Michal Čajan

The first iron(III) complexes with cyclin-dependent kinase inhibitors: Magnetic, spectroscopic (IR, ES+ MS, NMR, 57Fe Mössbauer), theoretical, and biological activity studies

The first Fe(III) complexes 1-6 with cyclin-dependent kinase (CDK) inhibitors of the type [Fe(L(n))Cl(3)].nH(2)O (n=0 for 1, 1 for 2, 2 for 3-6; L(1)-L(6)=C2- and phenyl-substituted CDK inhibitors derived from 6-benzylamino-9-isopropylpurine), have been synthesized and characterized by elemental analysis, IR, (57)Fe Mössbauer, (1)H and (13)C NMR, and ES+ mass spectroscopies, conductivity and magnetic susceptibility measurements, and thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The study revealed that the compounds are mononuclear, tetrahedral high-spin (S=5/2) Fe(III) complexes with an admixture of an S=3/2 spin state originating probably from five-coordinated Fe(III) ions either connecting with a bidentate coordination mode of the CDK inhibitor ligand or relating to the possibility that one crystal water molecule enters the coordination sphere of the central atom in a portion of molecules of the appropriate complex. Nearly spin-only value of the effective magnetic moment (5.82micro(eff)/micro(B)) was determined for compound 1 due to absence of crystal water molecule(s) in the structure of the complex. Based on NMR data and DFT calculations, we assume that the appropriate organic ligand is coordinated to the Fe(III) ion through the N7 atom of a purine moiety. The cytotoxicity of the complexes was tested in vitro against selected human cancer cell lines (G-361, HOS, K-562 and MCF-7) along with the ability to inhibit the CDK2/cyclinE kinase. The best cytotoxicity (IC(50): 4-23muM) and inhibition activity (IC(50): 0.02-0.09microM) results have been achieved in the case of complexes 2-4, and complexes 3, 4 and 6, respectively. In addition, the X-ray structure of 2-chloro-6-benzylamino-9-isopropylpurine, i.e. a precursor for the preparation of L(1), L(4) and L(5), is also described.

One-Pot Quinazolin-4-yl-thiourea Synthesis via N-(2-Cyanophenyl) benzimidoyl isothiocyanate

1-substituted-3-(2-phenylquinazolin-4-yl) thioureas (7) were produced by an intramolecular cycloaddition reaction of 1-substitued-3-[(2-cyanophenyl- imino)phenylmethyl] thioureas (3). These compounds in turn were prepared by the reaction of N-(2-cyanophenyl)benzimidoyl isothiocyanate (2) with primary amines. The structures of products 7 were confirmed by FTIR, 1H-NMR, 13C-NMR, mass spectroscopy and X-ray crystallography.

One-Pot Quinazolin-4-ylidenethiourea Synthesis via N-(2- Cyanophenyl)benzimidoyl isothiocyanate

1,1-Disubstituted-3-(2-phenyl-3H-quinazolin-4-ylidene)thioureas (8) were synthesized in a one pot reaction of N-(2-cyanophenyl)benzimidoyl isothicyanate (3) with secondary amines. The products underwent transamination reactions. Compounds 8a-8g were identified by FTIR, 1H-NMR, 13C-NMR, mass spectroscopy and X-ray crystallography.

Stability of complexes of aromatic amides with bromide anion: quantitative structure--property relationships

Most of the theoretical studies published to-date on the structural and electronic properties of supramolecules have been devoted to the neutral or cationic complexes, while little is known about anionic systems. A detailed theoretical study of the interaction between simple aromatic amides and the bromide anion has recently been published (Cajan, M.; Stibor, I.; Koca, J. J. Phys. Chem. A 1999, 103, 3778). The present work focuses on the structural and physicochemical parameters of simple aromatic amides related to their ability to form the 1:1 complex with a bromide anion. A quantitative structure-property relationships (QSPR) model for the prediction of association constants is proposed. The model based on 22 complexes and nine molecular descriptors explained 96% (84% cross-validated) of the variance in association constants. The descriptors employed in this model included parameters for the characterization of conformational behavior and the 3D structure of amide molecules, distribution of electron density on the amidic functional group, and parameters for substitution on aromatic units. The quantitative structure-property relationship approach predicted the association constants with comparable quality, but significantly lower computational demand, than molecular modeling or standard quantum chemistry calculations.

Mechanism of Hydrogen-Bond Array Isomerization in Tetrahydroxycalix[4]arene and Tetrahydroxythiacalix[4]arene

Possible rearrangement mechanisms of hydrogen-bond arrays formed at the lower rim of tetrahydroxycalix[4]arene and tetrahydroxythiacalix[4]arene were studied by means of density functional theory and the resolution identity approximation modification of Møller-Plesset perturbation theory (RI-MP2). Influence of solvent to height of energy barriers was quantified by use of the conductorlike screening model (COSMO) of implicit solvent (chloroform). Generally, two types of mechanisms were investigated. The first is represented by a synchronous single-step jump of all four hydroxyl protons. Pathways of the second mechanism include the rotation of one or more hydroxyl groups around the CAr-O bond. Theoretical results, in agreement with recently published experimental data (Lang et al. J. Chem. Phys. 2005, 122, 044056), prefer a jump mechanism for the methylene-bridged calix[4]arene. Concerning the thiacalix[4]arene, results obtained by COSMO as well as RI-MP2 calculations show that the rotational mechanism is very competitive and it could even be more favorable.