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

• towards 113 upon acidic treatment and TBDMS-protection. Reduction, cleavage of the silyl-protecting groups and acetylation led to tetrahydropyran 114. Lewis acid-catalyzed C-allylation, cross metathesis, basic cleavage of the acetate motifs and transesterification enabled the DBU-induced isomerization of

• , Nicolaou and co-workers merged both building blocks within a Ni(II)/Cr(II)-catalyzed NHK reaction using chiral ligand 206 (Scheme 23) [95]. Upon treatment with DBU, 3-methylenetetrahydrofuran 201 was obtained in 56% yield over two steps. PMB-deprotection, iodination and selective reduction of the ester

• to afford 245. HWE-reaction with 250 towards 246 and reduction with PhSiH3 led to 247 as a separable mixture of epimers (247:epi-247 = 1.5:1). Notably, by the treatment of epi-247 with DBU, again an epimeric mixture was formed (247:epi-247 = 1:1) and another fraction of 247 was isolated. The products

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

• , following the method reported by Camiolo and Gale [21], affording a yield of 85%. Among several procedures used for the direct hydroxyaminolysis of carboxylic ester substrates, Beillard et al. highlighted the superiority of a DBU (1,8-diazabicyclo[5.4.0]undec-7-ene)-mediated route over the classical methods

• , particularly when the starting compounds are sterically hindered [50]. In this regard, a methanolic solution of PCP ester was allowed to react with a large excess of methanolic hydroxylamine in the presence of DBU for one night. At this stage, the formation of precipitated PCP hydroxamic acids was verified

• by the disappearance of the characteristic signals of the ethyl group and an upfield shift of 0.27 ppm for the O–CH2 protons compared to the spectrum of the PCP ester. However, signals corresponding to DBU at 1.5, 2.3, and 3.1 ppm were still observed (Supporting Information File 1, Figure S7) despite

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

• in the synthetic route. Therefore, the reaction conditions of 2 and a selected benzaldehyde 3a with two MOM-protected OH groups were optimized. Firstly, various organic and inorganic bases were screened (Table 1). The commonly used organic bases, such as Et3N, DBU, and pyridine, seemed not effective

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

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

• barbiturates [25]. Other methods include the DBU-mediated stereospecific cyclopropanation of barbiturate-based olefins with benzyl chlorides, developed by Chang’s group for the synthesis of spirobarbiturate-cyclopropanes [26]. Another interesting structural fragment is the pyrrolizidine heterocycle, which is a

Synthesis and applications of alkenyl chlorides (vinyl chlorides): a review

• Daniel S. Müller

Beilstein J. Org. Chem. 2026, 22, 1–63, doi:10.3762/bjoc.22.1

• reagents such as Grignards (not shown) [81]. More recently, a collaborative study between Bayer and researchers at the University of Strasbourg disclosed a ruthenium-catalyzed halide exchange of vinyl fluorosulfonates, which were prepared from ketones and sulfuryl fluoride (SO2F2) in the presence of DBU

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

• hydrolysis of 9e furnished ethylmaltol (1) in 95% yield. Screening of different bases for the methylation step of 8e revealed LiHMDS to be superior to NaHMDS. Various tert-butoxide bases as well as 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) were ineffective for deprotonation (see Supporting Information File 1

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

• rearrangement was carried out with trifluoromethanesulfonic anhydride leading to a mixture of regioisomers 23 and 27, with 23 being convertible to 27 by addition of DBU. The A–E-rings have, thus, been installed with correct stereoconfiguration, therefore the last steps of the sequence focused on the

Efficient solid-phase synthesis and structural characterization of segetalins A–H, J and K

• Liangyu Liu,
• Wanqiu Lu,
• Quanping Guo and
• Zhaoqing Xu

Beilstein J. Org. Chem. 2025, 21, 2612–2617, doi:10.3762/bjoc.21.202

• resin as the solid support, enabling mild cleavage of the partially protected linear peptide precursor [21]. Efficient Fmoc deprotection was achieved using a solution of 1% pyridine and 1% 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) in N,N-dimethylformamide (DMF) [22]. For the assembly of the linear

Assembly strategy for thieno[3,2-b]thiophenes via a disulfide intermediate derived from 3-nitrothiophene-2,5-dicarboxylate

• Roman A. Irgashev

Beilstein J. Org. Chem. 2025, 21, 2489–2497, doi:10.3762/bjoc.21.191

• formation of carboxylic acid 9bA, isolated in 71% yield (Scheme 7). In addition, an attempt to cyclize 6b in the presence of DBU without a solvent at 110 °C led to significant destruction of the substrate and product 9b was obtained with a yield of about 20%. Cyclization of substrate 4a with NaH in toluene

Ex-situ generation of gaseous nitriles in two-chamber glassware for facile haloacetimidate synthesis

• Nikolai B. Akselvoll,
• Jonas T. Larsen and
• Christian M. Pedersen

Beilstein J. Org. Chem. 2025, 21, 2465–2469, doi:10.3762/bjoc.21.188

• used building blocks in glycosylations. For the synthesis chamber (A) was loaded with trifluoroacetamide (6 equiv) in pyridine. In the other chamber (B), the hemiacetal (ca. 500 mg, 1 equiv) was dissolved in CH2Cl2 together with a catalytic amount of DBU. Upon addition of trifluoroacetic anhydride

• is not easily done as the system is now under pressure. The chamber was then opened to release excess gas (on small scale) and the product in chamber B can be obtained by concentration and purification. The use of other bases than DBU, was also investigated. Similar to the synthesis of

• trichloroacetimidates K2CO3 was effective for the synthesis of β-acetimidates [26], whereas polystyrene-supported DBU [27] was found to be less effective and DBU was therefore the preferred catalyst. The synthesis of perbenzylated α-glucosyl trifluoroacetimidate 3 proceeded in 52% yield on a preparative scale, with DBU

Transformation of the cyclohexane ring to the cyclopentane fragment of biologically active compounds

• Natalya Akhmetdinova,
• Ilgiz Biktagirov and
• Liliya Kh. Faizullina

Beilstein J. Org. Chem. 2025, 21, 2416–2446, doi:10.3762/bjoc.21.185

• ]undec-7-ene (DBU) in benzene resulted in high yield of β-hydroxyaldehyde 6. Through a series of synthetic transformations, the target products (−)-taiwaniaquinones A (7), F (8), G (9), and H (11), (−)-taiwaniaquinol B (10) and (−)-dichroanone (12) were obtained from intermediate 6 (Scheme 2). An

• destruction of the main amount of dialdehyde, cyclopentanediol 21 was isolated with a yield of 24%. This synthetic block is promising for the synthesis of gibboside (22) [20]. Following the second direction, ozonolysis of the double bond in compound 14 and subsequent treatment of the ozonide with DBU resulted

• acid (DMOA), are a large series of hybrid natural products with a huge structural diversity and impressive biological activity [50]. Attempts by the authors to use acidic (TiCl4, TMSI, SnCl4), basic (NaOMe, t-BuONa, Et3N, DBU, DMAP) and thermal conditions (PhMe, 110 °C) failed to give the desired

Electrochemical cyclization of alkynes to construct five-membered nitrogen-heterocyclic rings

• Lifen Peng,
• Ting Wang,
• Zhiwen Yuan,
• Bin Li,
• Zilong Tang,
• Xirong Liu,
• Hui Li,
• Guofang Jiang,
• Chunling Zeng,
• Henry N. C. Wong and
• Xiao-Shui Peng

Beilstein J. Org. Chem. 2025, 21, 2173–2201, doi:10.3762/bjoc.21.166

• at the anode to generate imine intermediate C. Simultaneously, treatment of 39a with I+ and the following intramolecular nucleophilic cyclization produced C. The elimination of a proton from C afforded the intermediate D. In the presence of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), the intramolecular

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

The application of desymmetric enantioselective reduction of cyclic 1,3-dicarbonyl compounds in the total synthesis of terpenoid and alkaloid natural products

• Dong-Xing Tan and
• Fu-She Han

Beilstein J. Org. Chem. 2025, 21, 2085–2102, doi:10.3762/bjoc.21.164

• 69 and lactone 70 at 456 nm with fac-Ir(ppy)3 as the photocatalyst furnished a mixture of isomeric olefins. Finally, DBU-promoted the isomeric olefins conjugation and removal of the two silyl ether completed the first total synthesis of (+)-randainin D (13). Total synthesis of (−)-hunterine A and

Bioinspired total syntheses of natural products: a personal adventure

• Zhengyi Qin,
• Yuting Yang,
• Nuran Yan,
• Xinyu Liang,
• Zhiyu Zhang,
• Yaxuan Duan,
• Huilin Li and
• Xuegong She

Beilstein J. Org. Chem. 2025, 21, 2048–2061, doi:10.3762/bjoc.21.160

• additions, respectively. This result suggests that the addition fully went from the upper face and the left-oriented isopropyl showed no steric effect to control the regioselectivity. With free amide 50a and 50b in hand, the mixture was treated with DBU to promote aza-Michael addition to afford lactam

Synthesis of N-doped chiral macrocycles by regioselective palladium-catalyzed arylation

• Shuhai Qiu and
• Junzhi Liu

Beilstein J. Org. Chem. 2025, 21, 1917–1923, doi:10.3762/bjoc.21.149

• could be viewed as the aza[14]metacyclophane derivatives, in which two benzene rings are replaced by two pyrenes. The Pd-catalyzed arylation of 3a with Pd(OAc)2, PMe(t-Bu)2·HBF4 and DBU under microwave conditions gave two isomeric macrocycles MC1 and MC2 with four newly formed C–C bonds in yields of 5

• . Synthesis of N-doped macrocycles MC1, MC2, and MC3. Reaction conditions: a) Pd2(dba)3, Pt-Bu3·HBF4, NaOt-Bu, toluene, 110 °C, 24 h. 3a: 16%; 3b: 10%. b) Pd(OAc)2, PMe(t-Bu)2·HBF4, 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), DMAc, microwave, 170 °C, 5 h. MC1: 5%; MC2: 90%; MC3: 85%. Supporting Information

Catalytic asymmetric reactions of isocyanides for constructing non-central chirality

• Jia-Yu Liao

Beilstein J. Org. Chem. 2025, 21, 1648–1660, doi:10.3762/bjoc.21.129

• ring were proven to be suitable substrates to react with tert-butyl isocyanoacetate, affording 3-heteroarylpyrroles 41 in 55–99% yield with 70–96% ee. In these cases, additional 2.0 equivalents of DBU were required to facilitate the conversion from the [3 + 2] cycloadducts to the final products

Reactions of acryl thioamides with iminoiodinanes as a one-step synthesis of N-sulfonyl-2,3-dihydro-1,2-thiazoles

• Vladimir G. Ilkin,
• Pavel S. Silaichev,
• Valeriy O. Filimonov,
• Tetyana V. Beryozkina,
• Margarita D. Likhacheva,
• Pavel A. Slepukhin,
• Wim Dehaen and
• Vasiliy A. Bakulev

Beilstein J. Org. Chem. 2025, 21, 1397–1403, doi:10.3762/bjoc.21.104

• thioamides 1h,i,k,n,o,s,t,v,w,y,z (general procedure). A mixture of the corresponding thioacetamide (1.0 equiv), aldehyde (1.1–4.0 equiv) and DBU (0.1 equiv or 1.0 equiv for 1h,o) in ethanol was stirred for 2–23 h at room temperature. For thioamide 1i, the reaction time was 96 h at 80 °C. The formed

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

Recent advances and future challenges in the bottom-up synthesis of azulene-embedded nanographenes

• Bartłomiej Pigulski

Beilstein J. Org. Chem. 2025, 21, 1272–1305, doi:10.3762/bjoc.21.99

• two azulene moieties (Scheme 19) [97]. Precursors 148 and 149 were annulated using DBU (1,8-diazabicyclo(5.4.0)undec-7-ene) in NMP (N-methyl-2-pyrrolidone) at 180 °C. The resulting PAHs 150 and 151 were isolated in relatively good yields (40% and 48%, respectively) and exhibited typical azulene-like

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

• heteroatom for the synthesis of functionalized oxindoles was also reported in 2013 [3]. In this study, DBU was employed as a ligand and TBHP as an oxidant. A series of ethers, including 1,2-dimethoxyethane, THF, 1,4-dioxane, tetrahydro-2H-pyran, 2,3-dihydrobenzofuran, tetrahydro-2H-thiopyran, and N

Recent advances in synthetic approaches for bioactive cinnamic acid derivatives

• Betty A. Kustiana,
• Galuh Widiyarti and
• Teni Ernawati

Beilstein J. Org. Chem. 2025, 21, 1031–1086, doi:10.3762/bjoc.21.85

• with a catalytic base has also been applied to prepare cinnamate esters. For example, Heller and co-workers (2021) synthesized the ester 141 catalyzed by DBU which functioned as a Brønsted base for the alcohol (Scheme 43A) [81]. Impressively, the method could be scaled up to a multigram scale

Substituent effects in N-acetylated phenylazopyrazole photoswitches

• Radek Tovtik,
• Dennis Marzin,
• Pia Weigel,
• Stefano Crespi and
• Nadja A. Simeth

Beilstein J. Org. Chem. 2025, 21, 830–838, doi:10.3762/bjoc.21.66

• further issue, we observed some instability at acidic pH during analysis. Thus, we tested the stability of NAc-PAP-H (1 mM, MeOH, ambient conditions, 2 h) at pH 2, 12, and in the presence of DBU (10−2 M) and found that the acetyl group was lost (cf. Supporting Information File 1, section 2.4). UV–vis

Recent advances in the electrochemical synthesis of organophosphorus compounds

• Babak Kaboudin,
• Milad Behroozi,
• Sepideh Sadighi and
• Fatemeh Asgharzadeh

Beilstein J. Org. Chem. 2025, 21, 770–797, doi:10.3762/bjoc.21.61

• ). Although using other solvents improved the solubility, it reduced the reaction yield. Ammonium thiocyanate is used as a sulfur source in the presence of DBU as a base and n-Bu4NBF4 as an electrolyte. When electron-donating groups were present at the C2-benzene ring, the reaction yield was higher than when

• the rings contained electron-withdrawing groups. It is suggested that the reaction proceeded via single-electron oxidation of thiocyanate at the anode. DBU was used in the reaction for a simple nucleophilic substitution of phosphonate with a cyanide group in the formed intermediate (Scheme 28). In