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Search for "linkers" in Full Text gives 172 result(s) in Beilstein Journal of Organic Chemistry.
An azobenzene container showing a definite folding – synthesis and structural investigation
Beilstein J. Org. Chem. 2019, 15, 1534–1544, doi:10.3762/bjoc.15.156
- macrocycles: In the elongated trans,trans-isomer this distance shows a value of 14.1 Å, in the more compact cis,cis-isomer the distance amounts to 11.3 Å. The replace of the isopropyl groups by recognition units and the enlargement of the two linkers, which makes a shielding of a guest from the environment
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
- File 1). Conclusion In summary, we reported the synthesis of two new tetralactam macrocycles with 2,3-dibutoxynaphthalenes as the sidewalls. The macrocycle with isophthalamide as the linkers is able to bind chloride ions and precious metal chloride complexes in nonpolar solvent, while the macrocycle
Synthesis of dipolar molecular rotors as linkers for metal-organic frameworks
Beilstein J. Org. Chem. 2019, 15, 1331–1338, doi:10.3762/bjoc.15.132
- linkers in MOFs with potential applications as ferroelectric materials and for optical signal processing. Keywords: benzothiadiazole; dipolar rotor; fluorescence; large dipole moment; metal organic framework linker; Introduction Rotors are among the fundamental functional units in engineering in our
- compromise between the size and dipole moment of the rotor/linker has to be aimed at, and care has to be taken that the rotational barriers are as low as possible. Figure 1 shows the interaction of a pair of dipolar rotors with parallel axes at a distance of 10 Å, which is a typical distance of the linkers
- . We interpret these data as the lower limits of the rotational barriers in a MOF environment. Interactions with other linkers or neighbouring dipoles probably will increase the barriers. The dipole moments of the cyano-substituted rotors are considerably higher than those with fluoride substitution
Insertion of [1.1.1]propellane into aromatic disulfides
Beilstein J. Org. Chem. 2019, 15, 1172–1180, doi:10.3762/bjoc.15.114
- , 76344 Eggenstein-Leopoldshafen, Germany 10.3762/bjoc.15.114 Abstract Herein we present the synthesis of symmetrically and unsymmetrically substituted 1,3-bissulfanylbicyclo[1.1.1]pentanes from disulfides and [1.1.1]propellane. Bicyclo[1.1.1]pentanes (BCPs) recently gained interest as rigid linkers and
- in most cases. Single crystal X-ray diffraction analysis confirms the rod-like structure of the [2]staffanes that is often required in material applications. Keywords: bicyclo[1.1.1]pentane; bioisosteres; disulfides; linkers; [1.1.1]propellane; Introduction Rigid structures are emerging in both
Electrophilic oligodeoxynucleotide synthesis using dM-Dmoc for amino protection
Beilstein J. Org. Chem. 2019, 15, 1116–1128, doi:10.3762/bjoc.15.108
- linkers for ODN synthesis [40][41]. Due to the low acidity of H-2 (pKa ≈31) in the Dmoc function, these groups and linkers were expected to be stable under ODN synthesis conditions. However, once the dithioketal in the group is oxidized, the acidity of H-2 (pKa ≈12) is drastically increased [42][43
- ]. Considering that the widely used Fmoc protecting group, of which the H-9 has a pKa of ≈22 [42], can be readily removed with a weak base such as piperidine, we hypothesized that the oxidized Dmoc groups and linkers could be cleaved under weakly basic and non-nucleophilic conditions via β-elimination. Indeed
New α- and β-cyclodextrin derivatives with cinchona alkaloids used in asymmetric organocatalytic reactions
Beilstein J. Org. Chem. 2019, 15, 830–839, doi:10.3762/bjoc.15.80
- as the promoter (not in a catalytic amount) of a Henry reaction and obtained the product with 99% ee. Subsequently, Doyagüez et al. [17] attached L-proline to β-CD via different linkers (including a triazole linker) and used the resulting organocatalysts in an aldol reaction in water, albeit with a
Tuning the stability of alkoxyisopropyl protection groups
Beilstein J. Org. Chem. 2019, 15, 746–751, doi:10.3762/bjoc.15.70
- applications, where easily cleavable linkers are needed [1]. The stability and properties of acetals/ketals widely varies depending on their structure, which widens the scope of their applicability. The acid lability is increased markedly by attaching electron-donating alkyl groups on the acetal carbon. The
Polyaminoazide mixtures for the synthesis of pH-responsive calixarene nanosponges
Beilstein J. Org. Chem. 2019, 15, 633–641, doi:10.3762/bjoc.15.59
- -triazol-1-yl)alkylidene chains as the linkers between the calixarene monomer units. Even these materials were proven effective in sequestrating organic model pollutants, such as p-nitroaniline derivatives or dyes, from aqueous solution. However, their synthesis required much longer times in comparison
Design and synthesis of multivalent α-1,2-trimannose-linked bioerodible microparticles for applications in immune response studies of Leishmania major infection
Beilstein J. Org. Chem. 2019, 15, 623–632, doi:10.3762/bjoc.15.58
- stable to acidic and basic conditions, but incompatible with reducing conditions. To conserve the relatively expensive TAMRA fluorophore and prevent loss through the synthetic sequence, amino linkers were first conjugated to the dendrimer core. The Nα-Fmoc group of 19 was first removed and coupled to Nε
LCST phase behavior of benzo-21-crown-7 with different alkyl chains
Beilstein J. Org. Chem. 2019, 15, 437–444, doi:10.3762/bjoc.15.38
- and molecular structures. Results and Discussion Two series of B21C7s, comprising carbamate-based linkers 3a–e and urea-based linkers 5a–e, were designed and synthesized, as shown in Scheme 1 and Scheme 2. All structures were confirmed by NMR spectroscopy and high-resolution mass spectrometry (details
- between the amine groups and isocyanate units (yields, 44.6–76.5%), or between hydroxy groups and isocyanate units (yields, 57.4–84.9%), respectively. We also investigated the role of linkages in LCST behavior by the introduction of urea-based and carbamate-based linkers. The water solubility of the
- ethers with urea-based linkers show higher water solubility (5a–e), compared to crown ethers with carbamate-based linkers (3a–e). As amide groups are more hydrophilic compared with ester groups, it is reasonable that 5a–e show stronger hydration effects and exhibit a larger water-accessible surface area
First synthesis of cryptands with sucrose scaffold
Beilstein J. Org. Chem. 2019, 15, 210–217, doi:10.3762/bjoc.15.20
- -O-benzyl-sucrose). The latter approach is probably more convenient since it allows preparing cryptands of various size of cavity just by simple elongation of all three terminal positions with linkers of different size. In our model studies we have elongated these positions with the same linker
- . However, since all three terminal positions can be differentiated (as we have proven during our earlier studies see ref. [10]), it is possible to introduce different linkers at the C1’, C6, and C6’ fragments. Thus, our first syntheses of cryptands from ‘sucrose triol’ may open a possibility to prepare
Synthesis of a tubugi-1-toxin conjugate by a modulizable disulfide linker system with a neuropeptide Y analogue showing selectivity for hY1R-overexpressing tumor cells
Beilstein J. Org. Chem. 2019, 15, 96–105, doi:10.3762/bjoc.15.11
- synthesis of suitable linkers is a task of crucial importance and synthetic challenge that still is underestimated by many entering the field. The most promising PDC payloads, often also referred to as ‘warheads’, are toxins of limited molecular size but with outstanding potency in the picomolar or lower
- of linkers are unsuitable, as they rendered the peptide inactive (results not shown). However, disulfide-bonded linkers retained activity, presumably by cleavage in the reductive milieu of cancer cells, if connected via a short ester or amide linkage at the C-terminus. The retrosynthetic analysis
- disulfide linkage was chosen for the tubugi-1 coupling to the peptide moiety due to own promising preliminary work. Several linker chemistries were tested with tubulysin-like peptides – amongst them amide and ester linkers, hydrazone linker, VC linker etc. – the disulfide linker described herein, however
Selective ring-opening metathesis polymerization (ROMP) of cyclobutenes. Unsymmetrical ladderphane containing polycyclobutene and polynorbornene strands
Beilstein J. Org. Chem. 2019, 15, 44–51, doi:10.3762/bjoc.15.4
- ][8][9][10][11][12][13][14][15] or from biscyclobutene [16] linked with a range of different rigid linkers. When a flexible linker is used, bisnorbornene derivatives undergo cascade metathetical cyclopolymerization giving the corresponding polynorbornenes with hammock-like pendants [17][18
The design and synthesis of an antibacterial phenothiazine–siderophore conjugate
Beilstein J. Org. Chem. 2018, 14, 2646–2650, doi:10.3762/bjoc.14.242
- -cleavable linker. A polyethylene glycol (PEG) linker was selected as PEG linkers demonstrate enhanced water solubility in comparison to alkyl chain linkers. We then had to make a decision on the position of attachment for the PEG linker to compound 1. For siderophore conjugates, it is crucial that the
Applications of organocatalysed visible-light photoredox reactions for medicinal chemistry
Beilstein J. Org. Chem. 2018, 14, 2035–2064, doi:10.3762/bjoc.14.179
- . Naturally occurring amino acids, e.g., glycine, are often used in medicinal chemistry as linkers, structural components of scaffolds or even as precursors to useful building blocks. Wallentin and co-workers have described a method for the reductive decarboxylation of amino acids, using bis(4-chlorophenyl
- identical nature of the substituents on the product. This severely limits its potential applications, and the usefulness of this protocol is likely limited to the creation of linkers or pendant groups. Benzo-fused five-membered heterocycles also find widespread use in medicinal chemistry, with indoles
Coordination-driven self-assembly vs dynamic covalent chemistry: versatile methods for the synthesis of molecular metallarectangles
Beilstein J. Org. Chem. 2018, 14, 2027–2034, doi:10.3762/bjoc.14.178
- and metallacages [6][7][8][9]. Following this approach, two self-assembled metallarectangles with different bridging linkers 3a,b were synthesized by utilizing the [Cp*2Rh2(μ-η2-η2-C2O4)Cl2] unit as molecular clips (Scheme 1, method A). Precursor complex 1, which bears two labile triflato ligands was
Chiral bisoxazoline ligands designed to stabilize bimetallic complexes
Beilstein J. Org. Chem. 2018, 14, 2002–2011, doi:10.3762/bjoc.14.175
- available. This led to the selection of naphthyridine, pyridazine, pyrazole, and phenol building blocks. We opted to connect these linkers to oxazolines via amide bonds. The reasoning for this was twofold. Firstly, this should provide ligands with significantly improved stabilities over for instance imine
- linkers. In addition, each amide moiety, upon deprotonation (a requirement for complex formation), would provide a formal negative charge on the ligand, thus resulting in increased complex stability while reducing the number of spectator anions associated with the two metals. Different combinations of
- contrast, a distorted square pyramidal binding mode is observed for Zn(2). Phenol-bridged bisoxazoline ligands. Ligands incorporating naphthyridine, pyridazine and pyrazole linkers discussed thus far bridge two metal atoms by attachment to two different nitrogen donor atoms. As a result, metal∙∙∙metal
A hemicryptophane with a triple-stranded helical structure
Beilstein J. Org. Chem. 2018, 14, 1885–1889, doi:10.3762/bjoc.14.162
- / UCBL, Université Claude Bernard Lyon 1, 6 rue victor Grignard, 69622 Villeurbanne cedex, France 10.3762/bjoc.14.162 Abstract A hemicryptophane cage bearing amine and amide functions in its three linkers was synthesized in five steps. The X-ray molecular structure of the cage shows a triple-stranded
- helical arrangement of the linkers stabilized by intramolecular hydrogen bonds between amide and amine groups. The chirality of the cyclotriveratrylene unit controls the propeller arrangement of the three aromatic rings in the opposite part of the cage. 1H NMR studies suggest that this structure is
- part). They display recognition properties toward neurotransmitters and carbohydrates, and can act as molecular switches and supramolecular catalysts [11]. Their C3 symmetry makes them promising candidates to build molecular cages displaying a triple helical arrangement of the linkers. Furthermore, we
Efficient catenane synthesis by cucurbit[6]uril-mediated azide–alkyne cycloaddition
Beilstein J. Org. Chem. 2018, 14, 1846–1853, doi:10.3762/bjoc.14.158
- linkers between the terminal azide and alkyne groups, so that any other possible preorganization effects, except that of the ammonium binding to CB[6] could be eliminated to study the efficiency of CBAAC in the catenane formation. In our first trial, a 1:1:2 mixture of DN-N3, DN-CC and CB[6] in 0.2 M HCl
Synthesis and photophysical studies of a multivalent photoreactive RuII-calix[4]arene complex bearing RGD-containing cyclopentapeptides
Beilstein J. Org. Chem. 2018, 14, 1758–1768, doi:10.3762/bjoc.14.150
- carbon atoms of RGDfK units exceed 30 Å. Along the MD simulations, we noticed that the Ru complex remained far from the cyclic pentapeptides. This is due to the fact that the linkers of each arm are smaller than the size of the calixarene platform, preventing contacts between the Ru complex and the RGDfK
- and the cyclic pentapeptides. This large variation in the distance is due to the flexibility of the linkers between the calixarene platform and the RGDfK units, together with the many possibilities of H-bonding between: (i) oxygen atoms at C=O in the linker and the hydrogen atoms of (N–H) of arginine
Design, synthesis and structure of novel G-2 melamine-based dendrimers incorporating 4-(n-octyloxy)aniline as a peripheral unit
Beilstein J. Org. Chem. 2018, 14, 1704–1722, doi:10.3762/bjoc.14.145
- central building blocks (A–C) already contain a standard m-trivalent core (benzene-1,3,5-triyl or s-triazin-2,4,6-triyl) connected to 1,4-disubstituted six-membered (hetero)cycle linkers. These linkers were chosen based on their intimate nature: flexible (piperazin-1-yl)methyl (in A), rigid 1,4-phenylene
- installation of the piperazine linkers on 2a (Table 1, entry 3) and on D-Cl (Table 1, entry 5) was ensured by the use of a 300% molar excess of this inexpensive reagent. We note the long-reaction time and large temperature domains (Table 1) required in order to obtain the quantitative results shown in Scheme 2
- realised by covalent and/or (carboxyl/amino) ionic trimerisations, to recommend two G-1 N-substituted melamine dendrons with piperzine-1,4-diyl (linkers) and 4-(n-octyloxyphenyl)amino (peripheral units), D-Cl and D-N
NH, as promising scaffolds for future dendritic elaborations. Tandem DFT-(VT) NMR
Hyper-reticulated calixarene polymers: a new example of entirely synthetic nanosponge materials
Beilstein J. Org. Chem. 2018, 14, 1498–1507, doi:10.3762/bjoc.14.127
- , V.le delle Scienze ed. 17, 90128 Palermo, Italy 10.3762/bjoc.14.127 Abstract New calixarene-based nanosponges (CaNSs), i.e., hyper-reticulated polymers constituted by calixarene monomer units joined by means of bis(1,2,3-trialzolyl)alkyl linkers, were synthesized, characterized and subjected to
- was assessed by means of FTIR and 13C{1H} CP-MAS solid-state NMR techniques, whereas morphological characterization was provided by SEM microghaphy. The materials were proved to possess pH-dependent sequestration abilities, due to the presence of the weakly basic triazole linkers. Sequestration
- . For instance, increased porosity of the CyNS obtained has been recently claimed by the use of a rigid terephthalonitrile unit as the linker [13]. On the other hand, it has been recently shown that polyamine linkers give rise to pH-sensitive materials with tunable adsorption abilities [12]. In order to
Novel unit B cryptophycin analogues as payloads for targeted therapy
Beilstein J. Org. Chem. 2018, 14, 1281–1286, doi:10.3762/bjoc.14.109
- to investigate whether the high biological activity of the parent compound is retained and thus, construction of ADCs and PDCs would be feasible. This preparation could be done using traceless cleavable linkers that are sensitive to the distinct physiology of the tumour with enhanced level and
An overview of recent advances in duplex DNA recognition by small molecules
Beilstein J. Org. Chem. 2018, 14, 1051–1086, doi:10.3762/bjoc.14.93
- and 10 with longer linkers exhibit relatively higher cytotoxicity in comparison to both distamycin and uramustine. The distamycin fragment directs binding to the A·T-rich sequences in the minor groove, and higher flexibility due to the longer linker allows optimal positioning of the mustard for DNA
- , including quinolyl and benzoyl derivatives, and alkenes as linkers in order to investigate their antimicrobial properties [58][59]. One of these structural analogs, MGB-BP-3 (Figure 4), containing a stilbene like fragment as head group and two N-methylpyrroles attached to an aminoethylmorpholine as tail
- –indole amide minor groove binders connected through alkyl or ethoxyethyl linkers were developed by Tecilla et al. [111]. The authors confirmed that these conjugates with tach units, either free or Zn(II)-complexed forms, bind strongly to the minor groove through electrostatic interactions with the
On the design principles of peptide–drug conjugates for targeted drug delivery to the malignant tumor site
Beilstein J. Org. Chem. 2018, 14, 930–954, doi:10.3762/bjoc.14.80
- as prodrugs, due to the covalent coupling of a peptide to a drug via specific linkers. The main building blocks of a simple PDC include a cytotoxic agent (drug), a tumor-homing peptide (navigating/targeting moiety) and a linker between them (Figure 2B). This class of prodrugs is continuously gaining
- not to perturb the binding affinity of the peptide to its receptor and the drug efficacy. An inappropriate linker may impede the release of the drug from the PDC and therefore diminish its overall therapeutic potency. Linkers utilized in PDCs exist in different categories and vary on their length
- , stability, release mechanism, functional groups, hydrophilicity/hydrophobicity etc. This linker can be designed to bear an enzyme-hydrolyzable unit (EHU) like a carboxylic ester or an amide bond, cleaved by esterases and amidases, respectively. The most commonly utilized linkers that bear a carboxylic ester
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