Site-specific labelling of native peptides and proteins: chemical and enzymatic strategies

• Antonio Angelastro,
• Jonathan Bargh,
• Subhajit Guria,
• Victor Laserna and
• Louis Luk

Beilstein J. Org. Chem. 2026, 22, 857–881, doi:10.3762/bjoc.22.67

• modification. The chemical or enzymatic steps are generally mild (room temperature, aqueous buffer) yet highly specific. However, the main limitation is that only glycosylated proteins (especially IgGs) can be targeted. Intrinsic glycan heterogeneity can also lead to incomplete functionalisation. Biological

The trans-influence in gold chemistry from a catalytic perspective

• Manfred Bochmann

Beilstein J. Org. Chem. 2026, 22, 838–856, doi:10.3762/bjoc.22.66

• (II) congener, K[PtCl3(ethylene)] [28], as well as the first examples of gold(III) alkyne [29], CO [30], hydride [31] and σ-complexes [32] (Scheme 3). The olefin complexes were isolated as microcrystalline powders which as dry solids are fairly stable in air at room temperature. The olefin bonding is

• ^C^N complex 12 (H trans to C) is stable in THF solution at −20 °C but decomposes at room temperature. This instability of 12 may in part also be due to the tendency of the pyridine arm to dissociate; for example, on addition of LiHBEt3 the pyridine is displaced to give the dihydrido complex Li[(N–C

• ^C)AuH2] [50]. Goldberg’s complex 13, on the other hand, which is stabilised by two strongly donating P(t-Bu)2 moieties, is stable at room temperature and could be crystallographically characterised [53]. A gold hydride of type 12 has been postulated as an intermediate in the thermal decomposition of

Unsymmetrical sulfoxides with sterically hindered catechol fragment: synthesis, structure, electrochemical properties, and antiradical activity

• Daria A. Burmistrova,
• Vasiliy A. Fokin,
• Oleg P. Demidov,
• Mikhail A. Kiskin,
• Maxim V. Arsenyev,
• Andrey I. Poddel’sky,
• Nadezhda T. Berberova and
• Ivan V. Smolyaninov

Beilstein J. Org. Chem. 2026, 22, 828–837, doi:10.3762/bjoc.22.65

• , frequently employed as a model system to study the activity of catechol oxidase and tyrosinase. Although hydrogen peroxide is a strong oxidant, its reaction with 3,5-DTBC is often slow at room temperature in the absence of a catalyst, typically requiring metal ions such as Cu2+, Fe3+, or Co2+ [43]. Moreover

• {1H} NMR spectroscopy (Figures S1–S20), HRMS (Figures S21–S26) in Supporting Information File 1, and elemental analysis. X-ray data The X-ray suitable crystals of 1a, 4a–7a were grown by slow recrystallization of the compounds from acetonitrile or chloroform (for 7a) solutions at room temperature. The

Synthesis and structural elucidation of a novel bis-spirooxindole from isatin and ethylenediamine

• Irene Moreno-Gutiérrez,
• Josefa L. López-Martínez,
• Sonia Berenguel-Gómez,
• Irene Torres-García,
• Duane Choquesillo-Lazarte,
• Manuel Muñoz-Dorado,
• Miriam Álvarez-Corral and
• Ignacio Rodríguez-García

Beilstein J. Org. Chem. 2026, 22, 813–820, doi:10.3762/bjoc.22.63

• ). Reduction of 24 with NaBH4. NaBH₄ (95 mg, 2.52 mmol, 2 equiv) was added in portions to a stirred solution of 24 (0.40 g, 1.26 mmol, 1 equiv) in MeOH (15 mL) at room temperature. The mixture was stirred for 2 h, poured onto ice, and the resulting yellow precipitate of 25 was collected by filtration (295 mg

Knoevenagel condensation of 4,5- and 1,8-diazafluorenes

• Darya S. Cheshkina,
• Christina S. Becker,
• Alina A. Sonina and
• Maxim S. Kazantsev

Beilstein J. Org. Chem. 2026, 22, 803–812, doi:10.3762/bjoc.22.62

• ), ammonium acetate (60.5 mg, 0.79 mmol), and aldehyde (0.20 mmol) in glacial acetic acid (5 mL) was heated to 110 °C with stirring for 12 h. The resultant solution was cooled to room temperature and neutralized with aqueous ammonia solution (25%) to pH 6. The precipitate of a product was filtered off and

• toluene (5 mL) was heated to 110 °C with stirring for 12 h. The resultant solution was cooled to room temperature and neutralized with aqueous ammonia solution (25%) to pH 6. The precipitated compounds (see Table 1) were isolated by filtration followed by washing sequentially with portions of water

• stirred at room temperature for 2 h and then poured into water and extracted with chloroform. The extract was dried over MgSO4 and concentrated under reduced pressure. The products were purified by column chromatography on silica gel using ethyl acetate as eluent. General method (B2) for the condensation

Synthetic study of vic-bromination of diarylacetylenes, easy purification and separation

• Akane Togo,
• Hiyono Suzuki,
• Yuto Akai,
• Makoto Matsumoto,
• Yoshinori Suzuma,
• Hidehiko Kodama and
• Kouichi Matsumoto

Beilstein J. Org. Chem. 2026, 22, 795–802, doi:10.3762/bjoc.22.61

• ) with NBS (N-bromosuccinimide, X equiv), FeBr3 (1.0 equiv), n-Bu4NBr (Y equiv), and TEMPO (2,2,6,6-tetramethylpiperidine 1-oxyl free radical, Z equiv) in solvent (2 mL) at the desired temperature was conducted for 23 h or 2 h. After the reaction, the typical work-up procedure was carried out and the

• 2). The use of a smaller amount of NBS (1.2 equiv) did not result in a decrease of yield, indicating that FeBr3 is thought to be one of the sources of bromine (Table 1, entry 3). To increase the chemical yield and ratio of E-2a/Z-2a/1a, various parameters such as NBS, n-Bu4NBr, TEMPO, temperature

• heated by a heating gun. After cooled to room temperature, the flask was filled with N2. FeBr3 (154.2 mg, 0.52 mmol) and NBS (N-bromosuccinimide, 196.0 mg, 1.10 mmol) were added to the glass flask. Then, CH2Cl2 (dry, 2.0 mL) and 1,2-diphenylacetylene (1a, 89.4 mg, 0.502 mmol) were added and the mixture

Halogenated azobenzene acrylates: from efficient solution photoswitching to stable solid-state photochromic materials

• Martina Vachtlová,
• Michaela Fecková,
• Vítězslav Zima,
• Jan Podlesný,
• Milan Klikar,
• Oldřich Pytela,
• Patrik Pařík,
• Jakub Opršal,
• Eliška Juhaňáková,
• Veronika Chrtová and
• Filip Bureš

Beilstein J. Org. Chem. 2026, 22, 782–794, doi:10.3762/bjoc.22.60

• to a photoresponsive polymeric material imparting unique properties. A switchable glass-transition temperature (Tg) and thus resulting self-healing ability is a typical example [6]. As reported by Yu et al. [7], the different Tg of E and Z-isomers can lead to so called surface photofluidization due

• fluorescence intensity linearly dependent on the temperature [19][20]. Priimagi et al. reported thermal sensors based on the simple azobenzenes B1–3 by exploiting the dependence of the protonation rate on the temperature, which is accompanied by a color change [21]. Four different azobenzenes C1–4 were used as

• liquid crystalline copolymeric pendants in macromolecules capable to change their reflectance with the temperature. This feature potentially enables their usage in temperature sensing labels [22]. These representative applications clearly demonstrate a wide interest in a light-driven control over the

Rongalite addition to dienones: diastereoselectivity in cyclic sulfone synthesis; stereochemical rationalization and prospects as a general conjugate nucleophile

• Melina Goga,
• Hao Zong,
• James Franco,
• Jazmine Prana,
• Rudolph Michel,
• Antonia Muro,
• Elana Rubin,
• Janet Brenya,
• Henk Eshuis and
• Magnus W. P. Bebbington

Beilstein J. Org. Chem. 2026, 22, 742–752, doi:10.3762/bjoc.22.56

• -methyl groups cannot freely rotate past the nearby sulfone oxygen atoms. Calculations suggested a rotation barrier of 18 kcal/mol, consistent with it being insurmountable at room temperature, vs only 4 kcal/mol for the unsubstituted phenyl ring (see Supporting Information File 1). The combined results of

• sulfinates. In contrast, performing the competition experiment at room temperature gave a different product profile in which a good yield of 26 (62%) precipitated from the reaction mixture. No other products were observed in either the precipitate or the extracted filtrate from that reaction. The high

• selectivity for formation of 26 at room temperature suggests a profile that is more reflective of kinetic control, such that we can argue that 26 forms between 1 and 2 orders of magnitude more rapidly than cyclic products 1a and 1b, such that they are not detectable in the 1H NMR spectra. Further anecdotal

Synthesis of heterocycles based on azomethine ylides from α-amino acids (or amines) and carbonyl compounds

• Ekaterina V. Berezhnaya,
• Alexander I. Ponyaev,
• Vitali M. Boitsov and
• Alexander V. Stepakov

Beilstein J. Org. Chem. 2026, 22, 705–741, doi:10.3762/bjoc.22.55

• )benzylamine (92) as an azomethine ylide precursor in (3 + 2)-dipolar cycloaddition reactions with electron-deficient exo-cyclic 93 and endo-cyclic alkenes 94 (Scheme 36) [77][78][79]. To generate the azomethine ylide from reagent 92, TFA in methylene chloride at room temperature or LiF in acetonitrile with

Anti-invasive and cytotoxic evaluation of a (+)-pinoresinol-based semisynthetic library against glioblastoma

• Chen Zhang,
• Kah Yean Lum,
• Jonathan M. White,
• Paul I. Forster,
• Nicholas Booth,
• Sunita A. Ramesh and
• Rohan A. Davis

Beilstein J. Org. Chem. 2026, 22, 691–704, doi:10.3762/bjoc.22.54

• reaction using N-bromosuccinimide (NBS) in CH2Cl2 at room temperature (1 h), we produced 5 as a single enantiomer (i.e., (+)-5,5'-dibromopinoresinol). Herein, we report the full spectroscopic and spectrometric characterization of this molecule. Furthermore, analogues 6 and 7 are new semisynthetic molecules

• plates were used for TLC and analyzed under UV light at 254 and 365 nm. For large-scale studies, the plant material was extracted at room temperature using an Edwards Instrument Company Bio-line orbital shaker set to 200 rpm. All chemical reagents used throughout the experiments were purchased from Sigma

• (+)-pinoresinol derivatives 3–7 Methylation of (+)-pinoresinol (2) (+)-Pinoresinol (2, 15.8 mg, 0.044 mmol) was dissolved in MeOH/CH2Cl2 1:1 (250 μL) before (trimethylsilyl)diazomethane (2.0 M in diethyl ether, 150 μL) was added dropwise. The reaction mixture was stirred for 20 min at room temperature and then

Harnessing light energy with molecules

• Grace G. D. Han,
• Mogens Brøndsted Nielsen and
• Hermann A. Wegner

Beilstein J. Org. Chem. 2026, 22, 680–682, doi:10.3762/bjoc.22.52

• junction at ambient conditions and hence be used as an 8-bit operation unit. Molecular photoswitches are also interesting for temperature sensing applications. Thus, in their publication, Priimagi and co-workers [14] show a strong temperature-dependence of azobenzene protonation in 1,2-dichloroethane

Photoorganocatalytic trifluoromethylation of (het)arenes in green conditions

• Egor N. Boronin,
• Svetlana E. Kaurkina,
• Milena M. Svetlakova,
• Anton S. Bolshakov,
• Maxim V. Arsenyev,
• Vasilii F. Otvagin,
• Alexey Yu. Fedorov,
• Timothy Noël and
• Alexander V. Nyuchev

Beilstein J. Org. Chem. 2026, 22, 662–671, doi:10.3762/bjoc.22.50

• -trimethoxybenzene (TMB) as the substrate and 3 equivalents of TFAA as the CF3 source, over 6 hours at room temperature (25 °C). Initially, white light irradiation was selected owing to its broad coverage of the visible spectrum (Supporting Information File 1, Figure S6). Screening of various organic photocatalysts

• CF3 source loading showed that 3 equivalents of TFAA (Table 1, entry 5) afforded superior results compared to 1, 2, 5, or 10 equivalents (Table 1, entry 9). Finally, varying the temperature did not lead to further improvements in yield (Table 1, entry 10), in line with observations reported in Pan’s

• reaction conditions were established as follows: 2 mol % 3DPAFIPN in EtOAc under blue-light irradiation (450 nm) at room temperature (23 °C) for 6 h under an argon atmosphere. Using the optimized conditions, the scope of the developed protocol was evaluated with a range of arenes and heteroarenes (Scheme 2

Hydrogen production from formic acid catalyzed by NHC–Cu complexes

• Orlando Santoro and
• Catherine S. J. Cazin

Beilstein J. Org. Chem. 2026, 22, 620–627, doi:10.3762/bjoc.22.48

• ); conversely, by increasing the catalyst loading to 30 mol % (with respect to FA), an encouraging 26% conversion was observed at 110 °C (see Supporting Information File 1, Table S1, entry 5). However, to decrease the temperature and the catalyst loading, the generation of the Cu–H species by means of a silane

• our delight, upon reacting in toluene equimolar amounts of FA and PhSiH3, efficiency increased (Figure 2). Indeed, by using 1a and its tert-butoxide congener 1c ([Cu] = 10 mol %) a violent evolution of gas was observed at room temperature, resulting into a considerable increase of pressure which

• experiments were carried out (Scheme 2). By reacting FA and PhSiH3 (1:1 molar ratio) in the presence of 10 mol % of 1a, in deuterated toluene at room temperature under D2 atmosphere (1 atm), no H–D scrambling was observed (Scheme 2a). Furthermore, the 1a-catalyzed reaction of FA labeled at the acidic position

Regioselective approach to 5-arylsulfonylisoxazoles and their antimicrobial activity

• Artem S. Sazonov,
• Dmitry A. Vasilenko,
• Denis V. Porfiriev,
• Yuri K. Grishin,
• Rimma A. Gazzaeva,
• Alisa P. Chernyshova,
• Maxim A. Kryakvin,
• Anna A. Baranova,
• Vera A. Alferova and
• Elena B. Averina

Beilstein J. Org. Chem. 2026, 22, 592–602, doi:10.3762/bjoc.22.45

• times (Table 1). It was found that the reaction proceeds completely to give the exhaustive oxidation product 3a, when 2a was treated with 2.5 equivalents of mCPBA at room temperature. Thus, we used these conditions as the standard reaction conditions for our further studies. Additionally, it was found

• temperature did not have any effect on the result. The rate of oxidation of 5-thioisoxazoles 2 to sulfoxides 4, and then of sulfoxides 4 to sulfones 3, can vary significantly [31]. To verify this hypothesis, the progress of the reaction of 5-thioisoxazoles 2a with mCPBA (2.5 equiv) in CDCl3 was monitored

Continuous-flow carbonyl hydrogenation under subatmospheric to atmospheric hydrogen pressure enabled by robust heterogeneous Pt–Fe catalysts

• Hiroyuki Miyamura,
• Ryosuke Kajiyama,
• Shun-ya Onozawa,
• Yoshihiro Kon and
• Shū Kobayashi

Beilstein J. Org. Chem. 2026, 22, 575–582, doi:10.3762/bjoc.22.43

• , including ketones and aldehydes, to alcohols is a fundamental and important reaction in organic synthesis. One of the most ideal methods is catalytic hydrogenation, however, the hydrogenation of ketones generally requires harsh reaction conditions, such as high temperature and high pressure. We developed a

• temperature and under subatmospheric to atmospheric hydrogen pressure. High durability of the heterogeneous catalysts was confirmed by a long-term continuous-flow operation. Interestingly, both the combination of metal species and the metal ratio strongly influenced the catalytic performance. Keywords

• often suffers from insufficient reactivity and conversion, even under harsh reaction conditions, such as high temperature and pressurized hydrogen, or when employing advanced technologies [8][9][11][12]. The selective hydrogenation of carbonyl moieties often needs to overcome the problem of

Kinetic resolution of racemic planar-chiral vinylcymantrenes by molybdenum-catalyzed asymmetric metathesis dimerization

• Haruna Imazu,
• Hitoshi Izu,
• Yasuhiro Ohki and
• Masamichi Ogasawara

Beilstein J. Org. Chem. 2026, 22, 568–574, doi:10.3762/bjoc.22.42

• benzene at the indicated temperature in the presence of an appropriate chiral Mo-precatalyst (10 mol %), which was generated in situ from the Mo-precursor, (pyrrolyl)2Mo(=CHCMe2Ph)(=N-C6H3-2,6-iPr2) [36], and an axially chiral biphenol ligand. The chiral Mo/(R)-L1 precatalyst [21] facilitated the

• , entry 5). On the other hand, the effects of lowering the temperature were minimal in the reactions using Mo/(R)-L3 (Table 1, entries 6 and 7). The optimized conditions as in entries 4 and 6 were applied to the AMD/KR reactions of rac-1b and 1c as well. The AMD/KR of rac-1b using Mo/(R)-L1 proceeded with

Experimental and DFT studies on the regioselective methanolysis of 5-azido-9-oxabicyclo[6.1.0]nonan-4-yl 4-nitrobenzoate isomers

• İlknur Polat,
• Selçuk Eşsiz and
• Emine Salamci

Beilstein J. Org. Chem. 2026, 22, 547–556, doi:10.3762/bjoc.22.40

• -(dimethylamino)pyridine (DMAP, 2 mg) were added and the mixture was stirred at room temperature for 24 hours. Then, the solution was cooled to 0 °C and 100 mL of 2 M HCl added and stirred for 5 min. The mixture was extracted with ethyl acetate (4 × 30 mL). The organic phase was washed with saturated NaHCO3 (2

• 0 °C. m-CPBA (77%, 0.73 g, 3.26 mmol) and NaHCO3 (0.282 g, 3.36 mmol) were added and the mixture was stirred at room temperature for 36 hours. Then, the solution was cooled to 0 °C and 100 mL of 3 M NaOH added, and stirring continued for 40 min. The mixture was extracted with CH2Cl2 (4 × 30 mL). The

• at room temperature to obtain colourless crystals, mp: 101–102 °C. Compound 11 was recrystallized from the same solvent mixture at 0 °C and obtained as slightly yellow crystals, mp: 117–119 °C. (1S*,2S*,5S*,6S*)-6-Acetoxy-2-azido-5-chlorocyclooctyl 4-nitrobenzoate (10): 1H NMR (400 MHz, CDCl3) δ 8.34

Melifoliox B, a novel phloroglucin derivative isolated from Melicope barbigera (Rutaceae) and synthesis of new oxidation products from melifoliones A and B

• Horst Weber,
• Kim-Thao Tran-Cong,
• Bernhard Mayer,
• Guido J. Reiss,
• Iryna S. Konovalova,
• Marc S. Appelhans,
• Kenneth R. Wood and
• Claus M. Passreiter

Beilstein J. Org. Chem. 2026, 22, 535–546, doi:10.3762/bjoc.22.39

• -toluenesulfonic acid at 80 °C in toluene afforded benzoxocin (7) as the only product. On the other hand, melifolione A (1) was completely decomposed under these conditions. Irradiation of 5 in methanol with UV-light (300 nm) for 3 days at room temperature gave melifolione B (2) with traces of melifolione A (1

• reagents were of analytical grade. Melting points were determined on a Büchi SMP 20. Microwave experiments were performed in sealed tubes on a CEM, model DISCOVER, power 300 Watt apparatus with a special temperature programme. Isolation of compound 4 Compound 4 was isolated from the VLC-fraction MB-IX-5-P1

• -trihydroxyacetophenone (3.7 g, 20 mmol), citral (3.2 g, 21 mmol) and pyridine (1.6 g, 20 mmol) was heated with stirring in a water bath at max. 60 °C for 8 h. After cooling to room temperature, the reaction mixture was diluted with 200 mL diethyl ether and extracted with 0.1 N H2SO4 (3 × 20 mL) to remove the pyridine

Get a better glimpse on sequential photoreactions of trisnorbornadienes with ¹⁹F NMR spectroscopy

• Julian Felix Maria Hebborn,
• Ben Eric Merten,
• Thomas Paululat and
• Heiko Ihmels

Beilstein J. Org. Chem. 2026, 22, 527–534, doi:10.3762/bjoc.22.38

• mass, indicating decomposition above this temperature (see Supporting Information File 1, Figure S3). The cycloreversion of trisquadricyclane 2f0,3 was also initiated in a ground-state reaction with magic blue (5), which has already been shown to be an effective catalyst for this reaction [46][47][48

• be considered an improved property, the energy density of this compound is lower than that of the parent compound 2b because of the higher molecular mass. The experimental results showed a decomposition of trisquadricyclane 2f0,3 at higher temperature, which is accompanied by significant loss of mass

• ]heptadien-2-yl)-1,3,2-dioxaborolane (1e, 501 mg, 2.30 mmol), Pd(PPh3)4 (66.5 mg, 57.5 µmol, 5 mol %), THF (5.0 mL), and aq. NaOH (5.7 mmol, 2.7 M, 2.1 mL) was stirred at 80 °C for 16 h under anaerobic conditions [22]. After cooling the emulsion to room temperature, EtOAc (15 mL) was added and the organic

Modern synthetic pathways towards eribulin and its subunits

• Sebastian Dominik Graf

Beilstein J. Org. Chem. 2026, 22, 495–526, doi:10.3762/bjoc.22.37

• products were fused together by the nucleophilic attack of deprotonated alkyne 265 to aldehyde 261 (Scheme 31). The obtained diastereomers 266 were oxidized to the respective ketone 267, and again, Noyori reduction was performed to access 268 [105]. Treatment with AgBF4 at elevated temperature induced a

Synthesis and uranyl(VI) extraction performance of a calix[4]pyrrole–tetrahydroxamic acid receptor

• Sara Karnib,
• Rana Baydoun,
• Wissam Zaidan,
• Nancy AlHaddad,
• Omar El Samad,
• Bilal Nsouli,
• Francine Cazier-Dennin and
• Pierre-Edouard Danjou

Beilstein J. Org. Chem. 2026, 22, 486–494, doi:10.3762/bjoc.22.36

• calixarene tetraethylacetate [53]. In the original procedure, KOH was added at −5 °C, and the mixture was stirred for 5 hours at this temperature, followed by 5 days of stirring at room temperature. In our hands, both the addition of KOH and stirring were performed entirely at room temperature, and 1H NMR

• experiments, parameters like temperature, shaking time and volume of uranyl solution used were kept constant. In a typical experiment, 20 mL of a 1 mM aqueous uranyl acetate solution was adjusted to the target pH and then added to solid PCP HA. The solution was shaken at a fixed temperature of 25 °C for 4 h

Structural reassignment of compound 968, an allosteric glutaminase inhibitor

• Lindsey A. Albertelli,
• Sainabou Jallow,
• Chun Li and
• Scott M. Ulrich

Beilstein J. Org. Chem. 2026, 22, 455–460, doi:10.3762/bjoc.22.33

• -dimethylaminobenzaldehyde 4-Dimethylaminobenzaldehyde (4.02 g, 26.9 mmol) was dissolved in 1,4-dioxane (52 mL) and NBS (5.01 g, 28.2 mmol) was added in small portions with stirring over 5 minutes. The reaction mixture was stirred at room temperature for 20 minutes then poured into 50 mL water. The mixture was diluted with

• × 0.124 × 0.064 mm3) and quality was selected from a representative sample of crystals of the same habit using an optical microscope, mounted onto a Mitegen MicroLoopsTM (MiTeGen, LLC., Ithaca, NY) and placed in a cold nitrogen stream of nitrogen. Low temperature (100 K) X-ray data were obtained on a

• solution of the test compound in DMSO or DMSO itself was added (1 µL), mixed by gently pipetting up and down, then incubated for seven minutes at room temperature. The glutaminase reaction was initiated by addition of 20 µL of a solution of glutamine (100 mM) and K2HPO4 (500 mM), then mixed by gently

A facile and practical method for the synthesis of trans-(±)-taxifolin and its derivatives via Darzens reaction

• Bo Peng,
• Panpan Yang,
• Maaz Khan,
• Xiaotong Lin,
• Jiang Wu,
• Peng Fu and
• Qingqing Wu

Beilstein J. Org. Chem. 2026, 22, 443–450, doi:10.3762/bjoc.22.31

• give protected acetophenone 1 in an excellent yield of 78%. Next, the reaction conditions for the following α-bromination of acetophenone 1 to intermediate 2 were screened (Table S1, Supporting Information File 1). The treatment of compound 1 with CuBr2 in EtOAc at either room temperature or 60 °C

• all the Lewis acids screened, ZnCl2 was associated with best yield of 90%. Overall, the optimal conditions for the Darzens reaction involved treatment of 2 (1.0 equiv) with 3a (1.2 equiv) in MeCN at room temperature, using t-BuOLi (1.2 equiv) as the base and ZnCl2 (0.1 equiv) as Lewis acid catalyst

• mmol, 1.0 equiv), 3 (1.2 equiv), t-BuOLi (1.2 equiv) and ZnCl2 (10 mol %) in CH3CN (4.5 mL), stirred at room temperature for 4–6 h, N2 atmosphere. aZnCl2 was not added and the reaction time was 15 h. Yields are isolated yields. Synthesis of trans-(±)-taxifolin and its derivatives via the approach

Synthesis and stereochemical analysis of dynamic planar chiral oxa[7]orthocyclophene

• Yukiho Hashimoto,
• Yuuya Kawasaki,
• Kazunobu Igawa and
• Katsuhiko Tomooka

Beilstein J. Org. Chem. 2026, 22, 436–442, doi:10.3762/bjoc.22.30

• at ambient temperature. The phenyl-substituted oxacyclophene showed more pronounced dynamic planar chirality than the iodo- and methyl-substituted derivatives. The planar chirality of the oxacyclophene was successfully transformed into central chirality by epoxidation without loss of enantiomeric

Cone p-aminocalix[4]arenes enriched with ‘clickable’ alkyne or azide functionalities

• Ilia Korniltsev,
• Vasily Bazhenov,
• Alexander Gorbunov,
• Dmitry Cheshkov,
• Stanislav Bezzubov,
• Vladimir Kovalev and
• Ivan Vatsouro

Beilstein J. Org. Chem. 2026, 22, 399–415, doi:10.3762/bjoc.22.28

• (to ≈1 M), reducing the content of acetic acid in the mixture (to 1 mol per mol of HNO3) and extending the room-temperature reaction time to 72 h. Yet, under these conditions, the desired calix[4]arene 11 was obtained in only 31% yield (Scheme 2), and further variations in reagent excess/concentration

• , the room-temperature nitration of the silylated p-tert-butylcalix[4]arene ether 8 using 2.5 equiv of HNO3 per calixarene aromatic unit resulted in di- or trinitrated macrocycles 12 and 14 as the major products, when ≈0.2 and ≈1 M nitric acid concentrations were used. Similarly, the wide-rim

• -temperature preparation of the tetrapropargyl ether 24 from its silylated precursor 21. Surprisingly, attempts to apply these conditions to a complete removal of TBS groups in the less sterically hindered propargyl ethers 22 and 23 failed, and large amounts of the starting materials (as well as the partially