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Search for "quenching" in Full Text gives 408 result(s) in Beilstein Journal of Organic Chemistry. Showing first 200.
Safe and highly efficient adaptation of potentially explosive azide chemistry involved in the synthesis of Tamiflu using continuous-flow technology
Beilstein J. Org. Chem. 2019, 15, 2577–2589, doi:10.3762/bjoc.15.251
- vial at room temperature. Azide 5 selectivity was reduced with time in the vial. Therefore, the development of a suitable quenching procedure may be helpful. The TBAA procedure seems to be a promising NaN3 procedure replacement when considering the aforementioned anhydrous telescoping due to its
Synthesis of novel sulfide-based cyclic peptidomimetic analogues to solonamides
Beilstein J. Org. Chem. 2019, 15, 2544–2551, doi:10.3762/bjoc.15.247
- reported for solonamides. Keywords: antivirulence drug; bacteria; macrocyclization; pathoblocker; quorum quenching; Introduction The cyclodepsipeptides called solonamides A and B are natural molecules extracted from the marine bacterium Photobacterium halotolerans [1][2] (Figure 1). They are able to
In search of visible-light photoresponsive peptide nucleic acids (PNAs) for reversible control of DNA hybridization
Beilstein J. Org. Chem. 2019, 15, 2500–2508, doi:10.3762/bjoc.15.243
- effect of the scrambled PNA 19 is the opposite, i.e., signal decrease. We determined a slightly lower fluorescence value than in the case of BHQ-ssDNA; this can be probably attributed to the quenching ability of both PNA probes [52]. Along these lines, the quenching ability of oF4Azo-containing PNA was
Ultrafast processes triggered by one- and two-photon excitation of a photochromic and luminescent hydrazone
Beilstein J. Org. Chem. 2019, 15, 2438–2446, doi:10.3762/bjoc.15.236
- be responsible for the fluorescence quenching in the Z-form. A comparison of the kinetic traces recorded on the maximum of the excited state absorption band in the three analyzed solvents (Figure 6) demonstrates that the excited state decay time decreases on going from acetonitrile to toluene, and
Sugar-derived oxazolone pseudotetrapeptide as γ-turn inducer and anion-selective transporter
Beilstein J. Org. Chem. 2019, 15, 2419–2427, doi:10.3762/bjoc.15.234
- the rate of quenching in fluorescence at λem = 535 nm (λex = 455 nm) was monitored using transporter 2a by creating a Cl– gradient across the lipid membrane by applying NaCl in the extravesicular buffer (Figure S14 in Supporting Information File 1). The compound 2a showed a significant decrease in the
![[Graphic 2]](/bjoc/content/inline/1860-5397-15-234-i4.svg?max-width=637&scale=1.18182)
lucigenin (A). Conce...
Targeted photoswitchable imaging of intracellular glutathione by a photochromic glycosheet sensor
Beilstein J. Org. Chem. 2019, 15, 2380–2389, doi:10.3762/bjoc.15.230
- broad and strong absorption makes the 2D MnO2 nanosheets a potential energy acceptor for the fluorophores which are stacked on the nanosheets plane, leading to the fluorescence quenching through FRET mechanism [32][34]. The transmission electron microscopy (TEM) image of the prepared product revealed
- effective FRET between the attached Glyco-DTE and 2D MnO2, which again suggested the close stacking of Glyco-DTE to the nanosheet surface. Aggregation-caused quenching might be another reason for the fluorescence quenching because of the close distance between fluorescence molecules when absorbed on the
- ” sensor towards GSH, which is illustrated as fluorescence turn-on and sequential on-off cycles. Besides, the quenching of the reporter fluorescence by MnO2 contributes to a significantly lowered background signal, which makes it an excellent material for intracellular precision imaging. Cell-targeted
Current understanding and biotechnological application of the bacterial diterpene synthase CotB2
Beilstein J. Org. Chem. 2019, 15, 2355–2368, doi:10.3762/bjoc.15.228
- carbocation (3) and finally the quenching of the carbocation by a base or water [16][17]. TPSs can be divided into two distinct classes, which are distinguished by their substrate activation mechanism. Whereas ionization of an isoprenoid diphosphate is caused by hydrolysis of the pyrophosphate by a trinuclear
Synthesis of a dihalogenated pyridinyl silicon rhodamine for mitochondrial imaging by a halogen dance rearrangement
Beilstein J. Org. Chem. 2019, 15, 2333–2343, doi:10.3762/bjoc.15.226
- negative value of the HOMO energy level and/or the oxidation potential [15], but it is also influenced by other factors. Nonradiative quenching (e.g., bond rotation) can effectively contribute to depopulation of the fluorophore’s excited state [28], yielding a lower quantum yield. However, the rational
Functionalization of 4-bromobenzo[c][2,7]naphthyridine via regioselective direct ring metalation. A novel approach to analogues of pyridoacridine alkaloids
Beilstein J. Org. Chem. 2019, 15, 2304–2310, doi:10.3762/bjoc.15.222
- metalation at C-5 with TMPMgCl∙LiCl at −40 °C. Quenching with various electrophiles gives a broad range of 5-substituted products, which are building blocks for the synthesis of heterocyclic natural products and analogues thereof. In combination with a Parham-type cyclization a novel approach to pyrido[4,3,2
- 5-subsituted products (Scheme 1). Quenching of metalated 9d with aldehydes 11a–d while warming to room temperature led to the formation of the expected racemic secondary alcohols 12a–d in moderate to good yields (50–66%, Scheme 1). Any attempts to improve the yields failed. The use of 2.2
- equivalents of base, longer reaction times, higher or lower temperatures did not increase the yields. In order to explore additional metalations at other positions than C-5 or imaginable halogen dance reactions [24] during the metalation process, we performed a D2O quenching experiment after the metalation
Fluorescent phosphorus dendrimers excited by two photons: synthesis, two-photon absorption properties and biological uses
Beilstein J. Org. Chem. 2019, 15, 2287–2303, doi:10.3762/bjoc.15.221
- quenching is prevented thanks to the design of the fluorophore [42]. It should be noted that the largest dendrimers, in particular generation 4, display very large two-photon absorption cross-sections (σ2 up to 55,900 GM), which are comparable to those measured for the best quantum dots [43]. Thus these
- the previous examples of dendrimers bearing as terminal functions compounds having TPA properties is soluble in water, and thus they cannot be used for biological purposes. Furthermore, many fluorophores are sensitive to the presence of water, which induces in many cases a quenching of the
Recent advances in transition-metal-catalyzed incorporation of fluorine-containing groups
Beilstein J. Org. Chem. 2019, 15, 2213–2270, doi:10.3762/bjoc.15.218
Aggregation-induced emission effect on turn-off fluorescent switching of a photochromic diarylethene
Beilstein J. Org. Chem. 2019, 15, 2204–2212, doi:10.3762/bjoc.15.217
- aggregation (aggregation-caused quenching (ACQ)). The luminogenic materials with AIE have attracted much interest since Tang et al. reported the AIE concept [12]. The introduction of photo-switching ability in the system will be interesting for creating new AIE systems. In addition, organic photochromic
- was dropped to the UV light irradiated crystal 1o (Supporting Information File 3, Movie 2). The rate of fluorescence quenching (τ1/2 is less than 0.2 s) in the crystalline state is much faster than those observed in solutions. This is attributed to the degree of condensation which is much higher in
- the crystalline state. The mechanism of the fast quenching is expected to be related to the amplification of photo-switching of a photochromic organic nanoparticle system as well as the crystalline system reported by Fukaminato and co-workers [29][30]. A detailed study of the amplification will be
Naphthalene diimides with improved solubility for visible light photoredox catalysis
Beilstein J. Org. Chem. 2019, 15, 2043–2051, doi:10.3762/bjoc.15.201
- catalysis is mainly [Ru(bpy)3]2+ [21], due to its strong MLCT (metal-to-ligand charge transfer) absorption, the excellent yield of its triplet state and the long lifetime, the versatile redox behavior (Ru3+ vs Ru+) in quenching processes and the chemical and photochemical robustness. Despite their positive
Synthesis of 1-azaspiro[4.4]nonan-1-oxyls via intramolecular 1,3-dipolar cycloaddition
Beilstein J. Org. Chem. 2019, 15, 2036–2042, doi:10.3762/bjoc.15.200
- moieties, and careful basification resulted in intramolecular cyclisation givnig 5b,c with a yield of 51% and 42%, respectively. Nitrones 5a–c readily react with 4-pentenylmagnesium bromide. Quenching of the reaction mixtures with water under aerobic conditions leads to partial oxidation of resultant N
Synthesis, enantioseparation and photophysical properties of planar-chiral pillar[5]arene derivatives bearing fluorophore fragments
Beilstein J. Org. Chem. 2019, 15, 1601–1611, doi:10.3762/bjoc.15.164
- enantiopure P5A-DPA and P5A-Py. It was found that the CD signals were enhanced by aggregation. P5A-DPA showed aggregation-induced emission enhancement, while P5A-Py showed aggregation-induced emission quenching, accompanied by excimer emission when aggregating in water and THF mixed solution. Keywords
- to aggregation-caused quenching (ACQ), as was demonstrated by UV–vis absorption and CD studies. For compound P5A-Py, however, the fluorescence intensity continuously decreased when adding water into the THF solutions, and at 70% water content, a new emission peak at 540 nm was observed which was
- the THF solution. P5A-DPA and P5A-Py showed an enhancement of the CD signals by adding water due to restriction of the conformers’ rotations by aggregation. P5A-DPA showed a fluorescence enhancement when less than 50% of water was added, while P5A-Py showed emission quenching and excimer emission when
Different reactivity of phosphorylallenes under the action of Brønsted or Lewis acids: a crucial role of involvement of the P=O group in intra- or intermolecular interactions at the formation of cationic intermediates
Beilstein J. Org. Chem. 2019, 15, 1491–1504, doi:10.3762/bjoc.15.151
- (Table 2, entry 4), we conducted reactions with the series of arenes (Table 3). An excess of methanol was used for quenching of reaction mixtures instead of water. This treatment produced dimethoxyphosphoryl groups [(MeO)2P=O] in the reaction products, rather than the acidic group [(HO)2P=O] in compounds
- complex mixtures of oligomeric compounds. In the same reaction with benzene, allene 1b afforded alkene Z-11n in high yield (Scheme 5). The use of morpholine for quenching of the superacidic reaction mixture gave amide Z-11o in the reaction of 1a with benzene (Scheme 6). We also conducted a large-scale one
- cations A, B, and F–H. Large-scale one-pot solvent-free synthesis of amides 6a,b from the corresponding propargylic alcohols. AlCl3-promoted hydroarylation of allene 1b by benzene leading to alkene Z-11n. Reaction of allene 1a with benzene under the action of AlCl3 followed by quenching of the reaction
2,3-Dibutoxynaphthalene-based tetralactam macrocycles for recognizing precious metal chloride complexes
Beilstein J. Org. Chem. 2019, 15, 1460–1467, doi:10.3762/bjoc.15.146
- macrocycle, which make it conformationally adaptive to maximize the binding affinities. In addition, the macrocycle shows fluorescent quenching when adding the chloride metal complexes in its solution and may be used as a fluorescent sensor for the detection of these coordination complexes. Keywords: host
- maximum of 1 is located at 350 nm (Figure S22, Supporting Information File 1). It is known that the binding of metal ions could cause fluorescence quenching through photo-induced electron transfer [44]. Indeed, the fluorescence intensity of 1 is quenched gradually upon addition of TBA[AuCl4] (Figure 6a
Complexation of a guanidinium-modified calixarene with diverse dyes and investigation of the corresponding photophysical response
Beilstein J. Org. Chem. 2019, 15, 1394–1406, doi:10.3762/bjoc.15.139
- luminescent dyes. Fluorescein, eosin Y, rose bengal, tetraphenylporphine sulfonate and sulfonated aluminum phthalocyanine were employed as classical aggregation-induced quenching dyes. 2-(p-Toluidinyl)naphthalene-6-sulfonic acid and 1-anilinonaphthalene-8-sulfonic acid were selected as representatives of
- with carboxylated bipyridyl ligands (Ru(dcbpy)3), were screened as model guests on account of the desired strong host–guest binding affinity (Scheme 2). Fl, EY, RB, TPPS and AlPcS4 were employed as classical aggregation-caused quenching (ACQ) dyes; 2,6-TNS and 1,8-ANS were selected as intramolecular
- as well-demonstrated fluorescence quenchers acting through a photoinduced electron transfer (PET) mechanism [8][28][29], we hypothesize an electron transfer-induced quenching in the GC5A–Fl complex as underlying mechanism. The binding stoichiometry between GC5A and Fl was determined to be 1:1
Selenophene-containing heterotriacenes by a C–Se coupling/cyclization reaction
Beilstein J. Org. Chem. 2019, 15, 1379–1393, doi:10.3762/bjoc.15.138
- dehydrocoupling with ZnCl2 and CuCl2. Selenophene precursor 10 itself was readily obtained in 68% yield from selenophene (9) in a one-pot procedure by successive lithiation with n-BuLi and quenching with trimethylsilyl chloride and iodine, respectively. We reacted biselenophene 11 with K2S as sulfur source and
Anomeric sugar boronic acid analogues as potential agents for boron neutron capture therapy
Beilstein J. Org. Chem. 2019, 15, 1355–1359, doi:10.3762/bjoc.15.135
- position. The analogues were obtained by hydroboration of proper open-chain terminal alkenes that, after quenching with water, spontaneously afforded cyclic boronic acids with hemiacetal-like structures. Keywords: antitumor agents; boron neutron capture therapy; boronic acid; hydroboration; sugar analogue
- the desired product 7 by the simple treatment of 6 with an excess of borane-THF complex (5 molar equiv) followed by quenching with water, while in the same conditions compound 5 again gave extensive decomposition. These conditions allowed the isolation of the cyclic anomeric boron analogue 7 in
Efficient resolution of racemic crown-shaped cyclotriveratrylene derivatives and isolation and characterization of the intermediate saddle isomer
Beilstein J. Org. Chem. 2019, 15, 1339–1346, doi:10.3762/bjoc.15.133
- belongs to the saddle isomer, its isolation and characterization was necessary. First, we tried to generate 1-S by heating a DMSO solution of (rac)-1 to 200 °C for 5 minutes and quenching the mixture by pouring it into ice water according to the procedure established by Luz for the methoxy-substituted CTV
- corresponds to the saddle conformer and is marked with 1-S. a) 1H NMR spectrum of the neat crown isomers of (rac)-1 in CD3OD (400 MHz, 298 K); b) 1H NMR spectrum in CD3OD (400 MHz, 298 K) of a sample of (rac)-1 after heating it to 200 °C in DMSO and quenching the solution by pouring it into an ice water
N-doped carbon dots covalently functionalized with pillar[5]arenes for Fe3+ sensing
Beilstein J. Org. Chem. 2019, 15, 1262–1267, doi:10.3762/bjoc.15.123
- a good linear correlation (R2 = 0.992) and the lowest detection limit (LOD) was determined to be 1.2 μM [16][24][25]. Subsequently, the quenching mechanism of Fe3+ toward CCDs was investigated. As demonstrated in Figure 3e, the UV–vis absorption of Fe3+ overlaid with the emission peak of CCDs, thus
- , quenching performance can be contributed to the energy transfer between ions and the materials [26]. Meanwhile, the UV–vis absorption peaks of CCDs exhibited no shift and regeneration before and after Fe3+ sensing, indicating that the fluorescence quenching is not resulted from the formation of new
- nm, Em. 5 nm. Fluorescence quenching degrees of a) CCDs and b) CN-dots in the presence of different metal ions. The concentrations of metal ions were 400 μМ. c) Fluorescence spectra of a CCDs system in the presence of different concentrations of Fe3+ ions (0–500 μM). d) Linear curve of the relative
Self-assembly behaviors of perylene- and naphthalene-crown macrocycle conjugates in aqueous medium
Beilstein J. Org. Chem. 2019, 15, 1203–1209, doi:10.3762/bjoc.15.117
- -assembly behavior in various solvents was investigated particularly in aqueous medium, due to the recently discovered hydrophilic properties of B21C7 crown macrocycle. An unexpected fluorescence quenching phenomenon was observed in the PDI-B21C7 macrocycle conjugate in chloroform. The detailed UV–vis
- quenching (ACQ) effect, the fluorescence of 1 in MeCN decreased dramatically, and was almost totally quenched in MeOH and H2O. It is surprising to us that the fluorescence of 1 in CHCl3 is also quenched even at such a low concentration (5.0 × 10−6 M), as only a faint blue fluorescent emission of 1 could be
- detected (Figure 1b inset). According to previous reports, such a fluorescent quenching indicated the formation of a dimeric structure [67][95], and the electron rich substituents at the imide nitrogen should play an important role [96][97]. For comparison, UV–vis absorption and fluorescence spectra of 2
Alkylation of lithiated dimethyl tartrate acetonide with unactivated alkyl halides and application to an asymmetric synthesis of the 2,8-dioxabicyclo[3.2.1]octane core of squalestatins/zaragozic acids
Beilstein J. Org. Chem. 2019, 15, 1194–1202, doi:10.3762/bjoc.15.116
- significantly (>90:10, 17:18) if the reaction was maintained at −78 °C for several hours before quenching at that temperature, giving isolated yields of 30–50% for 17. The absolute configuration of 17 was based on the chemical correlation studies of Seebach [17][18][19] and of Pan [26] for benzylations, and
- principally arose from alkylation (then protonation, by unreacted 7) [19] of the (achiral) dienolate 36 (Scheme 10) of 7. In the current work, where the major difference is prolonged reaction time at low temperature and no warming before quenching, the minor diastereomer is not observed – but dialkylated
- time at −78 °C, followed by quenching at that temperature; these conditions also avoid cogeneration of the (racemic) diastereomer side-product originally observed on warming. Essentially racemic dialkylated tartrate is observed as a minor side-product under our modified conditions. The reaction
Precious metal-free molecular machines for solar thermal energy storage
Beilstein J. Org. Chem. 2019, 15, 1096–1106, doi:10.3762/bjoc.15.106
- other processes, quenching the photoisomerization; (v) the energy storing MOST materials have to utilize light in the visible range of the spectrum; (vi) it will be a crucial benefit for the MOST technology, if toxic and precious metals are avoided. Focusing on environmentally friendly MOST system is an
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