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Search for "linker" in Full Text gives 386 result(s) in Beilstein Journal of Organic Chemistry. Showing first 200.
Exploring mechanochemistry to turn organic bio-relevant molecules into metal-organic frameworks: a short review
Beilstein J. Org. Chem. 2017, 13, 2416–2427, doi:10.3762/bjoc.13.239
- chemistry relies on the formation of intermolecular interactions between linker molecules. This combination results in 1D, 2D or 3D porous frameworks. The pore size can be adjusted by varying the size of the linkers, a modification that can be associated to the change in functional groups in the organic
- (encapsulated) as a guest within the pores of the MOF. In the second situation, the choice of the linker is crucial, as it needs to be an organic molecule listed of the generally regarded as safe (GRAS) compounds, an endogenous compound or a bioactive molecule. In both classes, the judicious choice of the
- /elimination from the body [88]. The examples given here will be separated according to the function of the APIs in the BioMOF: linker or guest. BioMOFs with active pharmaceutical ingredients (APIs) as linkers Several BioMOFs with APIs as building blocks have been synthesized recurring to mechanochemistry and
Structure–property relationships and third-order nonlinearities in diketopyrrolopyrrole based D–π–A–π–D molecules
Beilstein J. Org. Chem. 2017, 13, 2374–2384, doi:10.3762/bjoc.13.235
- were further investigated by differential scanning calorimetry (DSC), electrochemistry, absorption and emission spectra, DFT calculations, and THG measurements. Results and Discussion Synthesis of DPP derivatives 1–5 According to the π-linker structure, two series of target chromophores a and b can be
- decompose far beyond their melting points (e.g., 2a with Tm = 244 °C and Td = 345 °C). Compounds in series b bearing an additional acetylene linker decompose almost immediately after their melting (e.g., 2b with Tm = 175 °C and Td = 189 °C). In pairs of chromophores, the substance without triple bond has an
- approximately 50 °C higher melting point (e.g., 1a/1b with Tm = 261/215 °C). Thus, the insertion of an acetylene linker decreases the melting point and causes thermal instability in the liquid phase. Derivatives 1a/2a containing a 1,4-phenylene linker showed the highest Tm and Td values of 261/244 and 330/345
Synthesis and application of trifluoroethoxy-substituted phthalocyanines and subphthalocyanines
Beilstein J. Org. Chem. 2017, 13, 2273–2296, doi:10.3762/bjoc.13.224
- coupling between each unit [72]. The authors noted that this intramolecular electronic coupling is likely to be dependent on the overall planarity of the molecules. Rigid TFEO-Pc dimers with a diacetylene moiety as a linker have also been reported [73][74]. There are reports of dimers via two kinds of
- diacetylene linkers, via a butadiyne and via an aryldiacetylene moiety (Figure 2). Such binuclear phthalocyanines that are connected via a rigid acetylene linker synthesized by Glaser or Sonogashira reactions have attracted attention due to their interesting effects resulting from further expansion of
- [75][76]. However, phthalocyanine dimers with high rigidity and flatness exhibit a stronger aggregation effect as π-conjugation expands. For example, a tert-butyl-substituted phthalocyanine dimer connected via diacetylene linker (9) strongly aggregates in solution although tert-butyl-substituted
Structural diversity in the host–guest complexes of the antifolate pemetrexed with native cyclodextrins: gas phase, solution and solid state studies
Beilstein J. Org. Chem. 2017, 13, 2252–2263, doi:10.3762/bjoc.13.222
- spectrum of β-CD/PTX complex (Figure 4) displays clear cross-peaks between accordingly phenyl (H7 and H8, region A), pyrrole (H4, region B), and aliphatic linker (H5-H6, region C) protons of the PTX guest with the C–H ring protons of the β-CD host (H2, H3, H4 and H5). Protons H3 and H5 of β-CD which are
Novel approach to hydroxy-group-containing porous organic polymers from bisphenol A
Beilstein J. Org. Chem. 2017, 13, 2131–2137, doi:10.3762/bjoc.13.211
- t-plot method of PPOP-1 are smaller than those of PPOP-2 and PPOP-3. The difference between the pore volumes and BET specific surface area results of PPOPs may be related to the monomer strut length. With the shortest linker of M1, PPOP-1 possesses the lowest pore volume and BET specific surface
Complexation of molecular clips containing fragments of diphenylglycoluril and benzocrown ethers with paraquat and its derivatives
Beilstein J. Org. Chem. 2017, 13, 2056–2067, doi:10.3762/bjoc.13.203
- calculations show that the substitution of methyl groups in the molecule of paraquat by oxyethylene linker results in a decrease of the positive charge on the dipyridinium fragment (Figure 2) that, in turn, should lead to a reduction in the stability of the inclusion complexes of 8–10 with molecular clips 1–5
Intramolecular glycosylation
Beilstein J. Org. Chem. 2017, 13, 2028–2048, doi:10.3762/bjoc.13.201
- tethers Ziegler and co-workers investigated the use of a flexible succinoyl linker to link the glycosyl donor and acceptor counterpart. This reaction was named “intramolecular glycosylation of prearranged glycosides” [52][53]. Like in all “molecular clamp” applications, the tethering of the reaction
- modification of the macrocycle ring size, torsional rigidity of the spacer, position of the attachment to both donor and acceptor, relative configuration of hydroxy groups, and the length of the linker [58][60][61][62][63][64][65][66][67][68][69][70][71][72]. Among early examples, xylylene and phthalimido
- linker showed very high efficiency, and will be highlighted below. Another early development discussed below is the peptide-templated synthesis. Beyond these influential early studies that led to further developments, this topic was comprehensively overviewed and for early developments the reader should
β-Cyclodextrin- and adamantyl-substituted poly(acrylate) self-assembling aqueous networks designed for controlled complexation and release of small molecules
Beilstein J. Org. Chem. 2017, 13, 1879–1892, doi:10.3762/bjoc.13.183
- = 100%. Representation of ditopic complexation of an ADddn substituent of PAAADddn, by two β-CDen substituents of PAAβ-CDen through initial complexation of the adamantyl group followed by complexation of the dodecyl linker in the sequence (a) to (b) to (c). 2D NOESY 1H NMR spectrum of 0.44 wt % PAAβ
The chemistry and biology of mycolactones
Beilstein J. Org. Chem. 2017, 13, 1596–1660, doi:10.3762/bjoc.13.159
Synthesis of oligonucleotides on a soluble support
Beilstein J. Org. Chem. 2017, 13, 1368–1387, doi:10.3762/bjoc.13.134
- by Bonora et al. [37] on polyethylene glycol (PEG 5000) monomethyl ester. The overall strategy was rather similar to that of the solid-supported chemistry (Scheme 2). Accordingly, the 3´-terminal nucleoside, 5´-O-DMTr-N6-Bz-dA, was attached to the support via a 3´-succinyl linker, the 5´-O-DMTr group
- . Support loaded with longer fully protected oligomers may precipitate less quantitatively or interchain aggregation may reduce the coupling efficiency. A closely related support 6, incorporating additionally a Q-linker moiety [44], has been used for preparation of fully protected ODN trimers having only
- linker by 5 mmol L−1 K2CO3 in a 3:43:10 mixture of DCM, dioxane and MeOH (30 min), followed by neutralization with pyridinium chloride, left the 5´-O-DMTr group, 2-chlorophenyl phosphate protections and base moiety protections untouched. Silica gel chromatographic purification and conventional
Sugar-based micro/mesoporous hypercross-linked polymers with in situ embedded silver nanoparticles for catalytic reduction
Beilstein J. Org. Chem. 2017, 13, 1212–1221, doi:10.3762/bjoc.13.120
- .13.120 Abstract Porous hypercross-linked polymers based on perbenzylated monosugars (SugPOP-1–3) have been synthesized by Friedel–Crafts reaction using formaldehyde dimethyl acetal as an external cross-linker. Three perbenzylated monosugars with similar chemical structure were used as monomers in order
- temperature. Results and Discussion All the sugar-based porous organic polymers (SugPOP-1–3) were synthesized by Friedel–Crafts reaction using FDA as an external cross-linker in a similar way. The preparation routes are shown in Scheme 1. Using benzylated monosaccharides as monomers and FDA as the cross
- -linker, the Friedel–Crafts cross-linking polymerization is promoted smoothly by anhydrous FeCl3 in dry 1,2-dichloroethane (DCE). The monomers were either commercially available (Sug-1) or prepared (Sug-2 and Sug-3) by benzylation of free sugars with benzyl bromide and sodium hydride. The chemical
Glyco-gold nanoparticles: synthesis and applications
Beilstein J. Org. Chem. 2017, 13, 1008–1021, doi:10.3762/bjoc.13.100
- . Proteins, like lectins, are characterized by different subunits possessing characteristic distances between the active pockets, so a controlled carbohydrate density can result in a better presentation of the molecules [60]. Saccharidic functionalization: the importance of the linker The linker employed to
- thio-amphiphilic linker to impart improved solubility and flexibility to the glycosyl-ligand. UV–vis spectroscopy and dynamic light scattering measurements have been exploited to detect at low picomolar concentrations lactose-AuNP, mannose-AuNP and GlcNAc-AuNP interactions with their cognate lectins
Interactions between shape-persistent macromolecules as probed by AFM
Beilstein J. Org. Chem. 2017, 13, 938–951, doi:10.3762/bjoc.13.95
- AFM tip and found enhancement factors up to 2, depending on the force loading rate [46]. We have previously explored the adhesion characteristics of dense CD layers on an AFM tip and a planar silicon surface connected by various ditopic linker molecules. In this system we were able to switch adhesion
- , synthesized from polymer 8 (Scheme 3) through Cu(I)-catalyzed azide–alkyne cycloaddition (CuAAC) with the triethylene glycol linker 11 (N3-TEG-NH2) which had been prepared in a five-step procedure [62][63]. Probing multivalent interactions by AFM The adhesive forces of 12, due to supramolecular interactions
Opportunities and challenges for the sustainable production of structurally complex diterpenoids in recombinant microbial systems
Beilstein J. Org. Chem. 2017, 13, 845–854, doi:10.3762/bjoc.13.85
- -directed mutagenesis (indicated through wrench) of TPS (green) for product modulation or introduction of a linker-coding sequence for co-expression of P450 monooxygenase and reductase (blue and red); 4: Heterologous expression in E. coli (depicted in orange). Construction of synthetic operons and screening
Structure–efficiency relationships of cyclodextrin scavengers in the hydrolytic degradation of organophosphorus compounds
Beilstein J. Org. Chem. 2017, 13, 417–427, doi:10.3762/bjoc.13.45
- study focusing on the impact of covalently bound functional groups to macrocyclic β-cyclodextrin that are involved in the OP hydrolysis. Four new derivatives 2–5 were prepared (Figure 3) for this purpose. Compared to analog 1, scavenger 2 has a longer linker between the iodosobenzoate group and the
- methylated-β-cyclodextrin scaffold whilst scavenger 3 is characterized by a longer linker binding the imidazole ring to the CD derivative. Finally, compounds 4 and 5 are analogs of 2 bearing only one of these groups, either the α nucleophile or the imidazole ring, respectively. All five derivatives 1–5 were
- conditions as applied for derivatives 13 and 14. HSQC NMR analysis of 16 allowed the assignment of the three CH2 groups of the propyl linker bearing the benzene ring. Correlation signals were observed for the diastereotopic protons at 3.59 and 3.90 ppm with the 13C signal at 73.1 ppm belonging to the carbon
Dynamics and interactions of ibuprofen in cyclodextrin nanosponges by solid-state NMR spectroscopy
Beilstein J. Org. Chem. 2017, 13, 182–194, doi:10.3762/bjoc.13.21
- confined in CDNS linked by IbuH∙∙∙IbuH interactions. However, it should be kept in mind that other types of hydrogen bonds may be established, such as those between IbuH and the free OH groups of CD or the COOH and amino functional groups of the cross-linker. The acidic IbuH form present in the network can
- spectrum. The maximum signal intensity SCPMAX is observed around 750 μs for all the cyclodextrin carbon atoms and around 1100 μs for the carbonyl groups of the cross-linker. Such small values indicate a fast cross-polarization process, consistent with a rigid polymeric system. Therefore, strong
- monomeric β-cyclodextrin are listed [26]. All the carbon atoms revealed short T1ρ values in the range of 3–5 ms and similar for β-CD C atoms and the carbonyl atom of the cross-linker, suggesting that their chemical environments are equally proximate to the 1H reservoirs. This result is indicative of the
Total synthesis of a Streptococcus pneumoniae serotype 12F CPS repeating unit hexasaccharide
Beilstein J. Org. Chem. 2017, 13, 164–173, doi:10.3762/bjoc.13.19
- glycosylation of the liberated hydroxy groups. Formation of the β-mannosazide glycoside containing a protected C5 amino linker that serves in the final product as an attachment point for glycan array surfaces or carrier proteins was central to the assembly of trisaccharide 3. To avoid a challenging and often
- C2-participating levulinyl ester protecting group ensured selective formation of the trans-glycoside upon activation of 11 by NIS/TfOH in the presence of the C5 linker to produce glucoside 12 in 70% yield [24]. Cleavage of the C2 levulinyl ester of 12 by treatment with hydrazine acetate furnished 13
- [25]. Silylation of the C3 hydroxy group furnished thioglycoside 17. Glycosylation of the C5 linker by activation of 17 using NIS/TfOH as the promoter at −20 °C produced mainly β-mannoside 15 (4:1 β:α) [26]. The identity of the β-isomer was confirmed by NMR analysis (1JCH β = 159.0 Hz, see Supporting
Synthesis of structurally diverse 3,4-dihydropyrimidin-2(1H)-ones via sequential Biginelli and Passerini reactions
Beilstein J. Org. Chem. 2017, 13, 54–62, doi:10.3762/bjoc.13.7
- the Passerini reaction for the first time in a sequential multicomponent tandem reaction approach. After evaluation of all possible linker components and a suitable solvent system, highly functionalized dihydropyrimidone–α-acyloxycarboxamide compounds were obtained in good to excellent yields. In a
- Biginelli–Passerini reaction are represented in Figure 1. Compared to the above mentioned multicomponent tandem approaches, our strategy provides higher yields and makes use of more bifunctional linker components. Careful evaluation of the bifunctional components allowed a pre-selection: A3, B3 and C3 in
- diastereomers (Figure 4). Conclusion The Biginelli reaction was successfully combined with the Passerini reaction to obtain highly functionalized DHMP heterocyclic products. For this purpose, different DHMP acids were prepared by variation of the components and the bifunctional linker. The DHMP acids were then
Supramolecular frameworks based on [60]fullerene hexakisadducts
Beilstein J. Org. Chem. 2017, 13, 1–9, doi:10.3762/bjoc.13.1
- , Germany 10.3762/bjoc.13.1 Abstract [60]Fullerene hexakisadducts possessing 12 carboxylic acid side chains form crystalline hydrogen-bonding frameworks in the solid state. Depending on the length of the linker between the reactive sites and the malonate units, the distance of the [60]fullerene nodes and
- HFF-2 and HFF-3 in the solid state. Different extensions of the linker arms have been investigated for newly synthesized C4 and compared to the known C2 and C3 lengths. Depending on the length of the linker arms, the distance of the fullerene moieties in the framework compounds increases resulting in
Biochemical and structural characterisation of the second oxidative crosslinking step during the biosynthesis of the glycopeptide antibiotic A47934
Beilstein J. Org. Chem. 2016, 12, 2849–2864, doi:10.3762/bjoc.12.284
- ), peptidyl carrier protein with phosphopantetheine linker (PCP; green), condensation (C; red), epimerisation (E; dark blue), P450-recruitment (X; blue) and thioesterase (TE; light grey) domain; the peptide is shown at its distinct stages of biosynthesis; the amino acid cyclisation steps are depicted with
- ring formation between D-Tyr2 and D-Hpg4. 3) The reaction is quenched by the addition of methylamine, which cleaves off the peptide from the phosphopantetheine linker thus liberating the peptide methylamide. 4) The peptide is purified by solid phase extraction (SPE) and 5) analysed by LC–MS in single
Chemical probes for competitive profiling of the quorum sensing signal synthase PqsD of Pseudomonas aeruginosa
Beilstein J. Org. Chem. 2016, 12, 2784–2792, doi:10.3762/bjoc.12.277
- . Variations of linker length and side group decorations between the reactive group and the alkyne handle were introduced to investigate potential differences in selectivity. Different alkyne amines were used to generate α,β-unsaturated amide probes UA1–3 by reaction with acrylic acid chloride (Figure 2A) and
A versatile route to polythiophenes with functional pendant groups using alkyne chemistry
Beilstein J. Org. Chem. 2016, 12, 2682–2688, doi:10.3762/bjoc.12.265
- electrochemically redox active. The stability of the linker would thus constitute an additional parameter to consider when designing functional polymers. The alkyne group is a versatile synthetic building block which can be functionalized in a number of fashions [20][21][22][23]. These include, e.g., well-developed
Robust C–C bonded porous networks with chemically designed functionalities for improved CO2 capture from flue gas
Beilstein J. Org. Chem. 2016, 12, 2274–2279, doi:10.3762/bjoc.12.220
- , cyanovinylene bridged porous networks are not studied extensively and our previously reported COP-100 structure [18] suffered from low porosity. In order to obtain a cyanovinylene-bridged porous network with tangible surface area, different core and linker combinations were tested leading to the synthesis of
- COP-156 and COP-157 (Scheme 1). Tetraphenylmethane cores are well-known tetrahedral building blocks that are commonly employed to form highly porous materials [4][19]. A trivalent 1,3,5-phenylenetriacetonitrile linker led to COP-156 whereas a divalent 1,4-phenylenediacetonitrile formed COP-157 (Scheme
- linker used for COP-157 is linear [22][23]. After post-modification, the surface area diminishes, which is a common observation [13][24]. Yet, the pore volume of COP-156-amine increases to 0.99 cm3/g at P/P0 = 0.99, due to newly created pores from the reduction reaction (Figure 2). COP-156-amidoxime has
Elongated and substituted triazine-based tricarboxylic acid linkers for MOFs
Beilstein J. Org. Chem. 2016, 12, 2267–2273, doi:10.3762/bjoc.12.219
- the methoxy group gave the respective amino and hydroxy-substituted triazine linkers. Keywords: isoreticular; linker; MOF; Suzuki coupling; triazine; Introduction A typical building block for many metal–organic frameworks (MOFs) [1][2][3][4] carries two functional groups such as carboxylic acids or
- heterocycles resulting in a bridging ligand for the metal-containing „edges“ of the porous structures. Linkers with more than two ligating sites (carboxylic acids or heterocycles) have also been used successfully. Tri- to hexatopic linkers are also known. The prototype for a trivalent linker is 1,3,5
- -benzenetricarboxylic acid. By elongating the „arms“ of the linkers, larger pores can be achieved, and often the MOF structures containing extended linkers resemble those obtained with the smaller parent linker (isoreticular structures, see for instance [5]). In the case of the tritopic linker 1,3,5
Silica-supported sulfonic acids as recyclable catalyst for esterification of levulinic acid with stoichiometric amounts of alcohols
Beilstein J. Org. Chem. 2016, 12, 2173–2180, doi:10.3762/bjoc.12.207
- strategy is tethering the active species with the support via covalent bonds [35]. This approach increases the stability of the catalyst itself compared to impregnation (Figure 1). Furthermore, the activity of the catalyst can be tuned through adoption of a suitable linker. Results and Discussion As part
- consists of the immobilisation of a functional moiety on an inorganic support via covalent bonds ensured by a suitable linker [35]. In preliminary experiments reactions were carried out with a five-fold molar excess of alcohol. We started from this ratio as in the literature we did not retrieve any
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