Phosphated cyclodextrins as water-soluble chiral NMR solvating agents for cationic compounds

• Cira Mollings Puentes and
• Thomas J. Wenzel

Beilstein J. Org. Chem. 2017, 13, 43–53, doi:10.3762/bjoc.13.6

• higher degree of complexation. However, in some spectra there have been an overlap of one of the substrate resonances with other resonances of the substrate or CD in such a way that it was not possible to determine in a regular one-dimensional NMR spectrum whether enantiomeric differentiation was present

Stabilization of nanosized titanium dioxide by cyclodextrin polymers and its photocatalytic effect on the degradation of wastewater pollutants

• Tamás Zoltán Agócs,
• István Puskás,
• Erzsébet Varga,
• Mónika Molnár and
• Éva Fenyvesi

Beilstein J. Org. Chem. 2016, 12, 2873–2882, doi:10.3762/bjoc.12.286

• when linked to nanoTiO2 colloids leading to restriction of charge–hole recombination [35]. The efficiency is further improved by keeping the ligands close to the surface of nanoTiO2 via inclusion complexation. In other studies the presence of CDs caused a delay in the photocatalytic degradation of

• -stabilized nanoTiO2 as additive hardly any decrease in the drug concentration upon UV irradiation was measured especially in tap water. It is well-known that the complexation often has a protective effect on the included guest molecules [8]. Either catalysis or inhibition of the light-induced cleavage can

• is deeply included into the cavity [51], while MB is too large to be completely shielded by complexation. The too strong association between IBR and the cavities of CMBCD-P can be a possible reason of protection instead of catalytic decomposition in this process. Further experiments are needed to

Biochemical and structural characterisation of the second oxidative crosslinking step during the biosynthesis of the glycopeptide antibiotic A47934

• Veronika Ulrich,
• Clara Brieke and
• Max J. Cryle

Beilstein J. Org. Chem. 2016, 12, 2849–2864, doi:10.3762/bjoc.12.284

• protein’s N-terminus. Spectral analysis of StaF showed that it exhibits the typical P450 absorption spectra, but with only half of the StaF species being in the catalytically competent state upon reduction and CO-complexation. Despite this, we successfully reconstituted the StaF activity in vitro and could

New approaches to organocatalysis based on C–H and C–X bonding for electrophilic substrate activation

• Pavel Nagorny and
• Zhankui Sun

Beilstein J. Org. Chem. 2016, 12, 2834–2848, doi:10.3762/bjoc.12.283

• chloride complexation, the provided X-ray data are consistent with L13 acting as hydrogen bond donors (Scheme 10B). The published X-ray data for the chloride and bromide salts of L13 with R2 = C6F5 indeed provide evidence of anion–π bonding with the C6F5 group. In addition, we also noted that there is

• bond-donor catalysts by Bibal and co-workers [53][54]. Tetraalkylammonium catalyst (L6)-catalyzed dearomatization of isoquinolinium salts [50]. Tetraalkylammonium catalyst L6 complexation to halogen-containing substrates [51]. Tetraalkylammonium-catalyzed aza-Diels–Alder reaction by Maruoka and co

Interactions between cyclodextrins and cellular components: Towards greener medical applications?

• Loïc Leclercq

Beilstein J. Org. Chem. 2016, 12, 2644–2662, doi:10.3762/bjoc.12.261

• solution, the complexation is enthalpically and entropically driven. In addition, complementary interactions (e.g., van der Waals forces, H-bonds, etc.) appear between the CD and the guest. The non-polar suitably-sized guest may be bound in numerous molar ratios (e.g., 1:1, 2:1, 1:2, etc.). In all cases

• , the knowledge of the binding constants (Kass) is crucial because these values provide an index of host–guest binding forces. CDs can also form exclusion complexes where the CDs are bound to the guest through a H-bond network. For instance, the complexation of [PMo12O40] anion by β- and γ-CD results in

• complexation of endogenous substances are of potential interest for many applications. Biomolecule/cyclodextrin inclusions complexes Native and modified CDs can be used to complex certain chemicals produced naturally present in cells and tissues (i.e., endogenous substances). Indeed, CDs are able to form

A self-assembled cyclodextrin nanocarrier for photoreactive squaraine

• Ulrike Kauscher and
• Bart Jan Ravoo

Beilstein J. Org. Chem. 2016, 12, 2535–2542, doi:10.3762/bjoc.12.248

• complexation. In that way, it was possible to decorate CDVs with carbohydrates [32][33], with peptides [34], and also with DNA [35]. Moreover CDVs were also shown to form very dense membranes in combination with phospholipids and cholesterol [36]. Previous studies also showed promising results for PDT

• the presence of the aggregated form of AdSq (see Figure S2 in Supporting Information File 1). The fluorescence spectra show a saturation of the intensity maximum for a concentration of 60 µM CDV. Assuming that the accessible concentration of cyclodextrin available for the complexation of guest is only

Radical polymerization by a supramolecular catalyst: cyclodextrin with a RAFT reagent

• Kohei Koyanagi,
• Yoshinori Takashima,
• Takashi Nakamura,
• Hiroyasu Yamaguchi and
• Akira Harada

Beilstein J. Org. Chem. 2016, 12, 2495–2502, doi:10.3762/bjoc.12.244

• decreased with the addition of competitive molecules, indicating that complexation between CD-CTA and the monomer plays an important role in determining polymerization rate. Results and Discussion Preparation of α-CD-CTA We designed a CTA reagent with α-CD or β-CD. Figure 1 illustrates the preparation of α

• inhibiting the molecular recognition of α-CD, the inclusion complexation ratio between the monomer and α-CD-CTA was decreased, which lead to lower yields and higher molecular weight of the resulting polymers due to preceding free radical polymerization. In the reaction of AAm monomer, which has a low

Synthesis, dynamic NMR characterization and XRD studies of novel N,N’-substituted piperazines for bioorthogonal labeling

• Constantin Mamat,
• Marc Pretze,
• Matthew Gott and
• Martin Köckerling

Beilstein J. Org. Chem. 2016, 12, 2478–2489, doi:10.3762/bjoc.12.242

• explored in terms of their NMR and complexation behavior. However, unsymmetrically substituted piperazines are rarely investigated [12][13]. N,N’-Unsymmetrically functionalized piperazines are the basis of the development of our new building blocks. In this case, one of the nitrogen atoms is used for the

Efficient mechanochemical synthesis of regioselective persubstituted cyclodextrins

• Laszlo Jicsinszky,
• Marina Caporaso,
• Katia Martina,
• Emanuela Calcio Gaudino and
• Giancarlo Cravotto

Beilstein J. Org. Chem. 2016, 12, 2364–2371, doi:10.3762/bjoc.12.230

• very strong complexes with not only the native but with the substituted CDs, too. Although a solvent-free synthetic method does not solve the problem of complexation but the reduced amount of reagents can simplify the purification. Heptakis(6-azido-6-deoxy)-β-CD is the precursor to per-6-amino-β-CD

• /halogen molar ratios did not change such extent (Table 1). This can be explained satisfactorily by the complexation of the leaving group which might have high affinity to the CD cavity [3][25][26] preventing its departure from the reaction centres resulting in steric blocking. While the halogen → azide

• . The resulting crude mixture was only partially soluble in methylene chloride and MeOH precipitation gave a difficult-to-filter product, which still contained at least one mole of complexed DDS. This complexation resulted in not only technical difficulties, but also confounded the removal of impurities

Diels–Alder reactions in confined spaces: the influence of catalyst structure and the nature of active sites for the retro-Diels–Alder reaction

• Ángel Cantín,
• M. Victoria Gomez and
• Antonio de la Hoz

Beilstein J. Org. Chem. 2016, 12, 2181–2188, doi:10.3762/bjoc.12.208

• acid sites in the solids We have prepared Ti-Beta [31], Sn-Beta [32] and Al-Beta (Si/Al = 50) [33] considering that Lewis acid catalyzes the DAR [1]. This effect is known to occur by complexation of the carbonyl group of the dienophile with the Lewis acid that increases the electron deficiency of the

Cross-linked cyclodextrin-based material for treatment of metals and organic substances present in industrial discharge waters

• Élise Euvrard,
• Nadia Morin-Crini,
• Coline Druart,
• Justine Bugnet,
• Bernard Martel,
• Cesare Cosentino,
• Virginie Moutarlier and
• Grégorio Crini

Beilstein J. Org. Chem. 2016, 12, 1826–1838, doi:10.3762/bjoc.12.172

• material was initially activated by NaHCO3. Discussion To explain the adsorption performance of polyBTCA-CD, a chemisorption mechanism involving several interactions can occur including ion exchange, electrostatic interactions, inclusion complexation and/or precipitation [3][12][13][14][15][16]. The

Amidofluorene-appended lower rim 1,3-diconjugate of calix[4]arene: synthesis, characterization and highly selective sensor for Cu²⁺

• Rahman Hosseinzadeh,
• Mohammad Nemati,
• Reza Zadmard and
• Maryam Mohadjerani

Beilstein J. Org. Chem. 2016, 12, 1749–1757, doi:10.3762/bjoc.12.163

• mode of complexation of L with Cu2+, 1H NMR titrations were carried out (Figure 7). Upon the initial addition of Cu2+ into the CD3CN solution of L, signals related to OH phenolic groups (Hb) and amidic protons (Ha) were first broadened and then finally disappeared. Furthermore, the signals of Ar–CH2

• (Hd, He) and –O–CH2 (Hf) porotons, which are close to the binding site of receptor L were affected and downfield shifted by the complexation of L with Cu2+. A detailed analysis of the 1H NMR spectra reveals the significant changes of almost all the other proton signals in the ligand. For instance, the

• indicated that the synthesized chemosensor L has a lower LOD and a higher Ka in comparison with other chemosensors, which shows a stable and selective complexation with Cu2+. Conclusion In this study, the amidoflourene-appended calix[4]arene 1,3-diconjugated L was synthesized as an efficient colorimetric

Cp₂TiCl/D₂O/Mn, a formidable reagent for the deuteration of organic compounds

• Antonio Rosales and
• Ignacio Rodríguez-García

Beilstein J. Org. Chem. 2016, 12, 1585–1589, doi:10.3762/bjoc.12.154

• cyclic voltammetry, theoretical calculations and electro-paramagnetic resonance techniques studies [28][34]. These results are in agreement with the previously reported results by Wood et al. [35] and Renaud et al. [36] describing the effect of complexation with a Lewis acid on the strength of the O–H

Biosynthesis of oxygen and nitrogen-containing heterocycles in polyketides

• Franziska Hemmerling and
• Frank Hahn

Beilstein J. Org. Chem. 2016, 12, 1512–1550, doi:10.3762/bjoc.12.148

• contribute significantly to their structural and physical properties as well as to their biological activity [1][2][3]. Heterocycles can for example be involved in cation complexation as known for ionophoric polyethers or introduce conformational rigidity into a molecule, which is crucial for target binding

Flow carbonylation of sterically hindered ortho-substituted iodoarenes

• Carl J. Mallia,
• Gary C. Walter and
• Ian R. Baxendale

Beilstein J. Org. Chem. 2016, 12, 1503–1511, doi:10.3762/bjoc.12.147

• aryl halide, an associative mechanism for the complexation of carbon monoxide on the d8 square planar intermediate would occur prior to the key migratory insertion step. In the complex, the aryl group would be oriented perpendicularly to the plane to minimise steric interactions thus placing the ortho

NeoPHOX – a structurally tunable ligand system for asymmetric catalysis

• Jaroslav Padevět,
• Marcus G. Schrems,
• Robin Scheil and
• Andreas Pfaltz

Beilstein J. Org. Chem. 2016, 12, 1185–1195, doi:10.3762/bjoc.12.114

• from the secondary phosphines by deprotonation with KH in refluxing THF. The NeoPHOX ligands, which were obtained by this route in high overall yield, proved to be air and moisture stable and could be obtained in analytically pure form by simple filtration through silica gel [19]. Complexation with [Ir

• –76% yields (Scheme 7). From these ligands a library of iridium catalysts was prepared by complexation with bis(1,5-cyclooctadiene)diiridium(I) dichloride, followed by anion exchange with NaBArF. Comparative hydrogenation studies with iridium catalysts derived from 1st and 2nd generation NeoPHOX

Enantioselective carbenoid insertion into C(sp³)–H bonds

• J. V. Santiago and
• A. H. L. Machado

Beilstein J. Org. Chem. 2016, 12, 882–902, doi:10.3762/bjoc.12.87

• reagents, also used as solvent, were cyclopentane, cyclohexane and cycloheptane. Two factors are noteworthy in this work. Unlike the carboxamide complexes (R)-18 and (S)-18 previously reported by Doyle and coworkers (Table 2), where the complexation of the chiral ligand to rhodium atoms occurs through the

A modular approach to neutral P,N-ligands: synthesis and coordination chemistry

• Vladislav Vasilenko,
• Torsten Roth,
• Clemens K. Blasius,
• Sebastian N. Intorp,
• Hubert Wadepohl and
• Lutz H. Gade

Beilstein J. Org. Chem. 2016, 12, 846–853, doi:10.3762/bjoc.12.83

• 7 were prepared. It should be noted that ligands 2, 5, and 7 feature a distinct shift of the 31P NMR resonance to lower fields upon complexation of a rhodium(I) or iridium(I) center, whereas a shift to higher fields is observed for ligand 3 [11]. We were able to obtain single crystals of compounds

• ,N-ligand scaffold, ligands 2a and 5 were reacted with the Lewis-acidic precursors [Cp*RhCl2]2 and [Cp*IrI2]2 (Figure 3). As has been pointed out for the analogous Rh(I) and Ir(I) compounds, complexation is accompanied by a 31P NMR shift to lower fields (from 49.7 ppm to 108.9 ppm and 80.6 ppm for

Scope and mechanism of the highly stereoselective metal-mediated domino aldol reactions of enolates with aldehydes

• M. Emin Cinar,
• Bernward Engelen,
• Martin Panthöfer,
• Hans-Jörg Deiseroth,
• Jens Schlirf and
• Michael Schmittel

Beilstein J. Org. Chem. 2016, 12, 813–824, doi:10.3762/bjoc.12.80

• analyzing the harmonic vibrational frequencies, using analytical second derivatives. To predict the energies plausibly, as recommended for organometallic compounds, single point calculations with M06 functional [52] were performed using the same basis sets (Scheme 6). Complexation of the metal enolate E

From steroids to aqueous supramolecular chemistry: an autobiographical career review

• Bruce C. Gibb

Beilstein J. Org. Chem. 2016, 12, 684–701, doi:10.3762/bjoc.12.69

• complexation is as expected. The smallest of guests form 1:1 complexes, whereas with guests larger than ethane a 2:2 or 2:1 capsular complex is formed. In contrast the binding profile of TEMOA is non-monotonic: very small and medium sized guests form 1:1 complexes, whereas small and large guests form dimeric

• facet of these collaborations is the SAMPL exercise in which we and other supramolecular chemists a priori determine the thermodynamics of complexation for a series of processes, and keep the results under wraps whilst computational groups around the world attempt to predict the data [52]. This

Creating molecular macrocycles for anion recognition

• Amar H. Flood

Beilstein J. Org. Chem. 2016, 12, 611–627, doi:10.3762/bjoc.12.60

• counter cations, their binding constants were not constant! In our case, when we changed concentrations, the binding constants for the 1:1 triazolophane–chloride complexes were not constant. We ended up taming our menagerie of ion pairing and complexation equilibria in a tour de force thermodynamics study

• points after 0.5 equiv of chloride are added, which is the equivalence point for the 2:1 complex. We observe the ion pairing of the TBA+ with the 1:1 complex in the cation’s α proton (≈3 ppm), which has an inflection point at 1 equiv. Consistent with its complexation as a 1:1:1 species, the diffusion NMR

• fitting of 1H NMR titration data. Both software have their limitations but their usage as tools to unravel complex equilibria is without parallel. Cooperativity of ion–pair complexation The most recent undertaking of ion pairing is to make it a feature and to examine, in glorious detail, how ion pairs can

Interactions between 4-thiothymidine and water-soluble cyclodextrins: Evidence for supramolecular structures in aqueous solutions

• Vito Rizzi,
• Sergio Matera,
• Paola Semeraro,
• Paola Fini and
• Pinalysa Cosma

Beilstein J. Org. Chem. 2016, 12, 549–563, doi:10.3762/bjoc.12.54

• complexation mode of the inclusion complexes involving 4-thiothymidine (S4TdR, a known photosensitizer) and five CDs, namely 2-hydroxypropyl-α-cyclodextrin (2-HP-α-CD), 2-hydroxypropyl-β-cyclodextrin (2-HP-β-CD), 2-hydroxypropyl-γ-cyclodextrin (2-HP-γ-CD), heptakis-(2,6-di-O-methyl)-β-cyclodextrin (DIMEB CD

• (TdR) as the main product was obtained [26]. The use of a delivery system could be a method to improve the photochemical behavior and to prevent the degradation of the thiobase [27]. In fact, literature suggests that one method to avoid the drug degradation is the complexation with CDs, and, as

• get further insight into the complexation constants, the thermodynamic stability of the 2-HP-CD complexes was studied as described in [40], using Equation 2 and the obtained results are reported in Figure 4D. Interesting results were obtained (Figure 4D) by comparing experimental data with theoretical

New synthetic strategies for xanthene-dye-appended cyclodextrins

• Milo Malanga,
• Andras Darcsi,
• Mihaly Balint,
• Gabor Benkovics,
• Tamas Sohajda and
• Szabolcs Beni

Beilstein J. Org. Chem. 2016, 12, 537–548, doi:10.3762/bjoc.12.53

• known that β-CD has the ability to preferably complex the cyclic form of rhodamine B [21], complexation may play a role in the stabilization of the lactam form of the rhodamine-appended CD derivative. All this information taken together confirms the presence of the product/conjugate and add to the

• scaffold. Because of the chirality of the cyclodextrin part, the two phenyl rings of the xanthene moiety are formally diastereotopic, and consequently, anisochronous even without any complexation. This fact can be proven by recording the 1H NMR spectrum of the Rho-β-CD in deuterated DMSO, a solvent known

• model for the supramolecular assembly is also in agreement with previous data about the inclusion complexation of organic dyes with β-CD dimers [26]. In more detail, the analysis of the 2D ROESY spectrum reveals that the methyl units of the rhodamine side chains that resonate at 0.81 ppm (the side

Optimized methods for preparation of 6^I-(ω-sulfanyl-alkylene-sulfanyl)-β-cyclodextrin derivatives

• Eva Bednářová,
• Simona Hybelbauerová and
• Jindřich Jindřich

Beilstein J. Org. Chem. 2016, 12, 349–352, doi:10.3762/bjoc.12.38

• derivatives [3] which have been prepared up to now can be divided into several groups according to their intended use. The largest group is the one containing CD derivatives with modified complexation properties, used mainly as solubilizers and/or stabilizers in pharmaceutical, cosmetic, agricultural and food

Study on the synthesis of the cyclopenta[f]indole core of raputindole A

• Nils Marsch,
• Mario Kock and
• Thomas Lindel

Beilstein J. Org. Chem. 2016, 12, 334–342, doi:10.3762/bjoc.12.36

• . Alternatively, for a similar 1,3-shift, Nolan and coworkers proposed two sequential 1,2-shifts to occur after π-complexation of the triple bond by Au(I) [49]. Methanolysis (NaOMe/MeOH) of cyclopentenylacetate 50 afforded cyclopenta[f]indolinone 48 (96%). Conclusion It was our goal to explore how to efficiently