixture 2 and 3 to the ratio ca. 95 : 5. With 8 eq of Ac(2)O at reflux, after another hour, the compounds 3, 4 and 6 appear about equal amounts. After a longer time, the compound, which appears most in this mixture is triacetylated derivative 6. The structural and spectroscopic characteristics of compounds 1-6 have been given and the methods for their preparation have been provided.

Annular Tautomerism of 3(5)-Disubstituted-1H-pyrazoles with Ester and Amide Groups.

Abstract: A series of disubstituted 1H-pyrazoles with methyl (1), amino (2), and nitro (3) groups, as well as ester (a) or amide (b) groups in positions 3 and 5 was synthesized, and annular tautomerism was investigated using X-ray, theoretical calculations, NMR, and FT-IR methods. The X-ray experiment in the crystal state showed for the compounds with methyl (1a, 1b) and amino (2b) groups the tautomer with ester or amide groups at position 3 (tautomer 3), but for those with a nitro group (3b, 4), tautomer 5. Similar results were obtained in solution by NMR NOE experiments in CDCl3, DMSO-d6, and CD3OD solvents. However, tautomer equilibrium was observed for 2b in DMSO. The FT-IR spectra in chloroform and acetonitrile showed equilibria, which can be ascribed to conformational changes of the cis/trans arrangement of the ester/amide group and pyrazole ring. Theoretical analysis using the M06-2X/6-311++G(d,p) method (in vacuo, chloroform, acetonitrile, and water) and measurement of aromaticity (NICS) showed dependence on internal hydrogen bonds, the influence of the environment, and the effect of the substituent. These factors, pyrazole aromaticity and intra- and inter-molecular interactions, seem to have a considerable influence on the choice of tautomer.

Pyrazole amino acids: hydrogen bonding directed conformations of 3-amino-1H-pyrazole-5-carboxylic acid residue.

Abstract: A series of model compounds containing 3-amino-1H-pyrazole-5-carboxylic acid residue with N-terminal amide/urethane and C-terminal amide/hydrazide/ester groups were investigated by using NMR, Fourier transform infrared, and single-crystal X-ray diffraction methods, additionally supported by theoretical calculations. The studies demonstrate that the most preferred is the extended conformation with torsion angles ϕ and ψ close to ±180°. The studied 1H-pyrazole with N-terminal amide/urethane and C-terminal amide/hydrazide groups solely adopts this energetically favored conformation confirming rigidity of that structural motif. However, when the C-terminal ester group is present, the second conformation with torsion angles ϕ and ψ close to ±180° and 0°, respectively, is accessible. The conformational equilibrium is observed in NMR and Fourier transform infrared studies in solution in polar environment as well as in the crystal structures of other related compounds. The observed conformational preferences are clearly related to the presence of intramolecular interactions formed within the studied residue. Copyright © 2017 European Peptide Society and John Wiley & Sons, Ltd.

Structure-Based Design of Novel Potent Protein Kinase CK2 (CK2) Inhibitors with Phenyl-azole Scaffolds

Abstract: Protein kinase CK2 (CK2) is a ubiquitous serine/threonine protein kinase for hundreds of endogenous substrates. CK2 has been considered to be involved in many diseases, including cancers. Herein we report the discovery of a novel ATP-competitive CK2 inhibitor. Virtual screening of a compound library led to the identification of a hit 2-phenyl-1,3,4-thiadiazole compound. Subsequent structural optimization resulted in the identification of a promising 4-(thiazol-5-yl)benzoic acid derivative.

Revisiting the Structure and Chemistry of 3(5)-Substituted Pyrazoles.

Abstract: Pyrazoles are known as versatile scaffolds in organic synthesis and medicinal chemistry, often used as starting materials for the preparation of more complex heterocyclic systems with relevance in the pharmaceutical field. Pyrazoles are also interesting compounds from a structural viewpoint, mainly because they exhibit tautomerism. This phenomenon may influence their reactivity, with possible impact on the synthetic strategies where pyrazoles take part, as well as on the biological activities of targets bearing a pyrazole moiety, since a change in structure translates into changes in properties. Investigations of the structure of pyrazoles that unravel the tautomeric and conformational preferences are therefore of upmost relevance. 3(5)-Aminopyrazoles are largely explored as precursors in the synthesis of condensed heterocyclic systems, namely pyrazolo[1,5-a]pyrimidines. However, the information available in the literature concerning the structure and chemistry of 3(5)-aminopyrazoles is scarce and disperse. We provide a revision of data on the present subject, based on investigations using theoretical and experimental methods, together with the applications of the compounds in synthesis. It is expected that the combined information will contribute to a deeper understanding of structure/reactivity relationships in this class of heterocycles, with a positive impact in the design of synthetic methods, where they take part.

Five-Membered Ring Systems: With More than One N Atom

Abstract: The synthesis and chemistry of pyrazoles, imidazoles, 1,2,3-triazoles, 1,2,4-triazoles, and tetrazoles were actively pursued in 2013. No attempt was made to incorporate all the exciting chemistry and biological applications that were published in 2013.

Interaction of E. coli DNA with diazine-bridged late first row transition metal complexes derived from hexadentate compartmental ligands: an approach to DNA cleavage/binding studies

Abstract: A series of binuclear CoII, NiII, CuII and ZnII complexes having μ-1,2 diazine bridging have been prepared and characterized by various physico-chemical methods The hexadentate ligands were synthesized by condensing 3,5-dichloroformyl-1H-pyrazole with 2-hydrazinobenzothiazole (L1H) or 4-aminoantipyrine (L2H) in 1:2 ratio Gel electrophoresis data indicate cleavage of E coli DNA to a minute extent by both [Co2L2(μ-Cl)Cl2(H2O)2]·H2O and [Ni2L2(μ-Cl)Cl2(H2O)2] Conversely, the data for the remaining complexes indicated binding but not cleavage These results were confirmed by viscosity measurements and absorption spectral studies An intercalative binding mode is predicted when the title complexes interact with DNA