Synthesis,antioxidant and antimicrobial properties of novel pyridyl-carbonyl thiazoles as dendrodoine analogs

Marine compound dendrodoine was first obtained from tunicate species ( Dendrodo grossularia ). It has a five-membered ring, namely, it is a heterocycle thiadiazole, which is found rarely in natural sources . Following its biological activities, novel analogs have been investigated recently. Synthesis of the analogs for this study is realized with uncommon thiazole closure, including methylene-carbonyl condensation. Structures are elucidated by NMR ( ¹ , ¹³ C) and HRMS spectrums. As an alkaloid derivative, antioxidant properties were evaluated with DPPH and FRAP assays and antimicrobial effect with microdilution method. Among the series, 3bc-3cf showed higher antioxidant activity than those having 3 or 4-pyridyl substituents. There is lesser activity for 2-pyridyl activity for 2-pyridyl containing group, which may be a result of intramolecular interactions. No activity was observed against gram-negative bacteria at 250 μg/mL. 3ae and 3ce showed activity at 64 μg/mL against S. aureus and 3ae showed activity at 16 μg/mL against S. epidermidis gram-positive bacteria. Chloramphenicol showed activity against all microorganisms at 8–16 μg/mL. Sixteen original dendrodoine analogs have been defined by close/higher activity compared to dendrodoine analogs and Trolox.     

15N NMR spectra and specific intramolecular interactions in N-vinylazoles

The factors that affect the chemical shifts in the ¹⁵N NMR spectra of N-vinylazoles were investigated. It was shown that an additional positive contribution to the shielding constant of the pyridine nitrogen atom occurs in the s-cis-(N₍₂₎) conformation of N-vinylpyrazoles due to overlapping of the electron cloud of its unshared electron pair and the s-orbital of the vinyl group hydrogen -cis-atom.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1055–1059, August, 1991.     

H-bonding effects on the IR and NMR spectra of N-tosyl-amino acid 2,6-bishydroxylmethyl pyridine monoesters

H-bonding in the title monoesters affects the most utilized types of spectrometries-infrared (IR) and nuclear magnetic resonance (NMR). The shifts of the three kinds of A-H stretching bands to lower wavenumbers in the vibrational spectra, and the 1H chemical shifts, which are to the low field, are observed and reasonably explained in this paper.     

2-Isoxazolidineethanols: an NMR study of the effect of intramolecular H-bonding on the population of nitrogen invertomers and inversion process

A series of (betaR,5R)- and (betaR,5S)-2,5-disubstituted isoxazolidines: 5-(substituent)-beta-phenyl-2-isoxazolidineethanols, have been prepared by asymmetric nitrone cycloaddition reactions and their NMR spectra recorded over a wide range of temperatures. The spectra at low temperatures indicate the presence of the (betaR,5S) diasteromer almost exclusively as a single invertomer having trans disposition of the substituents at N(2) and C(5), while the (betaR,5R) diasteromer remained as a mixture of two interconverting invertomers in deuterated chloroform. The effect of H-bonding - intramolecular in CDCl(3) and intermolecular in CD(3)OD - on the population ratio of the invertomers and nitrogen inversion process has been investigated. The nitrogen inversion barriers are determined using complete line-shape analysis, and their dependence on solvent is discussed. Due to steric factor the trans-invertomers are found to be more stable than their cis counterparts.     

Synthesis and DSSC application of novel dendrimers with benzothiazole and triazole units

Synthesis of novel dendrimers with benzothiazole as surface group and triazole as branching unit is achieved through click chemistry. The presence of more number of benzothiazole and triazole units increases the molar absorption coefficient and alters the fluorescence as well as electrochemical behaviors in the dendrimers. Dye-sensitized solar cell (DSSC) studies reveal that dendrimers with more number of benzothiazole and triazole groups exhibit better current generating capacity than the dendrimers with lesser number of benzothiazole and triazole groups. Dendrimer 2b shows the maximum current conversion efficiency (η) of 7.1%.     

NMR spectra of a hydrocarbon-soluble organosodium compound and its lithium analogs

¹H,²³Na, and⁷Li NMR spectra of 2-ethyl hexylsodiurn, 2-ethylhexyllithium, and isobutyllithium obtained in the reaction of the corresponding alkyl chlorides and metals have been recorded. The¹H N MR signal for the protons of the CH₂Na group is shifted upheld compared with that for the protons of the CH₂Li group (doublets at -0.88 and -0.83, respectively). The composition of the products of reaction of 2-ethylhexyl chloride with sodium depends on the form of the metal reagent employed. The use of sodium balls with diameter up to 2 mm results in the formation of products containing ionic chlorine (30–50 % with respect to Na); the reaction with the dispersion proceeds faster and the reaction product is chlorine-free. The²³Na NMR spectra of these substances are also different, which is explained by the formation of 2-ethylhexylsodium complexes with NaCl in the former case.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 883–885, April, 1996.     

Hydrolysis study: Synthesis of novel styrenic Schiff bases derived from benzothiazole

Novel styrenic Schiff base derivatives of benzothiazole are synthesized. The condensation of 4-vinylbenzaldehyde 1 with either benzothiazol-2-amine or 4-methoxy-benzothiazol-2-amine leads to a mixture of two isomers. From 4-methyl-benzothiazol-2-amine and 6-fluoro-benzothiazol-2-amine, the N-(4-vinylbenzylidene)-4-methyl-benzothiazol-2-amine 8 and N-(4-vinylbenzylidene)-6-fluoro-benzothiazol-2-amine 9 are isolated, respectively. The structures of the synthesized Schiff bases are confirmed through a combination of various spectroscopic techniques including IR, UV, ¹H and ¹³C NMR. A kinetic study of the hydrolysis process of derivatives 6 and 9 in buffered aqueous medium at pH 4.4, 7.4 and 8.5 is conducted by UV spectroscopy. It is shown that the hydrolysis of these compounds is a first order reaction showing an increasing rate as the medium acidity is enhanced.     

19F NMR spectra and structure for pentafluorophenyl-substituted analogs of the perfluoroallyl cation

Perfluorinated allyl cations containing a pentafluorophenyl group in positions 1 or 2 are formed in the reaction of SbF₅ with the corresponding olefins. The parameters of the¹⁹F NMR spectra of these cations were also obtained and discussed. According to the¹⁹F NMR data, the pentafluorophenyl groups of these cations are partially removed from the plane of the allyl triad.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 8, pp. 1773–1777, August, 1989.     

Synthesis of polyimides with lower H2O-absorption and higher thermal properties by incorporation of intramolecular H-bonding

To introduce intramolecular hydrogen bonds in the polyimides (PIs), 5(6)-amino-2-(5-aminopyridin-2-yl)-benzimidazole (PyPABZ) were designed and synthesized. The intramolecular interaction was indicated by Fourier transform infrared when different copolyimides were prepared with 4,4′-oxydianiline and PyPABZ. These modified poly(benzimidazole imide)s eliminate the problem of high water absorption for benzimidazole (BI)-containing PIs in the materials applications. Moreover, the high packing coefficient and rigidity of these copolyimides caused by the strong intramolecular interaction from the H-bonding and the resulting PIs exhibited outstanding thermal properties such as high glass-transition temperature (T_g) and low coefficient of thermal expansion.     

Synthesis and anticancer activity of some novel benzothiazole-thiazolidine derivatives

Sixteen new 2-(benzothiazol-2-ylthio)-N′-(3-substituted-4-(3,4-substitutedphenyl)thiazol-2(3H)-ylidene)acetohydrazide derivatives (4a-4p) were synthesized. The structures of the synthesized compounds were elucidated using FT-IR, ¹H-NMR, ¹³C-NMR, and HRMS spectral data. Anticancer activity of the compounds 4a-4p against C6 (rat brain glioma) and A549 (human lung adenocarcinoma) cell lines was evaluated by using MTT, inhibition of DNA synthesis, and flow cytometric analysis assays. According to MTT assay, 4a and 4d were found to be the most active compounds against C6 cell line with an IC₅₀ value of 0.03 mM. Moreover, IC₅₀ values of 4a (0.2 mM) and 4d (0.1 mM) against NIH3T3 (mouse embryo fibroblast cell line) were higher than their IC₅₀ values (0.03 mM) against C6 cell line. Accordingly, selectivity of compound 4a against C6 cell line was two-fold higher than that of compound 4d. Flow cytometry analysis showed that these compounds display anticancer activity by inducing apoptosis. As a result, compound 4a has a remarkable anticancer activity and a good selectivity towards C6 cell lines.     

Synthesis, mechanism and NMR spectra of lanthanide complexes with a novel unsymmetrical Schiff base

Owing to its two unsymmetrical-NH_2 groups sited on different terminals, 2, 6-diaminocaproic acid (lysine) was used as a reactant for synthesizing a novel unsymmetrical Schiff base with salicylaldehyde on one side and ovanillin on the other for the first time. It is a new way to synthesize such a special unsymmetrical Schiff base. It is named "hetero bis-Schiff base" for distinguishing it from others. The synthesis method, formation mechanism as well as twelve new lanthanide complexes with the above ligand are reported and discussed herein. They were characterized by elementary analysis, molar conductivity, IR-spectra and especially by ~1H and ~(13)C NMR spectra. The results obtained may provide a new promising method for synthesizing similar unsymmetrical Schiff bases and their complexes.     

Spectroscopic effects and intramolecular interactions in the1H and13C NMR spectra of five-membered N-vinyllactams

In 1-vinylpyrrolidone, 1-vinyl-1,2,4-triazole-5-ones, 1,3-divinylimidazolidine-2-thione, and 1-vinylbenzimidazole-1-thione the vinyl groups exist predominantly in the s-trans-, but in 1-vinyl-4,5-diphenylimidazole-2-ones in the s-cis(0)-conformations relative to the exocyclic heteroatom. In 1-vinylbenzimidazole-2-ones, 3-vinylbenzoxazole-2-one, and 1-vinylindole-2,3-diones the vinyl group is present as a mixture of the s-cis(0)- and s-trans(0)-conformations. According to¹H and¹³C NMR results there are specific intramolecular interactions in 1-vinylpyrrolidone and in 1,3-divinylimidazolidine-2-thione resembling weak hydrogen bonding between the -hydrogen atoms of the vinyl group and the oxygen or the sulfur atom. In 1-vinylsuccinimide, 2-vinylphthalimide, and 1,3-divinyl-4,5-diphenylimidazole-2-one there is the same type of interaction with the -cis-hydrogen atom of the vinyl group, while in 1,3-divinyl-1,2,4-triazole-5-one there is interaction between the same hydrogen atom and the nitrogen atom.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 9, pp. 1983–1990, September, 1990.     

Synthesis of novel iodo derived bicalutamide analogs

A series of optically active nonsteroidal selective androgen receptor modulators with structures analogous to bicalutamide was prepared by replacing the trifluoromethyl group with iodine and the sulfonyl linker by oxygen.     

Telluride clusters of molybdenum: Synthesis, structures, and NMR spectra

High-temperature reactions of Mo, chalcogen (S or Se), Te, and Br₂ in molar ratio Mo: S/Se: Te: Br = 3: 1: 6: 4 were carried out. The reaction products were subjected to mechanochemical activation with K(Dtp) (Dtp = (EtO)₂PS₂) in a vibrational mill, resulting in the formation of new compounds [Mo₃(μ₃-Q)_0.5(μ₃-O)_0.5(μ₂-Te₂)₃(Dtp)₃](Dtp) (Q = Se (I) and S (II)). The structure of compound I has been established by X-ray diffraction analysis. Solutions of compounds I and II contain mixtures of [Mo₃(μ₃-Q)(μ₂-Te₂)₃(Dtp)₃]⁺ and [Mo₃(μ₃-O)(μ₂-Te₂)₃(Dtp)₃]⁺, which is confirmed by mass spectrometry and ³¹P, ⁷⁷Se, and ¹²⁵Te NMR spectroscopy. Quantum-chemical calculations of the ¹²⁵Te NMR chemical shifts were performed. The compounds are also characterized by IR spectroscopy, Raman spectroscopy, and elemental analysis. Structure I contains short nonvalent contacts between the sulfur atom of the out-of-sphere Dtp anion and the axial tellurium atoms of the cluster.     

Determination of the rate of intramolecular exchange between two complex spin systems from the NMR spectra

Reversible 1,2-shifts of the ethyl group in the 9-ethyl-9, 10-dimethylphenanthrenonium ion lead to a reversible change of the ring hydrogen states (A′B′C′D′ ? A″B″C″D″). Line shape analysis for the determination of the exchange rate was performed for this case of intramolecular exchange between the two multi-spin systems. The calculations are based on density matrix formalism.