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

• sampling. Their translational power is evident from the success of biotherapeutics: antibody–drug conjugates (ADCs), in which cytotoxic payloads covalently linked to targeting antibodies, are at the forefront of cancer therapy, delivering tumour-selective killing for improved patient outcomes; Neulasta, an

• transformations [3][4]. However, the limited abundance of free cysteine residues in proteins has driven the development of alternative approaches targeting other chemical motifs. This review summarizes current strategies for site-specific modifications of these alternative sites, followed by a comparative

• difference is often not sufficient for site-specific modifications. Consequently, recent effort has shifted towards targeting alternative less-frequent amino acid residues [82], as well as novel mechanisms such as linchpin-directed modifications summarized below. Various chemoselective methods for

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

• -complexes stabilised by C^N^C and C^N chelate ligands [28][29][30][31][32] and an example of a gold(III) complex targeting oestrogen-receptor positive (ER+) breast cancer cells [11][33][34][35][36]. Gold(III) C^C chelate complexes. Gold hydride complexes supported by tridentate pincer ligands and

Total synthesis of the capsular polysaccharide repeating unit towards the development of a glycoconjugate vaccine against Klebsiella pneumoniae ST512

• Shuo Zhang,
• Ondřej Daněk and
• Peter H. Seeberger

Beilstein J. Org. Chem. 2026, 22, 821–827, doi:10.3762/bjoc.22.64

• conjugation-ready oligosaccharides, equipped with aminopentyl linkers, enables glycan microarray-based identification of minimal immunogenic epitopes. This work establishes a robust chemical foundation for the rational development of semi-synthetic glycoconjugate vaccines targeting K. pneumoniae ST512

Design, synthesis, and biological evaluation of FXR/ASK1 dual-target modulators

• Xi Zhang,
• Jingyan Wang,
• Ziqiang Zhao,
• Caiyi Wang,
• Zenghui Ye,
• Wei-Yuan Ma,
• Jian-Xing Xu and
• Fengzhi Zhang

Beilstein J. Org. Chem. 2026, 22, 771–781, doi:10.3762/bjoc.22.59

• desired outcomes, recent research has shifted towards investigating the potential of dual FXR agonists. A number of dual-targeting drugs, which engage FXR in conjunction with other pathways, have demonstrated considerable potential in enhancing the efficacy of MASH treatment outcomes [11][12] (Scheme 1

• study, we present the rational design and characterization of a balanced dual modulator targeting the nuclear receptors FXR and ASK1 [32], with the objective of advancing this experimental therapeutic concept (Scheme 3) [33][34]. The conception of this class of dual ligands was achieved by the merging

• compounds, an MTT assay was conducted. The results of this assay demonstrated that neither compound caused a decrease in cell viability at concentrations of up to 10 µM (Figure 3C). Conclusion Given the respective pharmacological roles of FXR and ASK1 in MASH, we hypothesized that a dual modulator targeting

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

• , Hangzhou 310053, China College of Pharmaceutical Sciences, Zhejiang University, Hangzhou, 310058, China 10.3762/bjoc.22.49 Abstract Proteolysis-targeting chimeras (PROTACs) have emerged as a promising therapeutic modality and now represent an important addition to the toolkit of medicinal chemists

• targeting an E3 ubiquitin ligase and the other binding to a protein of interest (POI), covalently joined by a flexible linker [12]. Upon cellular entry, the PROTAC molecule facilitates the formation of a ternary complex by simultaneously recruiting the POI and the E3 ligase (Figure 1). This proximity

• technology from an academic concept to clinical application underscores its transformative potential. In recent years, numerous PROTAC candidates have entered clinical trials, marking a significant milestone for the field [23]. Notably, multiple degraders targeting the androgen receptor (AR), such as ARV-110

Towards the targeted protein degradation of CK2: design and synthesis of CAM4066-based PROTACs

• Sophie Day-Riley,
• Sona Krajcovicova,
• Aryaman Raj Sokhal,
• Jan L. Venne,
• Paul Brear,
• Marko Hyvönen,
• Benjamin C. Whitehurst,
• Jason S. Carroll and
• David R. Spring

Beilstein J. Org. Chem. 2026, 22, 611–619, doi:10.3762/bjoc.22.47

• off-target effects and incomplete or transient CK2 suppression. PROTACs offer an alternative strategy by inducing proteasome-mediated degradation, with potential advantages in potency, selectivity, and duration of action. Herein, a series of CK2-targeting PROTACs has been designed and synthesised. By

• occupancy-driven pharmacology. Proteolysis-targeting chimeras (PROTACs) represent a rapidly advancing strategy for induced protein degradation. By transiently engaging both a target protein and an E3 ubiquitin ligase, PROTACs promote proteasomal elimination of the target rather than sustained binding [8

• PROTAC targeting CK2 was reported in the literature. This used CX-4945, a potent CK2 inhibitor, as the CK2 warhead [9][10]. However, as CX-4945 targeted the ATP-binding site of CK2, it also displayed nanomolar affinity for the ATP-binding sites of other kinases, like CLK2 [11]. Therefore, finding a

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

• growth factor receptor 2 (FGFR2) to overcome the issues of drug resistance and adverse reactions associated with traditional inhibitors in the treatment of FGFR2-driven tumors. Erdafitinib was employed as the targeting ligand, and its aliphatic amine site was conjugated with a CRBN E3 ligase ligand to

• cholangiocarcinoma [16][17][18]. Accordingly, research into therapeutics targeting FGFR2 has emerged as a major focus. To treat FGFR2-driven tumors, current research primarily focuses on two distinct classes of inhibitors, namely FGFR pan-inhibitors and FGFR2-selective inhibitors. Among these in Figure 1

• . Proteolysis-targeting chimera (PROTAC) is a chemical molecule which induce the target protein to approach the ubiquitin protein through the ubiquitin proteasome system, then it can be ubiquitinated and degraded [26][27][28]. This drives to form degraders through the unique properties of their own degradation

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

• enhances its therapeutic efficacy but also helps in overcoming resistance mechanisms that limit the effectiveness of other microtubule-targeting agents. Research continues to explore additional applications of 1 in various cancer types, including non-small cell lung cancer, ovarian cancer, and other soft

Synthesis of a HDAC inhibitor–nanogold probe for cryo-EM visualization in class I HDAC co-repressor complexes

• Wiktoria A. Pytel,
• John W. R. Schwabe and
• James T. Hodgkinson

Beilstein J. Org. Chem. 2026, 22, 480–485, doi:10.3762/bjoc.22.35

• functionalized this position with linkers for the development of HDAC1–3 proteolysis targeting chimeras (PROTACs) [14][18]. Alkyl-linker lengths of approximately 12 atoms and greater were the most effective degraders [18]. We chose the commercially available amine functionalized nanogold particles (Au–NH2

Synthesis and anti-cancer activity of naphthalimide–organylselanyl conjugates

• Rajkumar Ravi and
• Selvakumar Karuthapandi

Beilstein J. Org. Chem. 2026, 22, 416–435, doi:10.3762/bjoc.22.29

• approved therapy targeting EGFR in TNBC [10]. Selenium is one of the vital trace elements with numerous health benefits. Its adequate intake is essential, as a minimum quantity is required to support normal physiological functions [11][12]. Adults should eat at least 55 μg of selenium per day. However, the

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

• activity. They combine purine-like recognition features with the synthetic flexibility of heterocycles, offering a platform for selective targeting of tumor-related enzymes and receptors. Tumor cells overexpress kinases, DNA/RNA polymerases, and metabolic enzymes that bind purine nucleotides. Cancer cell

Streptoquinolines A and B, new antibacterial meroterpenoids produced by Streptomyces sp. TMPU-A0679

• Akiho Yagi,
• Hitomi Tomura,
• Ami Konno and
• Ryuji Uchida

Beilstein J. Org. Chem. 2026, 22, 185–191, doi:10.3762/bjoc.22.12

• Staphylococcus aureus, with minimum inhibitory concentrations ranging from 6.25 to 12.5 µg/mL. These results expand the structural and biological diversities of drimane–quinoline-type meroterpenoids and highlight their potential as lead compounds for the development of new antibacterial agents targeting drug

• . Compounds 1 and 2 both exhibited antibacterial activity against Gram-positive bacteria, including VRE and MRSA, with MICs ranging from 6.25 to 12.5 µg/mL. These results highlight their potential as lead compounds for the development of new antibacterial agents targeting drug-resistant Gram-positive

• formed during extraction. The discovery of streptoquinolines expands the structural and biological diversities of drimane–quinoline-type meroterpenoids and provides novel insights into their potential as scaffolds for the development of antibacterial agents targeting multidrug-resistant Gram-positive

Improved synthesis and physicochemical characterization of the selective serotonin 2A receptor agonist 25CN-NBOH

• Adrian G. Rossebø,
• Hannah G. Kolberg,
• Anders E. Tønder,
• Louise Kjaerulff,
• Poul Erik Hansen,
• Karla A. Frydenvang,
• Jesper Østergaard and
• Jesper L. Kristensen

Beilstein J. Org. Chem. 2026, 22, 175–184, doi:10.3762/bjoc.22.11

• ) permeability [13]. Moreover, in vivo experiments in rodents showed that maximal brain exposure was rapidly attained and further confirmed that 1 indeed has excellent BBB permeability [6]. Numerous metrics indicate preferred characteristics for central nervous system-targeting compounds, and it is generally

Isoorotamide-based peptide nucleic acid nucleobases with extended linkers aimed at distal base recognition of adenosine in double helical RNA

• Grant D. Walby,
• Brandon R. Tessier,
• Tristan L. Mabee,
• Jennah M. Hoke,
• Hallie M. Bleam,
• Angelina Giglio-Tos,
• Emily E. Harding,
• Vladislavs Baskevics,
• Martins Katkevics,
• Eriks Rozners and
• James A. MacKay

Beilstein J. Org. Chem. 2025, 21, 2513–2523, doi:10.3762/bjoc.21.193

• including regulation and catalysis [1][2][3][4][5][6]. As a result, targeting ncRNA through molecular recognition would afford important tools for molecular biology and biotechnology [7]. One approach focuses on recognition of double-helical regions of RNA (dhRNA) using oligomers called triplex-forming

Effect of a photoswitchable rotaxane on membrane permeabilization across lipid compositions

• Udyogi N. K. Conthagamage,
• Lilia Lopez,
• Zuliah A. Abdulsalam and
• Víctor García-López

Beilstein J. Org. Chem. 2025, 21, 2498–2512, doi:10.3762/bjoc.21.192

• organelles within the same cell [2]. Therefore, there is a great need to develop molecular tools capable of modulating membrane structure in a controlled manner, either to facilitate cargo transport (such as drug delivery) [3][4], to irreversibly disrupt membranes and induce cell death (e.g., for targeting

Synthesis of the tetracyclic skeleton of Aspidosperma alkaloids via PET-initiated cationic radical-derived interrupted [2 + 2]/retro-Mannich reaction

• Ru-Dong Liu,
• Jian-Yu Long,
• Zhi-Lin Song,
• Zhen Yang and
• Zhong-Chao Zhang

Beilstein J. Org. Chem. 2025, 21, 2470–2478, doi:10.3762/bjoc.21.189

• , entries 11–13), the reaction in MeCN at 30 °C for 24 h gave the best result, namely a quantitative conversion and 90% yield. Substrate scope With the optimal conditions in hand, we then explored the substrate scope. Targeting on the total synthesis of Aspidosperma alkaloids, different tryptamine

C2 to C6 biobased carbonyl platforms for fine chemistry

• Jingjing Jiang,
• Muhammad Noman Haider Tariq,
• Florence Popowycz,
• Yanlong Gu and
• Yves Queneau

Beilstein J. Org. Chem. 2025, 21, 2103–2172, doi:10.3762/bjoc.21.165

Discovery of cytotoxic indolo[1,2-c]quinazoline derivatives through scaffold-based design

• Daniil V. Khabarov,
• Valeria A. Litvinova,
• Lyubov G. Dezhenkova,
• Dmitry N. Kaluzhny,
• Alexander S. Tikhomirov and
• Andrey E. Shchekotikhin

Beilstein J. Org. Chem. 2025, 21, 2062–2071, doi:10.3762/bjoc.21.161

• exceptional potential as ligands targeting secondary structures of nucleic acids, particularly G-quadruplexes (G4) [21][22]. The indolo[1,2-c]quinazolin-6(5H)-one scaffold 1 exemplifies this design principle, with its rigid polycyclic framework mimicking topologies of established DNA/RNA-interactive molecules

Chiral phosphoric acid-catalyzed asymmetric synthesis of helically chiral, planarly chiral and inherently chiral molecules

• Wei Liu and
• Xiaoyu Yang

Beilstein J. Org. Chem. 2025, 21, 1864–1889, doi:10.3762/bjoc.21.145

• has been recognized as the most straightforward and efficient strategy for synthesizing chiral molecules, with early development primarily targeting compounds featuring stereogenic centers. In the past decade, significant progress has been made in the asymmetric synthesis of diverse axially chiral

Research progress on calixarene/pillararene-based controlled drug release systems

• Liu-Huan Yi,
• Jian Qin,
• Si-Ran Lu,
• Liu-Pan Yang,
• Li-Li Wang and
• Huan Yao

Beilstein J. Org. Chem. 2025, 21, 1757–1785, doi:10.3762/bjoc.21.139

• processes. For example, supramolecular self-assembly technology enhances the targeting of chemotherapeutic drugs to tumor tissues, reducing systemic adverse reactions. (3) Macrocyclic aromatic supramolecular nano-valves have a pseudo-rotaxane structure with host–guest coordination and the kinetic properties

• specific release of DOX, significantly improving the delivery efficiency and tumor targeting of hydrophobic drugs. The release of DOX from PAs also can be regulated by a pH-responsive mechanism. In 2015, Wang and coworkers synthesized a novel supramolecular prodrug nanoparticle exploiting the host–guest

• strides have been achieved in boosting the targeting accuracy and clinical utility of drug release mechanisms. Tumor cells are characterized by unique attributes, such as acidity, hypoxia, and altered metabolism, which set them apart from healthy cells. These distinct features underscore the importance of

4-(1-Methylamino)ethylidene-1,5-disubstituted pyrrolidine-2,3-diones: synthesis, anti-inflammatory effect and in silico approaches

• Nguyen Tran Nguyen,
• Vo Viet Dai,
• Luc Van Meervelt,
• Do Thi Thao and
• Nguyen Minh Thong

Beilstein J. Org. Chem. 2025, 21, 817–829, doi:10.3762/bjoc.21.65

• hydrogen bonding with Cys200. These results underscore the potential of 4-(1-methylamino)ethylidenepyrrolidine-2,3-diones, especially compound 5e, as promising scaffolds for the development of anti-inflammatory agents targeting iNOS-related pathologies. Keywords: anti-inflammatory pyrrolidine-2,3-dione

• derivatives; iNOS; pyrrolidine-2,3-dione derivatives; pyrrolidine-2,3-diones; pyrrolidine-2,3-diones targeting reversible transimination reaction; Introduction Nitric oxide (NO) is an important signaling molecule in numerous physiological processes such as neuronal tranmission, immue response, inflammatory

• -disubstituted pyrrolidine-2,3-diones as scaffolds for the development of anti-inflammatory agents targeting iNOS-related pathologies. Results and Discussion Synthesis of 4-(1-methylamino)ethylidene-1,5-disubstituted pyrrolidine-2,3-diones 5a–e The reaction between 4-acetyl-3-hydroxy-1,5-disubstituted-3

Synthesis of HBC fluorophores with an electrophilic handle for covalent attachment to Pepper RNA

• Raphael Bereiter and
• Ronald Micura

Beilstein J. Org. Chem. 2025, 21, 727–735, doi:10.3762/bjoc.21.56

• used, although often with limited success. We believe that the electrophilic warheads presented here offer an excellent balance between reactivity and selectivity for labeling of nucleic acids, and therefore, may also stimulate new designs for RNA targeting and RNA drugging. Experimental General

Photocatalyzed elaboration of antibody-based bioconjugates

• Marine Le Stum,
• Eugénie Romero and
• Gary A. Molander

Beilstein J. Org. Chem. 2025, 21, 616–629, doi:10.3762/bjoc.21.49

• designed in the context of cancer therapy [1], which combines the precision targeting of monoclonal antibodies (mAbs) with the therapeutic effects of cytotoxic drugs [2]. The ADCs are thus designed to deliver potent cytotoxic agents selectively and directly to cancer cells while minimizing damage to

• healthy tissues. Notably, ADCs have started to enter clinical trials for non-oncology applications as well [3]. The importance and value of ADCs are several fold: Precise targeting: ADCs specifically recognize their target cells because of their antibody component. This minimizes collateral damage to

• different molecules, such as a drug and a targeting moiety. This technique has been shown to be useful in applications such as cell labeling, protein–protein interactions, and photoradiosynthesis of bioconjugates, but the most important challenge remains the lack of specificity to target one amino acid, and

Identification and removal of a cryptic impurity in pomalidomide-PEG based PROTAC

• Bingnan Wang,
• Yong Lu and
• Chuo Chen

Beilstein J. Org. Chem. 2025, 21, 407–411, doi:10.3762/bjoc.21.28

• contamination. Keywords: glutarimide; IMiD; impurity; nucleophilic acyl substitution; PROTAC; Introduction Targeted protein degradation capitalizing on the concept of chemically induced dimerization has emerged as a new therapeutic approach recently [1]. In particular, the modularity of proteolysis targeting

Antibiofilm and cytotoxic metabolites from the entomopathogenic fungus Samsoniella aurantia

• Rita Toshe,
• Syeda J. Khalid,
• Blondelle Matio Kemkuignou,
• Esteban Charria-Girón,
• Paul Eckhardt,
• Birthe Sandargo,
• Kunlapat Nuchthien,
• J. Jennifer Luangsa-ard,
• Till Opatz,
• Hedda Schrey,
• Sherif S. Ebada and
• Marc Stadler

Beilstein J. Org. Chem. 2025, 21, 327–339, doi:10.3762/bjoc.21.23

• exacerbates healthcare and economic burdens, thereby prompting the urgent need for novel therapeutic strategies and antibiofilm agents. During our ongoing research targeting potential antibiofilm metabolites from fungi, we explored entomopathogenic species such as those belonging to the genera Beauveria and