Search

Derivatives of pyrido[3,4-d]pyridazine, namely, 1-hydroxy-5-methyl-7-phenylpyrido[3,4-d]pyridazin-4(3H)-one dimethylformamide monosolvate, C14H11N3O2·C3H7NO (2), ethyl [1-(2-ethoxy-2-oxoethoxy)-5-methyl-4-oxo-7-phenyl-3,4-dihydropyrido[3,4-d]pyridazin-3-yl]acetate, C18H17N3O4 (3), and ethyl [(5-methyl-4-oxo-7-phenyl-3,4-dihydropyrido[3,4-d]pyridazin-1-yl)oxy]acetate, C22H23N3O6 (4), were synthesized with the aim of discovering new potential biologically active agents. The properties of all three derivatives were characterized by 1H NMR, 13C NMR and FT–IR spectroscopic analysis. All the crystals were obtained by a solvent diffusion method from dimethylformamide (DMF) or dimethyl sulfoxide (DMSO) and characterized by single-crystal X-ray diffraction. The collected X-ray data revealed that the crystals of 2 and 4 belong to the triclinic space group P-1, whereas the crystal of 3 belongs to the monoclinic space group P21/c. The presented derivatives crystallized with one molecule in the asymmetric unit, but only compound 2 crystallized as a solvate with DMF. Structure analysis showed that the molecule of 2 exists as its amide–imidic acid tautomer and that O-alkylation occurred before N-alkylation during the synthesis of the mono- and disubstituted derivatives, i.e. 3 and 4, respectively. The molecular geometries of the 5-methyl-7-phenylpyrido[3,4-d]pyridazine core within the studied derivatives differ in the mutual orientation of the rings. The interplanar angles between the heterocyclic ring and the bound aromatic ring are 1.71 (7), 18.16 (3) and 3.1 (1)° for 2, 3 and 4, respectively. The potential cytotoxicity of these compounds was evaluated against one normal (HaCat) and four human cancer cell lines (A549, DU145, MDA-MB-231 and SKOV-3).

Synthesis of compounds with improved physicochemical properties, including nonlinear optical phenomena such as second harmonic generation, might be considered as one of the most challenging aspects of crystal engineering. In this work, we examine the diversity of hydrogen bond networks and relative efficiencies of second harmonic generation in new noncentrosymmetric complexes comprising phenol-based hydrogen bond donors (2,5-dinitrophenol, 4-nitrophenol, 2,3,5,6-tetrachlorophenol) and pyridinium-based hydrogen bond acceptors (2-aminopyridine, 3,5-dimethylpyridine, 2,3,6-trimethylpyridine): 2-aminopyridinium 2,5-dinitrophenolate [(2APy)+·(2,5-DNP)−] (1), 2-aminopyridinium 4-nitrophenolate 4-nitrophenol [(2APy)+·(4-NP)−·(4-NP)] (2), 2,3,6-trimethylpyridinium 2,3,5,6-tetrachlorophenolate [(2,3,6C)+·(TCP)−] (3), and 3,5-dimethylpyridine 2,3,5,6-tetrachlorophenol [(3,5L)·(TCP)] (4). In compounds (1)–(3), proton transfer occurs; specifically, compounds (1) and (3) are classified as salts while compound (2) belongs to the ionic co-crystal class. Only in the case of compound (4), no evidence of proton transfer is found, attesting to its co-crystal nature. The 2,5-DNP molecule was found to possess a short intramolecular O–H⋯O hydrogen bond and crystallize in the monoclinic crystal system with space group P21. Crystal structure analysis reveals that the substituted phenol–pyridine complexes crystallize as salts linked by N–H⋯O hydrogen bonds in the orthorhombic crystal system with space group Pna21, (1) and (2), or P212121 (3), whereas (4) crystallizes in the monoclinic Cc space group as a formally molecular complex (1 : 1) linked by O–H⋯N hydrogen bonds. Additionally, the vibrational study results are also presented. These results have been discussed in the context of the hydrogen bond network present in the investigated crystals. The relative efficiencies of the second harmonic generation (SHG) process for compounds (1)–(4) were examined under 800 nm irradiation using the Kurtz–Perry powder technique. Low SHG efficiency on the order of 10−4vs. that of KDP was observed for compounds (1) and (4), which is ascribed to the self-filtering effect. For these compounds, the two-photon excited fluorescence was additionally registered.

Thiazolo[4,5-d]pyrimidine derivatives are considered potential therapeutic agents, particularly in the development of anticancer drugs. In this study, new 7-oxo-(2a-e), 7-chloro-(3a-e) and also three 7-amino-(4a-c) 5-trifluoromethyl-2-thioxo-thiazolo[4,5-d]pyrimidine derivatives have been synthesized and evaluated for their potential anticancer activity. These derivatives were characterized by spectroscopic methods and elemental analysis, and the single-crystal X-ray diffraction was further performed to confirm a 3D structure for compounds 2e and 4b. The antiproliferative activity evaluation of twelve new compounds was carried out on a variety of cell lines including four human cancer (A375, C32, DU145, MCF-7/WT) and two normal cell lines (CHO-K1 and HaCaT). Four of them (2b, 3b, 4b and 4c) were selected by the National Cancer Institute and evaluated for their in vitro anticancer activity using the NCI-60 screening program. 7-Chloro-3-phenyl-5-(trifluoromethyl)[1,3]thiazolo[4,5-d]pyrimidine-2(3H)-thione (3b) proved to be the most active among the newly synthesized compounds.

Pyrimidine displays a wide array of bioactivities, and thence, it is still considered a potent unit of new drug research. Its derivative, 5-hydroxymethylpyrimidine, can be found as a scaffold of nontypical nitrogen bases in DNA and as a core of some natural bioactive compounds. In this study, we obtained a series of 5-hydroxymethylpyrimidines that vary in the 4-position by the reduction of proper esters. All compounds were characterized by spectroscopic analysis, and single-crystal X-ray diffraction was performed for some of them. Biological investigations estimated cytotoxic properties against normal (RPTEC) and cancer (HeLa, HepaRG, Caco-2, AGS, A172) cell lines. It was found that the derivatives with an aliphatic amino group at the 4-position are generally less toxic to normal cells than those with a benzylsulfanyl group. Moreover, compounds with bulky constituents exhibit better anticancer properties, though at a moderate level. The specific compounds were chosen due to their most promising IC50 concentration for in silico study. Furthermore, antimicrobial activity tests were performed against six strains of bacteria and one fungus. They demonstrated that only derivatives with at least three carbon chain amino groups at the 4-position have weak antibacterial properties, and only the derivative with 4-benzylsulfanyl constituent exhibits any antifungal action.

The crystal and molecular structure and physicochemical properties of 2-N-methylamino-3-methylpyridine N-oxide (MA3MPO) have been studied. MA3MPO was synthesized from 2-amino-3-methylpyridine by several steps to form colorless crystals suitable for crystallographic analysis. The data reveal that MA3MPO crystallizes in the monoclinic space group P21/n. The studied compound contains a nearly flat triply substituted pyridine skeleton whose structure is stabilized by an intramolecular N–H⋅⋅⋅O hydrogen bond. The N-oxide molecules are connected together by weak C–H⋯O hydrogen bonds, an acceptor of which is the oxygen atom from the N-oxide group. This leads to creation of two-dimensional network of hydrogen bonds. Its IR, Raman, UV–Vis and luminescence spectra have been measured and analyzed on the basis of DFT and NBO quantum chemical calculations in which the B3LYP/6-311++G(d,p) approach was applied. The distribution of the electron levels in the studied compound has been analyzed in terms of the possibility of its participation in the ligand-to-lanthanide ion energy transfer., Graphical abstract Image 10178, Highlights • The 2-N-methylamino-3-methylpyridine N-oxide (MA3MPO) was synthesized and characterized. • The studied compound structure is stabilized by an intramolecular N–H⋯O hydrogen bond. • The molecules are connected together by weak C–H⋯O hydrogen bonds. • The amino group plays the role of effective hydrogen-bond donor but the N-oxide group is a hydrogen-bond acceptor. • X-ray, IR, Raman and DFT methods recognized the existence of the intramolecular N–H⋯O hydrogen bond in the studied compound.

The crystal and molecular structures of 4,4′-dimethyl-3,3′,5,5′-tetranitro-2,2′-hydrazobipyridine have been determined by X-ray diffraction studies and DFT quantum chemical calculations. The 6-311G (2d, 2p) basis set with the B3LYP functional has been used to discuss the optimised structure and vibrational dynamics of the studied compound. It crystallizes in the monoclinic C 2/ c space group with one-half molecule in the asymmetric unit. The intramolecular N H⋯O hydrogen bonds and weak intermolecular C H⋯O contacts play an important role in stabilization of the structure. Structural and vibrational properties of the studied compound have been compared to those of other similar compounds. The conformation of the hydrazo bridge has been analysed in relation to the intramolecular N H⋯O interactions inside the monomeric form. Low temperature behavior of the studied compound has been discussed.

Enterococcus faecalis is known as a significant nosocomial pathogen due to its natural resistance to many antibacterial drugs. Moreover, it was found that E. faecalis infection causes inflammation, production of reactive oxygen species, and DNA damage to human gastric cancer cells, which can induce cancer. In this study, we synthesized and tested the biological activity of a new Schiff base, 5-[(4-ethoxyphenyl)imino]methyl-N-(4-fluorophenyl)-6-methyl-2-phenylpyrimidin-4-amine (3), and compared its properties with an analogous amine (2). In the biological investigation, (3) was found to have antibacterial activity against E. faecalis 29212 and far better anticancer properties, especially against gastric adenocarcinoma (human Caucasian gastric adenocarcinoma), than (2). In addition, both derivatives were non-toxic to normal cells. It is worth mentioning that (3) could potentially inhibit cancer cell growth by inducing cell apoptosis. The results suggest that the presence of the –C=N– bond in the molecule of (3) increases its activity, indicating that 5-iminomethylpyrimidine could be a potent core for further drug discovery research.

Thiazolo[4,5-d]pyrimidine derivatives are considered potential therapeutic agents, particularly in the development of anticancer drugs. In this study, new 7-oxo-(2a-e), 7-chloro-(3a-e) and also three 7-amino-(4a-c) 5-trifluoromethyl-2-thioxo-thiazolo[4,5-d]pyrimidine derivatives have been synthesized and evaluated for their potential anticancer activity. These derivatives were characterized by spectroscopic methods and elemental analysis, and the single-crystal X-ray diffraction was further performed to confirm a 3D structure for compounds 2e and 4b. The antiproliferative activity evaluation of twelve new compounds was carried out on a variety of cell lines including four human cancer (A375, C32, DU145, MCF-7/WT) and two normal cell lines (CHO-K1 and HaCaT). Four of them (2b, 3b, 4b and 4c) were selected by the National Cancer Institute and evaluated for their in vitro anticancer activity using the NCI-60 screening program. 7-Chloro-3-phenyl-5-(trifluoromethyl)[1,3]thiazolo[4,5-d]pyrimidine-2(3H)-thione (3b) proved to be the most active among the newly synthesized compounds.

Thanks to the progress in oncology, pharmacological treatment of cancer is gaining in importance and in the near future anti-cancer chemotherapeutics are expected to be the main method of treatment for cancer diseases. What is more, the search for new anti-cancer compounds with the desired application properties is constantly underway. As a result of designed syntheses, we obtained some new N’-substituted 5-chloro-3-methylisothiazole-4-carboxylic acid hydrazide derivatives with anticancer activity. The structure of new compounds was determined by mass spectrometry (MS), elemental analysis, proton nuclear magnetic resonance spectroscopy (1H-NMR), carbon nuclear magnetic resonance spectroscopy (13C-NMR), 1H-13C NMR correlations and infrared spectroscopy (IR). Moreover, the structures of the compounds were confirmed by crystallographic examination. The antiproliferative MTT tests for 11 prepared compounds was conducted towards human biphenotypic B cell myelomonocytic leukemia MV4-11. SRB test was used to examine their potential anticancer activity towards human colon adenocarcinoma cell lines sensitive LoVo, resistant to doxorubicin LoVo/DX, breast adenocarcinoma MCF-7 and normal non-tumorigenic epithelial cell line derived from mammary gland MCF-10A. The most active compound was 5-chloro-3-methyl-N′-[(1E,2E)-(3-phenyloprop-2-en-1-ylidene]isothiazole-4-carbohydrazide, which showed the highest antiproliferative activity against all tested cell lines.

Thanks to the progress in oncology, pharmacological treatment of cancer is gaining in importance and in the near future anti-cancer chemotherapeutics are expected to be the main method of treatment for cancer diseases. What is more, the search for new anti-cancer compounds with the desired application properties is constantly underway. As a result of designed syntheses, we obtained some new N&rsquo, substituted 5-chloro-3-methylisothiazole-4-carboxylic acid hydrazide derivatives with anticancer activity. The structure of new compounds was determined by mass spectrometry (MS), elemental analysis, proton nuclear magnetic resonance spectroscopy (1H-NMR), carbon nuclear magnetic resonance spectroscopy (13C-NMR), 1H-13C NMR correlations and infrared spectroscopy (IR). Moreover, the structures of the compounds were confirmed by crystallographic examination. The antiproliferative MTT tests for 11 prepared compounds was conducted towards human biphenotypic B cell myelomonocytic leukemia MV4-11. SRB test was used to examine their potential anticancer activity towards human colon adenocarcinoma cell lines sensitive LoVo, resistant to doxorubicin LoVo/DX, breast adenocarcinoma MCF-7 and normal non-tumorigenic epithelial cell line derived from mammary gland MCF-10A. The most active compound was 5-chloro-3-methyl-N&prime, [(1E,2E)-(3-phenyloprop-2-en-1-ylidene]isothiazole-4-carbohydrazide, which showed the highest antiproliferative activity against all tested cell lines.

New europium and terbium [LnCl3L3(H2O)2] polycrystalline complexes were synthesized with the ligand L = 3-bromo-4-methylthio-2,6-lutidine N-oxide. IR, Raman, electron absorption UV-VIS and emission spectra measurements were carried out for these compounds. Re-crystallization of these materials led to formation of single crystals with another composition [LnL(H2O)7]Cl3∙L3, they were characterized by X-ray diffraction technique and spectroscopic measurements. Both types of the materials consist of eight coordinated LnCl3O3O’2 or LnOO’7 polyhedrons containing O - oxygen atoms of the N-oxide group, chlorine atoms or O’ - oxygen atoms of the water units. The crystal structure was solved for two complexes of the formula [Ln(L)(H2O)7]Cl3∙(L)3 where Ln = Eu and Tb. X-ray diffraction analysis reveals that these complexes are isostructural with P21/m space group. The optimization of the molecular system and frequency calculations were carried out using density functional theory (DFT). The DFT quantum chemical calculations of the vibrational wavenumbers were performed for the ligands used for the Eu3+ and Tb3+ ions complexation. The emission measurements were carried out with the femtosecond excitation. The effective ligand-to-metal energy transfer was discovered in the [LnCl3L3(H2O)2] complexes formed in the polycrystalline state.

The crystal and molecular structures of 6,6′-dimethyl-3,3′,5,5′-tetranitro-2,2′-hydrazobipyridine have been determined by X-ray diffraction and DFT quantum chemical methods. The B3LYP/6-311G(2d,2p) approach has been used in the theoretical calculations. The studied compound crystallizes in the monoclinic P21/n space group (Z = 2) with one-half molecule in the asymmetric unit. In the molecular structure of the studied compound the intramolecular N H⋯O hydrogen bonds play a crucial role. These molecules also interact in the unit cell by means of weak intermolecular C H⋯O contacts. IR and Raman spectra have been measured and simulated from the optimized geometry. In the calculations the monomeric unit has been taken into account because the intermolecular interactions between the components of the unit cell are weak and the factor group splitting is not observed in the experimental spectra. The structural and vibrational properties of the hydrazo bonds have been described with their relation to the intramolecular N H⋯O interaction existing in the structure of the monomeric form.

The synthesis of a series of novel 7-aminooxazolo[5,4-d]pyrimidines 5, transformations during their synthesis and their physicochemical characteristics have been described. Complete detailed spectral analysis of the intermediates 2&ndash, 4, the N&prime, cyanooxazolylacetamidine by-products 7 and final compounds 5 has been carried out using MS, IR, 1D and 2D NMR spectroscopy. Theoretical research was carried out to explain the privileged formation of 7-aminooxazolo[5,4-d]pyrimidines in relation to the possibility of their isomer formation and the related thermodynamic aspects. Additionally, the single-crystal X-ray diffraction analysis for 5h was reported. Ten 7-aminooxazolo[5,4-d]pyrimidines 5 (SCM1&ndash, 10) were biologically tested in vitro to preliminarily evaluate their immunological, antiviral and anticancer activity. Compounds SCM5 and SCM9 showed the best immunoregulatory profile. The compounds displayed low-toxicity and strongly inhibited phytohemagglutinin A-induced proliferation of human peripheral blood lymphocytes and lipopolysaccharide-induced proliferation of mouse splenocytes. Compound SCM9 caused also a moderate suppression of tumor necrosis factor &alpha, (TNF-&alpha, ) production in a human whole blood culture. Of note, the compounds also inhibited the growth of selected tumor cell lines and inhibited replication of human herpes virus type-1 (HHV-1) virus in A-549 cell line. Molecular investigations showed that the compounds exerted differential changes in expression of signaling proteins in Jurkat and WEHI-231 cell lines. The activity of SCM5 is likely associated with elicitation of cell signaling pathways leading to cell apoptosis. The compounds may be of interest in terms of therapeutic utility as inhibitors of autoimmune disorders, virus replication and antitumor agents.

This article presents the synthesis of three new 4-thiopyrimidine derivatives obtained from ethyl 4-methyl-2-phenyl-6-sulfanylpyrimidine-5-carboxylate as the starting material, namely, ethyl 4-[(4-chlorobenzyl)sulfanyl]-6-methyl-2-phenylpyrimidine-5-carboxylate, C21H19ClN2O2S, (2), {4-[(4-chlorobenzyl)sulfanyl]-6-methyl-2-phenylpyrimidin-5-yl}methanol, C19H17ClN2OS, (3), and 4-[(4-chlorobenzyl)sulfanyl]-5,6-dimethyl-2-phenylpyrimidine, C19H17ClN2S, (4), which vary in the substituent at the 5-position of the pyrimidine ring. The compounds were characterized by 1H NMR, 13C NMR, IR and mass spectroscopies, and also elemental analysis. The molecular structures were further studied by single-crystal X-ray diffraction. Compound (2) crystallizes in the space group P-1 with one molecule in the asymmetric unit, whereas compounds (3) and (4) crystallize in the space group P21/c with two and one molecule, respectively, in their asymmetric units. The conformation of each molecule is best defined by the dihedral angles formed between the pyrimidine ring and the planes of the two aryl substituents attached at the 2- and 4-positions. The only structural difference between the three compounds is the substituent at the 5-position of the pyrimidine ring, but they present significantly different features in the hydrogen-bond interactions. Compound (2) displays a one-dimensional chain formed by hydrogen bonds and the chains are further extended into a two-dimensional network. Molecules of (3) and (4) generate one-dimensional chains formed through intermolecular interactions. The study examines the cytotoxicity of compounds (3) and (4) against Human umbilical vein endothelial cells (HUVEC) and HeLa, K562 and CFPAC cancer cell lines. The presence of the hydroxymethyl and methyl groups in (3) and (4), respectively, offers an interesting new insight into the structures and behaviour of these derivatives. Compound (4) was found to be nontoxic against CFPAC and HUVEC; however, it shows weak activity against the HeLa and K563 cell lines. The presence of a hydroxy group in (3) significantly increases its cytotoxicity towards both, i.e. the cancer (HeLa, K562 and CFPAC) and normal (HUVEC) cell lines.

The crystal and molecular structures of 6-methyl-3,5-dinitro-2-[(E)-phenyldiazenyl]pyridine have been determined by X-ray diffraction and quantum chemical DFT calculations. The crystal is monoclinic, space group Cc (No. 9) with Z = 4 with the unit cell parameters: a = 12.083(7), b = 12.881(6), c = 8.134(3) A and β = 97.09(5)°. The azo-bridge appears in the trans conformation in which C2-N2-N2′-C1′ torsion angle takes a value − 178.6(3)°, whereas the dihedral angle between the planes of the phenyl and pyridine rings is 3.5(2)°. The IR and Raman spectra measured in the temperature range 80–350 K and quantum chemical calculations with the use of B3LYP/6-311G(2d,2p) approach confirmed the trans configuration of the azo-bridge as the most stable energetically and allowed determination of the energy other virtual structures. The observed effects were used in the discussion of vibrational dynamics of the studied compound. The energy gap between cis and trans conformers equals to 1.054 eV (0.03873 Hartree). The electron absorption and emission spectra have been measured and analyzed on the basis of DFT calculations. The life time of the excited state is 12 μs and the Stokes shift is close to 5470 cm− 1.

Two proton transfer hydrogen-bonded complexes of 5-sulfosalicylic acid (3-carboxy-4-hydroxybenzenesulfonic acid, 5-SSA) with the aromatic amides: nicotinamide (NA) and isonicotinamide (INA), are characterized by X-ray diffraction and spectroscopic studies. In the crystal structures of nicotinamidium 3-carboxy-4-hydroxybenzenesulfonate, 1, and isonicotinamidium 3-carboxy-4-hydroxybenzenesulfonate monohydrate, 2, the ions are linked into three dimensional frameworks by a combination of O–H⋯O, N–H⋯O and C–H⋯O hydrogen bonds and cation–anion π–π stacking interactions. The hydrogen-bonding behavior of the pyridine N atom is different in the two crystals, bonding to a sulfonate O atom of anion in 2 but to a carbonyl O atom of cation in 1. The complex 1 shows relatively efficient second harmonic frequency generation.

The crystal and molecular structure of 4,4′-dimethyl-3,3′-dinitro-2,2′-hydrazobipyridine have been determined by X-ray diffraction and quantum chemical DFT analysis. The title compound crystallizes in P 1 ¯ space group, with one-half molecule in the asymmetric unit. The molecular structure is stabilized by intramolecular N H···O hydrogen bonds. The molecules are linked by a combination of weak intermolecular C H⋯O interactions and also aromatic π–π stacking. The molecular structure of the studied compound has been determined using the DFT B3LYP/6-311G(2d,2p) approach and compared to that derived from X-ray studies. The IR and Raman wavenumbers have been calculated for the optimized geometry of a possible monomer structural model. The structural and vibrational properties of the intramolecular N H···O interaction are described.

Two molecular complexes of amides (nicotinamide and isonicotinamide) with 3-nitrophenol are characterized by X-ray diffraction and spectroscopic studies. Crystal structure analyses at 100 K revealed different features to distinguish the co-crystals. The asymmetric unit of the crystal structure of nicotinamide–3-nitrophenol (1:1), 1 , consists of two symmetry-independent nicotinamide molecules and two symmetry-independent 3-nitrophenol molecules. The crystal structure of 1 displays an extended hydrogen bond network generated by O H⋯O, N H⋯O and N H⋯N interactions. The structure of isonicotinamide–3-nitrophenol (1:1), 2 , contains O H⋯N hydrogen bonds engaging the pyridine N atom. In 2 , the amide forms a R 2 2 ( 8 ) homodimer which is absent in 1 . The complex 1 shows relatively efficient second harmonic frequency generation.

New organic–organic salt, 2-amino-4-methyl-3-nitropyridinium trifluoroacetate, has been synthesised and characterised by FT-IR, FT-Raman, DSC and single crystal X-ray crystallography. The 2-amino-4-methyl-3-nitropyridinium trifluoroacetate undergoes a reversible phase transition at ∼162 K. The X-ray structures, vibrational spectra and quantum chemical DFT calculations (B3LYP/6-31G(d,p) approach) have been analysed for high-temperature and low-temperature modifications of the compound, which both crystallize in orthorhombic space group Pbca with two non-equivalent cations and two anions in the asymmetric unit. Their crystal and molecular structures have been compared and the role of the intermolecular interactions in these crystals has been analysed. The mechanisms of the phase transition have been proposed.

Solid state NMR spectroscopy and gauge including atomic orbital (GIAO) theoretical calculations were employed to establish structural restraints (ionization, hydrogen bonding, spatial arrangement) for O-phosphorylated l-threonine derivatives in different ionization states and hydrogen bonding strengths. These structural restraints are invaluable in molecular modeling and docking procedures for biological species containing phosphoryl groups. Both the experimental and the GIAO approach show that 31P delta ii chemical shift tensor parameters are very sensitive to the ionization state. The negative values found for the skew kappa are typical for -2 phosphates. The distinct span Omega values reflect the change of strength of hydrogen bonding. For species in the -1 ionization state, engaged in very strong hydrogen bonds, Omega is smaller than for a phosphate group involved in weak hydrogen bonding. For phosphates in the -2 ionization state, Omega is significantly smaller compared to -1 species, although the kappa for -1 samples never reaches negative values. For -1 phosphate residues, in the case when 1H one pulse and/or combined rotation and multiple pulse spectroscopy (CRAMPS) sequences fail and assignment of proton chemical shift is ambiguous, a combination of 1H-(13)C and 1H-(31)P 2D heteronuclear correlation (HETCOR) correlations is found to be an excellent tool for the elucidation of 1H isotropic chemical shifts. In addition, a 2D strategy using 1H-(1)H double quantum filter (DQF) correlations [a back-to-back (BABA) sequence in this work] is useful for analyzing the topology of hydrogen bonding. In the case of a multicenter phosphorus domain, 2D 31P-(31)P proton driven spin diffusion experiments give information about the spatial arrangement of the phosphate residues.

A new organic–organic salt, 2-aminopyridinium-4-hydroxybenzenosulfonate, has been synthesised and characterised by means of FT-IR and FT-Raman spectroscopies, differential scanning calorimetry (DSC) and single crystal X-ray crystallography. Its vibrational spectra have been discussed on the basis of quantum chemical density functional theory (DFT) calculations using the B3LYP/6-31G(d,p) approach. The role of the intermolecular interactions in this crystal is analysed. The N–H ··· O interactions between the hydrogen atoms of the pyridinium cation and oxygen atoms of hydroxybenzenosulfonate anion built the supramolecular arrangement in three-dimensional space. Copyright  2008 John Wiley & Sons, Ltd.

The crystal structure of the title compound {systematic name: dicyclohexylaminium (2S,3R)-2-[(tert-butoxycarbonyl)amino]-3-hydroxybutanoate}, C12H24N+·C9H16NO5 −, contains Boc-L-threoninate anions and dicyclohexylaminium cations. A network of O—H...O and N—H...O hydrogen bonds leads to chains of ions running along the b axis.

Ethyl butyryloxy(phenyl)methane(P-phenyl)phosphinate was hydrolyzed using four bacterial species as biocatalysts. In all cases the reaction was stereoselective and isomers bearing an α-carbon atom with an (S)-configuration were hydrolyzed preferentially. Also a lack of stereoselectivity toward the phosphorus atom was observed. Hydrolysis of one enantiomeric mixture, namely mixture of (SP,R) and (RP,S) configuration afforded enantiomerically pure ethyl (RP,S)-hydroxy(phenyl)methane(P-phenyl)phosphinate, configuration of which was established by X-ray crystallography. The observed 1H and 31P NMR chemical shifts of Mosher esters of ethyl hydroxy(phenyl)methane(P-phenyl)phosphinate were correlated with the configurations of both stereogenic centers of all four stereoisomers.

Solvent-free (2S)-methyl 2-ammonio-3-(4-hydroxyphenyl)propionate chloride, C10H14NO3+.Cl-, (I), and its methanol solvate, C10H14NO3+.Cl-.CH3OH, (II), are obtained from different solvents: crystallization from ethanol or propan-2-ol gives the same solvent-free crystals of (I) in both cases, while crystals of (II) were obtained by crystallization from methanol. The structure of (I) is characterized by the presence of two-dimensional layers linked together by N-H...Cl and O-H...Cl hydrogen bonds and also by C-H...O contacts. Incorporation of the methanol solvent molecule in (II) introduces additional O-H...O hydrogen bonds linking the two-dimensional layers, resulting in the formation of a three-dimensional network.

Summary Interactions of O-phospho-DL-threonine (DL-PThr) in the different ionization states with potassium, sodium and ammonium cations have been studied on five crystals (denoted as I-V). In semipotassium salt of DL-PThr (I), the phosphate group adopts the nearly trans conformation, whereas in mono- and disodium salts (II and III) and in mono- and diammonium salts of DL-PThr (IV and V) the phosphate group is situated anticlinal to the rest of the molecule, showing its conformational flexibility depending on the crystal environment, where significant differences are observed in interactions of K+, Na+ and NH4 + cations with PThr. The crystal packing in each of I-V is dominated by interactions between PThr moieties and the cations and hydrogen bond networks involving the phosphate, carboxyl, and amino groups of PThr moieties and water molecules. In crystal I, water molecules are not involved in potassium cation complexation. In crystals II and III, sodium cations show a preference for water molecules over PThr anions as ligands in coordination spheres. Especially in crystals I-III, water molecules are involved in very extensive networks of hydrogen-bond interactions.

Three polymorphic forms of dipotassium salt of O-phospho-L-serine were obtained from water solutions at different pH. Two forms (α and β) crystallize in the monoclinic space group P2, while the third (γ) crystallizes in the orthorhombic space group P212121. All crystals are composed of O-phospho-L-serine ions, potassium cations and water molecules of hydration. In all salts, the O-phospho-L-serine moiety exists as a dianion with two negatively charged phosphate groups, one negatively charged carboxyl group and one positively charged ammonium group. The molecular geometry of O-phospho-L-serine (PSer) dianions resembles that found for the zwitterions in crystalline L- and DL-forms of O-phosphoserine. The orientation of the phosphate group relative to the serine backbone is almost trans (–ap) in all three forms. In all forms, there are no significant differences in the values of the bond lengths in the O-phospho-L-serine moiety. The crystal packings are dominated by K…O interactions and intermolecular hydrogen bonds. The polyhedrons around the K+ cations are rather irregular. However, a specific spatial arrangement of potassium cations is similar in all three crystals.

The crystal and molecular structures of the potassium (I), ammonium (II) and diammonium (III) salts of O-phospho- l -threonine were determined by X-ray methods. The crystal structure of I contains two independent monoanions [denoted as (1) and (2)] and that of II four independent monoanions [denoted as (1), (2), (3) and (4)], while III contains one independent dianion in an asymmetric unit. The monoanions of O-phospho- l -threonine contain the ionized carboxyl group (more acidic) and singly protonated phosphate group which is double ionized in the dianion of III. The overall conformation of the threonine moiety in all anions is similar to that found in the zwitterions of phosphothreonine but differs from that in l -threonine. The carbon atom chains adopt antiperiplanar conformation in all anions of O-phospho- l -threonine. The anions differ slightly in the orientation of the terminal phosphate O atoms with regard to the threonine moiety. In all three crystals, the molecules are arranged in three-dimensional networks via N–H⋯O [and O–H⋯O in I and II] hydrogen bonds in which all N-bonded [and O-bonded in I and II] H atoms are involved. Additionally, the crystal structures are stabilized by C–H⋯O interactions of less than 3.5 A.

N-(p-dimethylaminophenyl)-α-(3acetamido-4-nitrophenyl)nitrone (I) and 3-acetamido-4-nitrobenzylpyridinium bromide (II) were synthesized and their crystal structures were determined by X-ray diffraction methods. The geometry of carbon–nitrogen bond in nitrone is trans. In I the acetamido moiety slightly deviates from plane to the rest of molecule. The intramolecular N–H⋯O and C–H⋯O as well as intermolecular C–H⋯O hydrogen bonds stabilize the crystal structures of both the compounds. NMR investigations of II have given spectra with extra signals in comparison to the number of expected that suggests that dominating structure of this compound observed in crystal state coexists in solution with comparable amount of the additional form due to an interaction with solvent and increasing conformational freedom. For II duplication of signal number is observed for the 3-acetamido-4-nitrobenzyl substituent due to formation only of two different edge to face structures of this compound in DMSO and D2O solution. For I in DMSO solution the major form has perpendicular orientation of N,N-dimethylaniline substituent on nitrone bond against the plane containing the rest of the molecule.

The title compound, C26H23F3N4O, crystallizes with two symmetry-independent molecules in the asymmetric unit, denotedAandB, which differ mainly in the rotation of the methoxyphenyl ring. The –CF3group of moleculeBis disordered by rotation, with the F atoms split over two sets of sites; the occupancy factor for the major component is 0.853 (4). The dihedral angles between the pyrimidine ring and the attached phenyl, methoxyphenyl and trifluoromethylphenyl rings are 8.1 (2), 37.5 (2) and 70.7 (2)°, respectively, in moleculeA, and 9.3 (2), 5.3 (2) and 79.7 (2)° in moleculeB. An intramolecular N—H...N hydrogen bond occurs in each molecule. In the crystal, two crystallographically independent molecules associate into a dimerviaa pair of N—H...N hydrogen bonds, with a resultingR22(12) ring motif and π–π stacking interactions [centroid–centroid distance = 3.517 (4) Å] between the pyrimidine rings. For theAmolecules, there are intermolecular C—H...O hydrogen bonds between an aryl C atom of methoxyphenyl ring and a methoxy O atom of an adjacent molecule. A similar interaction is lacking in theBmolecules.

The title compound, 2Na+·C6H4NO6P2−·3H2O, crystallizes from acetone with one 4-nitrophenyl phosphate dianion, two Na+ cations and three water molecules in the asymmetric unit. In the crystal packing, layers parallel to the ab plane are formed by Na+ cations chelated by dianions, and bridged by dianions and water molecules. Adjacent layers are linked through O—H...O hydrogen bonds.

The title compound, C24H21N3O6·2CH2Cl2, crystallizes with two independent mol­ecules in the asymmetric unit, each with a different conformation. In the crystal structure, mol­ecules form two-dimensional sheets in the ab plane due to a combination of O—H⋯O and N—H⋯O hydrogen bonds. Only edge-to-face stacking inter­actions are observed between fluorenyl aromatic groups of adjacent sheets. Solvent mol­ecules are located within the inter­molecular voids along the b axis and fill the spaces between carbamate linkages or lie between the fluorenyl aromatic groups.

Two polymorphic forms of the title compound, C24H20Cl2N4, were obtained and characterized using X-ray crystal structure analysis. Colourless crystals of polymorph (Ia) were obtained from the oily mother residue. Recrystallization of polymorph (Ia) from an acetone-methanol mixture resulted in pale-yellow crystals of polymorph (Ib). The major feature distinguishing the two polymorphic forms is their interaction modes, and hence their packing arrangements. In the crystal structure of polymorph (Ia), there are N-H...N hydrogen bonds and also aromatic pi-pi stacking interactions between molecules. The molecules of polymorph (Ib) are linked by N-H...Cl hydrogen bonds only.

Two new organic-organic salts, 2-amino-4-methyl-5-nitropyridinium trifluoroacetate monohydrate (AMNP-TFA), and 2-amino-4-methyl-5-nitropyridinium 4-hydroxybenzenesulfonate (AMNP-HBS), were obtained and characterized by means of FT-IR, FT-Raman and single crystal X-ray crystallography. In the former crystal, the cations, anions and water molecules are linked into layers by three types of hydrogen bonds, NPH⋯O, NAH⋯O and OH⋯O. These layers are connected by weaker CH⋯O hydrogen bonds. In the latter crystal, the cations and anions form one-dimensional structure through a number of hydrogen-bonding interactions involving the OH, NH(+) and NH2 groups as donors. In this case the NPH⋯O and NAH⋯O hydrogen bonds are formed. The combination of interactions between cations and anions results in the formation of columns. Additionally, there are π-π stacking interactions between the columns. The obtained X-ray structural data are related to the vibrational spectra of the studied crystals.