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Spectral signatures in the terahertz(THz) frequency region are mainly due to bulk vibrations of the molecules.These resonances are highly sensitive to the relative position ofatoms in a molecule as well as the crystal packing arrangement. Tounderstand the variation of THz resonances, THz spectra (2–10THz) of three structural isomers: 2-, 3-, and 4-cyanobenzaldehydehave been studied. THz spectra obtained from Fourier transform infrared(FTIR) spectrometry of these isomers show that the resonances aredistinctly different especially below 5 THz. For understanding theintermolecular interactions due to hydrogen bonds, four molecule clustersimulations of each of the isomers have been carried out using theB3LYP density functional with the 6-31G(d,p) basis set in Gaussian09software and the compliance constants are obtained. However, to understandthe exact reason behind the observed resonances, simulation of eachisomer considering the full crystal structure is essential. The crystalstructure of each isomer has been determined using X-ray diffraction(XRD) analysis for carrying out crystal structure simulations. Densityfunctional theory (DFT) simulations using CRYSTAL14 software, utilizingthe hybrid density functional B3LYP, have been carried out to understandthe vibrational modes. The bond lengths and bond angles from the optimizedstructures are compared with the XRD results in terms of root-mean-square-deviation(RMSD) values. Very low RMSD values confirm the overall accuracy ofthe results. The simulations are able to predict most of the spectralfeatures exhibited by the isomers. The results show that low frequencymodes (<3 THz) are mediated through hydrogen bonds and are dominatedby intermolecular vibrations. [ABSTRACT FROM AUTHOR]

The efficient preparation of four C3-symmetric (star-shaped) pyridine and bipyridine derivatives is reported. The key steps are Suzuki couplings of 4-pyridyl nonaflates with 4-acetyl-phenylboronic acid followed by an acid-promoted cyclocondensation reaction converting the methyl ketone moiety into the central benzene ring of the target compounds. Based on STM studies at a graphite–solution interface the twodimensional arrangements of the compounds are discussed, showing the influence of the pyridine substitution pattern. [ABSTRACT FROM AUTHOR]

Like likes like! A novel fluorescent C2‐symmetric guanosine‐based dinucleoside has been engineered by chemical ligation of two guanosine units with a biocompatible dansyl tag. The nucleoside exhibits high selectivity for c‐myc G‐quadruplex DNA through fluorescence enhancement over duplex DNA and other promoter G‐quadruplexes (see scheme). It stains the nucleus preferentially, arrests the cell cycle at the G2/M phase, inhibits cell growth, and induces apoptosis in A375 cancer cells. [ABSTRACT FROM AUTHOR]

An efficient, one‐step method has been used to access a variety of substituted indenones in a regiospecific manner by Grignard addition to indene‐1,3‐dione. This method provides straightforward access to natural products such as neo‐lignans and isoampelopsin D analogues. Moreover, diallyl indenones have been synthesized and employed as ring‐closing metathesis (RCM) precursors for the facile synthesis of substituted fluorenone derivatives through an RCM‐aromatization sequence. [ABSTRACT FROM AUTHOR]

Herein, we demonstrate for the first time that noncanonical DNA can direct macrocyclization‐like challenging reactions to synthesize gene modulators. The planar G‐quartets present in DNA G‐quadruplexes (G4s) provide a size complementary reaction platform for the bio‐orthogonal macrocyclization of bifunctional azide and alkyne fragments over oligo‐ and polymerization. G4s immobilized on gold‐coated magnetic nanoparticles have been used as target templates to enable easy identification of a selective peptidomimetic macrocycle. Structurally similar macrocycles have been synthesized to understand their functional role in the modulation of gene function. The innate fluorescence of the in situ formed macrocycle has been utilized to monitor its cellular localization using a G4 antibody and its in cell formation from the corresponding azide and alkyne fragments. The successful execution of in situ macrocyclization in vitro and in cells would open up a new dimension for target‐directed therapeutic applications. [ABSTRACT FROM AUTHOR]

A three-component reaction with lithiated alkoxyallenes, nitriles, and periluorinated carboxylic acids as precursors led to a series of perfluoroalkyl- or perfluoroaryl-substituted 4-hydroxypyridine derivatives. These compounds were converted into 4-pyridyl nonaflates which can be employed as versatile building blocks for the synthesis of r-conjugated compounds with use of palladium-catalyzed couplings. Suzuki reactions at C-4 and C-3 of the pyridine ring proceeded with moderate to high yields. In addition, Suzuki—Miyaura, Stifle, or Buchwald—Hartwig coupling reactions have also been studied and afforded the corresponding highly substituted pyridinc derivatives. Starting from an arylated propargylic ether the three-component reaction led to a pentasubstituted 4-hydroxypyridine derivative that could also be employed in palladiuns-catalyzed processes at C-4 and at C-3 of the pyridine core. With this simple approach the sterically highly crowded 3,4,5-triphenyl-substituted pyridine derivative 37a could be prepared and studied by an X-ray analysis. With acetonitrile as precursor a different reaction pathway was found when this component was used in excess resulting in a pyridine derivative with a new substitution pattern. In summary, the methods described here allow a flexible and fairly efficient entry to a variety of highly substituted pyridine derivatives bearing perfluorinated alkyl or aryl groups. [ABSTRACT FROM AUTHOR]

A stereoselective strategy for the replacement of the 1,2-dihaloalkene bridge of tetrahalonorbornyl derivatives by an oxygen bridge involving stepwise controlled oxidation, cleavage of the dione thus formed, and reiterative intramolecular SN2 displacement of two bridgehead halogens is devised. The synthesis of four highly strained pentacyclic bis-oxa-bridged derivatives 10, 27, 28, and 29 with interesting structural variations is presented. The two oxa bridges are syn to each other, separated by central cyclohexane and cycloheptane rings in 10 and 27, while they are anti to each other and are separated by central cyclopentane and furan rings in 28 and 29. In the case of the highly symmetric bis-oxa-bridged derivative 10 the two syn oxa bridges constrain the central cyclohexane ring into the boat form. The endo,anti,endo 2:1 bis adducts of 1,2,3,4-tetrahalo-5,5-dimethoxycyclopenta-l,3-diene with cyclopentadiene were prepared for the first time, while the reactivites of previously unexplored bis adducts derived from furan and cycloheptatriene were revealed. [ABSTRACT FROM AUTHOR]

A rapid access to 7-azaspiro[4.5]decan-6-ones 1 involving three regio- and chemoselective reactions starting from tetrabromonorbornyl derivatives is described. The alkaline H[sub 2]O[sub 2] cleavage reaction of monosubstituted α-diketones 9 furnished the potential bridged bicyclic lactones 10 in a highly regio- and stereoselective manner. The radical-mediated, intermolecular bridgehead C-C bond formation of the versatile bridged lactones 10 with acrylonitrile followed by LAH reduction of the adduct 13 intriguingly leads to the formation of novel spirolactam building blocks 1. [ABSTRACT FROM AUTHOR]

Examines the method for easy access to γ-lactone-fused cyclopentanoids. Use of lead and alkaline to cleave the tricyclic α-keto hemiacetals; Elaboration of α-keto hemiacetal 3b to spiroepoxide derivative; Transformation of α-halo ester moiety.

Keywords: biophysics; carbazole ligands; G-quadruplexes; ligand design; NMR spectroscopy EN biophysics carbazole ligands G-quadruplexes ligand design NMR spectroscopy 1 1 1 09/08/21 20210906 NES 210906 B This Minireview provides b a survey of carbazole-based ligands targeting G-quadruplexes. Biophysics, carbazole ligands, G-quadruplexes, ligand design, NMR spectroscopy. [Extracted from the article]

We report an efficient, metal free method for synthesizing tetracyclic spirooxindole derivatives from N-protected isatins and propargyl bromide via Huisgen cycloaddition. This simple and practicle method provides access to spirooxindoles containing five-, six-, or seven-membered rings fused to a triazole ring. [ABSTRACT FROM AUTHOR]