Rh(III)-catalyzed chelation-assisted C–H activation/annulation of 2-arylimidazolines with cyclic diazo-1,3-dicarbonyl compounds: a novel approach to tetracyclic annulated derivatives of 2,3-dihydroimidazo[2,1-a]isoquinoline

• Ivan Lyutin,
• Grigory Kantin,
• Olga Bakulina and
• Dmitry Dar'in

Beilstein J. Org. Chem. 2026, 22, 997–1003, doi:10.3762/bjoc.22.78

• biologically active compounds. a,b) Structure of biologically active 2,3-dihydroimidazo[2,1-a]isoquinolines (1) and their published syntheses. c) A novel approach to annulated 2,3-dihydroimidazo[2,1-a]isoquinolines via chelation-assisted C–H activation/annulation of 2-arylimidazolines proposed in this work. d

The role of spacer length and flexibility in peptide self-assembly

• Julian Link,
• Albin Lahu,
• Manfred Wagner,
• Tanja Weil and
• David Y. W. Ng

Beilstein J. Org. Chem. 2026, 22, 986–996, doi:10.3762/bjoc.22.77

• the sequence, similar to the primary structure of proteins, therefore enabling on-demand production of hierarchical nanostructures. Besides the sequence, the implementation of hydrophobic elements, such as aromatic π-blocks, steroids or alkyl chains, have been successfully applied to enable and

Electrochemical reduction of unsaturated carbon–carbon bonds via 3d transition-metal catalysis

• Geon Kang,
• Minki Jeon,
• Pooja Kumari Jat,
• Cheoljae Kim and
• Isaac Choi

Beilstein J. Org. Chem. 2026, 22, 955–981, doi:10.3762/bjoc.22.75

• mechanistic design principles are particularly highlighted. By correlating catalyst structure, electrochemical behavior, and reaction outcome, this review aims to provide a unified framework for understanding how electrochemical control enables new reactivity modes in 3d metal-catalyzed hydrogenation

• operate through hydride transfer or hydride-free pathways depending on ligand environment and applied potential. Consequently, the selection of mechanistic mode is not intrinsic to a single pathway but is instead governed by the interplay between metal identity, ligand structure, and electrochemical

Synthesis of sterically shielded piperidine nitroxides via acid-catalyzed heterocyclization of β-aminoketone derivatives with ketones

• Mark M. Gulman,
• Yurii I. Glazachev and
• Sergey A. Dobrynin

Beilstein J. Org. Chem. 2026, 22, 948–954, doi:10.3762/bjoc.22.74

• ), the N-adjacent methine (2.71 ppm), and diastereotopic methylene protons (1.39, 1.58 ppm) supported the assigned structure. Compound 4b exhibited spectral data identical to those previously described [31]. The aminodioxolanes 4a,b were subjected to acid-catalyzed heterocyclization with the

• -tripropyl-substituted piperidines 5a,b were isolated in approximately 50% yield (Scheme 2). The full-line shape analysis of the 1H NMR spectrum of piperidine 5a was simulated using the gNMR software (version 5.0) [32] and the extracted spin-system parameters were consistent with the proposed structure (see

A practical CO₂-mediated synthesis of 5,6-carboxylated silicon-rhodamines for targeted probe development

• Dongjie Hou,
• Shaowei Wu,
• Ning Xu,
• Pengjun Bao,
• Wenhao Jia,
• Qinglong Qiao and
• Zhaochao Xu

Beilstein J. Org. Chem. 2026, 22, 915–924, doi:10.3762/bjoc.22.72

• -resolution imaging. Overall, this work improves the synthetic accessibility of functionalized SiR dyes and provides a concise and versatile platform for the rapid development of targeted super-resolution probes. (a) Modular structure of spirocyclic rhodamines. (b) Conventional carboxylation strategies. (c

Cascade transformation of 2-(diazoacetyl)-2H-azirines to 2-aroyl-3-hydroxy-1H-pyrroles via condensation with aromatic aldehydes

• Timur O. Zanakhov,
• Ekaterina E. Galenko,
• Mikhail S. Novikov and
• Alexander F. Khlebnikov

Beilstein J. Org. Chem. 2026, 22, 897–904, doi:10.3762/bjoc.22.70

• of the molecular ion by HRMS for this crude product. The IR spectrum of the compound contains a band of the diazo group at 2087 cm−1. According to the 1H NMR spectrum, the product consists of more than 90% of one diastereoisomer, the spatial structure of which was established using a 2D NOESY

• experiment (see Supporting Information File 1). The entire set of spectral data allows us to assign the structure (1RR,3SR,6RR)-4-diazo-3-(4-iodophenyl)-1-(3-methoxyphenyl)-2-oxa-7-azabicyclo[4.1.0]heptan-5-one (4b) to the main product (Scheme 2). The presence of cross peaks of the HN proton with both the

• , using the found optimal conditions (Table 1), a series of 2-aroyl-3-hydroxypyrroles 5a–p were synthesized (Scheme 5). The structure of compound 5a was confirmed by an X-ray structural analysis (CCDC 2536266). The yield of products 5a–m,p was 25–62% in 2 synthetic steps, with complete conversion of the

Chiral cyclopropenimine-catalyzed enantioselective Michael reactions of phenol and benzofuran-derived α,β-unsaturated pyrazolamides with benzophenone-imine of glycine esters

• Ya Bai,
• Xue-Ying Wang,
• Si-Kai Zhu,
• Yan-Ting Shen,
• Sheng-Yong Zhang and
• Ping-An Wang

Beilstein J. Org. Chem. 2026, 22, 888–896, doi:10.3762/bjoc.22.69

• only provided trace product 6a (Table 1, entry 2), although its structure is very similar to CSB-1. CSB-3 based on vicinal amino-alcohol backbone also afforded trace product. The other catalysts resulted in no reaction of 2a and 5a (Table 1, entries 3–9). These results show the unique catalytic and

Diastereodivergent electrophilic trapping of α-boryl lithium derivatives

• Tereza Pavlíčková,
• Noam Orbach and
• Ilan Marek

Beilstein J. Org. Chem. 2026, 22, 882–887, doi:10.3762/bjoc.22.68

• results suggest that the stereochemical outcome is independent of the initial configuration at C2 and is instead dictated by conformational preferences of the α-boryl lithium intermediate. A simplified steric model is proposed in which lithium coordination induces a pseudo-chelated structure that controls

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

• documented in monographs and special themed journal issues, see for example [1][2][3][4][5][6][7][8][9][10]. Of special interest here are gold complexes supported by bidentate and tridentate ligands; their chemistry has been the subject of a number of reviews, covering different aspects of structure, bonding

• -mediated reaction mechanisms. Following a brief discussion of general considerations, this Perspective examines how ligand structure and the resulting trans-influence determine reactivity and stability of gold(III) complexes supported by tridentate (pincer) ligands and in bidentate chelates, including

• 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

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

• soft sulfoxide group within a single molecule also provides a basis for the preparation of metal complexes with unusual properties. The aim of the present work is to synthesize new unsymmetrical sulfoxides bearing hydrocarbon fragments derived from catechol thioethers, to study their structure and

• depending on the structure of the hydrocarbon substituent (Figure 2, curves 2–3; Figures S28–S32 in Supporting Information File 1). For compounds 1a–7a, the first irreversible two-electron redox transition is observed at 1.19–1.27 V and corresponds to the oxidation of the catechol moiety. The presence of

• ) and to 3,5-DTBC (13.1 ± 1.3 μM). The number of converted DPPH molecules per one molecule (nDPPH) for 1a is more than two. The high antiradical activity of sulfoxide 1a may be attributed to its structure, specifically to the smaller size of the alkyl substituent at the S=O group relative to the other

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

• . pneumoniae ST512. These structurally defined synthetic glycans serve as a precise molecular platform for elucidating structure-immunogenicity relationships and guiding the rational design of glycoconjugate vaccines. Results and Discussion The CPS of K. pneumoniae ST512 consists of a branched hexasaccharide

• evaluation. This work represents a key step toward the development of semi-synthetic glycoconjugate vaccines against multidrug-resistant K. pneumoniae. Structure of the K. pneumoniae ST512 CPS repeating unit and retrosynthetic analysis. Preparation of building blocks 1–4. Synthesis of hexasaccharide

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

• :1 isatin-to-diamine ratio provides the diiminoisatin, whereas a 1:2 ratio leads to the formation of a highly symmetric bis-spirooxindole scaffold. The new spirocyclic product was fully characterized by HRMS, IR and extensive 1D/2D NMR analysis, and its structure was unequivocally established by

• -proline (7), which leads to the formation of the dispirocyclic product 9 whose structure was ultimately established by X-ray diffraction after initial ambiguity based on spectroscopic data alone (Scheme 1) [16][17]. This case illustrates how condensations of isatin with bifunctional nitrogen nucleophiles

• nucleophiles are highly sensitive to subtle variations in the nucleophile structure and reaction conditions, and may lead to markedly divergent outcomes. While simple diimines are often formed under controlled stoichiometry, alternative pathways can give rise to unexpectedly condensed spirocyclic architectures

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

• products’ structure, physicochemical properties and coordination behavior (for 4,5-derivative). Both 4,5- and 1,8-diazafluorenes reacted with di(pyrid-2-yl)ketone forming di(pyridin-2-yl)methylene)-9H-4,5-diazafluorene (4,5-DPDAF) and 9-(di(pyridin-2-yl)methylene)-9H-1,8-diazafluorene (1,8-DPDAF) in 54

• -DPDAF and 1,8-DPDAF, respectively. Accordingly, the HOMO energies were −6.38 eV and −6.25 eV for 4,5-DPDAF and 1,8-DPDAF being in accordance with the high electron affinity of diazafluorenes. As a next step we solved the crystal structures of both compounds. Here we discuss the structure of 4,5-DPDAF

• -DPDAF) where Zn is four-coordinated to the nitrogens of the diazafluorene and pyridine rings forming a positively charged cyclic dimer (Figure 2d). The dimers are arranged in a herringbone-type structure via C–H···π, C–Cl···π and π-stacking interactions between diazafluorene and pyridine (Figure 2f

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

• solid-state E/Z isomerization [8][9]. Azobenzene was also incorporated into the structure of liquid crystal elastomers (LCEs) [10][11], where UV-light curing increases thermally induced LCE film actuation or even locks the film in a specific shape during flipping [10]. The phenomenon of photoactuation

• calorimetry (DSC), thermogravimetric analysis (TGA), cyclic voltammetry (CV), UV–vis absorption spectroscopy, 1H and 13C NMR, and theoretical DFT calculations were employed. Furthermore, the target compounds are designed for incorporation as photoactive copolymers into the structure of functionalized

• photoconversion could be higher. The type of halogen has only a negligible effect. The reverse switch of 1a–f induced by 430 nm light afforded the E/Z molar ratios of 73:27–92:8 with no straightforward structure–switching property relationships. The recorded half-lives of the Z-isomer in the dark () range from

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

• of insulin resistance, inflammation, and hepatic steatosis [15]. The most advanced ASK1 inhibitor in clinical development is the compound celonsertib (Scheme 2). Following this, a series of new ASK1 inhibitors were derived using selonsertib as a lead compound in a variety of structure-optimized ways

• of the minimal pharmacophores of the selective FXR agonist GW4064 and the selective ASK1 inhibitor selonsertib (GS-4997) [35][36][37]. Published structure–activity relationship (SAR) studies have identified the isoxazole moiety and terminal carboxylic acid of GW4064 [38], along with the 4

• -aliphatically substituted 4H-1,2,4-triazolopyridine biaryl scaffold of selonsertib [31][39][40], as key pharmacophores. In the co-crystal structure of hFXR-LBD with GW4064 [41], the isoxazole core coordinates the π-cation interaction between His 447 and Trp 469; the 5-isopropyl group is embedded into a

Preparation of 3-(alkylamino)imidazo[1,2-a]pyridine-2-carbaldehydes via Kornblum oxidation and unexpected ring-opening reactions of the corresponding alcohols under oxidative conditions

• Sandile J. Mkhize,
• Memory Zimuwandeyi,
• Manuel A. Fernandes,
• Amanda L. Rousseau and
• Moira L. Bode

Beilstein J. Org. Chem. 2026, 22, 763–770, doi:10.3762/bjoc.22.58

• transcriptase in due course. Examples of biologically active imidazo[1,2-a]pyridines. Compounds envisaged for synthesis. Previously reported 3-amino-2-carboxylic acid derivatives. Single crystal X-ray structure of 18a. ORTEP diagram drawn at 50% probability level. Different oxidative cleavage products obtained

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

• inhibition of root growth of Arabidopsis thaliana. The RLIT data is compared with those previously reported for two series of compounds having the same substitution pattern at C-22 but different structure in ring A. This comparison revealed that a 2α,3α-dihydroxy configuration is more active than a 3

• -carbonyl or 3β-hydroxy function in this ring. Additionally, the accumulation of the dephosphorylated form of the BES1 protein, which is part of the BRs signaling pathway and control their activity, has been evaluated as well. The results are analyzed in terms of BR analog’s structure and compared with

• binding energies obtained from a docking study. In this way, it is intended to assess the effect of chemical structure on the initial and one intermediate step, and on the final plant response. Our results show that the binding of BR analogs to the active site, which initiate the signaling process, and

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

• product, we used density functional theory (DFT) and conformational search techniques based on tight-binding methods to find the energetically minimized structure of 7 (see Supporting Information File 1 for details on all computations). The lowest energy structure is depicted in Figure 3. It shows a

• structure somewhat rotated out of planarity (dihedral angles between aromatic C–C and vinylic CH are 34°). This presumably still allows for some conjugative stabilization from the aromatic rings to the enone π-systems and reduces eclipsing interactions between the ortho-methyl groups and the vinylic H

• calculated transition state structure TS-12a shows a flattened half-chair conformer, which has the aryl rings in pseudo-equatorial positions. TS-12b adopts a different shape, closer to a flattened chair which again allows both aryl groups to be equatorial. There has been much debate in the literature

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

• efficient synthesis of a series of polysubstituted enantioenriched pyrrolidine derivatives 48 possessing a spiroindene molecular structure (Scheme 22) [59]. Based on the results of DFT calculations, it was suggested that the [6 + 3] cycloaddition product for benzofulvene 47 loses aromatic stability and

• configuration and the structure of the transition state [88]. In [1], we developed an efficient protocol for the diastereo- and regioselective synthesis of spiro[cyclopropa[a]pyrrolizine-2,2'-indenes] 128–131 using 1,3-dipolar cycloaddition reactions of stable azomethine ylide 123, obtained in situ by

• constructing the structure of spiro[indoline-3,2'-pyrrole]. In a study by Zhao and co-workers, asymmetric 1,3-dipolar cycloaddition of azomethine ylides derived from isatin and benzylamines to maleimides was catalyzed by Cinchona alkaloid-based squaramide L24 (Scheme 49) [99]. The cycloaddition proceeded

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

• analysis. During our comparison of spectroscopic and chiro-optical data for (+)-salicifoliol (1) with reported literature values [16], we noted that an earlier paper [15] reporting the chemical structure of 1 had misdrawn the stereochemistry. The stereochemical assignment for (+)-salicifoliol (1) has been

• and were also fully characterized following NMR, UV–vis, [α]D, ECD, and ESIMS data analyses. An example of our structure elucidation studies is described below, which focuses on the brominated pinoresinol enantiomer (+)-5,5'-dibromopinoresinol (5). HRESIMS data revealed an ion at m/z 536.9519 [M + Na

• planar structure assignment for 5. Moreover, the relative configuration of the semisynthetic derivative 5 was assigned following ROESY data analysis. Following the slow evaporation of a methanolic solution of (+)-eudesmin (3), suitable crystals were obtained for X-ray crystallographic studies (Figure 4

Synthesis of depressin, cryptomeridiol and 4-epi-cryptomeridiol enabled by a terpenoid chiral pool-producing platform

• Yao Kong,
• Tao Wang,
• Chen Wang,
• Pengcheng Zhang,
• Yuanning Liu,
• Kaibiao Wang,
• Fen Liu,
• Hongli Jia and
• Zhengren Xu

Beilstein J. Org. Chem. 2026, 22, 683–690, doi:10.3762/bjoc.22.53

• ). Depressin (1) was isolated from the soft coral Simularia depressa collected from Hainan Province of China [13]. Its structure contains the typical bicyclo[12.1.0]pentadecane casbane diterpenoid skeleton with a cis-disubstituted cyclopropane unit, and a keto group at C5, which is the most frequently oxidized

• ). Supporting Information Supporting Information File 5: Materials, synthetic methods and copies of NMR spectra for all compounds. Supporting Information File 6: X-ray crystal structure of 16. Funding We are grateful to the National Natural Science Foundation of China (No. 82574274) for the financial support.

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

• structure by a heteroatom (oxygen or nitrogen) in donor–acceptor, push–pull NBD derivatives are reported. In a computational study, Pawar and co-workers [7] further expanded the NBD structure by elongating the unsaturated bridge with different heteroatoms or functional groups. Azobenzenes, interconverting

Using generative AI to transform peptide hits into small molecule leads

• Joshua Mills and
• Yu Heng Lau

Beilstein J. Org. Chem. 2026, 22, 672–679, doi:10.3762/bjoc.22.51

• potential for new AI-based tools to expedite the structure-based transformation of peptide hits into small molecule leads. In this Perspective, we highlight how AI-enabled prediction and design tools can potentially span the entire workflow from peptide to small molecule: target protein structure prediction

• drugs derived from native peptide substrates. A classic example is the ACE inhibitor captopril, an analogue of a snake venom peptide, the development of which has been cited as an early success story for structure-based rational drug design [12][13]. Despite the long history, there is still no

• experimental co-crystal structure of the bound complex, standard medicinal chemistry principles are used to probe structure–activity relationships (SAR) and determine the key interactions that form a minimal pharmacophore, supported by classical physics-based molecular modelling methods such as molecular

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

• ; PROTAC; protein–protein interaction; selectivity; ubiquitination; Introduction The cell is the fundamental unit of structure and function in the human body [1][2]. More than 20,000 proteins act in concert to regulate the entire cellular life process [1]. To date, dysregulated protein function has been

• imperative to minimize the degradation of non-targeted proteins. While conventional inhibitors often exhibit lacking selectivity towards proteins with high sequence similarity, PROTACs leverage their heterobifunctional structure to achieve exquisite selectivity [24][27]. This is accomplished by fine-tuning

• -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

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

• broader kinome perturbation. The first design objective was therefore to identify a suitable exit vector for linker attachment that would allow productive E3-ligase recruitment without compromising the established binding geometry of CAM4066. Inspection of the co-crystal structure of 1 bound to CK2α

• geometry, and E3 ligase selection. Conclusion In summary, we have developed a modular synthetic platform for the construction of CK2-targeting degraders 23–26, 28, and 29 based on the selective bivalent inhibitor CAM4066. Structure-guided design enabled identification of a solvent-accessible exit vector

• degraders and lays the groundwork for future optimisation toward achieving effective and selective CK2 degradation. Design strategy and validation. A) Structure of CAM4066 (1) that served as a model design for the development of CK2 targeted PROTACs with a general structure 2. Crystal structures showcased