Shift of the reaction equilibrium at high pressure in the continuous synthesis of neuraminic acid

• Jannis A. Reich,
• Miriam Aßmann,
• Kristin Hölting,
• Paul Bubenheim,
• Jürgen Kuballa and
• Andreas Liese

Beilstein J. Org. Chem. 2022, 18, 567–579, doi:10.3762/bjoc.18.59

• to allow the bed to settle and refilled, if needed. Once the bed was packed, buffer solution was pumped through to compress the material. The reactor was then opened and new particles were added until the whole space was occupied. Residence time distribution In order to verify that this method yields

• similar packed beds, the residence time distribution (RTD) was measured and compared. The pump, autosampler, and refraction index (RI) detector were used to measure the RDT (HPLC 1100er Series by Agilent). Five µL of a 10 mM buffer were used as a tracer with an injection rate of 1 mL/min, resulting in a

• , a mean residence time of 1.5 ± 0.01 min was calculated. The mean residence time of the system itself needs to be considered and was determined to be 0.801 ± 0.003 min. The residence time distribution of the reactor was calculated assuming that the cumulative distributions are additive with respect

Synthesis of a new water-soluble hexacarboxylated tribenzotriquinacene derivative and its competitive host–guest interaction for drug delivery

• Man-Ping Li,
• Nan Yang and
• Wen-Rong Xu

Beilstein J. Org. Chem. 2022, 18, 539–548, doi:10.3762/bjoc.18.56

• TBTQ-CB6. Host−guest complexation of TBTQ-CB6 with spermine (SM). As a biomarker overexpressed in some tumor cells, SM was hypothesized to bind TBTQ-CB6 more strongly than MV and DOX because of its positive charge distribution. To verify this hypothesis, the host–guest complexation between TBTQ-CB6 and

Substituent effect on TADF properties of 2-modified 4,6-bis(3,6-di-tert-butyl-9-carbazolyl)-5-methylpyrimidines

• Irina Fiodorova,
• Tomas Serevičius,
• Rokas Skaisgiris,
• Saulius Juršėnas and
• Sigitas Tumkevicius

Beilstein J. Org. Chem. 2022, 18, 497–507, doi:10.3762/bjoc.18.52

• the similar molecular structures, the studied chromophores showed somewhat different electronic properties, mainly due to the variation of the acceptor structure. The DFT computed spatial distribution of frontier molecular orbitals (FMOs) of compounds tCbz-mPYR and 1–6 is presented in Figure 2. A

• comparison of the electronic structures revealed that the electron density distribution in the HOMO is rather similar for all molecules and tended to localize on the electron-donating carbazole moiety partially extending to the pyrimidine ring. The main differences in the electronic structure can be observed

• in the LUMO distribution. For the 2-methylthio- and 2-(tert-butylphenyl)thio-substituted compounds (tCbz-mPYR and 5) or the corresponding sulfonyl derivatives (3 and 6), the LUMO is localized over the electron-withdrawing pyrimidine unit with low extension to tCbz, being very similar to the LUMO

A resorcin[4]arene hexameric capsule as a supramolecular catalyst in elimination and isomerization reactions

• Tommaso Lorenzetto,
• Fabrizio Fabris and
• Alessandro Scarso

Beilstein J. Org. Chem. 2022, 18, 337–349, doi:10.3762/bjoc.18.38

• and 4). The reaction promoted by acetic acid (4) as purely Brønsted acid led to comparable conversion of the substrate with respect to the use of 16, albeit with much similar product distribution between isopulegol and neoisopulegol, even extending the reaction time up to 72 h at 60 °C (Table 1

• Brønsted acid and the presence of the accessible cavity of the capsule steers product distribution. It is worth to note that the preferred product isopulegol is an important intermediate product in the industrial production of menthol by the Takasago and BASF processes [46][47]. Many catalytic methods for

• tetrahedral polyanionic metal-ligand capsule as supramolecular catalyst, observing lower catalytic activity and product distribution favoring isopulegol but also with large amounts of neoisopulegol and neoisoisopulegol (52%, 32% and 11%, respectively) [51]. More favorable selectivity towards isopulegol was

Diametric calix[6]arene-based phosphine gold(I) cavitands

• Gabriele Giovanardi,
• Andrea Secchi,
• Arturo Arduini and
• Gianpiero Cera

Beilstein J. Org. Chem. 2022, 18, 190–196, doi:10.3762/bjoc.18.21

• , Table 1) [38][39]. This result was compared with the one obtained using the macrocyclic analogue A(AuCl)2 (1 mol %). Hence, we did not observe a significant variation in the product distribution (entry 2, Table 1). Analogously, the reactivity in the presence of meta-substituted catalysts B’(AuCl) and B

• (AuCl)2 was investigated. Also in this case, the reactivity and selectivity of the parental catalysts were comparable (entries 3 and 4, Table 1). Taken together, these outcomes suggest that the role of the macrocycle for catalysts A/B(AuCl)2 is not determining in changing the product distribution and

Multi-faceted reactivity of N-fluorobenzenesulfonimide (NFSI) under mechanochemical conditions: fluorination, fluorodemethylation, sulfonylation, and amidation reactions

• José G. Hernández,
• Karen J. Ardila-Fierro,
• Dajana Barišić and
• Hervé Geneste

Beilstein J. Org. Chem. 2022, 18, 182–189, doi:10.3762/bjoc.18.20

• -fluoroacetanilide as the internal standard. Similar product distribution was obtained when a mixture of 1c (0.59 mol) and NFSI (1.18 mmol) was milled in a stainless steel milling jar (15 mL of internal volume) using one milling ball (4.0 g) of the same material: 2c yield = 7%; 2c' yield = 16%; 2c'' yield = 79

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

• are acceptable although those with narrow molecular weight distribution are always desirable. These PEGs can be synthesized conveniently by polymerization of ethylene oxide under basic or acidic conditions [7]. The polymerization methods are inexpensive and PEGs with high molecular weight can be

Adjusting the length of supramolecular polymer bottlebrushes by top-down approaches

• Tobias Klein,
• Franka V. Gruschwitz,
• Maren T. Kuchenbrod,
• Ivo Nischang,
• Stephanie Hoeppener and
• Johannes C. Brendel

Beilstein J. Org. Chem. 2021, 17, 2621–2628, doi:10.3762/bjoc.17.175

• methods represent an easily implementable technique toward 1D polymer nanostructures with an adjustable length in the range of interest for perspective biomedical applications. Keywords: distribution; dual centrifugation; filomicelles; self-assembly; ultrasonication; Introduction Cylindrical polymer

• known size window for a potential enhanced permeability and retention effect (EPR) [22][23]. As an alternative for the assembly pathway control, we opted to apply easy-to-use top-down approaches to tune the length distribution in a straightforward fashion over the above-mentioned length range of

• coupled to a UV detector and a multiangle laser light scattering detector (AF4–MALLS technique) to estimate the apparent structure length and the length distribution of the SPBs. Results and Discussion The general structure of the tested BTP and BTU is depicted in Figure 1 [19][20]. While the hydrogen

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

• thickness, and incorporation of fillers or additives also affect the cryogel properties. Cryogel wall thickness and density, pore size and pore size distribution can be influenced by the method used for preparation, for example, by increasing the freezing rate smaller pores can be observed [13]. Final

• that during cryogelation a temperature gradient will be present. The exterior of the sample will be first exposed to the cold temperature, leading to enhanced freezing rates and smaller pore sizes compared to the inner cryogel material, resulting in a heterogeneous pore size distribution, see Figure 2

• [18]. This has led to concerns over producing cryogels with dimensions greater than 25 mm [19]. Although, a report by Macková et al. outlines the benefits of graduated pore size distribution in hydrogels used in tissue engineering, since many human body tissues also exhibit a heterogeneous morphology

In-depth characterization of self-healing polymers based on π–π interactions

• Josefine Meurer,
• Julian Hniopek,
• Johannes Ahner,
• Michael Schmitt,
• Jürgen Popp,
• Stefan Zechel,
• Kalina Peneva and
• Martin D. Hager

Beilstein J. Org. Chem. 2021, 17, 2496–2504, doi:10.3762/bjoc.17.166

• noticeable broadening during heating, which is most significant for the C=O vibration at 1656 cm−1. This indicates a broader distribution of species contributing to the IR spectrum, which is consistent with increased mobility of the perylene moieties which allows for more possible geometries. Furthermore, it

• polymer, indicating a reversible cause for the shifts. Additionally, all bands exhibit broadening during heating, especially noticeable at 150 °C, indicating a broader distribution of species contributing to the IR spectrum. Schematic representation of the first healing of P1 at 150 °C. Schematic

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

• adequately demonstrated the presence and the distribution of P atoms that are attributed to BPNs in the cross-linked polymer in addition to C and N atoms (Figure 7d). In contrast to the cross-linked polymer, the distribution of BPNs in the block copolymer structure could not be visualized by TEM, HAADF-STEM

Synthesis and investigation on optical and electrochemical properties of 2,4-diaryl-9-chloro-5,6,7,8-tetrahydroacridines

• Najeh Tka,
• Mohamed Adnene Hadj Ayed,
• Mourad Ben Braiek,
• Mahjoub Jabli and
• Peter Langer

Beilstein J. Org. Chem. 2021, 17, 2450–2461, doi:10.3762/bjoc.17.162

• product 4a. As well, the phenyl ortho-substituent in the aryl ring for 4f was twisted out of the plane and was not involved in the electronic orbital distribution (Figure 8). As shown in Figure 9, the HOMO and LUMO frontier orbitals of products 4a–d are extended over the π-conjugated part of the molecules

• outside the carbon cores. It was observed for compound 4c that the two trifluoromethoxy groups were twisted out of the plane and consequently did not participate in the orbital distribution. The HOMO electronic distributions of 4b and 4d were spread over the two non-twisted methoxy groups. The calculated

• adopted a distorted molecular geometry. In contrast to methoxy groups, the trifluoromethoxy groups are twisted out of plane and, therefore, are not involved in the electronic orbital distribution. Experimental energy band gaps of the prepared tetrahydroacridines were found to be an average of 3 eV which

Isolation and characterization of new phenolic siderophores with antimicrobial properties from Pseudomonas sp. UIAU-6B

• Emmanuel T. Oluwabusola,
• Olusoji O. Adebisi,
• Fernando Reyes,
• Kojo S. Acquah,
• Mercedes De La Cruz,
• Larry L. Mweetwa,
• Joy E. Rajakulendran,
• Digby F. Warner,
• Deng Hai,
• Rainer Ebel and
• Marcel Jaspars

Beilstein J. Org. Chem. 2021, 17, 2390–2398, doi:10.3762/bjoc.17.156

• ]. One way out of this is an extensive search for novel bioactive natural products from microbial sources [2][3]. There is focus on the genus Pseudomonas for scientific research due to its widespread distribution in water, soil, and extreme habitats, including the exceptional ability to colonize the

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

• subject to CC BY 4.0. Summary of the pPEGMA and pMPC block copolymers prepared by PISA at 70 °C including the hydrodynamic diameter Dh and particle size distribution PdI obtained by DLS and the drug loading content (DLC) calculated using DLC = m(PENAO)/[m(PENAO) + m(polymer)]. The table here contains the

Nomimicins B–D, new tetronate-class polyketides from a marine-derived actinomycete of the genus Actinomadura

• Zhiwei Zhang,
• Tao Zhou,
• Taehui Yang,
• Keisuke Fukaya,
• Enjuro Harunari,
• Shun Saito,
• Katsuhisa Yamada,
• Chiaki Imada,
• Daisuke Urabe and
• Yasuhiro Igarashi

Beilstein J. Org. Chem. 2021, 17, 2194–2202, doi:10.3762/bjoc.17.141

• canonical structures of 4 (4a–d in Figure 5). The calculated ECD spectra of 4a–d and the one of 4, which includes all contributions from each tautomer according to the energy distribution, are shown in Figure 5 and Figure 4, respectively. The experimental ECD spectrum of 4, with positive and negative Cotton

• the above-obtained spectra (half-width: 0.29 eV) according to the Boltzmann distribution, corrected by a red-shift of 15 nm, and scaled to adjust the strength of the vertical axis. The spectra of structures 4b, 4c, and 4d were similarly simulated using 122, 126, and 475 OPLS3e-minimized structures and

• 26, 22, and 31 DFT-optimized structures, respectively. The spectrum of 4 was created using the weighted average of the spectra of all low-lying conformers of 4a–d according to the respective Boltzmann distribution. The Cartesian coordinates and the energies of the most stable conformers for each

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

• ). The striking feature of azulene is its permanent dipole moment (1.08 D) and blue color unlike its colorless isomer naphthalene [4]. Azulene possesses an unequal distribution of electron density between its highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO

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

• for any real polymer solution. Every polymer always exhibits a molar mass distribution. Therefore, a quasi-binary mixture is usually considered. It is possible to measure the cloud-points, but the obtained cloud-point (Tcp) curve differs from a simple bimodal. Thus, the critical point (LCST or UCST

• state is characterized by the change of the segment distribution from a parabolic to a step profile and a rearrangement of the chain ends [126]. This collapse can be described by the classical Flory–Huggins model. It follows that this vertical collapse above the LCST or below the UCST is merely a

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

• coating and corroborates the inhomogeneous distribution of PHEMA inside the boxes (Figure 3). Compared to the pristine scaffold (Figure 3A and Figure 3B), the PHEMA coat can be clearly distinguished both as a thin coat on the fibers as well as in form of films between fibers and spanning boxes (Figure 3C

A study on selective transformation of norbornadiene into fluorinated cyclopentane-fused isoxazolines

• Zsanett Benke,
• Attila M. Remete and
• Loránd Kiss

Beilstein J. Org. Chem. 2021, 17, 2051–2066, doi:10.3762/bjoc.17.132

• enhance the pharmacokinetic properties of lead candidates in drug research through the improvement in lipophilicity, absorption, distribution, hydrophobicity and metabolism. Considering the high importance of organofluorine chemistry and that of fluoroalkyl groups in pharmaceutical chemistry, a wide range

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

• and enzymatic methods have been optimized to obtain samples with well-defined substitution patterns and narrow molecular weight distribution. Chemical synthesis has granted access to polysaccharides with full control over the length. Here, we review the progress towards the synthesis of well-defined

• amylose with narrow MW distribution, amylose hybrids, and amylose-functionalized materials [186]. Linear and branched oligosaccharides with mixed α(1–3) and α(1–4) linkages were synthesized using a glucansucrase from Lactobacillus reuteri [187][188]. Even though several chemical methods are available for

Regioselective N-alkylation of the 1H-indazole scaffold; ring substituent and N-alkylating reagent effects on regioisomeric distribution

• Ryan M. Alam and
• John J. Keating

Beilstein J. Org. Chem. 2021, 17, 1939–1951, doi:10.3762/bjoc.17.127

• distribution. For example, employing C-7 NO2 or CO2Me substituted indazoles conferred excellent N-2 regioselectivity (≥ 96%). Importantly, we show that this optimized N-alkylation procedure tolerates a wide structural variety of alkylating reagents, including primary alkyl halide and secondary alkyl tosylate

• , respectively). Substituting potassium carbonate (K2CO3) for Cs2CO3 did not show any improvement in the regioisomeric distribution of 10 and 11 (ratio N-1 (10)/N-2 (11) = 1.4:1) (Table 1, entry 4). Similarly, the use of sodium carbonate under identical conditions gave a notably lower combined yield of 10 and 11

• equivalents of 15-crown-5 from one to five equivalents (with respect to NaH) gave a similar regioisomeric distribution of N-substituted indazoles 10 and 11 (Table 5, entry 2). These control experiments show that 15-crown-5 disrupts tight ion pair formation, providing further support for our mechanistic

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

• endogenous nucleic acid targets, thereby inhibiting the gene expression. Although ASOs have great potential in the treatment of many diseases, the search for favorable toxicity profiles and distribution has been challenging and consequently impeded the widespread use of ASOs as conventional medicine. One

Sustainable manganese catalysis for late-stage C–H functionalization of bioactive structural motifs

• Jongwoo Son

Beilstein J. Org. Chem. 2021, 17, 1733–1751, doi:10.3762/bjoc.17.122

• electron-rich benzylic position, rationalizing the involvement of electrophilic metallonitrene intermediate 18A. Manganese-catalyzed late-stage C–H methylation The incorporation of methyl groups has the potential to manipulate absorption, distribution, metabolism, and excretion (ADME), solubility, and

A systems-based framework to computationally describe putative transcription factors and signaling pathways regulating glycan biosynthesis

• Theodore Groth,
• Rudiyanto Gunawan and
• Sriram Neelamegham

Beilstein J. Org. Chem. 2021, 17, 1712–1724, doi:10.3762/bjoc.17.119

• cancer type must be greater than the median RPKM expression of the TF across all 29 different cancer types; ii) the RNA expression of the TF and target gene should be correlated. To determine this, Cistrome first compares the selected TF–gene correlation with a null distribution computed by randomly

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