National Repository of Grey Literature 32 records found  previous11 - 20nextend  jump to record: Search took 0.01 seconds. 
Solid-state NMR study of structure and segmental dynamics of pharmaceutical materials based on the solid dispersions of drugs in polymer matrices.
Policianová, Olívia ; Brus, Jiří (advisor) ; Smrček, Stanislav (referee) ; Dračínský, Martin (referee)
Highly-exact structural characterization is the crucial step in the development and manufacturing process of pharmaceutical materials. Their structural composition is, however, often very complex and hardly identifiable. The eligible way for obtaining definite structural interpretation of these systems appears the high-resolution solid-state nuclear magnetic resonance (ssNMR) spectroscopy. For this purpose the reliable tool - the ssNMR toolbox for comprehensive characterization of various pharmaceutical solids is described. The rigorous optimization of ssNMR techniques is carried out on enormous number of measured samples containing active pharmaceutical ingredients (APIs) with systems ranging from APIs formulated in solid dispersions to pure forms revealing extensive molecular disorder. In this study the influence of polymeric matrix on the creation of solid dispersion type susceptible for finely tuned controlled drug release is likewise discussed. The distinction between variable structural alignments of API molecules in 3D dimension of complicated pharmaceutical solids is allowed via simple strategy - factor analysis applied to hardly describable ssNMR spectra (13 C CP/MAS NMR and 19 F MAS NMR). The results of this ssNMR investigation contribute to better understanding of solid dispersion...
Molecular Dynamics in Selected Polycyclic Aromatic Compounds Monitored by Measurement of Selected Structural Parameters
Sýkora, Jan ; Strašák, Tomáš ; Blechta, Vratislav ; Dračínský, Martin ; Císařová, I.
The polycyclic aromatic compounds attract scientific attention namely due to their conjugated π-π aromatic systems which promise many interesting and unusual optical and electronic properties. Some of these compounds were shown to be effective in the development of materials useful e.g. in molecular-based electronics.
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Novel conformationally locked nucleosides and nucleotides based on bicyclo[3.2.1]octane scaffold as a pseudosugar moiety
Šála, Michal ; Dejmek, Milan ; Procházková, Eliška ; Hřebabecký, Hubert ; Rybáček, Jiří ; Dračínský, Martin ; Novák, Pavel ; Rosenbergová, Šárka ; Fukal, J. ; Sychrovský, Vladimír ; Rosenberg, Ivan ; Nencka, Radim
A route to a series of novel carbocyclic nucleosides locked in North conformation with bicyclo[3.2.1]octane scaffold was developed. Prepared nucleosides served as a starting material for the synthesis of modified oligomers [d(GCATATCAC), r(GCAUAUCAC), and A9]. Biological effects of the prepared nucleosides as well as the hybridization properties of the appropriate duplexes were evaluated.
Enzymatic decomposition of a locked nucleoside phosphoramidate monitored by 31P NMR spectroscopy
Procházková, Eliška ; Hřebabecký, Hubert ; Nencka, Radim ; Dračínský, Martin
Phosphoramidate derivatives are often used as prodrugs of modified nucleosides. The crucial step for the biologically active compound release in cells is then enzymatic hydrolysis of the phosphoramidate derivative. The enzymatic decomposition of a nucleoside prodrug 1 was monitored using 31P NMR spectroscopy and the structure of the reaction products was determined by 1D and 2D (COSY, HSQC, HMBC) NMR experiments and compared with the products obtained with non-enzymatic hydrolysis of the prodrug.
Synthesis and biological properties of polysubstituted 5-nitrosopyrimidines
Janeba, Zlatko ; Čechová, Lucie ; Žurek, Jiří ; Procházková, Eliška ; Dračínský, Martin
2,4,6-Triamino-5-nitrosopyrimidines have been reported to contain a strong intramolecular hydrogen bond between the 5-nitroso and 4- or 6-amino groups, thus forming an additional pseudoring. Such analogues were speculated to be good mimics of fused bicyclic derivatives, e.g. purines. A series of novel polysubstituted 2-amino-5-nitrosopyrimidines, as potential structural mimics of modifi ed purine nucleos(t)ides well-known for their important biological properties, has been designed and synthesized. The physicochemical and biological properties of the prepared polysubstituted 2-amino-5-nitrosopyrimidines are being evaluated.
Switchable intramolecular hydrogen bond in polysubstituted 5-nitrosopyrimidines
Procházková, Eliška ; Čechová, Lucie ; Žurek, Jiří ; Janeba, Zlatko ; Dračínský, Martin
The formation of strong intramolecular hydrogen bonds was observed in a series of 2-amino-5-nitrosopyrimidines with alkylamino and arylamino substituents in the positions 4 and 6. Mixtures of two rotamers differing in the orientation of the nitroso group were observed in the NMR spectra of the compounds where two distinct intramolecular hydrogen bonds could be formed. In several cases, we were able to isolate and characterize the two hydrogen bond isomers (two conformers) by column chromatography. The ratio of the two rotamers in equilibrium depends strongly on the character of the substituents in the positions 4 and 6 and can be finely tuned in a broad range of conformation ratios. The experimental results were supported by DFT calculations.
New amphiphilic prodrugs of adefovir and cidofovir
Tichý, Tomáš ; Andrei, G. ; Dračínský, Martin ; Holý, Antonín ; Balzarini, J. ; Snoeck, R. ; Krečmerová, Marcela
New adefovir (PMEA) prodrugs with a pro-moiety consisting of decyl(oxyethyl) chain bearing hydroxyl function(s), hexaethyleneglycol or a (5-methyl-2-oxo-1,3-dioxolen-4-yl)methyl unit were prepared from the tetrabutylammonium salt of the phosphonate drug and an appropriate alkyl bromide or tosylate. Analogously, two esters of Cidofovir [(S)-HPMPC] bearing a hexaethyleneglycol moiety were prepared. The antiviral activity of the prodrugs was evaluated in vitro. A loss in the antiviral activities of the hydroxylated decyl(oxyethyl) esters and hexaethyleneglycol esters of PMEA against HIV and herpesviruses. (S)-HPMPC prodrugs exhibited anticytomegalovirus activities in the same range as the parent drug, whereas the anti-HSV and anti-VZV activities were one- to seven-fold lower than that of Cidofovir.
The mechanism of isotopic exchange reaction of hydrogen H-5 of uracil derivatives in water and in non-protic solvents
Dračínský, Martin ; Jansa, Petr ; Chocholoušová, Jana ; Vacek, Jaroslav ; Kovačková, Soňa ; Holý, Antonín
The mechanism of isotopic exchange reaction of hydrogen H-5 of uracil and its methyl-derivatives in water and in organic solvents was studied. The key intermediate of the reaction is a C-5 tautomer of uracil. We have used 1H NMR spectroscopy to follow the kinetics of the hydrogen-to-deuterium exchange reaction. In aqueous media, a general base catalysis was observed and in organic solvents we propose a reaction mechanism with participation of the solvent molecules. These findings could be effectively used for the tritium labeling of pyrimidine nucleic acid bases.
Nucleosides containing 8-aza-7,9-dedeazaxanthine
Mařák, David ; Otmar, Miroslav ; Dračínský, Martin ; Krečmerová, Marcela
8-aza-7,9-dideazaxanthine nucleosides were prepared from 5-nitrouracil employing a Barton-Zard reaction.
9-[2-hydroxy-3-(phosphonomethoxy)propyl] ("iso-HPMP")derivatives of purine bases and their side-chain modified analogues: synthesis and antimalarial activity
Krečmerová, Marcela ; Holý, Antonín ; Hocková, Dana ; Dračínský, Martin ; Keough, D. T. ; Guddat, L. W.
Hypoxanthine and guanine iso-HPMP derivatives substsituted in 2´-position were prepared and studied as potential inhibitors of a key enzyme of the malarial parasite Plasmodium falciparum HGXPRT.

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