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

• , including IgG (trastuzumab) [56], EGFR [57], the adenosine A1 receptor [58] and P2X7 [59], have been labelled in vitro and/or in cellular systems. Catalytic approaches generate reactive species in situ, thus enhancing both selectivity and efficiency. A notable example involves rhodium (Rh)-based catalysis

• sortase. Optimisations using depsipeptides or coupling strategies have further improved conversion efficiency and reduced reagent consumption [144]. Due to its ease of preparation, large libraries of sortase variants have been generated and screened to expand substrate scope [143]. In one example, sortase

• sortase variant engineered to recognise amyloid proteins was highly selective for the altered sequence (KM = 128 µM) but achieved only modest catalytic efficiency (143 M−1 s−1, compared with 103–104 M−1 s−1 in wild-type), likely because the FACS-based screening was based on single-turnover events. The

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

• antiradical efficiency (AE). This complex parameter captures both the hydrogen-atom-donating ability of a compound and the kinetics of its reaction with the DPPH radical. Among catechol thioethers 1, 2, and 7, compound 2, bearing a tert-butyl substituent on the sulfur atom, exhibited the highest activity

• , indicating low radical scavenging activity. For sulfoxides 1a–7a, the TEC50 ranged from 30 to 70 min, which was longer than that for thioethers 1–7 (20–40 min). The antiradical efficiency (AE = 1/(IC50·TEC50)) values point out a moderate neutralizing capacity for catechol sulfoxide 1a (AE = 3.56) and its

• (7/7a) substituents, where an increase in the IC50(ABTS∙+) was observed upon going from the thioethers to the sulfoxides. Furthermore, sulfoxides 5a and 7a showed a decreased efficiency in the ABTS assay relative to 3,5-DTBC. Overall, all studied catechols possessed antioxidant activity comparable to

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

• the smelly solvent pyridine, moisture-sensitive environmentally aggressive reagent (TiCl4) and subsequent complicated treatment of the resulting reaction mixture making it inapplicable for large-scale high-efficiency production of functional materials. Therefore, analyzing the literature examples we

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

• a very useful tool to tune the thermal and optical properties, light-induced switching in particular. Monohalogen derivatives exhibited up to 93% E → Z photoconversion efficiency in solution, whereas the efficiency of dihalogen analogues is lower by 20%, which is ascribed to their nonplanar

• derivatives 1a, 1c, and 1e exhibited superior photoswitching in solution, reaching the Z-isomer with 92–93% efficiency. In contrast, dihalogen analogues showed ≈20% lower efficiency of the photoconversion rate. It has been shown that planarity of the E-isomers depends on the substitution. While monohalogen

• derivatives are planar, nonplanar disubstituted derivatives with diminished conjugation possess blue-shifted absorption and lower conversion efficiency. The stability of the resulting Z-isomers ( values) can be tuned similarly. In solution, the difluoro derivative 1b was identified as the most stable and

Synthesis and biological evaluation of new brassinosteroid analogs with C-22 benzoate function

• María Núñez,
• Camila Escobar,
• Mario Párraga,
• Mauricio Soto,
• Luis Espinoza-Catalán,
• Katy Díaz and
• Andrés F. Olea

Beilstein J. Org. Chem. 2026, 22, 753–762, doi:10.3762/bjoc.22.57

• highest relative accumulation in dBES1, are exhibited by analogs 12 and 19. On the other hand, analogue 19 forms the most stable complex in the active site. From these results it can be concluded that the efficiency of BR analogs to initiate the signaling process is not a determining factor in the final

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

• the catalytic precursor and chiral bis-ferrocenyl amide phosphine (FAP) (L1) as ligand [36] (Scheme 2). The obtained results demonstrated the high efficiency of the Ag(I)-FAP catalytic system for this transformation. In particular, most α-(arylimino)esters yielded cycloaddition products 3 in excellent

• , acetoxy, benzyloxy, etc. It was established that the reaction of glycine methyl ester arylimines 1 with racemic cyclopentene-1,3-diones 28 leads to bicyclic pyrrolidines 29 and enantiomerically enriched cyclopentenediones (R)-28 in moderate yields. The Ag(I)/L3 catalytic system also showed high efficiency

• /bisoxazoline L19 as a chiral catalyst system, high enantioselectivity (up to 97% ee) and moderate to high exo-selectivity were achieved in the reactions with N-methylmaleimide. The high efficiency of iminoesters as azomethine precursors is due to the high acidity at the enolizable Cα position and the formation

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

• approaches of optimization with regard to their light harnessing efficiency, energy storage capacity, and storage time. Structural modifications and studies of the norbornadiene/quadricyclane (NBD/QC) photo-/thermoswitch couple are covered in several articles. In a publication by Kerzig, Ihmels, and co

• a key property for characterizing the light harnessing efficiency of a photoswitch. In the article by Volker, Steen, and Crespi [18], a convenient and reliable fiber optic spectroscopic setup for determining this quantum yield is reported and was benchmarked for azobenzene against other methods

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

• -catalyzed [8], organic photocatalyst-mediated, or electrochemical transformations [9], and also include continuous-flow processes [6][10][11][12][13]. Given that photocatalytic reactions align with the principles of green chemistry, particularly energy efficiency and the use of catalytic pathways, such

• ; however, this 2.5-fold increase in catalyst loading did not provide a commensurate improvement in efficiency. Moreover, owing to the high molecular weight of 3DPAFIPN, a 5 mol % loading cannot be considered compatible with the development of a green methodology. Consequently, 2 mol % 3DPAFIPN under blue

• substrates are shown in Supporting Information File 1. Radical trapping reactions. Proposed mechanism. Addition of CF3 radical to benzene and TMB. Comparison of atom efficiency and prices of the CF3 sources.a Optimization of reaction conditions. Scaling-up of the trifluoromethylation of TMB. Supporting

Advantages of PROTACs in achieving selective degradation of homologous protein families

• Luxi Yang,
• Xinfei Mao,
• Jingyi Zhang,
• Jing Shu,
• Wenhai Huang,
• Xiaowu Dong,
• Yinqiao Chen and
• Mingfei Wu

Beilstein J. Org. Chem. 2026, 22, 628–661, doi:10.3762/bjoc.22.49

• inhibitors that rely on sustained occupancy of conserved ATP-binding pockets, PROTACs induce transient yet specific protein–protein interactions that dictate ubiquitination efficiency. By fine-tuning the length and composition of the linker, as well as the choice of E3 ligase and its attachment geometry

• -length linker (n = 5, m = 1) within the C4-linker series achieved the most potent selective degradation (compared to HDAC1, 3, 4) in the subseries 20a–e (m = 1, n = 2–6). For the subseries 20f–h (m = 2, n = 2–4), when the linker length increased, the molecular degradation efficiency increases, and 20h (n

• -containing compound 33 can almost completely degrade p38δ, but in the degradation of p38α, it is restricted. In contrast, the structure of compound 30 having additional carbon atoms added to the linker, resulted in less than 50% degradation of both subtypes at the maximum efficiency. It can be seen that the

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

• equimolar mixture of H2 and CO2. The efficiency of the catalysis showed to be strongly dependent on the nature of the amine. Keywords: copper N-heterocyclic carbene; formic acid dehydrogenation; hydrogen storage; metal hydride; silanes; Introduction The discovery and utilization of alternative and

• 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

Design and synthesis of an erdafitinib-based selective FGFR2 degrader

• Yumeng Jin,
• Shidong Wang,
• Sihan Pan,
• Shuqi Huang,
• Weichen Zhou,
• Xiaohao Huang,
• Lei Zheng and
• Lingfeng Chen

Beilstein J. Org. Chem. 2026, 22, 583–591, doi:10.3762/bjoc.22.44

• effectively degrade FGFR2 via the proteasomal pathway, while the VHL E3 ligase-based degrader DGY-09-192 is capable of degrading both FGFR1 and FGFR2 simultaneously [40]. These findings suggest that different E3 ligase ligands may influence the selectivity and efficiency of degradation [41]. Nevertheless, due

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

• process, highlighting its precision and efficiency. Keywords: azides; 8-azidocyclooct-4-en-1-yl 4-nitrobenzoate; DFT; epoxycyclooctane azide; methanolysis; Introduction Organic azides are very important precursors for the preparation and synthesis of various nitrogen-containing compounds, as well as

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

• C1–C13 fragment 11 with C14–C35 fragment 12 [66][67][68]. Despite these great advances, still, the research on improving synthetic efficiency, reducing production costs, omitting toxic chemicals, as well as on new pathways towards 1`s 4 heterocyclic precursor fragments is rigorously ongoing [69][70

• . Here, 121 bears the right configuration needed for Halaven synthesis, but the authors also showed that 122 was easily converted to 121 via Mitsunobu inversion. Although 121 only represents a small building block for the total assembly of 1, this method especially stands out for its cost-efficiency and

• competitive reaction sequence for the large-scale process currently applied by Eisai [66]. Furthermore, this method stands out for its cost-efficiency, since only an enantiomeric pair of ruthenium catalysts is needed in addition to other standard chemicals. A similar building block as from Kaghad and co

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

• % yield. Its structure was confirmed by 1H NMR, 13C NMR, and HRMS. The uranium(VI) extraction efficiency of PCP HA was evaluated by solid–liquid extraction experiments, using uranyl acetate as the uranium source, with measurements performed by gamma spectroscopy. PCP HA demonstrated good performance

• , removing up to 95% of uranyl(VI) from aqueous solutions (1 mM) at acidic pH, likely due to the strong coordination provided by its hydroxamic acid groups. Further studies revealed that the extraction efficiency also depends on the ligand-to-metal molar ratio. These findings establish PCP HA as a promising

• solid–liquid approach as previously described for calixarenes [58]. Extraction experiments In this study, two parameters that can influence the solid-liquid extraction efficiency of PCP-HA toward uranyl, namely pH and ligand-to-metal ratio, were studied. To ensure comparison between extraction

Recent advances in the stereoselective synthesis of distal biaxially chiral molecules

• Fanxing Zhou,
• Chen Zhang,
• Lingyu Sun,
• Yiyun Fang,
• Siming Zheng,
• Lina Hu,
• Mengyang Shen,
• Zhen Zhao,
• Wei Xu,
• Yunqiang Sun and
• Zi-Qiang Rong

Beilstein J. Org. Chem. 2026, 22, 461–479, doi:10.3762/bjoc.22.34

• one chiral axis followed by the second, and transformation from central chirality to axial chirality. We anticipate that this review will facilitate the development of novel synthetic strategies for remote biaxial chiral molecules, improve asymmetric synthesis efficiency, and expand their applications

• [41]. This strategy delivered excellent enantioselectivity, diastereoselectivity, and overall efficiency, underscoring its unique advantages in the synthesis of multiaxially chiral scaffolds. In parallel, Tanaka and co-workers advanced a [2 + 2 + 2] cycloaddition strategy to realize an asymmetric

• diastereoselectivity. Notably, this system overcame the limitations of previous methodologies that required elevated temperatures and suffered from poor efficiency and narrow substrate scope. Later, in 2011, the group extended this approach using a bisphosphine-ligated rhodium complex to efficiently synthesize

Concept-driven strategies in target-oriented synthesis

• David Yu-Kai Chen,
• Chao Li and
• Yefeng Tang

Beilstein J. Org. Chem. 2026, 22, 451–454, doi:10.3762/bjoc.22.32

• complex organic architectures have witnessed remarkable achievements in recent years, continuously redefining the boundaries of creativity, efficiency, and practicality. On the other hand, it has been suggested that the field of complex molecular assembly is transitioning (or ought to transition) from an

• advancements, and strategic innovations. However, while efficiency and practicality remain essential design considerations in targeted synthesis, it is worth pondering whether the pursuit of efficiency (along with its associated elements) truly captures the underlying scientific essence of target-oriented

• , a generalized approach can address multiple target classes simultaneously, but typically exhibits reduced efficiency as molecular complexity increases. Integrating elements from both a customized and a generalized approach may represent an “ideal” strategy, although achieving such integration

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

• (1.2 equiv) was performed in CH3CN, using t-BuOLi (1.2 equiv) as base in the presence of a catalytic amount of ZnCl2. Due to the high efficiency of the reaction, no purification of product (±)-4a by column chromatography was necessary after post-treatment and the product could be directly used in the

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

• macrocyclic core through simple acylation of p-aminocalix[4]arenes with the respective phosphorous-containing activated esters. Such grafting of well-known receptor units onto a common platform has led to substantial amplification of the efficiency of lanthanide and actinide extraction from acidic media by

• propargylated and 2-azidoethylated calix[4]arenes revealed their enhanced efficiency, resulting in the preferential formation of exhaustively triazolated macrocycles over mixed triazolated/propargylated or triazolated/2-azidoethylated ones [79][80]. Furthermore, it has been proved that triazolated calixarenes

• next the TBS-protecting groups were removed from the acetylene units in the Boc-protected tetraamines 21–23 (Scheme 4). For the removal of the TBS groups, instead of using an equivalent amount of n-Bu4NF, it was used as a catalyst in a water/THF mixture, which showed excellent efficiency for the room

Electrosynthetic access to unsymmetrical oxaza[8]helicenes with high chiral stability and strong circularly polarized luminescence (CPL)

• Tin Zar Aye,
• Rubal Sharma,
• Muthu Karuppasamy,
• Daiya Suzuki,
• Haruka Nakajima,
• Yoshitane Imai,
• Mitsuhiro Arisawa,
• Mohamed S. H. Salem and
• Shinobu Takizawa

Beilstein J. Org. Chem. 2026, 22, 372–382, doi:10.3762/bjoc.22.25

• frontier orbitals, intermolecular interactions, and excited-state dynamics, frequently enhancing fluorescence efficiency and circularly polarized luminescence (CPL) [16][17][18][19][20][21][22]. Consequently, heterohelicenes have emerged as attractive platforms for optoelectronic devices, 3D displays

• Supporting Information File 1), we developed a one-pot electrochemical annulation between 3 and β-naphthol derivative 4. Using n-Bu4NPF6 as the electrolyte in CH2Cl2 at room temperature, this protocol furnished oxaza[8]helicenes 5 in good-to-moderate yields with >75% Faradaic efficiency, and no homo-coupling

• with the observed trends in emission efficiency. Fluorescence quantum yields (Φf, in chloroform, 1 × 10−3 M) for 5a and 5b were 25.1% and 22.6%, slightly lower than those of 6a (40.5%) and 6b (38.9%). This difference can be rationalized by their radiative rate constants (kf). The calculated kf,calcd

Recent advances in the cleavage of non-activated amides

• Eun-Sol Choi and
• Hyo-Jun Lee

Beilstein J. Org. Chem. 2026, 22, 352–369, doi:10.3762/bjoc.22.23

• (SO2F2) was demonstrated to be a powerful electrophilic reagent for amide-bond cleavage by Qin et al. (Scheme 8) [56]. Under an atmosphere of SO2F2, esterification of tertiary amides 28, 35–37 smoothly afforded esters 34 in high yields, although the efficiency was reduced when a bulky substituent was

• secondary 2-iodo-N,N-dimethylbenzamides 69–71 afforded 2,2,2-trifluoroethyl 2-iodobenzoate (68) in moderate yield. Higher yields were observed when tertiary amides 72 and 73 were employed for esterification. Among these, pyrrolidine-based amide 73 exhibited the highest efficiency, furnishing the ester 68 in

• N,N-dimethylamides possessing primary, secondary, and tertiary alkyl moieties at the α-position, furnishing the corresponding amides 86–89 in good to high yields. The efficiency of transamidation decreased with increasing steric congestion. Mechanistically, the carbonyl group is first activated by

Synthesis of tricyclic fused pyrrolidine nitroxides from 2-alkynylpyrrolidine-1-oxyls

• Mark M. Gulman,
• Yuliya F. Polienko,
• Sofia Yu. Trakhininа,
• Yuri V. Gatilov,
• Tatyana V. Rybalova,
• Sergey A. Dobrynin and
• Igor A. Kirilyuk

Beilstein J. Org. Chem. 2026, 22, 344–351, doi:10.3762/bjoc.22.22

• nitroxides are incorporated into macromolecular or nanosized supramolecular structures, which modulate nitroxide properties. For example, the efficiency of ORCA (relaxivity) directly depends on the rotational correlation time of the radicals attached to the scaffold [13][14][15]. Large structures in which

Ring contraction and ring expansion reactions in terpenoid biosynthesis and their application to total synthesis

• Nicolas Kratena,
• Nicolas Heinzig and
• Peter Gärtner

Beilstein J. Org. Chem. 2026, 22, 289–343, doi:10.3762/bjoc.22.21

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

• , lifetime, and efficiency, make them highly versatile for integration into advanced optoelectronic devices [9][10][11]. The performance limits of these devices, particularly in terms of their brightness, longevity, and efficiency, are largely dependent on the ability to precisely control the dynamics of the

• the excitons within the crystal, thus facilitating the generation of room-temperature phosphorescence. The presence of these intermolecular π–π interactions enhances the efficiency of phosphorescence by providing a stable environment for the triplet excitons, which are otherwise prone to non-radiative

• increases the number of possible ISC pathways but also plays a crucial role in facilitating the efficient intersystem crossing process. This suggests that the intermolecular interactions in the solid-state environment are key factors in controlling the efficiency of the triplet exciton utilization

Circumventing Mukaiyama oxidation: selective S–O bond formation via sulfenamide–alcohol coupling

• Guoling Huang,
• Huarui Zhu,
• Shuting Zhou,
• Wanlin Zheng,
• Fangpeng Liang,
• Zhibo Zhao,
• Yifei Chen and
• Xunbo Lu

Beilstein J. Org. Chem. 2026, 22, 158–166, doi:10.3762/bjoc.22.9

• slightly lower yield (88%, Table 1, entry 6). The organic base Et3N afforded 3a in 89% yield (Table 1, entry 7). These data indicate that mild inorganic bases are generally more appropriate for this transformation, with NaHCO3 offering the best combination of efficiency and practicality. Moreover

• diminished yields (68% and 88%, respectively; Table 1, entries 9 and 10). We tentatively attribute the inferior performance of NCS to its lower halogen-transfer efficiency and oxidation potential under the present conditions, which likely result in a less efficient generation of the key electrophilic sulfur

• species and in increased competitive decomposition. In contrast, the more strongly oxidizing TCCA tends to promote non-productive overoxidation pathways, thus also failing to match the efficiency of NBS. These results underscore the critical role of halogen source and oxidative strength in modulating the

Design and synthesis of an axially chiral platinum(II) complex and its CPL properties in PMMA matrix

• Daiki Tauchi,
• Sota Ogura,
• Misa Sakura,
• Kazunori Tsubaki and
• Masashi Hasegawa

Beilstein J. Org. Chem. 2026, 22, 143–150, doi:10.3762/bjoc.22.7

• Luminescent materials based on metal complexes have been extensively studied due to their high phosphorescence efficiency, making them promising candidates for applications in organic light-emitting diodes (OLEDs) [1][2][3][4][5], sensors [6][7][8][9], and bioimaging materials [10][11]. Among these materials