Novel macrocyclic uracil derivatives: Structure in solid and solution

Isomeric pyrimidinophanes containing uracil moieties and nitrogen atoms in bridges have been synthesized and characterized by a variety of methods both in solid and in solution. Unambiguous assignment of mutual arrangement of C(4)_pyrO groups at different pyrimidine rings in isomers is made by X-ray diffraction. In solutions the arrangement of C(4)_pyrO groups of the isomeric pyrimidinophanes results in different dipole moments. Based on dipole moments simulations mutual orientation of uracil units in isomers is analysed. UV-data are discussed in terms of hypo- or hyperchromic effect.     

Novel derivatives of UDP-glucose: concise synthesis and fluorescent properties

A series of novel 5-substituted UDP-glucose derivatives with interesting fluorescent properties and potential applications as sensors for carbohydrate-active enzymes is reported. An efficient synthesis of the target molecules was developed, centred around the Suzuki-Miyaura reaction of (hetero)arylboronic acids with 5-iodo UDP-glucose. Interestingly, the optimised cross-coupling conditions could also be applied successfully to 5-bromo UMP, but not to 5-bromo UDP-glucose.     

Novel pyrazoline and pyrazole porphyrin derivatives: synthesis and photophysical properties

2-Vinyl-5,10,15,20-tetraphenylporphyrinatozinc(II) reacts with nitrile imines, generated in situ from ethyl hydrazono-α-bromoglyoxylates, affording the corresponding pyrazolines in good to excellent yields. Treatment of pyrazoline derivatives with DDQ affords the corresponding pyrazole derivatives with moderate to excellent yields. When the hydrolysis of ester group in the pyrazoline derivatives was considered, it was observed the concomitant oxidation of the heterocyclic unit, which allowed directly obtaining porphyrin-pyrazole derivatives with a carboxylic group, in very good yields.The photophysical properties of the pyrazoline and pyrazole porphyrin derivatives show that the influence of the heterocyclic substituents is limited by the tendency of these molecules to aggregate. All other properties and especially the triplet kinetics remain unaffected. The adducts with low tendency to aggregate showed very high singlet oxygen yield, which makes these compounds interesting for their use as photosensitizers for PDT.     

Bifunctional coumarin derivatives in solution and solid phase synthesis of fluorogenic enzyme substrates

The use of the fluorescent bifunctional compounds 7‐amino‐4‐coumarinyl‐acetic acid 1 , 7‐hydroxy‐4‐coumarinyl‐acetic acid 2 and ethyl 7‐amino‐4‐coumarinyl‐acetate 3 in solution and solid phase synthesis of fluorogenic enzyme substrates was examined. The intramolecularly quenched fluorogenic substrate N‐(7‐amino‐4‐coumarinyl‐acetyl)‐L‐phenylalanyl‐p‐nitroanilide 5 , and the fluorogenic one ethyl 7‐(glutaryl‐L‐phenylalanilamido)‐4‐coumarinyl‐acetate 8 , both suitable for chymotrypsin and/or chymotrypsin like enzymes determination, were prepared in solution. The substrates 7‐oleyloxy‐4‐coumarinyl‐acetic acid 13 and 7‐palmitoyloxy‐4‐coumarinyl‐acetic acid 14 , suitable for the enzymatic study of lipases, were prepared by solid phase technique using 2‐chloro‐chlorotrityl‐resin. The study of the fluorescence properties of the fluorophores 1, 2, 3 , and substrates 5, 8,13,14 showed that the examined bifunctional coumarin derivatives are suitable markers for solution and solid phase synthesis of fluorogenic enzyme substrates.     

Novel pyrano[3,2-b]indole derivatives: synthesis and some properties

Acid treatment of β-(3-acetoxyindol-2-yl)-α-cyanoacrylic acid derivatives (ethyl ester and nitrile) with aqueous or gaseous HCl afforded novel 3-substituted 2-oxo-2,5-dihydropyra-no[3,2-b]indoles. 2-Oxo-2,5-dihydropyrano[3,2-b]indole-3-carbonitrile was converted into ethyl 2-oxo-2,5-dihydropyrano[3,2-b]indole-3-carboximidate.     

Novel 1,4-benzothiazine derivatives: synthesis,crystal structure,and anti-bacterial properties

In order to develop relatively small molecules as pharmacologically active molecules, novel 1,4-benzothiazine derivatives with triazole and oxazolidinone were synthesized. In this study, a series of 1,2,3-triazolylmethyl-1,4-benzothiazine derivatives were developed by exploiting a click chemistry reaction using a CuI-catalyzed Huisgen [3 + 2] cycloaddition. Starting from 2-(substituted)-3,4-dihydro-2H-1,4-benzothiazi-3-one, a number of 1,4-benzothiazine derivatives were also synthesized using different alkylating agents to give a 4-(substituted)-2-(substituted)-3,4-dihydro-2H-1,4-benzothiazi-3-one in good yields. The crystal and molecular structure of compound oxazolidin-2-one in basic benzothiazine was established by single-crystal X-ray diffraction. The newly synthesized products were subjected to in vitro biological evaluation. The result indicated that the compounds show convincing antibacterial activities against different microorganisms. All structures of the synthesized compounds were elucidated on the basis of spectral analyses and chemical reactions.     

Novel bis-(3-cyano-2-pyridones) derivatives: synthesis and fluorescent properties

Research on Chemical Intermediates - Novel substituted bis-(3-cyano-2-pyridone) derivatives were prepared via a powerful method using enaminonitriles push–pull dienes as key building blocks....     

General and facile synthesis of ceria-based solid solution nanocrystals and their catalytic properties

Uniform Ce_1−xZr_xO₂ (x=0.2–0.8) nanocrystals with ultra-small size were synthesized through a thermolysis process, facilitated by the initial formation of precursor (hydrated (Ce,Zr)-hydroxides) at low temperature. TEM, XRD, EDAX, and Raman spectra were employed to study the formation of the solid solutions with various Ce/Zr ratios. Ultraviolet–visible (UV–vis) spectra showed that the ratios of Ce³⁺ to Ce⁴⁺ in both surface and bulk for the as-prepared Ce_1−xZr_xO₂ nanocrystals increased with the zirconium content x. The well-distributed Zr and Ce in the hydrated (Ce,Zr)-hydroxides before their thermolysis became the crucial factor for the structural homogeneity of the products. In addition, this strategy was extended to the synthesis of Ce_1−xGd_xO_1−x/2, Ce_1−xSm_xO_1−x/2, and Ce_1−xSn_xO₂ solid solutions. Catalytic measurements indicated that the ceria-based catalysts were active for CO oxidation at temperatures beyond 250 °C and the sequence of catalytic activity was Ce_0.5Zr_0.5O₂>Ce_0.8Zr_0.2O₂>Ce_0.2Zr_0.8O₂>Ce_0.5Sm_0.5O_1.75.     

Novel aroylhydrazine-amide derivatives bearing pyridine core: synthesis,characterisations and selective colorimetric recognition properties

Four aroylhydrazine-amides receptors AR1-4 with a hydrazine spacer have been designed, synthesised and characterised as novel colorimetric chemosensors by typical spectroscopic techniques. The receptors AR1–3 exhibited certainly selectivity and sensitivity towards F^?  and AcO^? , forming 1:1 stoichiometry complex by hydrogen-bond interaction. Furthermore, AR4 has especially shown obvious colour change in the presence of these two important biologically anions.     

Novel intramolecular rearrangement leading to the synthesis of biheterocyclic indole-benzoimidazole derivatives on solid phase

[reaction: see text] A novel intramolecular SNAr rearrangement observed during the S-alkylation of benzoimidazole-2-thione with alpha-haloacetophenone is reported. The rearrangement led to the formation of a new benzoimidazole-based intermediate, which is further utilized for the generation of a new biheterocyclic indole-benzimidazole derivatives with a two-point diversity.     

Novel pyrimidinone derivatives: synthesis, antitumor and antimicrobial evaluation

Starting from 6-aryl-4-oxo-2-thioxo-1,2,3,4-tetrahydropyrimidine-5-carbonitrile (4a-d), a series of mono- and dialkyl derivatives 5a-j and 6a, b was synthesized. Hydrazinolysis of 4a, b, d and 5d afforded the hydrazino derivatives 7a-c which were cyclised to give the triazolopyrimidinones 8a-c and the pyrimidotriazinones 9a-c through the reaction with formic acid and chloroacetyl chloride, respectively. Most of the newly synthesized compounds were evaluated for their in-vitro antitumor activity. Compounds 6a and b displayed promising anticancer activity against leukaemia, non-small cell lung, melanoma, and renal cancer. On the other hand, all compounds prepared were screened for their in-vitro antibacterial and antifungal activities. Compounds 5h and j showed significant activity against Staphylococcus aureus, while compounds 5e, 7c and 8c displayed moderate inhibitory activity against Candida albicans.     

Novel phenylazomethine dendrimers: synthesis and structural properties

The novel dendrimers consisting of a pi-conjugated backbone, the dendritic polyphenylazomethines (DPAs), were synthesized by the convergent method via the dehydration of aromatic ketones with aromatic amines in the presence of titanium(IV) tetrachloride. The obtained DPAs have a high solubility unlike the conventional linear polyphenylazomethines. NMR studies revealed the conformational rigidity of DPA G4. DPAs having many azomethine groups as the coordination site for metal ions are expected to be novel ligands.     

Novel diethynylcarbazole macrocycles: synthesis and optoelectronic properties

Diethynylcarbazole macrocycles 1b and 2b have been synthesized by oxidative coupling of appropriate precursors. In particular, macrocycle 2b was prepared by bimolecular Pd-catalyzed oxidative coupling in 35% isolated yield. The spectroscopic properties of these macrocycles and their precursors were measured in detail. The films of these macrocycles by the dipping method and the Langmuir-Blodgett technique were fabricated to study their photoinduced charge-transfer properties. A rapid and steady cathodic photocurrent of these films was produced in a three-electrode cell when irradiated with white light. A possible mechanism of the photoinduced electron-transfer pathway was suggested.     

Novel fluorophores: efficient synthesis and photophysical properties

The synthesis of new donor-acceptor acetylene-bridged compounds was realized via organophosphorus reactions and Sonogashira couplings. These systems exhibit high fluorescence quantum yields, and excitation induces very efficient charge redistribution in the molecules. [structure: see text]     

Novel synthesis of 2,6-benzothiazonine derivatives

The reaction of 1-alkylamino-1-alkylthio-3-phenyl-3-thioxopropenes with phthaloyl chloride in toluene at 60°C, followed by treatment with triethylamine, afforded 6-alkyl-3-phenyl-2,6-benzothiazonine-1,5,7-triones in good to excellent yields.     

Janus-type AT nucleosides: synthesis, solid and solution state structures

Novel Janus-type nucleoside analogues (1a-d) were synthesized. Their pyrimido[4,5-d]pyrimidine base moiety has one face with a bidentate Watson-Crick donor-acceptor (DA) H-bond array of adenine and the other face with an acceptor-donor (AD) H-bond array of thymine. These nucleosides may self-associate through the self-complementary base pair. Indeed, in the solid state, compound 6d displayed a honeycomb-like supramolecular structure with tetrameric membered cavities formed through the combination of reverse Watson-Crick base pairs and aromatic stacking, in which the solvent molecules were accommodated. The result of temperature-dependent CD studies showed that the free nucleosides can form higher order chiral structures in aqueous solution.     

Photophysical properties of tetracene derivatives in solution

Photophysical properties of three tetracene (TET) derivatives were investigated in solution. The quantum yield of intersystem crossing (Q_ISC) and the fluorescence lifetime (τ_F) or 5-monophenyltetracene (MPT) and 5-naphthyltetracene (NAT) are similar to the parent molecule: Q_ISC = 0.6–0.7, τ_F = 4.8–5.2 ns. Distinctly different properties were found for 5,12-diphenyltetracene (DPT): Q_ISC = 0.17, τ_F = 15.2 ns. Of the molecules investigated only in DPT is (S₁-T₂) ISC a thermally activated process. The frequency factor A and the experimental activation energy E_a were determined according to an Arrhenius-type relationship. With E_a the energy of the T₂ state can be estimated. The T₁ state energy of DPT was measured with the method of reversible triplet energy transfer. These results permit to explain photophysical properties on the basis of a schematic energy level diagram and emphasize the role of higher triplet states in molecular deactivation processes. Previously we found thermally activated ISC in rubrene (RUB). The frequency factor of DPT exceeds that of RUB by more than one order of magnitude. This difference is discussed with respect to the effect of steric hindrances in RUB.     

Carbofunctional fluorine-containing triethoxysilanes: synthesis,film forming and properties

Novel fluorine-containing carbofunctional organosilicon monomers were synthesized: 3-pentafluorobenzylideneaminopropylethoxysilane (EtO)₃Si(CH₂)₃N=CH-C₆F₅, N-3-methoxydiethoxysilylpropyltrifluoroacetamide (EtO)₂(MeO)Si(CH₂)₃NHC(O)CF₃, and 1,1,5-trihydrooctafluoroamyl N-3-triethoxysilylpropylaminopropanoate (EtO)₃Si(CH₂)₃NH(CH₂)₂C(O)OCH₂(CF₂)₃CHF₂. Compositions for the formation of transparent thermally stable films were prepared from these monomers. The films have low absorbance intensity near 1550 nm, i.e., in the region of photosignal transmission of modern optical communication systems. The compositions can dissolve complexes with organofluorine ligands and produce transparent homogeneous films doped with rare-earth metals. The concentrations of the complexes in the matrices are 3.7–21.4 wt.% (metal concentrations are 0.6–3.7%). Fluorescence and fluorescence excitation spectra of the matrices and electronic absorption spectra of the doped films were studied. __________ Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 1131–1138, May, 2005.     

Chemoenzymatic synthesis of O-mannosylpeptides in solution and on solid phase

O-mannosyl glycans are known to play an important role in regulating the function of α-dystroglycan (α-DG), as defective glycosylation is associated with various phenotypes of congenital muscular dystrophy. Despite the well-established biological significance of these glycans, questions regarding their precise molecular function remain unanswered. Further biological investigation will require synthetic methods for the generation of pure samples of homogeneous glycopeptides with diverse sequences. Here we describe the first total syntheses of glycopeptides containing the tetrasaccharide NeuNAcα2-3Galβ1-4GlcNAcβ1-2Manα, which is reported to be the most abundant O-mannosyl glycan on α-DG. Our approach is based on biomimetic stepwise assembly from the reducing end and also gives access to the naturally occurring mono-, di-, and trisaccharide substructures. In addition to the total synthesis, we have developed a "one-pot" enzymatic cascade leading to the rapid synthesis of the target tetrasaccharide. Finally, solid-phase synthesis of the desired glycopeptides directly on a gold microarray platform is described.     

Novel bisbenzopyronopyran derivatives: photochemical synthesis and their in-vitro antimicrobial studies

The present research work describes the productive synthesis of novel bisbenzopyronopyran derivatives 4(a-h) and 5(a-h) via the photocyclization reactions of bischromones 3(a-h) under the inert conditions. The latter compounds have been realized efficiently through the O-alkylation reactions of the 3-hydroxychromone 2 with suitable dihalogenated aliphatic/aromatic/heteroaromatic reagents in the presence of dry acetone/anhydrous K₂CO₃/Bu₄N⁺I⁻ (PTC). The cyclization reaction of chalcone 1 under the Algar-Flynn-Oyamada reaction conditions (KOH/H₂O₂) could results in the formation of compound 2 in the good yield. The structural scaffolds of the newly prepared bischromones and resultant bisbenzopyronopyrans have been certified from the meticulous analysis of their various spectroscopic parameters such as UV-Vis, IR, ¹H/¹³C-NMR, and ESI-MS. It was found that o/m/p-xylene and pyridine-linked final symmetrical bistetracycles exhibited higher antimicrobial potencies as compared to alkyl chain-linked cyclized products. The bischromones 3(a-h) could be able to endow modest level of antimicrobial behavior.