Tautomerism as primary signaling mechanism in metal sensing: the case of amide group

• Vera Deneva,
• Georgi Dobrikov,
• Aurelien Crochet,
• Daniela Nedeltcheva,
• Katharina M. Fromm and
• Liudmil Antonov

Beilstein J. Org. Chem. 2019, 15, 1898–1906, doi:10.3762/bjoc.15.185

• assignment of the monomer molecules, consequently, its absorption maximum should be blue shifted compared to the monomeric species. If we assume that in ethanol or in dimethylformamide only the monomeric keto form is present, the blue shift of the absorption in acetonitrile indicates that the keto form here

Identification of optimal fluorescent probes for G-quadruplex nucleic acids through systematic exploration of mono- and distyryl dye libraries

• Xiao Xie,
• Michela Zuffo,
• Marie-Paule Teulade-Fichou and
• Anton Granzhan

Beilstein J. Org. Chem. 2019, 15, 1872–1889, doi:10.3762/bjoc.15.183

• lines); c = 10 µM in all cases. Band assignment (when possible): M, monomer; H, H-aggregate; J, J-aggregate. Representative absorption spectra of the distyryl dyes (c = 10 µM in MeOH) demonstrating the influence of the molecular structure on the optical properties. A) Variation of Ar groups. B

Design, synthesis and biological evaluation of immunostimulating mannosylated desmuramyl peptides

• Rosana Ribić,
• Ranko Stojković,
• Lidija Milković,
• Mariastefania Antica,
• Marko Cigler and
• Srđanka Tomić

Beilstein J. Org. Chem. 2019, 15, 1805–1814, doi:10.3762/bjoc.15.174

• investigated in the mouse model using ovalbumin as an antigen. Their activities were compared to the previously described mannosylated adamantane-containing desmuramyl peptide and peptidoglycan monomer. Tested compounds exhibited adjuvant activity and the strongest enhancement of IgG production was stimulated

• of the peptidoglycan monomer (PGM, Figure 1) which is used in this work. PGM is a well-defined and characterized disaccharide pentapeptide, β-ᴅ-GlcNAc-(1→4)-ᴅ-MurNAc-ʟ-Ala-ᴅ-isoGln-mesoDAP(εNH2)-ᴅ-Ala-ᴅ-Ala, originating from Brevibacterium divaricatum [8][9]. Peptidoglycans activate macrophages via

Host–guest interactions in nor-seco-cucurbit[10]uril: novel guest-dependent molecular recognition and stereoisomerism

• Xiaodong Zhang,
• Wei Wu,
• Zhu Tao and
• Xin-Long Ni

Beilstein J. Org. Chem. 2019, 15, 1705–1711, doi:10.3762/bjoc.15.166

• Xiaodong Zhang Wei Wu Zhu Tao Xin-Long Ni Key Laboratory of Macrocyclic and Supramolecular Chemistry of Guizhou Province, Guizhou University, Guiyang 550025, China 10.3762/bjoc.15.166 Abstract The unique monomer and excimer fluorescence emissions of pyrene were first exploited as distinctly

• , the top–center isomer of G2 within both host-1 and host-2 could be characterized because of the novel monomer and excimer photophysical property of pyrene as fluorophore. As a result, we demonstrated here a novel guest-controlled molecular recognition and stereoisomerism for the first time. Results

• of G1 in host-1 and host-2, despite the clear split of resonances corresponding to the protons on the hosts. A number of studies suggest that pyrene is one of the most useful fluorogenic units, being sensitive to conformational change because of its relatively efficient monomer and excimer emissions

Synthesis, enantioseparation and photophysical properties of planar-chiral pillar[5]arene derivatives bearing fluorophore fragments

• Guojuan Li,
• Chunying Fan,
• Guo Cheng,
• Wanhua Wu and
• Cheng Yang

Beilstein J. Org. Chem. 2019, 15, 1601–1611, doi:10.3762/bjoc.15.164

• of 89.5%. This is comparable to the monomer DPA-6, while P5A-Py with two perylene (Py) pigments grafted on the pillar[5]arene showed a significantly reduced quantum yield of 46.4% vs 78.2% for the monomer Py-6. The oxygen-through-annulus rotation of the phenolic units was inhibited for both compounds

• showed strong absorptions in the visible range and high fluorescence quantum yield, e.g., P5A-DPA showed absorption at 350–410 nm and a quantum yield of 89.5% which is comparable to the monomer DPA-6. On the other hand, P5A-Py with two perylene (Py) pigments grafted on the pillar[5]arene showed intense

Reaction of oxiranes with cyclodextrins under high-energy ball-milling conditions

• László Jicsinszky,
• Federica Calsolaro,
• Katia Martina,
• Fabio Bucciol,
• Maela Manzoli and
• Giancarlo Cravotto

Beilstein J. Org. Chem. 2019, 15, 1448–1459, doi:10.3762/bjoc.15.145

• is lower than in the monomer. Particularly interesting results were observed when the same property of γ-CDP was compared to the corresponding (3-glycidyloxy)propylsilane γ-CD composite (next section). The complexation efficacy of the prepared CDPs is summarised in Table 4. No significant differences

Selenophene-containing heterotriacenes by a C–Se coupling/cyclization reaction

• Pierre-Olivier Schwartz,
• Sebastian Förtsch,
• Astrid Vogt,
• Elena Mena-Osteritz and
• Peter Bäuerle

Beilstein J. Org. Chem. 2019, 15, 1379–1393, doi:10.3762/bjoc.15.138

• subsequent electrochemical characterization of polymer P(DTS) P2 at various scan rates in a monomer-free electrolyte is shown (right). The other examples for P1, P3, and P4 are shown in Supporting Information File 1, Figure S14. After the oxidation of the monomer in the first scan, polymerization starts by

• P1–P4 in a monomer-free electrolyte showed broad and unstructured redox waves typical for conducting polymers reflecting the inhomogeneity of the material containing various electrophoric moieties due to variations in the (conjugated) chain length and conformational issues [52]. As well the

• of heterotriacenes 1–4. Electrochemical properties of poly(heterotriacenes) P1–P4 and film loss after conducting 30 scans in a monomer-free electrolyte solution. Supporting Information Supporting Information File 524: Additional spectral and crystallographic data. Acknowledgements We gratefully

Bambusuril analogs based on alternating glycoluril and xylylene units

• Tomáš Lízal and
• Vladimír Šindelář

Beilstein J. Org. Chem. 2019, 15, 1268–1274, doi:10.3762/bjoc.15.124

• Tomas Lizal Vladimir Sindelar Department of Chemistry and RECETOX, Masaryk University, Kamenice 5, 625 00 Brno, Czech Republic 10.3762/bjoc.15.124 Abstract The glycoluril monomer is a popular building block in supramolecular chemistry as it is used for the synthesis of versatile host molecules

• simple example of a chromophoric monomer (Scheme 1). The reaction took place under basic conditions using LiH in dry THF [16]. The LiClO4 salt was used originally as a template in order to drive the reaction towards the three-membered macrocycle (n = 3). Later it was found that the salt does not have a

Self-assembly behaviors of perylene- and naphthalene-crown macrocycle conjugates in aqueous medium

• Xin Shen,
• Bo Li,
• Tiezheng Pan,
• Jianfeng Wu,
• Yangxin Wang,
• Jie Shang,
• Yan Ge,
• Lin Jin and
• Zhenhui Qi

Beilstein J. Org. Chem. 2019, 15, 1203–1209, doi:10.3762/bjoc.15.117

• water [56]. Following this water-centered view, we further explored a new type of supramolecular polymeric adhesive based on B21C7 derived low–molecular weight (LMW) monomer, in which the water molecules serve as essential co-monomers to the polymerization process, rather than as solvent [57]. Compared

Mechanochemical synthesis of hyper-crosslinked polymers: influences on their pore structure and adsorption behaviour for organic vapors

• Sven Grätz,
• Sebastian Zink,
• Hanna Kraffczyk,
• Marcus Rose and
• Lars Borchardt

Beilstein J. Org. Chem. 2019, 15, 1154–1161, doi:10.3762/bjoc.15.112

• chloromethylene groups has occurred [43]. While this vibration is dominant in the monomer, it has completely vanished in the IR (infrared) spectrum of the polymer (Figure 2A). Moreover, several other changes in the spectrum are observed for the polymer as well. Especially in the region of the C–Hoop the vibration

• that even small amounts of the monomer (3.2 mmol) lead to a swift and rise in vessel pressure exceeding 12 bar (Figure 3A) caused by the released HCl in the course of the reaction. This behaviour can be handled under laboratory conditions but is hampering the potential scale up of the process. In the

• adsorptive solvent was dried using molecular sieves 4 Å and degassed under vacuum. A: Mechanochemical polymerization of BCMBP (4,4’-bis(chloromethyl)-1,1’-biphenyl) towards the porous polymer HCP. B: Picture of a vial of BCMBP (left) and LAG-HCP (right). A: IR spectra of the monomer BCMBP and NG-HCP showing

Electrophilic oligodeoxynucleotide synthesis using dM-Dmoc for amino protection

• Shahien Shahsavari,
• Dhananjani N. A. M. Eriyagama,
• Bhaskar Halami,
• Vagarshak Begoyan,
• Marina Tanasova,
• Jinsen Chen and
• Shiyue Fang

Beilstein J. Org. Chem. 2019, 15, 1116–1128, doi:10.3762/bjoc.15.108

• steps from 1,3-dithiane (6) according to a procedure we reported previously [44]. The dC phosphoramidite monomer 3a was synthesized from compound 9 [45]. The formation of the hindered O-tert-alkyl N-arylcarbamate 10 was found highly challenging [44][46][47]. We tried many conditions and finally found

• 14 to give the target monomer 3a (Scheme 2). The dA phosphoramidite monomer 3b was synthesized similarly starting from 15 [48]. The amino group of 15 was carbamylated with 5 in the presence of two equivalents LDA to give 16. The silyl groups were removed, and compound 17 was tritylated to give 18

• , which was phosphitylated to give 3b. The dG phosphoramidite monomer 3c had to be synthesized using a slightly different procedure (Scheme 2). The amide function in the nucleobase in the silyl protected nucleoside 19 [45] was temporarily protected with TBSCl to give 20 [49]. This intermediate was not

Mechanochemical synthesis of poly(trimethylene carbonate)s: an example of rate acceleration

• Sora Park and
• Jeung Gon Kim

Beilstein J. Org. Chem. 2019, 15, 963–970, doi:10.3762/bjoc.15.93

• brief ball milling of monomer and base [10]. The remarkable reactivity exemplified that the general concepts of mechanochemical synthesis are applicable to polymerization reactions. Other examples of polymer syntheses have followed. The Borchardt research team reported the efficient mechanochemical

• polymerization usually requires long reaction times to achieve high conversions (Table 1) [27]. The DBU-catalyzed polymerization of trimethylene carbonate in chloroform, tetrahydrofuran, toluene, and methylene chloride converted less than 5% monomer into poly(trimethylene carbonate) (PTMC) within 1 h (Table 1

• [28]. In the case of ball-milling polymerization, the time required for the physical mixing of monomer, catalyst, and initiator would result in a delayed initiation of the polymerization. However, the relatively slow propagation rate of DBU-mediated trimethyl carbonate polymerization allowed for well

Catalytic asymmetric oxo-Diels–Alder reactions with chiral atropisomeric biphenyl diols

• Chi-Tung Yeung,
• Wesley Ting Kwok Chan,
• Wai-Sum Lo,
• Ga-Lai Law and
• Wing-Tak Wong

Beilstein J. Org. Chem. 2019, 15, 955–962, doi:10.3762/bjoc.15.92

• structure with continuous and alternative inter- and intramolecular hydrogen bonds, whereas 6 forms a monomer without intermolecular hydrogen bonds for supramolecular formation. Together with compounds 1, 2 and 5, all were found to be active organocatalysts in oxo-DA reactions, with 2 resulting in the

Towards the preparation of synthetic outer membrane vesicle models with micromolar affinity to wheat germ agglutinin using a dialkyl thioglycoside

• Dimitri Fayolle,
• Nathalie Berthet,
• Bastien Doumeche,
• Olivier Renaudet,
• Peter Strazewski and
• Michele Fiore

Beilstein J. Org. Chem. 2019, 15, 937–946, doi:10.3762/bjoc.15.90

• horseradish peroxidase-labelled (WGA-HRP) to a GlcNAc-polyacrylamide conjugate following the procedure described in Figure 4. WGA is a homodimer in which each monomer is organized into four domains (A–D) containing adjacent “primary” (B and C) and “secondary” (A and D) domains binding sites with different

• GlcNAc monomer displays only 35 mM (Table 1). Compounds 4 and 7 bearing one and two glucose residues served as negative controls as WGA has no affinity towards glucose. This result clearly shows the high potential of the lipophilic n-alkyl thioglycoconjugates for lectine binding. In particular, compound

• 8 showed the highest inhibitory effect of this study with an IC50 of 11 µM corresponding to a 3000-fold improvement compared to the monomer control. This result suggests a higher participation of sugar units in the lectin binding for this compound. Docking calculation for model glycolipids To

Synthesis of polydicyclopentadiene using the Cp₂TiCl₂/Et₂AlCl catalytic system and thin-layer oxidation of the polymer in air

• Zhargolma B. Bazarova,
• Ludmila S. Soroka,
• Alex A. Lyapkov,
• Мekhman S. Yusubov and
• Francis Verpoort

Beilstein J. Org. Chem. 2019, 15, 733–745, doi:10.3762/bjoc.15.69

• ; polydicyclopentadiene; thin layers; Introduction Currently, polymerization of dicyclopentadiene and norbornene derivatives applying various catalyst systems is of great interest [1][2][3][4][5][6][7]. Dicyclopentadiene (DCPD) is a secondary product of the ethylene and propylene production and is used as a monomer to

• toluene solution of the monomer. However, before adding the catalytic complex, the monomer solution was placed in an adiabatic mixing reactor until the temperature was stabilized. To limit the development of the polymer chain and as a deactivator of the catalyst system, propylene oxide was used. The

• (curve 1) and 10 mmol/L (curve 2). The remaining conditions are the same: Ti/Al ratio 1:1.5, concentration of DCPD 1.5 mol/L. Mw(1) = 5.13·104, Mn(1) = 2.69·104, PDI(1) = 1.91; Mw(2) = 1.32·104, Mn(2) = 4.84·103, PDI(2) = 2.73 of additional monomer. Oxidizing of thin layers of PDCPD in air Oxidation in

Polyaminoazide mixtures for the synthesis of pH-responsive calixarene nanosponges

• Antonella Di Vincenzo,
• Antonio Palumbo Piccionello,
• Alberto Spinella,
• Delia Chillura Martino,
• Marco Russo and
• Paolo Lo Meo

Beilstein J. Org. Chem. 2019, 15, 633–641, doi:10.3762/bjoc.15.59

• nanosponge materials with tunable properties. Nanosponges (NSs) [7][8][9][10][11][12][13][14] are hyper-cross-linked polymers or copolymers obtained by reacting supramolecular host species as the monomer units with suitable reticulating agents. Of course, the structural, physical and chemical features of the

• obtained material critically depend on the host monomer and the linker used, on their molar ratio and, in the case of copolymers, on the molar ratio between the parent comonomers. Therefore, by a proper choice of the components, tunability in the properties of the materials obtained can be achieved. In

• -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

Aqueous olefin metathesis: recent developments and applications

• Valerio Sabatino and
• Thomas R. Ward

Beilstein J. Org. Chem. 2019, 15, 445–468, doi:10.3762/bjoc.15.39

• publication, catalyst 9 was used for an aqueous living ring-opening metathesis polymerization-induced self-assembly (ROMPISA). The authors demonstrated the possibility of performing living ROMP in water selecting a quaternary ammonium-based phenyl norbornene carboximide as core-forming monomer [60]. This

Application of olefin metathesis in the synthesis of functionalized polyhedral oligomeric silsesquioxanes (POSS) and POSS-containing polymeric materials

• Patrycja Żak and
• Cezary Pietraszuk

Beilstein J. Org. Chem. 2019, 15, 310–332, doi:10.3762/bjoc.15.28

• the type of olefin metathesis chain-growth polymerization that uses metathesis catalysts to generate polymers from cyclic olefins [38][39][40][41]. To obtain polymers functionalized with POSS in the side chain, a susceptible to the ROMP monomer connected via a suitable linker to the silsesquioxane

• dispersed over all loadings. No improvements in thermal properties were observed in the copolymers obtained. Another POSS-containing monomer – N-(propyl-POSS)-7-oxanorbornene-5,6-dicarboximide was tested in ring-opening metathesis copolymerization with 3-(trifluoromethyl)phenyl-7-oxanorbornene-5,6

• relatively controlled molecular weights (Mn = 17,900–26,300 Da) and narrow molecular weight distributions (in the range Mn/Mw = 1.19–1.29). Copolymerization was employed by a sequential monomer addition. At first, the POSS-NBE was introduced into the reaction system containing the catalyst and after its

Olefin metathesis in multiblock copolymer synthesis

• Maria L. Gringolts,
• Yulia I. Denisova,
• Eugene Sh. Finkelshtein and
• Yaroslav V. Kudryavtsev

Beilstein J. Org. Chem. 2019, 15, 218–235, doi:10.3762/bjoc.15.21

• monomers to living polymer chains after full consumption of a previous monomer [48][49]. This technique was effectively applied for the synthesis of di-, tri- and tetrablock carbohydrate copolymers mediated by Schrock’ and Grubbs’ catalysts of the 1st (Gr1) and 2nd (Gr2) generations (Scheme 1, Figure 1

• to copolymers with a limited number of blocks, such as tetrablocks or pentablocks [52], because each time a new monomer is added some of the living chains cannot initiate polymerization being terminated with trace impurities. Besides, in the course of ROMP main-chain double bonds are prone to

• secondary metathesis in a chain-transfer process that leads to reshuffling of the monomer unit sequences. Since less sterically encumbered groups are more easily involved into the secondary metathesis, this effect can be minimized by first polymerizing a more bulky monomer and then conducting a fast

Computational characterization of enzyme-bound thiamin diphosphate reveals a surprisingly stable tricyclic state: implications for catalysis

• Ferran Planas,
• Michael J. McLeish and
• Fahmi Himo

Beilstein J. Org. Chem. 2019, 15, 145–159, doi:10.3762/bjoc.15.15

• atoms that were kept fixed to their crystallographic positions during the geometry optimization. The BFDC active site has contributions from two monomers and primes re-used to indicate residues from the second monomer. For clarity, the non-polar hydrogens of the residues are not included. Optimized

Adhesion, forces and the stability of interfaces

• Robin Guttmann,
• Johannes Hoja,
• Christoph Lechner,
• Reinhard J. Maurer and
• Alexander F. Sax

Beilstein J. Org. Chem. 2019, 15, 106–129, doi:10.3762/bjoc.15.12

Fabrication of supramolecular cyclodextrin–fullerene nonwovens by electrospinning

• Hiroaki Yoshida,
• Ken Kikuta and
• Toshiyuki Kida

Beilstein J. Org. Chem. 2019, 15, 89–95, doi:10.3762/bjoc.15.10

• ) inclusion complex, γ-CD dimer, and γ-CD monomer in HFIP. Interestingly the γ-CD–C60 (1:1) inclusion complex, which is the supposed intermediate, is not detected (Figure 2c in Supporting Information File 1). Therefore, we considered that all C60 molecules in the solution should be present as the 2:1 complex

Selective ring-opening metathesis polymerization (ROMP) of cyclobutenes. Unsymmetrical ladderphane containing polycyclobutene and polynorbornene strands

• Yuan-Zhen Ke,
• Shou-Ling Huang,
• Guoqiao Lai and
• Tien-Yau Luh

Beilstein J. Org. Chem. 2019, 15, 44–51, doi:10.3762/bjoc.15.4

• ]. Unsymmetrical polynorbornene-based ladderphane is obtained by a replication protocol from a single stranded polynorbornene [19][20]. Alternatively, sequential polymerization of a monomer containing a norbornene moiety and other polymerizable group furnishes an unsymmetrical ladderphane having two structurally

• norbornene under certain ROMP conditions. As such, when monomer 1 containing a cyclobutene moiety and a norbornene moiety connected by a bridge are subjected to ROMP, it would be feasible that the cyclobutene moiety would react preferentially giving the corresponding norbornene-appended polycyclobutene 2

• (Scheme 2). This promising observation prompted us to pursue the synthesis of unsymmetrical double-stranded ladderphane 8 by sequential ROMPs of 9 (Scheme 3). Synthesis of monomer 9 4-Aminobutanol (11) was used to link norbornene and cyclobutene moieties via amide and ester groups. The use of such a

Ruthenium-based olefin metathesis catalysts with monodentate unsymmetrical NHC ligands

• Veronica Paradiso,
• Chiara Costabile and
• Fabia Grisi

Beilstein J. Org. Chem. 2018, 14, 3122–3149, doi:10.3762/bjoc.14.292

• group resulted in a lower catalyst activity. Indeed, complex 24a bearing the small methyl moiety on the nitrogen, revealed as the best performing catalyst, even surpassing the parent complex GII-SIMes. In the ROMP reaction (Scheme 5), carried out in different solvents and monomer/catalyst ratios, the

• pentiptycenyl side of the NHC ligand compared to the other less hindered side determines two differently accessible active sites around the metal and different rates of monomer incorporation, thus dominating the selectivity in the formation of alternating copolymers. The nature of the alkyl group also plays a

• (101 and 102, Figure 19). The basic idea was that these catalysts might be able to regenerate themselves upon consumption of the monomer in the reaction media. Variants of these complexes with a silyl ether or a perfluoroalkyl chain on one of the nitrogens of the NHC were also presented (103 and 104

Degenerative xanthate transfer to olefins under visible-light photocatalysis

• Atsushi Kaga,
• Xiangyang Wu,
• Joel Yi Jie Lim,
• Hirohito Hayashi,
• Yunpeng Lu,
• Edwin K. L. Yeow and
• Shunsuke Chiba

Beilstein J. Org. Chem. 2018, 14, 3047–3058, doi:10.3762/bjoc.14.283

• absorption [28][29][30][31][32][33][34][35][36][37]. In the area of polymer synthesis, visible-light-induced RAFT polymerization of xanthates with vinyl monomers under blue LED (light-emitting diode) irradiation has been reported [38][39][40][41]. Visible-light-induced single unit monomer insertion of the