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Search for "X-ray crystallography" in Full Text gives 276 result(s) in Beilstein Journal of Organic Chemistry. Showing first 200.
Synthesis and structures of ruthenium–NHC complexes and their catalysis in hydrogen transfer reaction
Beilstein J. Org. Chem. 2015, 11, 1786–1795, doi:10.3762/bjoc.11.194
- acetonitrile protons appear at 2.35 and 2.08 ppm as two singlets. The 13C NMR spectrum of 3 exhibits a resonance peak at 190 ppm, which is ascribed to the carbenic carbon atom. Complex 3 has been further identified by X-ray crystallography and the cationic structure of molecular 3 is depicted in Figure 3. The
- using nickel–NHC as the carbene source. Their structures have been definitely determined by X-ray crystallography. The catalytic behavior of di-, tetra- and tri-acetonitrile-coordinated ruthenium complexes in transfer hydrogenation reactions was studied. These ruthenium complexes were found to be highly
Structure and conformational analysis of spiroketals from 6-O-methyl-9(E)-hydroxyiminoerythronolide A
Beilstein J. Org. Chem. 2015, 11, 1447–1457, doi:10.3762/bjoc.11.157
- , with the structure and stereochemistry confirmed by X-ray crystallography. The two others were obtained during a total synthesis of erythronolide Al [55][56], as a result of deprotection of the 3,5-benzylidene acetal of erythronolide A (with or without a triethylsilyl protecting group on 6-O). However
Azobenzene-based inhibitors of human carbonic anhydrase II
Beilstein J. Org. Chem. 2015, 11, 1129–1135, doi:10.3762/bjoc.11.127
- , which are substituted by different functional groups in the 4´-position and were characterized by X-ray crystallography. We aimed to investigate the influence of electron-donating or electron-withdrawing substituents on the inhibitory constant Ki. With the aid of an hCAII crystal structure bound to one
- kinetics. Keywords: azobenzene chemistry; enzyme inhibitors; human carbonic anhydrase II; sulfonamide; X-ray crystallography; Introduction Carbonic anhydrase (CA) is an ubiquitously found zinc-containing metalloenzyme with many isoforms, which all catalyze the conversion of carbon dioxide and water to
A new and convenient synthetic way to 2-substituted thieno[2,3-b]indoles
Beilstein J. Org. Chem. 2015, 11, 1000–1007, doi:10.3762/bjoc.11.112
- unequivocally by X-ray crystallography analysis, thus supporting the data of 1H and 13C NMR spectroscopy (Figure 2). The Lawesson’s reagent appears to act firstly as a source of hydrogen sulfide to reduce the C=C double bond in compound 10a, and secondly, as the thiation agent to form thieno[2,3-b]indole 12a by
Interactions between tetrathiafulvalene units in dimeric structures – the influence of cyclic cores
Beilstein J. Org. Chem. 2015, 11, 930–948, doi:10.3762/bjoc.11.104
- according to X-ray crystallography they are not co-planar, and no electronic interactions were observed [21]; the cross-conjugated nature of the bridge needs of course to be taken into account here as well. For the derivative of 4 with SEt end-groups instead of SBu groups, we calculate a barrier for
- green oil. Crystals suitable for X-ray crystallography were grown from CH2Cl2/MeOH. 1H NMR (500 MHz, CDCl3) δ 2.83–2.80 (m, 8H), 1.64–1.60 (m, 8H), 1.46–1.41 (m, 8H), 1.15–1.14 (m, 42H), 0.93 (t, J = 7.4 Hz, 6H), 0.93 (t, J = 7.4 Hz, 6H) ppm; 13C NMR (126 MHz, CDCl3) δ 128.34, 127.75, 127.59, 121.79
Tuning of tetrathiafulvalene properties: versatile synthesis of N-arylated monopyrrolotetrathiafulvalenes via Ullmann-type coupling reactions
Beilstein J. Org. Chem. 2015, 11, 860–868, doi:10.3762/bjoc.11.96
- ; pyrrolotetrathiafulvalene; Ullmann-type coupling; X-ray crystallography; Introduction For the last four decades tetrathiafulvalenes [1][2] (Figure 1) 1 have been the subject of extensive studies due to their outstanding electron-donating properties and ability to induce reversible electrochemically-induced switching
- and 1.77 V, in 4e and 4f (see Figure S7, Supporting Information File 1), respectively. For the phenol derivative 4f, this oxidation is irreversible. Crystal structures Compounds 4a,b,d,e afforded high quality crystals that could be analysed using X-ray crystallography, allowing to unambiguously
- different analytical methods and X-ray crystallography. Experimental Copper-catalyzed N-arylation reaction of monopyrrolo-tetrathiafulvalenes, general procedure. The reaction was performed in a similar manner as described before [22]. A heavy walled Schlenk tube with a wide bore Teflon screw stopcock was
Further exploration of the heterocyclic diversity accessible from the allylation chemistry of indigo
Beilstein J. Org. Chem. 2015, 11, 481–492, doi:10.3762/bjoc.11.54
- between H6 and C4a. The structures of 7 (Figure 1), 8 and 9 were confirmed by X-ray crystallography analysis. Azepinodiindolones 7 and 8 were obtained in moderate yields. The addition of substituents in the terminal position of the allyl substrate resulted in a lowering of yield of the analogous products
- correlation between C8a and H2 and also between H2 and C17a through three bonds was observed, confirming the formation of the pyrrolizidine ring system. The proposed structure of 31 was also confirmed by X-ray crystallography analysis. Biological activities In preliminary screenings for biological activity
Anionic sigmatropic-electrocyclic-Chugaev cascades: accessing 12-aryl-5-(methylthiocarbonylthio)tetracenes and a related anthra[2,3-b]thiophene
Beilstein J. Org. Chem. 2015, 11, 273–279, doi:10.3762/bjoc.11.31
- not useful as this led only to increased amounts of inert xanthates through sulfur alkylation. However, in the case of 7h this approach did allow us to reach 50 ± 4% yields (range for 6 runs). Compounds 7a, d, f–h and j were subjected to single-crystal X-ray crystallography. This confirmed the
TEMPO-derived spin labels linked to the nucleobases adenine and cytosine for probing local structural perturbations in DNA by EPR spectroscopy
Beilstein J. Org. Chem. 2015, 11, 219–227, doi:10.3762/bjoc.11.24
- can be obtained by X-ray crystallography [1][2][3][4][5][6] and nuclear magnetic resonance (NMR) spectroscopy [7][8][9][10][11][12]. Electron paramagnetic resonance (EPR) and fluorescence spectroscopies are nowadays routinely used to study global structures and conformational changes under
- , significant broadening was observed in the EPR spectrum of the TA•G mismatch at pH 5. In fact, the spectrum of TA•G is nearly superimposable to that of the TA•T pair, indicating reduction in mobility due to formation of another hydrogen bond at pH 5. Studies by NMR and X-ray crystallography have shown that
Enhancing the reactivity of 1,2-diphospholes in cycloaddition reactions
Beilstein J. Org. Chem. 2015, 11, 169–173, doi:10.3762/bjoc.11.17
- only one product, 2e (Scheme 2). The molecular structure of 2e (Figure 1) was verified by X-ray crystallography. The crystal structure analysis of 2e showed that only the endo isomer was formed with the alkyl group in anti-orientation with respect to the double bond of the ring. In the case of 2a–c, it
Efficient deprotection of F-BODIPY derivatives: removal of BF2 using Brønsted acids
Beilstein J. Org. Chem. 2015, 11, 37–41, doi:10.3762/bjoc.11.6
- complexed ether, but uncomplexed 8 was obtained after recrystallization from ethyl acetate. The structure of this F-BODIPY derivative was determined by NMR and X-ray crystallography (Figure 1), and its purity confirmed by elemental analysis. Conversion of the nitro compound 8 to the corresponding azide 9
Molecular cleft or tweezer compounds derived from trioxabicyclo[3.3.1]nonadiene diisocyanate and diacid dichloride
Beilstein J. Org. Chem. 2015, 11, 1–8, doi:10.3762/bjoc.11.1
- Abstract The structures of two derivatives of the bisdioxine diisocyanate 1, the bisurea 4 and the biscarbamate 5, are established by X-ray crystallography and DFT calculations. These compounds possess endo,endo structures, in the case of the bisurea 4 with two nearly parallel pendant chains. The X-ray
- minima [1]. Optimization of the endo,exo structure leads to ring opening to a new diisocyanate (Scheme 1). Therefore, it is of some importance to ascertain the actual molecular structures of compounds of this type by X-ray crystallography. Here we report the X-ray crystal structures of two derivatives of
Come-back of phenanthridine and phenanthridinium derivatives in the 21st century
Beilstein J. Org. Chem. 2014, 10, 2930–2954, doi:10.3762/bjoc.10.312
- details that are not apparent from equilibrium measurements [51]. Another, very comprehensive approach, relying mostly on the experimental data of X-ray crystallography, UV–vis, fluorescence and NMR spectroscopy, determined that the fine interplay between electron donating and electron withdrawing effects
Stereoselective synthesis of perillaldehyde-based chiral β-amino acid derivatives through conjugate addition of lithium amides
Beilstein J. Org. Chem. 2014, 10, 2738–2742, doi:10.3762/bjoc.10.289
- hydrolysis of the ester groups under acidic conditions successfully led to amino acids 10A–D. In addition to the NOESY experiments, the relative configuration of 10D was determined by means of X-ray crystallography (Figure 1). The Michael addition was also carried out on 6, the 7,8-dihydro analogue of tert
Selenium halide-induced bridge formation in [2.2]paracyclophanes
Beilstein J. Org. Chem. 2014, 10, 2550–2555, doi:10.3762/bjoc.10.266
- in the way that provides only the thermodynamically stable (17E,19E)-[2.3.2](1,2,4)cyclophane derivative 13. The structure of this compound was unambiguously proved by X-ray crystallography (Figure 1). A colourless tablet 0.35 × 0.2 × 0.08 mm was used to record intensity data to 2θ 56.6° on an Oxford
De novo macrolide–glycolipid macrolactone hybrids: Synthesis, structure and antibiotic activity of carbohydrate-fused macrocycles
Beilstein J. Org. Chem. 2014, 10, 2215–2221, doi:10.3762/bjoc.10.229
- of the monosaccharide. The new macrocycles/macrolides were characterized by X-ray crystallography. Their structures showed that, in addition to the ester and alkene units, the dihedral angle about the glycosidic linkage (exo-anomeric effect) influenced the overall shape of the molecules
- column chromatography. Recrystallization of each, from a mixture of hexanes and ethyl acetate, provided crystals of sufficient quality to determine their structures by X-ray crystallography. We are broadly interested in understanding how molecular/conformational features such as planar multi-atom units
Molecular recognition of AT-DNA sequences by the induced CD pattern of dibenzotetraaza[14]annulene (DBTAA)–adenine derivatives
Beilstein J. Org. Chem. 2014, 10, 2175–2185, doi:10.3762/bjoc.10.225
- necessary to assess the structure of the AP dye/polynucleotide complex. Application of the most informative methods like NMR and X-ray crystallography was hampered by the tendency of the AP dye/DNA complexes to form colloidal systems at c > 0.1 mM, which neither crystalized nor were suitable for NMR studies
Scalable synthesis of 5,11-diethynylated indeno[1,2-b]fluorene-6,12-diones and exploration of their solid state packing
Beilstein J. Org. Chem. 2014, 10, 2122–2130, doi:10.3762/bjoc.10.219
- electronic devices. We report herein the preparation of a variety of diethynylated IF-diones 8a–j that are readily soluble in common organic solvents, and the exploration of their packing in the solid-state by X-ray crystallography. The prototypical molecule that served as inspiration for our studies was
- changing solvent polarity in going from n-hexane to acetone was 0.02 eV, supporting our hypothesis that the 450–550 nm absorption is indeed a π→π* transition as indicated by calculations. X-ray crystallography. We explored the solid-state packing geometries resulting from altering the substitution on the
Reaction of selected carbohydrate aldehydes with benzylmagnesium halides: benzyl versus o-tolyl rearrangement
Beilstein J. Org. Chem. 2014, 10, 1942–1950, doi:10.3762/bjoc.10.202
- possible mechanism for the Grignard reaction leading to the benzyl→o-tolyl rearrangement is also proposed. Keywords: aldehyde; benzyl versus o-tolyl; carbohydrate; Grignard reaction; rearrangement; X-ray crystallography; Introduction One of the most popular synthetic routes leading to the formation of
Multicomponent reactions in nucleoside chemistry
Beilstein J. Org. Chem. 2014, 10, 1706–1732, doi:10.3762/bjoc.10.179
- %. The diastereoisomers were separated and their absolute configuration was determined using X-ray crystallography and circular dichroism spectroscopy. The stereochemical outcome of the synthesis of compounds 79 and 80 was suggested to result from some internal asymmetric induction of the chiral residue
Aryl substitution of pentacenes
Beilstein J. Org. Chem. 2014, 10, 1692–1705, doi:10.3762/bjoc.10.178
- properties of the new pentacene chromophores have been analyzed by UV–vis spectroscopy (solution and thin films), thermoanalytical methods (DSC and TGA), cyclic voltammetry, as well as X-ray crystallography (for 8 derivatives). X-ray crystallography has been specifically used to study the influence of
- (Figure 1b). To determine the influence of aryl substitution, the obtained pentacenes have been studied by a variety of spectroscopic characterization methods as well as X-ray crystallography of eight derivatives. The studies reported herein offer an opportunity to interpret various properties of acenes
Rational design of cyclopropane-based chiral PHOX ligands for intermolecular asymmetric Heck reaction
Beilstein J. Org. Chem. 2014, 10, 1536–1548, doi:10.3762/bjoc.10.158
- Science Foundation (grant CHE-0079282) for funds to purchase the X-ray instrument and Dr. V. W. Day (X-ray Crystallography Laboratory, University of Kansas) for his assistance with X-ray crystallography.
Synthesis of the first examples of iminosugar clusters based on cyclopeptoid cores
Beilstein J. Org. Chem. 2014, 10, 1406–1412, doi:10.3762/bjoc.10.144
- to 2 orders of magnitude more efficient as CFTR correctors than the clinical candidate miglustat (N-Bu-DNJ, 1, Figure 1). The mechanisms underlying the inhibitory multivalent effect were studied with different methods such as isothermal titration calorimetry, competitive lectin-enzyme assays, X-ray
- crystallography or atomic force spectroscopy [7][11][12][13]. At this stage of research, one of the main challenges in the field is to design optimal systems that not only display large multivalent effects but also possess the desired properties for particular applications. In this context, the choice of the
Tandem Cu-catalyzed ketenimine formation and intramolecular nucleophile capture: Synthesis of 1,2-dihydro-2-iminoquinolines from 1-(o-acetamidophenyl)propargyl alcohols
Beilstein J. Org. Chem. 2014, 10, 1255–1260, doi:10.3762/bjoc.10.125
- %. Electron rich phenyl substrate 2l produced the corresponding product 9u in 65% yield while electron poor substrate 2m was found to be unreactive in the reaction. The structures of the products were confirmed by 1H NMR, 13C NMR and High Resolution Mass Spectrometry (HRMS). X-ray crystallography of one of
Syntheses of fluorooxindole and 2-fluoro-2-arylacetic acid derivatives from diethyl 2-fluoromalonate ester
Beilstein J. Org. Chem. 2014, 10, 1213–1219, doi:10.3762/bjoc.10.119
- structure of isolated diester 3 was confirmed by X-ray crystallography (Figure 1). In initial experiments, decarboxylation of 3 by reaction with potassium hydroxide gave good yields of the corresponding 2-fluoro-2-arylacetic acid 4a. However, in subsequent experiments, we found that further purification of
- transformed to the corresponding methyl esters 6a–e by stirring a mixture of the acid in hydrochloric acid and methanol (Table 2). The structure of 6a was confirmed unambiguously by X-ray crystallography (Figure 2) and all other methyl esters 6b–e were characterised by comparison with appropriate NMR data
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