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

• colorless and amorphous substance. The molecular formula was determined as C18H22O5 by high resolution electrospray ionization mass spectrometry (HRESIMS), thus containing one more oxygen atom than the melifoliones. The UV spectrum showed a maximum at 250 nm, typical for an α,β-unsaturated carbonyl

• atmospheric oxygen. Oxidation with potassium peroxodisulfate (Oxone®) according to a method by Carreño et al. [7] led to a complex mixture of compounds in which the quinols 3 and 4 could be excluded. While oxidation with alkaline hypochlorite solution gave a mixture of not identified chlorinated products

• ). Since all attempts to prepare the quinols 3 or 4 via oxidation of melifoliones had failed, the combined use of ferricyanide and hydrogen peroxide in alkaline solution was finally used. Under these conditions, superoxide and hydroxy radicals or even singlet oxygen can be formed [10][11]. After addition

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

• formation of 252. Next, conditions reported by Kishi and co-workers were applied for the nucleophilic substitution of the chloride by the oxygen from the tetrahydrofuran ring towards 253 [94], before an adjacent secondary alcohol group reopened the bicyclic cationic intermediate. Cleavage of the TBDMS

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

• donor atoms, a carbonyl oxygen and a hydroxy oxygen, that can simultaneously coordinate to a uranyl ion [77]. In supramolecular systems, not all hydroxamic acid groups necessarily bind uranyl ions, as steric hindrance and site accessibility can limit coordination to a subset of available sites [78]. A

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

• on the differences of the heteroatom and substituents on the (E)-alkene moiety [11][12]. The half-lives of the optical activity optt1/2 of 1aa (X = O, Y = H) and 1ba (X = NTs, Y = H) were 380 h and 56.7 h at 25 °C, respectively, indicating that the stereochemical stability of the oxygen-containing

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

• the compounds 7 and 8, as shown in Figure 5, reveals important insights into their electronic structures relevant to biomedical applications [60]. For compound 7, nitrogen and oxygen atoms exhibited high negative charges of −0.588 (N), −0.533 (O1), −0.511 (O2), and -0.500 (O3) as shown in Figure 5a

• character for (C1) and (C2), with a Mulliken charge value of 0.597 for compound 7, and for compound 8, (C1) and (C2) are 0.598 and 0.599. This electron charge distribution clearly indicates that the nitrogen atom has a more negative character than oxygen and selenium. Still, the oxygen atom has a

• regions indicate more electronegative areas. For both compounds 7 and 8, the oxygen atoms exhibit the highest electronegativity, indicating potential nucleophilicity and the ability to readily participate in hydrogen bonding with amino acids through non-covalent interactions. Overall, MEP mapping reveals

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

• possess just limited functionalization capabilities unless synthetically more valuable groups are introduced into their structures. Due to the synthetic approaches well-developed in the first decades of calixarene chemistry, these groups can be arranged in a certain number and order at the phenolic oxygen

• structures of calixarenes and related macrocycles [75][76][77][78]. Many of them relied on the introduction of propargyl or azidoalkyl groups to the phenolic oxygen atoms for synthesizing the CuAAC-ready calixarene cores. Within this area of research, our studies on the CuAAC reactions applied to cone

• calixarene tetraaryl- and tetraarylsulfonylureas if co-dissolved in a 1:1 molar ratio [51][52][53]. Furthermore, tetraureas 47–51 contain relatively bulky substituents at the phenolic oxygen atoms, which may influence the conformational behavior of the macrocycle (e.g., pinched cone-to-pinched cone

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

• remains a significant and persistent challenge in synthetic chemistry [41][42][43][44]. Classical approaches for activating non-activated amides typically rely on transition-metal catalysts acting as Lewis acids, which coordinate to the carbonyl oxygen and enhance electrophilicity (Scheme 1d). However

• employed as reliable tools to activate amide bonds through coordination with the amide oxygen lone pair [45]. Although the substrate scope of such methods remains limited, several successful examples with hindered amides have recently been reported. In 2019, Shimizu et al. reported the esterification of

• restored after recalcination prior to reuse. Based on DFT calculations, the authors proposed that octanol is deprotonated and coordinated to Ce, while the amide substrate is simultaneously activated electrophilically through coordination to the Ce center (A). This dual activation enables the lattice oxygen

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

• metalation of trimethylsilylacetylene or benzyl propargyl ether with ethylmagnesium bromide. After quenching, removal of the MOP protecting group, and oxidation by atmospheric oxygen the nitroxides 2d and 2e were isolated in 64% and 66% yields, respectively. Terminal alkynes can be converted into

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

• with oxygen via 2 the ketal structure 3 can decarboxylate [50], generating another high-energy ferryl-oxo species 4 (bound with succinate) which can lead to hydroxylation or carbocation chemistry [51]. Finally, other classes of tailoring enzymes can also act as electrophiles and lead to ring-size

• 78 after proton exchange. The same intermediate diketone could be theoretically obtained directly from singlet-oxygen-mediated oxidation of the olefin through hydroperoxide 81 and Hock rearrangement [130][131][132]. Finally, euphnerin B (76) is furnished after 1,2-alkyl shift in 83 towards the C-5

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

• contacts: the barbiturate ring forms hydrogen bonds with water molecules through C=O···H–O and N–H···O–H interactions; the amide group of the barbiturate ring is engaged in a C=O···H–N hydrogen bond with the carbonyl oxygen of the maleimide fragment; additionally, a C=O···H–CH2 contact is observed between

• the hydrogen atom of the maleimide methyl group and the carbonyl oxygen of an adjacent maleimide ring. The crystal structure of compound 4b exists as a solvate. The oxygen atom of a water molecule forms a hydrogen bond with the amide hydrogen of the barbiturate fragment (N–H···O–H = 2.783 Å), while

• corresponding intermolecular interactions cannot be precisely determined. However, the nature of these interactions can be described as follows: one of the hydrogen atoms of dichloromethane contacts with the oxygen atoms of carbonyl groups from two nearby barbiturate rings. The estimated contact distances are C

Arene activation via π-bond localization: concepts and opportunities

• Paul Meiners,
• Julian J. Melder and
• Tobias Morack

Beilstein J. Org. Chem. 2026, 22, 257–273, doi:10.3762/bjoc.22.19

• nucleophile toward diphenylketene to generate a cyclohexadienyl intermediate that captures a second ketene molecule (Figure 11B). Subsequent ring closure furnishes a product complex that, upon oxidation with molecular oxygen, liberates the [2 + 2 + 2] bis-adduct, dihydroisochroman-3-one, in 73% yield. This

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

• , is likely due to the electronic effects within pyranoquinoline. As an enol ester conjugated with an amide and an aromatic ring, electron-withdrawing groups decrease electron density on the enol OH, while aliphatic substituents (methyl, ethyl) increase electron density on the alcohol oxygen. This

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

• placed into a 250 mL three-necked round-bottomed flask, ensuring the proper amount of space for the reaction. It was then dissolved in 100 mL of glacial acetic acid, which served as the solvent. To create an inert atmosphere and prevent any unwanted reactions with oxygen, the solution was purged with

• no moisture or oxygen interfered with the reaction. Following this, 3-(9H-carbazol-9-yl)phenylboronic acid (5, 1.09 g, 3.80 mmol) was added to the flask. The mixture was stirred for 5 minutes to allow proper mixing. To facilitate the Suzuki coupling reaction, an aqueous solution of potassium

Base-promoted deacylation of 2-acetyl-2,5-dihydrothiophenes and their oxygen-mediated hydroxylation

• Vladimir G. Ilkin,
• Margarita Likhacheva,
• Igor V. Trushkov,
• Tetyana V. Beryozkina,
• Vera S. Berseneva,
• Vladimir T. Abaev,
• Wim Dehaen and
• Vasiliy A. Bakulev

Beilstein J. Org. Chem. 2026, 22, 192–204, doi:10.3762/bjoc.22.13

• methoxide afforded the deacylated products. Conversely, the treatment with sodium ethoxide in an oxygen saturated ethanolic solution produced 2-hydroxy substituted 2,5-dihydrothiophenes. Keywords: 2-acetyl-2,5-dihydrothiophenes; deacylation; 2-hydroxy-2,5-dihydrothiophenes; transformations; Introduction

• oxidation of ketones includes C‒C-bond cleavage, and carboxylic acids are predominantly formed. This can be achieved by the treatment of acyclic ketones with hypohalites [13], in the nitroarene-catalyzed oxidation with oxygen under basic conditions [14] or by the use of hypervalent iodine compounds (Scheme

• ], oxygen [23][24] or with m-CPBA (Scheme 1B) [25][26] or non-catalytic transformations [27]. The few known oxidative transformations of o- or p-hydroxy-substituted aromatic ketones, that in most cases lead to phenols, involve the use of hydrogen peroxide as an oxygen source (Scheme 1C) [20][25][26

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

• , oxygen atoms red, and chloride ion green. b) The crystal packing reveals alternating layers, a polar layer with hydrogen bonds (black dashed lines), and a hydrophobic layer with π–π-stacking (grey dashed lines). SCXRD and XRPD spectra of different preparations of 1·HCl. Blue: SCXRD spectrum of 1·HCl. Red

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

• its multiple oxidation states and ability to form diverse bonds with carbon, nitrogen, and oxygen. This versatility underpins the pivotal roles of organosulfur compounds in pharmaceuticals, catalysis, and materials science [1][2][3][4]. Among these, sulfilimines (R2S=NR') have attracted growing

• interest due to their unique reactivity and value as intermediates in molecular design and medicinal chemistry [5][6][7][8][9][10] (Figure 1). In contrast, sulfinimidate esters, which feature a tetravalent sulfur–oxygen (S(=N)–O) motif, remain a relatively underexplored subclass of organosulfur compounds

Total synthesis of natural products based on hydrogenation of aromatic rings

• Haoxiang Wu and
• Xiangbing Qi

Beilstein J. Org. Chem. 2026, 22, 88–122, doi:10.3762/bjoc.22.4

• catalytic hydrogenation are relatively rare. This is partly due to the high stability of six-membered aromatic heterocycles, such as pyridine, making it difficult to interrupt the aromaticity under mild conditions [34]. Furthermore, the heteroatoms (such as nitrogen and oxygen atoms) within the saturated

• oxygen atoms from the substrate and the metal catalyst, which fixed the conformation of the polycyclic scaffold. As a result, the top face is sterically less favored, thereby hydrogen approaches from the opposite face. The subsequent addition of another two equivalents of hydrogen also supported this

Advances in Zr-mediated radical transformations and applications to total synthesis

• Hiroshige Ogawa and
• Hugh Nakamura

Beilstein J. Org. Chem. 2026, 22, 71–87, doi:10.3762/bjoc.22.3

• alkyl radicals to afford compound 25 as a major product [16][17][18][19][20]. In contrast, this study revealed that the strong affinity of zirconium for oxygen reverses this trend, leading instead to compound 24 as a predominant product. The generality of the reaction was demonstrated with a variety of

• zirconocene catalysts using substrates 23l–n. In both cases, the regioselectivity was found to be reversed. With titanocene, the reaction proceeds through the more stable, substituted radical, whereas with zirconocene, the high oxygen affinity of zirconium is the key factor driving the opposite

• strong affinity of zirconium for oxygen atoms [4][21]. Building on this concept, they envisioned that a similar reaction system could be applied to the homolytic cleavage of C–O bonds in alcohols and ethers. When benzyl alcohol and ether derivatives 49 were treated with zirconocene in the presence of a

One-pot synthesis of ethylmaltol from maltol

• Immanuel Plangger,
• Marcel Jenny,
• Gregor Plangger and
• Thomas Magauer

Beilstein J. Org. Chem. 2025, 21, 2755–2760, doi:10.3762/bjoc.21.212

• through fermentation, or a synthetic intermediate derived thereof is being utilized. For example, the 1969 Pfizer patent describes the oxidation of kojic acid (3) with molecular oxygen to comenic acid, which is then decarboxylated to yield pyromeconic acid. An aldol addition with acetaldehyde followed by

Sustainable electrochemical synthesis of aliphatic nitro-NNO-azoxy compounds employing ammonium dinitramide and their in vitro evaluation as potential nitric oxide donors and fungicides

• Alexander S. Budnikov,
• Nikita E. Leonov,
• Michael S. Klenov,
• Andrey A. Kulikov,
• Igor B. Krylov,
• Timofey A. Kudryashev,
• Aleksandr M. Churakov,
• Alexander O. Terent’ev and
• Vladimir A. Tartakovsky

Beilstein J. Org. Chem. 2025, 21, 2739–2754, doi:10.3762/bjoc.21.211

• overcome existing constraints in functional group compatibility, efficiency, and reagent scope. In this regard, the direct formation of nitrogen-nitrogen or nitrogen-oxygen bonds presents a significant challenge due to the variety of possible side processes and the low thermodynamic driving force for N–N

Competitive cyclization of ethyl trifluoroacetoacetate and methyl ketones with 1,3-diamino-2-propanol into hydrogenated oxazolo- and pyrimido-condensed pyridones

• Svetlana O. Kushch,
• Marina V. Goryaeva,
• Yanina V. Burgart,
• Marina A. Ezhikova,
• Mikhail I. Kodess,
• Pavel A. Slepukhin,
• Alexandrina S. Volobueva,
• Vladimir V. Zarubaev and
• Victor I. Saloutin

Beilstein J. Org. Chem. 2025, 21, 2716–2729, doi:10.3762/bjoc.21.209

• conformation, with a deviation of the oxygen atoms O(1) by 0.5 Å for 5ctc and nitrogen atoms N(1) by 0.4 Å for 5ctt. In trans-junction, bicycles 4att, 4atc (Figure 2c,d) have a flattened fixed skeleton with a dihedral angle of 24.8–27.3° (see Table S9, in Supporting Information File 1), in which the

Recent advancements in the synthesis of Veratrum alkaloids

• Morwenna Mögel,
• David Berger and
• Philipp Heretsch

Beilstein J. Org. Chem. 2025, 21, 2657–2693, doi:10.3762/bjoc.21.206

Synthesis of new tetra- and pentacyclic, methylenedioxy- and ethylenedioxy-substituted derivatives of the dibenzo[c,f][1,2]thiazepine ring system

• Gábor Berecz,
• András Dancsó,
• Mária Tóthné Lauritz,
• Loránd Kiss,
• Gyula Simig and
• Balázs Volk

Beilstein J. Org. Chem. 2025, 21, 2645–2656, doi:10.3762/bjoc.21.205

• ring systems containing a two or three-carbon linker between the nitrogen atom of the thiazepine ring and the nitrogen (3), oxygen (4), or sulfur (5) atom linked to the C(11) atom [2][3]. In continuation of our efforts to study new ring systems, we decided to synthesize new tetra- and pentacyclic

Thiazolidinones: novel insights from microwave synthesis, computational studies, and potentially bioactive hybrids

• Luan A. Martinho,
• Victor H. J. G. Praciano,
• Guilherme D. R. Matos,
• Claudia C. Gatto and
• Carlos Kleber Z. Andrade

Beilstein J. Org. Chem. 2025, 21, 2618–2636, doi:10.3762/bjoc.21.203

• aldehyde 1, activated by protonation of the oxygen atom through structure ii, forming the intermediate aldol iii. In the presence of EDDA, water elimination occurs in intermediate iv, yielding the Knoevenagel adducts 3 or 4. Synthesis of novel imidazo[1,2-a]pyridine–thiazolidinone hybrids To further

Visible-light-driven NHC and organophotoredox dual catalysis for the synthesis of carbonyl compounds

• Vasudevan Dhayalan

Beilstein J. Org. Chem. 2025, 21, 2584–2603, doi:10.3762/bjoc.21.200

• /organophotocatalyzed oxidative Smiles rearrangement of O-aryl aldehydes 26 has been developed using oxygen as the terminal oxidant under visible-light dual catalysis. This approach afforded highly functionalized 2-hydroxyarylbenzoates 27, tolerating electron-deficient and electron-rich substituents. The C–O bond

• cleavage and the new C–O bond formation process were achieved using NHC (10 mol %), a photocatalyst (2 mol %), and DABCO (1.5 equiv), providing the corresponding aryl salicylates 27 in moderate to good yields. Mechanistic studies support the oxidation of the Breslow intermediate by oxygen in the presence