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

• a chemical label or crosslinking functionality (Scheme 3a). One of the earliest rebridging strategies employed bis-sulfone reagents 6 which, upon in situ activation, generate monosulfone Michael acceptors that selectively react with a reduced cysteine pair (Scheme 3b) [27]. This approach was later

• serine residue into a cysteine analogue. Examples of small molecule reagents. Modifications of a–c) methionine by oxaziridine 22, hypervalent iodine 23, Michael acceptors (24a/b), d) histidine by thiophosphorodichoridate 25, e) aspartic and glutamic acid by diazo-containing compounds 26. Labelling of

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

• structure and bonding in the transition state. As summarised in an early review by Appleton, Clark and Manzer [22], both σ-donation and π-effects of the ligands are important. Ligands with strong trans-influence are typically either strong π-acceptors such as CO and CN−, and strong σ-donors, like

• < C6F5− ≈ PH3 < C6H5− < CH3− < H− < SiH3−. Ligands in cis position exert a weaker influence, spanning about 6 ppm but with a trend in the opposite direction, with the weakest σ-donors, as well as the strongest π-acceptors, exhibiting the highest deshielding, resulting in the most positive 1H hydride

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

• -benzoquinones (−0.41 to −0.37) V [23]) and halogen-substituted 3,6-di-tert-butyl-4-chloro-o-benzoquinone (−0.44 V [50]), due to the electron-withdrawing effect of the sulfinyl group. This allows the electrogenerated o-benzoquinones to be considered as fairly strong electron acceptors. During electrolysis, the

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

• acceptors (carbonyl groups). Trifluoromethylation of anisole afforded product 11 in 57% yield, with the ortho-isomer identified as the major product. Compared with anisole, thioanisole, a less electron-rich substrate, produced a mixture of ortho-, meta-, and para-isomers 12 in a combined yield of 33%, with

Computational prediction of C–H hydricities and their use in predicting the regioselectivity of electron-rich C–H functionalisation reactions

• Rasmus M. Borup,
• Nicolai Ree and
• Jan H. Jensen

Beilstein J. Org. Chem. 2026, 22, 603–610, doi:10.3762/bjoc.22.46

• . These properties encompass the site of metabolism [25][27], the strengths of hydrogen bond donors and acceptors [28][29][30], the regioselectivity of electrophilic aromatic substitution reactions [10], C–H pKa values [3], and electro- and nucleophilicity [31]. Building on the methodology from Finkelmann

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

• ., chloroform) with the inclusion of one of the solvent molecules into the capsules. However, triazole heterocycles attached to the calixarene core can serve as weak hydrogen-bond acceptors [99] and thus may interfere with capsule formation, including the exclusive formation of heterodimeric capsules from the

• the other hand, this water content is apparently sufficient to disrupt weaker intermolecular contacts involving triazole heterocycles as hydrogen-bond acceptors. Since the structures of the above mentioned non-capsular aggregate(s) formed by calixarene 47 cannot be drawn based on the available data

Design, synthesis and biological evaluation of 2,5-diaryloxazolo[4,5-d]pyrimidin-7-ylamines as selective cytotoxic agents against HeLa cells

• Maryna V. Kachaeva,
• Agnieszka B. Olejniczak,
• Marta Denel-Bobrowska,
• Victor V. Zhirnov,
• Yevheniia S. Velihina,
• Stepan G. Pilyo and
• Volodymyr S. Brovarets

Beilstein J. Org. Chem. 2026, 22, 390–398, doi:10.3762/bjoc.22.27

• oxazolopyrimidine derivatives may demonstrate selective cytotoxicity against cancer cell lines like HeLa, HepG2, A549, and central nervous system (CNS) tumor models [1][2][3]. The introduction of heterocyclic molecules with different amino groups as hydrogen-bond donors (and sometimes acceptors via lone electron

Spirobarbiturates with a pyrrolizidine moiety: synthesis, structure and biological evaluation

• Arthur A. Puzyrkov,
• Andrew S. Drachuk,
• Ekaterina A. Popova,
• Alexander V. Stepakov and
• Vitali M. Boitsov

Beilstein J. Org. Chem. 2026, 22, 274–288, doi:10.3762/bjoc.22.20

• molecules [56]. By this rule, orally active drugs should not violate more than one of the following criteria: MW – molecular weight: < 500 Da; NHBD – number of hydrogen-bond donors, Log(P) – octanol/water partition coefficient: <5; NHBA – number of hydrogen-bond acceptors, NRotB – number of rotatable bonds

A mild and atom-efficient four-component cascade strategy for the construction of biologically relevant 4-hydroxyquinolin-2(1H)-one derivatives

• Dmitrii A. Grishin,
• Kseniia I. Sharkovskaia,
• Ilya G. Kolmakov,
• Daria A. Ipatova,
• Rostislav A. Petrov,
• Nikolai D. Dagaev,
• Dmitry A. Skvortsov,
• Maria G. Khrenova,
• Valeriy V. Andreychev,
• Sergei A. Evteev,
• Yan A. Ivanenkov,
• Roman L. Antipin,
• Olga А. Dontsova and
• Elena K. Beloglazkina

Beilstein J. Org. Chem. 2026, 22, 244–256, doi:10.3762/bjoc.22.18

• approach involves the 1,4-Michael addition of the ambident anion derived from 6-halo-4-hydroxyquinolin-2-one to suitably activated unsaturated compounds. Considering the target structures (Figure 2), suitable Michael acceptors include α,β-unsaturated esters, aldehydes, methyl ketones, arylidene malonates

• obtained via the two-step procedure. The 6-halo-4-hydroxyquinolin-2-ones 2a–c were then subjected to Michael addition reactions with various acceptors following the retrosynthetic approaches (Scheme 2), and the results are discussed below (Scheme 4). No Michael adducts were obtained from reactions of 2a–c

• ). Based on the results obtained, it can be concluded that a sufficiently reactive Michael acceptor is likely necessary to achieve successful 1,4-addition with the relatively weak nucleophile that is 4-hydroxyquinolin-2-one. Among the acceptors tested, arylidene malonates showed the best performance

Configuration–packing synergy enabling integrated crystalline-state RTP and amorphous-state TADF

• Ruiyan Wang and
• Yunan Wu

Beilstein J. Org. Chem. 2026, 22, 224–236, doi:10.3762/bjoc.22.16

• molecular design approaches for TADF include twisted donor–acceptor structures (for example, carbazole or phenoxazine as donors and triazine, nitrile, or carbonyl groups as acceptors) as well as B/N multiresonance frameworks [30][31][32]. These strategies have been successful in achieving efficient triplet

Asymmetric Mannich reaction of aromatic imines with malonates in the presence of multifunctional catalysts

• Kadri Kriis,
• Harry Martõnov,
• Annette Miller,
• Mia Peterson,
• Ivar Järving and
• Tõnis Kanger

Beilstein J. Org. Chem. 2026, 22, 151–157, doi:10.3762/bjoc.22.8

• malonate. It is known that N-atoms are the strongest XB acceptors in electroneutral compounds [26]. It has also been shown that imines protected with heteroarylsulfonyl groups provide higher enantioselectivity than those protected with the more commonly used phenylsulfonyl or tosyl groups in addition

Symmetrical D–π–A–π–D indanone dyes: a new design for nonlinear optics and cyanide detection

• Ergin Keleş,
• Alberto Barsella,
• Nurgül Seferoğlu,
• Zeynel Seferoğlu and
• Burcu Aydıner

Beilstein J. Org. Chem. 2026, 22, 131–142, doi:10.3762/bjoc.22.6

• , 13C NMR, and mass spectrometry methods. Dye structures were designed with alkylaminophenyl groups, known for their various electron-donating properties, as donors, and the dicyanovinyl group, with its strong electron-withdrawing properties, as acceptors, conjugated with an indan-2-one core (Figure 1

The high potential of methyl laurate as a recyclable competitor to conventional toxic solvents in [3 + 2] cycloaddition reactions

• Ayhan Yıldırım and
• Mustafa Göker

Beilstein J. Org. Chem. 2025, 21, 2389–2415, doi:10.3762/bjoc.21.184

• optimized [3 + 2] cycloaddition conditions. The primary strategy for the selection of these compounds as catalysts is predicated on their capacity to function as H-bond acceptors and/or H-bond donors. As has been documented in previous research, imine-based templates or [2]rotaxane that possess an amide

Conformational effects on iodide binding: a comparative study of flexible and rigid carbazole macrocyclic analogs

• Guang-Wei Zhang,
• Yong Zhang,
• Le Shi,
• Chuang Gao,
• Hong-Yu Li and
• Lei Xue

Beilstein J. Org. Chem. 2025, 21, 2369–2375, doi:10.3762/bjoc.21.181

• iodine ions, which is consistent with the conclusions reached by our NMR titration. The binding constants of the complexes (K), KPBG = (1.387 ± 0.02363) × 105 M−1, KWDG= (6.089 ± 0.3320) × 103 M−1 were measured (Tables S1 and S2 in Supporting Information File 1), indicating that both acceptors had strong

• peaks appeared, indicating that photoelectron transfer occurred between iodine ions and the macrocycles [27][28], and fluorescence quenching was due to the photoinduced electron transfer (PET) effect between iodine ions and acceptors, resulting in non-radiative dissipation of excited state energy rather

Thiadiazino-indole, thiadiazino-carbazole and benzothiadiazino-carbazole dioxides: synthesis, physicochemical and early ADME characterization of representatives of new tri-, tetra- and pentacyclic ring systems and their intermediates

• Gyöngyvér Pusztai,
• László Poszávácz,
• Anna Vincze,
• András Marton,
• Ahmed Qasim Abdulhussein,
• Judit Halász,
• András Dancsó,
• Gyula Simig,
• György Tibor Balogh and
• Balázs Volk

Beilstein J. Org. Chem. 2025, 21, 2220–2233, doi:10.3762/bjoc.21.169

• File 1, Figures S1–S3). Based on their calculated physicochemical properties, all compounds satisfied Lipinski’s Rule of Five suggested by Wager et al. [34] (molecular weight < 500 Da, logP < 5, number of hydrogen-bond donors < 5, number of hydrogen-bond acceptors < 10) [35], and the topological polar

Photoswitches beyond azobenzene: a beginner’s guide

• Michela Marcon,
• Christoph Haag and
• Burkhard König

Beilstein J. Org. Chem. 2025, 21, 1808–1853, doi:10.3762/bjoc.21.143

• picoseconds to several years. The presence of heteroatoms also introduces H-bond donors and acceptors and metal coordination sites [11]. Like azobenzenes, E–Z isomerisation of azoheteroarenes can be triggered by light irradiation, while Z–E isomerisation proceeds through irradiation with a different

• presence of H-bond acceptors [102][104][107]. The presence and the nature of the H-bond can be identified by 1H NMR spectroscopy since the N–H proton has a characteristic chemical shift depending on the H-bond acceptor [101]. Arylhydrazones based on pyridine have been intensively studied since the H-bond

• between hydrazone and pyridine can be broken by protonation with an acid and even by metal coordination, rendering these compounds photo- and acidochromic (Scheme 31) [102]. The equilibrium can also be modulated by introducing hydrogen-bond acceptors in R1 [107] or by introducing substituents to the

Approaches to stereoselective 1,1'-glycosylation

• Daniele Zucchetta and
• Alla Zamyatina

Beilstein J. Org. Chem. 2025, 21, 1700–1718, doi:10.3762/bjoc.21.133

• advances in 1,1′-glycosylation and provides an overview of selected glycosylation strategies, including those aimed at forming α,β-, β,β-, and α,α-1,1′-glycosidic linkages. Particular emphasis is placed on the challenges of achieving stereoselectivity with lactol glycosyl acceptors, which commonly exist as

• exploiting the participation effect of the neighboring protecting group [43][44], employing anomeric lactols as acceptors is more complex as lactols with the desired configuration are frequently difficult to obtain (e.g., through anomerization). In addition to the nature of the leaving group and promoter

• formation of an α-glycoside on the donor side [54]. On the acceptor side, the β-configuration was favored due to steric hindrance from the C-2 phthalimido group in the triacetylated GalN-lactol acceptors 6 or 3,4-di-O-benzylated acceptors 8, resulting in kinetically controlled formation of β,α-1,1

Structural analysis of stereoselective galactose pyruvylation toward the synthesis of bacterial capsular polysaccharides

• Tsun-Yi Chiang,
• Mei-Huei Lin,
• Chun-Wei Chang,
• Jinq-Chyi Lee and
• Cheng-Chung Wang

Beilstein J. Org. Chem. 2025, 21, 1671–1677, doi:10.3762/bjoc.21.131

• position. Additionally, THF was used as a solvent to enhance the α-selectivity of the reaction [41][42][43]. Next, while both compounds 8 and 9 can act as acceptors, compound 9, a primary alcohol, exhibits greater nucleophilicity. Using the TolSCl/AgOTf promoter system at −70 °C, the β-linked disaccharide

Photocatalysis and photochemistry in organic synthesis

• Timothy Noël and
• Bartholomäus Pieber

Beilstein J. Org. Chem. 2025, 21, 1645–1647, doi:10.3762/bjoc.21.128

• in the presence of electron donors and acceptors. Furthermore, [Ru(bpy)3]Cl2 can engage in Förster and Dexter energy transfer processes, enabling the transfer of excited-state energy to molecules that do not themselves absorb visible light. This versatility is arguably the reason for the tremendous

Tautomerism and switching in 7-hydroxy-8-(azophenyl)quinoline and similar compounds

• Lidia Zaharieva,
• Vera Deneva,
• Fadhil S. Kamounah,
• Nikolay Vassilev,
• Ivan Angelov,
• Michael Pittelkow and
• Liudmil Antonov

Beilstein J. Org. Chem. 2025, 21, 1404–1421, doi:10.3762/bjoc.21.105

• CH3 group) and 3 leads to destabilization of K, while placing a substituent in positions 5 (weakly) and 6 stabilizes it. The effect on position 4 is mixed – electron donors stabilize the K form, while acceptors rise its energy. All substituents in position 8 stabilize K, but the effect of the

• acceptors is more pronounced. The effect of the amino group is stronger comparing to NMe2 due to the steric hindrance in the latter. Since in 1 the azo group, an acceptor, is placed on position 8, it is also expended to bring additional inherent stabilization of the 1K tautomer. The effect of the

• donors in the phenyl ring, while N–NH is a donor, favored by acceptors in Ph [3][7][89]. Following this model, a suitable substitution in the Ph ring of 1 can stabilize or destabilized KE and KK in respect to E and K. This opens an additional channel for fulfilling the requirements for a clean switching

High-pressure activation for the solvent- and catalyst-free syntheses of heterocycles, pharmaceuticals and esters

• Kelsey Plasse,
• Valerie Wright,
• Guoshu Xie,
• R. Bernadett Vlocskó,
• Alexander Lazarev and
• Béla Török

Beilstein J. Org. Chem. 2025, 21, 1374–1387, doi:10.3762/bjoc.21.102

• the phenomena [17]. In addition, due to the availability of commercially accessible instruments, the applications of HHP in synthetic chemistry have expanded in the past decades. The studied reactions include hydrogenation [18], the addition of enamines to Michael acceptors [19], enantioselective

Oxetanes: formation, reactivity and total syntheses of natural products

• Peter Gabko,
• Martin Kalník and
• Maroš Bella

Beilstein J. Org. Chem. 2025, 21, 1324–1373, doi:10.3762/bjoc.21.101

• base [5]. In fact, its hydrogen-bond-accepting ability is even stronger than that of the other 3-, 5- and 6-membered cyclic ethers, as well as the carbonyls of aldehydes, ketones, esters and carbonates [6][7][8]. The only better carbonyl-based hydrogen-bond acceptors are amides, carbamates and ureas [9

Recent advances in oxidative radical difunctionalization of N-arylacrylamides enabled by carbon radical reagents

• Jiangfei Chen,
• Yi-Lin Qu,
• Ming Yuan,
• Xiang-Mei Wu,
• Heng-Pei Jiang,
• Ying Fu and
• Shengrong Guo

Beilstein J. Org. Chem. 2025, 21, 1207–1271, doi:10.3762/bjoc.21.98

• the system. In 2024, Liang’s group reported the replacement of N-arylacrylamides with 7-fluoro-3-homoallylquinazolin-4-ones, which are tethered to an alkenyl group at the nitrogen atom and function as radical acceptors (Scheme 17). This approach effectively facilitated photoelectrocatalytic

On the photoluminescence in triarylmethyl-centered mono-, di-, and multiradicals

• Daniel Straub,
• Markus Gross,
• Mona E. Arnold,
• Julia Zolg and
• Alexander J. C. Kuehne

Beilstein J. Org. Chem. 2025, 21, 964–998, doi:10.3762/bjoc.21.80

• functionalization with a much broader variety of donors (and even acceptors) than is possible through a radical-mediated nucleophilic aromatic substitution (SRN1, see also below) [3][46][47]. The I-TTM has a maximum emission at λem = 578 nm and a ϕ of 3% (in cyclohexane), indicating that the symmetry does not seem

Study of tribenzo[b,d,f]azepine as donor in D–A photocatalysts

• Katy Medrano-Uribe,
• Jorge Humbrías-Martín and
• Luca Dell’Amico

Beilstein J. Org. Chem. 2025, 21, 935–944, doi:10.3762/bjoc.21.76

• of D–A structures makes them the ideal structures to further understand the structure–property relationship of D–A molecules for optimizing their photocatalytic performance by simpler modification of the different D–A subunits. In particular, D–A structures featuring sulfur-based acceptors and

• nitrogen donors have gained increasing attention for their use as photoredox catalysts. This study introduces a new family of D–A molecules by exploring various sulfur-based acceptors and nitrogen donors, including a novel tribenzo[b,d,f]azepine (TBA) unit and 5H-dibenz[b,f]azepine (IMD). Our findings

• diverse scaffolds have been reported in the literature, the identification and use of novel PCs with tunable and diverse optical and redox properties can pave the way to uncharted reactivity. In this context, sulfur-based cores, widely used as acceptors in photoelectric materials [9][10][11][12][13][14