Synthesis, structure, and properties of switchable cross-conjugated 1,4-diaryl-1,3-butadiynes based on 1,8-bis(dimethylamino)naphthalene

• Semyon V. Tsybulin,
• Ekaterina A. Filatova,
• Alexander F. Pozharskii,
• Valery A. Ozeryanskii and
• Anna V. Gulevskaya

Beilstein J. Org. Chem. 2023, 19, 674–686, doi:10.3762/bjoc.19.49

• formally symmetrical structure of diynes 5, naphthalene rings A and B of molecules 5b and 5d differ in their structural parameters. At the same time, the monomer fragments of the nitro derivative 5e are identical. In the case of 5e, the naphthalene rings lie in parallel planes, while in crystals of 5b and

• DMAN fragments do not participate in nonvalent interactions and do not form short contacts. The recurring motif in the crystals is the coordination of the benzene meta proton by the nitrogen atom of the C≡N group. The structural parameters of both monomer fragments of nitro derivative 5e are identical

• nitro group. There are two types of independent non-equivalent dications, marked in blue and green, and two types of BF4− anions, marked in red and yellow, in the crystal structure of salt 11c (Figure S68 in Supporting Information File 1). Monomer fragments in both are identical (Table 2, Figure 5). The

Phenanthridine–pyrene conjugates as fluorescent probes for DNA/RNA and an inactive mutant of dipeptidyl peptidase enzyme

• Josipa Matić,
• Tana Tandarić,
• Marijana Radić Stojković,
• Filip Šupljika,
• Zrinka Karačić,
• Ana Tomašić Paić,
• Lucija Horvat,
• Robert Vianello and
• Lidija-Marija Tumir

Beilstein J. Org. Chem. 2023, 19, 550–565, doi:10.3762/bjoc.19.40

• basic and neutral conditions at which intramolecular stacking was less pronounced. At acidic conditions, the monomer signal (400 nm) was dominant (Figure 1). The emission of the excimer did not exclusively depend on the degree of overlapping of chromophores. Earlier theoretical examinations favored a

• DNA/RNA polynucleotides [37]. The monomer fluorescence emission at 400 nm was not changed except for titration with poly dGdC–poly dGdC where a small emission increase of emission at 400 nm was observed. At ratios of an excess of polynucleotide over compound (r[compound]/[polynucleotide] < 0.3

• polynucleotide secondary structure. Concurrently, no monomer fluorescence signal at 400 nm changed, except a small increase upon poly dGdC–poly dGdC addition. Negligible thermal stabilization (Table S1, Figures S6–S8, Supporting Information File 1) did not support the classical intercalation of phenanthridine

Investigation of cationic ring-opening polymerization of 2-oxazolines in the “green” solvent dihydrolevoglucosenone

• Solomiia Borova and
• Robert Luxenhofer

Beilstein J. Org. Chem. 2023, 19, 217–230, doi:10.3762/bjoc.19.21

• of view [28]. Accordingly, Hoogenboom et al. investigated the CROP of 2-alkyl-2-oxazoline in sulfolane and investigated its effect on monomer distribution and self-assembly of the performed copolymer [30][31][32]. However, the degradability of sulfolane into acidic components, its relatively high

• further optimizations can overcome these limitations remains to be seen. Experimental Materials and methods All substances were purchased from Sigma-Aldrich (Steinheim, Germany) and were used as received unless otherwise stated. The monomer 2-n-butyl-2-oxazoline (BuOx) was prepared following the procedure

• -oxazolines was performed as follows: 1.0 equiv of the initiator was placed into a dried and argon-flushed flask and dissolved in a respective amount of solvent. Once the monomer was added, the reaction mixture was placed into a preheated (up to the investigated temperature) oil bath and incubated till the

B–N/B–H Transborylation: borane-catalysed nitrile hydroboration

• Filip Meger,
• Alexander C. W. Kwok,
• Franziska Gilch,
• Dominic R. Willcox,
• Alex J. Hendy,
• Kieran Nicholson,
• Andrew D. Bage,
• Thomas Langer,
• Thomas A. Hunt and
• Stephen P. Thomas

Beilstein J. Org. Chem. 2022, 18, 1332–1337, doi:10.3762/bjoc.18.138

• (83%). This catalytic protocol was applied to the reduction of other aliphatic nitriles to their corresponding amine hydrochloride salts, such as cyclopropyl-bearing (1b, 72%) and branched aliphatic nitriles (1c, 91%). Hexane-1,6-diamine dihydrochloride (1d), a monomer of nylon 6,6 [1], was generated

Make or break: the thermodynamic equilibrium of polyphosphate kinase-catalysed reactions

• Michael Keppler,
• Sandra Moser,
• Henning J. Jessen,
• Christoph Held and
• Jennifer N. Andexer

Beilstein J. Org. Chem. 2022, 18, 1278–1288, doi:10.3762/bjoc.18.134

• model enzymes for PPK1 and PPK2 [9][10]. From a structure perspective, PPK1 enzymes form tetramers in solution with a mass of approximately 80 kDa for the monomer (Figure 2b). Although not being an integral membrane protein, the enzyme is described to be membrane-associated [11][12][13]. The phosphate

• , clearly demonstrating the necessity of the residues for catalysis [14]. PPK2-I enzymes are of lower molecular weight than their PPK1 counterparts, with an approximate molecular mass of 40 kDa for a monomer (Figure 2c) [5]. They form dimers or tetramers in solution and are not purified from membrane

• range from three to several thousands. Comparison of PPK1 and PPK2 enzymes. a) Reaction scheme; b) structure of the EcPPK1 monomer (PDB 1XDO) [13]; c) structure of the SmPPK2 monomer (PDB 3CZQ) [10]; d) proposed mechanism of PPK1 with phosphate transfer via a phosphor enzyme intermediate; e) PPK2

Mechanochemical bottom-up synthesis of phosphorus-linked, heptazine-based carbon nitrides using sodium phosphide

• Blaine G. Fiss,
• Georgia Douglas,
• Michael Ferguson,
• Jorge Becerra,
• Jesus Valdez,
• Trong-On Do,
• Tomislav Friščić and
• Audrey Moores

Beilstein J. Org. Chem. 2022, 18, 1203–1209, doi:10.3762/bjoc.18.125

• calculated 31P chemical shifts at 37.7 ppm (P1) and 23.3 ppm (P2), respectively, while that of the paddlewheel monomer is at 11.2 ppm (P3). The calculated shifts demonstrate phosphorus environments in the mechanochemically synthesized material are distinct to those calculated in ab initio predicted models of

Synthesis of protected precursors of chitin oligosaccharides by electrochemical polyglycosylation of thioglycosides

• Md Azadur Rahman,
• Kana Kuroda,
• Hirofumi Endo,
• Norihiko Sasaki,
• Tomoaki Hamada,
• Hiraku Sakai and
• Toshiki Nokami

Beilstein J. Org. Chem. 2022, 18, 1133–1139, doi:10.3762/bjoc.18.117

• thioglycosides as monomer is described. Oligosaccharides up to the hexasaccharide were synthesized under optimized reaction conditions. Further, a modified method enabled the synthesis of oligosaccharides up to the octasaccharide by repeating electrolysis with additional monomers. The mechanism of the

• electrochemical polyglycosylation is also discussed, based on the oxidation potential of the monomer and oligosaccharides. Keywords: electrochemical glycosylation; glucosamine; oligosaccharide; oxidation potential; polyglycosylation; Introduction Chitin oligosaccharides are partial structures of chitin, which

• one of a few examples of chemical synthesis of chitin oligosaccharides through polyglycosylation of a glucosamine monosaccharide [6]. Recently, we have reported electrochemical polyglycosylation using a glucosamine derivative as a monomer [7]. This is another example of polyglycosylation of a

First series of N-alkylamino peptoid homooligomers: solution phase synthesis and conformational investigation

• Maxime Pypec,
• Laurent Jouffret,
• Claude Taillefumier and
• Olivier Roy

Beilstein J. Org. Chem. 2022, 18, 845–854, doi:10.3762/bjoc.18.85

• to the Boc side chain protections. For the submonomer solution-phase synthesis of monomer 1 and oligomers 2–5, modifications from the standard synthesis conditions were required, notably for the substitution reaction. Thus, the first substitution reaction between benzyl bromoacetate and N-Boc-N

• -methylhydrazine (3.0 equiv) was conducted in water at a concentration of 2.5 M at room temperature (rt) for overnight to afford monomer 1a in 88% yield after SiO2 chromatography [41]. Standard substitution conditions in EtOAc or THF as solvent in the presence of triethylamine did not allow full conversion of the

• ]. Conformational analysis and self-assembling properties The 1H NMR analysis of monomer 1 in various solvents including CDCl3, CD3CN, C6D6, CD3OD, D2O, and DMSO-d6 showed two sets of resonances in proportions varying from 75:25 to 90:10 (Table 3). These two sets of signals were characterized as the backbone cis

Post-synthesis from Lewis acid–base interaction: an alternative way to generate light and harvest triplet excitons

• Hengjia Liu and
• Guohua Xie

Beilstein J. Org. Chem. 2022, 18, 825–836, doi:10.3762/bjoc.18.83

• . synthesized the conjugated polymer F8Py (compound 6 in Figure 5), in which the incorporation of the pyridine co-monomer provides a lone pair of electrons for binding Lewis acids [37]. The formation of acid–base adducts accurately regulated the band gap of the luminescent polymer. The PL spectra in solution

Structural basis for endoperoxide-forming oxygenases

• Takahiro Mori and
• Ikuro Abe

Beilstein J. Org. Chem. 2022, 18, 707–721, doi:10.3762/bjoc.18.71

• mammalian COXs revealed that COX-1 and COX-2 are both glycosylated by post-translational modifications [46][47][48][49][50][51]. These enzymes form homodimers, and the overall structures of COX-1 and COX-2 superimpose well, with root mean square values of ≈0.9 Å. Each COX monomer contains three domains

Syntheses of novel pyridine-based low-molecular-weight luminogens possessing aggregation-induced emission enhancement (AIEE) properties

• Masayori Hagimori,
• Tatsusada Yoshida,
• Yasuhisa Nishimura,
• Yukiko Ogawa and
• Keitaro Tanaka

Beilstein J. Org. Chem. 2022, 18, 580–587, doi:10.3762/bjoc.18.60

• in AIEE. To compare the electronic natures of the compounds with and without AIEE, we performed TD-DFT calculations on each monomer of 3a, 4a, and 4e. The graphical representations of the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) for the ground-state

• geometries of each monomer are shown in Figure 5. The dihedral angles between the pyrimidine and maleimide rings, the amine linkage, were nearly zero degrees for 4a and 4e in all three solvents, adopting a highly planar structure as well as compound 3a. The HOMO and LUMO were distributed on the entire

• discrepancy between the calculated and observed Exmax values for compounds 4a and 4e suggests that aggregation occurs in water, and such behavior cannot be reproduced using the monomer model (non-aggregated form). Conclusion To discover low-molecular-weight AIEE-based luminogens, we synthesized pyrido[1,2-a

Chemical and chemoenzymatic routes to bridged homoarabinofuranosylpyrimidines: Bicyclic AZT analogues

• Sandeep Kumar,
• Jyotirmoy Maity,
• Banty Kumar,
• Sumit Kumar and
• Ashok K. Prasad

Beilstein J. Org. Chem. 2022, 18, 95–101, doi:10.3762/bjoc.18.10

• , trihydroxy nucleoside 14b was protected with TBDPS to carry out the synthesis of the target nucleoside monomer 9b through a chemical pathway. However, the poor yield of this reaction compelled us to abandon the route as high solubility of the TBDPS-protected dihydroxy nucleoside in aqueous phase withstood

Stepwise PEG synthesis featuring deprotection and coupling in one pot

• Logan Mikesell,
• Dhananjani N. A. M. Eriyagama,
• Yipeng Yin,
• Bao-Yuan Lu and
• Shiyue Fang

Beilstein J. Org. Chem. 2021, 17, 2976–2982, doi:10.3762/bjoc.17.207

• phenethyl group was chosen for the development of the one-pot PEG elongation approach for PEG synthesis although other groups that meet the two criteria can be used as well. Using the phenethyl group for protection, the monomer 2 was chosen for the stepwise PEG synthesis. The simplest method for its

• synthesis would be to react (PEG)4, which is commercially available and inexpensive, with styrene to give 6 [32], and tosylation of 6 to give the monomer (Scheme 3). However, the reported conditions for the synthesis of 6 without using an expensive catalyst gave low yields. We did not test the conditions

• under basic conditions to give 7. Removal of the DMTr group of 7 under acidic conditions gave 6, which was tosylated to give 2. This route is longer than the other two, but the products of all the steps are easy to purify, and it is our preferred route. With the monomer 2 in hand, the stepwise synthesis

Cryogels: recent applications in 3D-bioprinting, injectable cryogels, drug delivery, and wound healing

• Luke O. Jones,
• Leah Williams,
• Tasmin Boam,
• Martin Kalmet,
• Chidubem Oguike and
• Fiona L. Hatton

Beilstein J. Org. Chem. 2021, 17, 2553–2569, doi:10.3762/bjoc.17.171

• properties Cryogels are macroporous hydrogels with interconnected porosity, with high swelling capacities and large surface areas. Ultimately, many of the final cryogel properties are dependent on the choice of polymer/monomer composition used. However, other factors such as crosslinking, pore size, wall

• crosslinking (ratio of monomer to crosslinking agent), while the degree of crosslinking is tuned in physically crosslinked cryogels by varying the number of freeze–thaw cycles. Pore size, wall thickness, and wall density are of significant importance for cryogels properties [16]. Thicker walls and higher wall

• densities typically result in improved mechanical properties and are influenced by the concentration of monomer or precursors used as well as the type of crosslinking in the cryogel. Moreover, the processing conditions used when synthesising cryogels have a vast effect on the internal structure. An

Exfoliated black phosphorous-mediated CuAAC chemistry for organic and macromolecular synthesis under white LED and near-IR irradiation

• Azra Kocaarslan,
• Zafer Eroglu,
• Önder Metin and
• Yusuf Yagci

Beilstein J. Org. Chem. 2021, 17, 2477–2487, doi:10.3762/bjoc.17.164

• ) Diazido monomer, bisphenol A di(3-azido-2-hydroxypropan-1-ol) (Az-3) was synthesized according to a described method [46]. Az-3 was obtained as light yellowish viscous oil and was directly used without further purification, yield 98%. 1H NMR (500 MHz, CDCl3) δ 7.15 (m, 4H), 6.82 (m, 4H), 4.16 (m, 2H), 4.0

Post-functionalization of drug-loaded nanoparticles prepared by polymerization-induced self-assembly (PISA) with mitochondria targeting ligands

• Janina-Miriam Noy,
• Fan Chen and
• Martina Stenzel

Beilstein J. Org. Chem. 2021, 17, 2302–2314, doi:10.3762/bjoc.17.148

• enabled not only comparison of nanoparticles with and without TPP, but also the effect of the shell material, pPEGMA and pMPC. The synthesis of p(MPC-co-PENAO)-b-p(MMA) and p(PEGMA-co-PENAO)-b-p(MMA) nanoparticles has been described in our earlier publication [28]. Initially, the monomer 4-(N-(S

• -((phenylcarbonothioyl)thio)pentanoic acid, but it was modified with ethylene glycol. During the polymerization of the water-soluble polymers, fluorescein O-methacrylate was added at a ratio of CTA to fluorescent monomer of 1:0.3. This means more that three out of ten polymer chains will be labelled, which is sufficient

Chemical syntheses and salient features of azulene-containing homo- and copolymers

• Vijayendra S. Shetti

Beilstein J. Org. Chem. 2021, 17, 2164–2185, doi:10.3762/bjoc.17.139

• of polymerization of ≈7) leaving speculation about a higher degree of polymerization for the THF-insoluble component of PAZ-Br2. The UV–vis spectrum of the chloroform-soluble fraction of PAZ-Br2 displayed absorption bands in the 190–330 nm region like the azulene monomer, and a long tail with a broad

• band spanning 400–800 nm in NMP solution with a maximum at 591 nm. Accordingly, the optical energy gap for the polymer 31 was the lowest (1.65 eV) in comparison to dimer 29 (2.15 eV) and monomer, 2-aminoazulene (24, 3.15 eV) emphasizing the advantage associated with inducing a 2,6-connectivity along

• forms of monomer 24, dimer 29, and polyazulene 31 were further red-shifted and their respective energy gaps were also reduced compared to their neutral forms. The oxidation potential for the neutral (−0.23 V) and protonated forms of polyaminoazulene 31 (0.70 V) was significantly different unlike the

Constrained thermoresponsive polymers – new insights into fundamentals and applications

• Patricia Flemming,
• Alexander S. Münch,
• Andreas Fery and
• Petra Uhlmann

Beilstein J. Org. Chem. 2021, 17, 2123–2163, doi:10.3762/bjoc.17.138

• . Interestingly, the individual monomers usually do not exhibit responsive properties. However, the combination within a copolymer leads to a pronounced thermoresponse. A prominent representative of such behavior is poly(acrylamide-co-acrylonitrile), which is assembled from a fully soluble, hydrophilic monomer

• continuous development and improvement of polymerization techniques, more and more diverse copolymers can be synthesized. Very recently, Kertsomboon et al. succeeded in preparing a copolymer (poly(AAm-co-MDO)) of acrylamide and a degradable, hydrophobic monomer based on a ring opening polymerisation of

An initiator- and catalyst-free hydrogel coating process for 3D printed medical-grade poly(ε-caprolactone)

• Jochen Löblein,
• Thomas Lorson,
• Miriam Komma,
• Tobias Kielholz,
• Maike Windbergs,
• Paul D. Dalton and
• Robert Luxenhofer

Beilstein J. Org. Chem. 2021, 17, 2095–2101, doi:10.3762/bjoc.17.136

• improved by a variety of methods like plasma treatment, NaOH hydrolysis treatment or a micro deposition system. This study outlines a potential approach to coat medical-grade PCL with a thin hydrogel that requires no initiator or catalyst – just a deoxygenated aqueous monomer solution and UV light. We

• coating and monomer concentration (Supporting Information File 1, Figure S2). As the next step, scaffolds were investigated with respect to their wettability. In order to simulate aqueous conditions in cell culture medium or after implantation, samples were immersed in water for 0, 10, 20 and 30 min

• . Results for three negative controls (cleaned scaffold, scaffold irradiated without monomer solution, and scaffold immersed in monomer solution without irradiation) can be found in Supporting Information File 1, Figure S3, and have no staining. The irradiation time was varied between 10 min, 20 min, and 30

Towards new NIR dyes for free radical photopolymerization processes

• Haifaa Mokbel,
• Guillaume Noirbent,
• Didier Gigmes,
• Frédéric Dumur and
• Jacques Lalevée

Beilstein J. Org. Chem. 2021, 17, 2067–2076, doi:10.3762/bjoc.17.133

• polymerization of acrylate/epoxy monomer blends) can also be carried out upon NIR light with the proposed systems. Keywords: cyanine; NIR light; photochemistry; Introduction Photopolymerization processes are well established due to the specific features and advantages. Indeed, the reaction is carried out at

• and the tertiary aromatic amines 3-(dimethylamino)benzyl alcohol (DABA) and N-phenylglycine (NPG), respectively, for the polymerization of a benchmark monomer (PETIA, Scheme 2). The polymerization profiles were recorded by real-time Fourier transform infrared spectroscopy (FTIR, the procedure is

• combination with an amine and an iodonium salt, iod, for the free radical polymerization of a benchmark acrylate monomer and compared to a reference initiating system based on IR 813 (Scheme 2) [7]. As the different dyes presented above exhibit good absorption properties at 785 nm, the photoinitiating

Progress and challenges in the synthesis of sequence controlled polysaccharides

• Giulio Fittolani,
• Theodore Tyrikos-Ergas,
• Denisa Vargová,
• Manishkumar A. Chaube and
• Martina Delbianco

Beilstein J. Org. Chem. 2021, 17, 1981–2025, doi:10.3762/bjoc.17.129

•  6C) [182]. To avoid the chemical formation of this challenging bond, natural compounds containing 1,2-cis linkages could be exploited. α-, β- and γ-cyclodextrins offered a good starting material to prepare stereoselectively a 6-O-methylated α(1–4)-glucopolysaccharides consisting of 6–20 monomer units

Cationic oligonucleotide derivatives and conjugates: A favorable approach for enhanced DNA and RNA targeting oligonucleotides

• Mathias B. Danielsen and
• Jesper Wengel

Beilstein J. Org. Chem. 2021, 17, 1828–1848, doi:10.3762/bjoc.17.125

• monomer has been used [27]. The reactivity of the above-mentioned chemical groups has enabled the attachment of various amine-functionalized groups onto the 5-position of pyrimidines via both the modified monomeric building blocks and post-synthetic ON chemistry [27][28][31][32][33][34][35][36][37][38][39

• as building blocks for incorporation into PS-ONs (Table 3B, 26, 27). In this study, two modifications of the N4-spermine-modified 2’-O-MOE-cytidine monomer 26 was incorporated into a 12-mer PS-ON centrally and at the 5’-end, resulting in significant increases in Tm (by more than 16 °C) towards

• at the C-5 position of a 2’-OMe-uridine monomer, positioning the group in the major groove of the formed duplex, had a significant stabilizing effect on RNA binding (Table 2A, 18) [62]. Another method for introducing spermine at the N4 position involved the reaction of spermine and 4-N-p

Chemical approaches to discover the full potential of peptide nucleic acids in biomedical applications

• Nikita Brodyagin,
• Martins Katkevics,
• Venubabu Kotikam,
• Christopher A. Ryan and
• Eriks Rozners

Beilstein J. Org. Chem. 2021, 17, 1641–1688, doi:10.3762/bjoc.17.116

• , appears to be the most promising conformationally constrained PNA analogue. Vilaivan and co-workers developed pyrrolidinyl PNA based on an α/β-dipeptide backbone that is one atom longer than the canonical PNA and contains two amide bonds and two cyclic moieties in one monomer (Figure 4) [61]. Cyclobutane

Recent advances in the application of isoindigo derivatives in materials chemistry

• Andrei V. Bogdanov and
• Vladimir F. Mironov

Beilstein J. Org. Chem. 2021, 17, 1533–1564, doi:10.3762/bjoc.17.111

• popular and most studied direction in the creation of OSCs is the use of polymer structures containing an isoindigo fragment in a monomer unit associated with a different number of thiophene substituents (Scheme 12). By the example of one of the simplest representatives of this type of polymers, a

• was only 0.99%, while the Stille method gave a polymer 24a characterized by an efficiency of 1.66% (Scheme 14). Strengthening the donor effect of the monomer unit can be achieved by lengthening the thiophene chain up to three fragments [37][38][39][40][41]. In this case, additional possibilities arise

• the above described study, Liu et al. demonstrated that this type of compounds is promising by means of introducing fluorine atoms into the thiophene ring [43]. The use of compound 29c (ratio of monomer units n/m = 2:1) as an acceptor component of the OSC made it possible to achieve one of the highest

Double-headed nucleosides: Synthesis and applications

• Vineet Verma,
• Jyotirmoy Maity,
• Vipin K. Maikhuri,
• Ritika Sharma,
• Himal K. Ganguly and
• Ashok K. Prasad

Beilstein J. Org. Chem. 2021, 17, 1392–1439, doi:10.3762/bjoc.17.98

• terminal carbons only. Double-headed nucleosides are synthetically derived nucleoside scaffolds that are known to impact significantly secondary structures in nucleic acids [29]. Some oligonucleotides containing a particular double-headed nucleotide monomer have been found to form a three-way junction

• phosphitylation at the secondary hydroxy group afforded the double-headed nucleoside monomer 19 (Scheme 5) [45]. The synthesized double-headed nucleoside 19 was introduced in oligonucleotides and its impact on the secondary nucleic acid structure was studied. It was revealed that the double-headed nucleoside 19

• was well accommodated in a hybrid DNA:RNA duplex and stabilized bulged duplex and three way junctions [45]. The potential of the double-headed nucleoside 19 in secondary nucleic acid structures was compared with the earlier reported monomer 11 and found to be inferior to double-headed nucleoside 11