Methyltransferases from RiPP pathways: shaping the landscape of natural product chemistry

• Maria-Paula Schröder,
• Isabel P.-M. Pfeiffer and
• Silja Mordhorst

Beilstein J. Org. Chem. 2024, 20, 1652–1670, doi:10.3762/bjoc.20.147

• ) as a co-product, which strongly inhibits various MTs [16][17][18][19]. To overcome these limitations, numerous in situ SAM supply and SAM regeneration systems have been developed [4][20][21][22][23][24][25][26], thereby enabling preparative biocatalytic scale methylation reactions [27]. Such

• biocatalytic applications. The co-crystallisation of LahSB with bound SAH provides important details about the structure–function relationship, the substrate–enzyme interaction, and the cofactor binding site (Figure 5). This structural information, including the residues involved in binding, is essential for

• cyclised core peptide to exert its effects on the precursor peptide. Furthermore, SAM was shown to be an obligate co-substrate for OlvSA [71]. Crystallographic data of OlvSA is not yet available. The predicted three-dimensional structure displays substantial differences from the crystal structure of LahSB

Polymer degrading marine Microbulbifer bacteria: an un(der)utilized source of chemical and biocatalytic novelty

• Weimao Zhong and
• Vinayak Agarwal

Beilstein J. Org. Chem. 2024, 20, 1635–1651, doi:10.3762/bjoc.20.146

• NRPS-derived macrolactam ureidopeptide, bulbiferamide (27, Figure 10), was isolated and characterized from a coral-derived Microbulbifer sp. C10-1 by Igarashi and co-workers [7]. The ureido linkage did not allow for the peptide main chain in 27 to possess a terminal primary amine and none of the side

• pseudobulbiferamides in Microbulbifer and pseudovibriamides in Pseudovibrio are quite similar and are located on plasmids, rather than chromosomal DNA. With the observation that Pseudovibrio and Microbulbifer co-inhabit commensal microbiomes of marine animals, it is tantalizing to speculate that this plasmid borne BGC

New triazinephosphonate dopants for Nafion proton exchange membranes (PEM)

• Fátima C. Teixeira,
• António P. S. Teixeira and
• C. M. Rangel

Beilstein J. Org. Chem. 2024, 20, 1623–1634, doi:10.3762/bjoc.20.145

• exchange membrane devices [5][6], such as proton exchange membrane fuel cells (PEMFCs) [3][7][8][9], due to their high-power density and high power-to-weight ratio, and CO2 electrolysers, which can reduce the polluting gas CO2 and produce syngas from the co-electrolysis of CO2 and water [10][11], or water

pKalculator: A pK_a predictor for C–H bonds

• Rasmus M. Borup,
• Nicolai Ree and
• Jan H. Jensen

Beilstein J. Org. Chem. 2024, 20, 1614–1622, doi:10.3762/bjoc.20.144

• complex molecules by exchanging a C–H bond with different functional groups to modify the biological activity of drugs [2]. However, pinpointing which C–H bond is reacting can be challenging. Grzybowski and co-workers recently addressed this gap by predicting pKa values for C–H bonds in dimethyl sulfoxide

• (DMSO) using a graph convolutional neural network (GCNN) [3]. Using a mix of experimental and computed pKa data, they achieved a mean absolute error (MAE) of 2.1 pKa units. Lee and co-workers also addressed this problem by creating a general machine learning (ML) model using either a neural network or

• database only contains an image of each molecule, we employ the “Deep Learning for Chemical Image Recognition” software (DECIMER v. 2.0), developed by Rajan and co-workers [8][9][10]. While DECIMER converts molecular images into SMILES, manual intervention is required to ensure the SMILES string correctly

Electrocatalytic hydrogenation of cyanoarenes, nitroarenes, quinolines, and pyridines under mild conditions with a proton-exchange membrane reactor

• Koichi Mitsudo,
• Atsushi Osaki,
• Haruka Inoue,
• Eisuke Sato,
• Naoki Shida,
• Mahito Atobe and
• Seiji Suga

Beilstein J. Org. Chem. 2024, 20, 1560–1571, doi:10.3762/bjoc.20.139

• Supporting Information File 16: Experimental part. Acknowledgements The authors thank Prof. Yuta Nishina (Okayama University) and his group members for their help in preparing the MEA. The authors also thank Ishifuku Metal Industry Co., Ltd. and De Nora Permelec Ltd. for providing the catalysts and DSE

Benzylic C(sp³)–H fluorination

• Alexander P. Atkins,
• Alice C. Dean and
• Alastair J. J. Lennox

Beilstein J. Org. Chem. 2024, 20, 1527–1547, doi:10.3762/bjoc.20.137

• have been used to effect the transformation of benzylic C(sp3)–H to C(sp3)–F bonds [22]. Shreeve and co-workers reported the use of KOH or n-BuLi to deprotonate acidic protons at benzylic positions adjacent to electron-withdrawing nitro or nitrile groups, respectively, generating benzylic anions that

• monofluorination of tertiary benzylic C(sp3)–H bonds adjacent to nitro groups was reported by Loghmani-Khouzani and co-workers in 2006, in which ammonium acetate and Selectfluor were employed under sonochemical conditions to effect the fluorination (Figure 3) [35]. The authors noted that the use of sonochemistry

• afforded higher yields and shorter reaction times compared to standard stirring conditions with DBU. When employing substrates bearing secondary benzylic sites in the reaction conditions, the difluorinated products were observed exclusively in high yields. In 2016, Britton and co-workers reported a method

Electrophotochemical metal-catalyzed synthesis of alkylnitriles from simple aliphatic carboxylic acids

• Yukang Wang,
• Yan Yao and
• Niankai Fu

Beilstein J. Org. Chem. 2024, 20, 1497–1503, doi:10.3762/bjoc.20.133

• -known to be highly susceptible to electroplating on the cathode and thus require the use of ligands to avoid detrimental cathode deposition during electrolysis (Table 1, entry 3). In addition, we discovered that the additional use of DMF as co-solvent is beneficial to the reaction efficiency–reactions

Bioinformatic prediction of the stereoselectivity of modular polyketide synthase: an update of the sequence motifs in ketoreductase domain

• Changjun Xiang,
• Shunyu Yao,
• Ruoyu Wang and
• Lihan Zhang

Beilstein J. Org. Chem. 2024, 20, 1476–1485, doi:10.3762/bjoc.20.131

• rings. The triangles indicate a product having α-substituents. (c) Crystal structure of DH-ER-KR tridomain (PDB ID 8G7W) [24]. DH, KRS, ER, KRC are colored in cyan, pink, yellow, and purple, respectively. The lid of KR catalytic pocket is colored in red. The co-crystallized cofactor is represented as

• Information File 1. (a) The position of fingerprint motifs in the KR structure (AmpKR2, A1-type, PDB ID 5XWV) [29]. Fingerprints are shown as sticks. The co-crystallized substrate mimic and co-factor are shown as lines. (b) Sequence logo comparation of the core moiety of β-module KRC based on the

Synthesis of 2-benzyl N-substituted anilines via imine condensation–isoaromatization of (E)-2-arylidene-3-cyclohexenones and primary amines

• Lu Li,
• Na Li,
• Xiao-Tian Mo,
• Ming-Wei Yuan,
• Lin Jiang and
• Ming-Long Yuan

Beilstein J. Org. Chem. 2024, 20, 1468–1475, doi:10.3762/bjoc.20.130

• of anilines through Brønsted acid or transition-metal-promoted conversion of 2-cyclohexanone oximes [15][16][17][18] (Scheme 1, (2)). Moreover, Strauss and co-workers described a green, multicomponent reaction of aromatic aldehydes, 2-cyclohexenone and amines to afford 2-arylmethyl N-substituted

Synthesis of 4-functionalized pyrazoles via oxidative thio- or selenocyanation mediated by PhICl₂ and NH₄SCN/KSeCN

• Jialiang Wu,
• Haofeng Shi,
• Xuemin Li,
• Jiaxin He,
• Chen Zhang,
• Fengxia Sun and
• Yunfei Du

Beilstein J. Org. Chem. 2024, 20, 1453–1461, doi:10.3762/bjoc.20.128

• , Yotphan and colleagues realized a direct thiocyanation of N-substituted pyrazolones under metal-free conditions [49]. Besides, Choudhury and co-workers developed an additive and metal-free methodology for the C–H thiocyanation of aminopyrazoles, using H2O2 as a benign oxidizing agent (Scheme 1b) [41]. Pan

Predicting bond dissociation energies of cyclic hypervalent halogen reagents using DFT calculations and graph attention network model

• Yingbo Shao,
• Zhiyuan Ren,
• Zhihui Han,
• Li Chen,
• Yao Li and
• Xiao-Song Xue

Beilstein J. Org. Chem. 2024, 20, 1444–1452, doi:10.3762/bjoc.20.127

• iodine [61][62][63][64][65][66][67][68][69][70][71][72][73][74][75][76] and the computational database of organic species by Paton and co-workers [77], geometry optimizations and single point energy calculations for homolytic BDEs are both performed using M06-2X/def2-TZVPP [78][79][80] in the gas phase

A comparison of structure, bonding and non-covalent interactions of aryl halide and diarylhalonium halogen-bond donors

• Nicole Javaly,
• Theresa M. McCormick and
• David R. Stuart

Beilstein J. Org. Chem. 2024, 20, 1428–1435, doi:10.3762/bjoc.20.125

• electropositive σ-hole region, which is quantitatively described by Vs,max on the halogen, though other factors have also been considered (Scheme 1a) [1][2][3][4][23][24][25]. Huber and co-workers have posed the question: “Is There a Single Ideal Parameter for Halogen-Bonding Based Lewis Acidity?”, and concluded

Challenge N- versus O-six-membered annulation: FeCl₃-catalyzed synthesis of heterocyclic N,O-aminals

• Giacomo Mari,
• Lucia De Crescentini,
• Gianfranco Favi,
• Fabio Mantellini,
• Diego Olivieri and
• Stefania Santeusanio

Beilstein J. Org. Chem. 2024, 20, 1412–1420, doi:10.3762/bjoc.20.123

• (entries 1–7, Table 1). Similarly to what was observed by Yu and co-workers for the intramolecular cyclization of alkynyl aldehyde acetals [28][29], it was found that the use of FeCl3 provided the better result in terms of overall yield (entry 3, Table 1). Moreover, the choice of iron(III) seemed to have

Generation of alkyl and acyl radicals by visible-light photoredox catalysis: direct activation of C–O bonds in organic transformations

• Mithu Roy,
• Bitan Sardar,
• Itu Mallick and
• Dipankar Srimani

Beilstein J. Org. Chem. 2024, 20, 1348–1375, doi:10.3762/bjoc.20.119

• , Wang and co-workers [30] demonstrated the photomediated synthesis of γ,γ-difluoroallylic ketones by reacting trifluoromethyl alkenes and acids in the presence of PPh3 additive and iridium photocatalyst in basic medium (Scheme 3). This methodology was suitable for a wide range of carboxylic acids in the

• presence of alkene, alkyne, halogen, and ether moieties. N-Boc-protected amines and esters also provided a good to excellent yield. Unfortunately, α,β-unsaturated carboxylic acids and aliphatic carboxylic acids were ineffective using this method. In 2024, Liu and co-workers [31] introduced a photocatalytic

• product. The photomediated formation of acyl radicals directly from acids mostly employs DMDC or phosphines (e.g., PPh3, PMe2Ph) as additives and [Ir(III)] as photocatalyst. In 2022, Chu and co-workers [32] developed a protocol to form acyl radicals directly from acids utilizing Ph2S as activator and the

Synthesis of 1,2,3-triazoles containing an allomaltol moiety from substituted pyrano[2,3-d]isoxazolones via base-promoted Boulton–Katritzky rearrangement

• Constantine V. Milyutin,
• Andrey N. Komogortsev and
• Boris V. Lichitsky

Beilstein J. Org. Chem. 2024, 20, 1334–1340, doi:10.3762/bjoc.20.117

• ionic liquids [8][9]. Also, thermal and photochemical variants of studied recyclization are known in the literature [10][11]. Besides that, an unusual procedure for Boulton–Katritzky reaction including the use of surfactants is suggested by Fontana and co-workers [12]. Other heterocyclic systems capable

Transition-metal-catalyst-free electroreductive alkene hydroarylation with aryl halides under visible-light irradiation

• Kosuke Yamamoto,
• Kazuhisa Arita,
• Masami Kuriyama and
• Osamu Onomura

Beilstein J. Org. Chem. 2024, 20, 1327–1333, doi:10.3762/bjoc.20.116

• [44], Ni [45], and Co [46] (Scheme 1a). The pioneering work by Savéant et al. demonstrated that electron-deficient (hetero)aromatics acted as efficient mediators for the metal-catalyst-free electroreductive hydroarylation of alkenes with some activated chloro-, bromo-, and iodoarenes, but the use of a

Diameter-selective extraction of single-walled carbon nanotubes by interlocking with Cu-tethered square nanobrackets

• Guoqing Cheng and
• Naoki Komatsu

Beilstein J. Org. Chem. 2024, 20, 1298–1307, doi:10.3762/bjoc.20.113

• , recently, a rigid metal-tethered macrocyclic host molecule “M-nanobrackets” (M = Cu, Co and Pd) [11]. While the concept of the mechanically interlocked carbon nanotubes (MINTs) has been established by Pérez and López [12][13], Cu-tethered tetragonal nanobrackets 1a not only interlocked SWNTs, but also

• Sigma-Aldrich Co., Nacalai Tesque Co., Tokyo Chemical Industry Co., Ltd., FUJIFILM Wako Pure Chemical Industries, Ltd. All organic solvents are purchased from Nacalai Tesque Co., FUJIFILM Wako Pure Chemical Industries, Ltd. and were used without purification unless indicated otherwise. The silica gel 60

• N (spherical, neutral) was purchased from Kanto Chemical Co., Ltd. All reactions were performed in oven-dried glassware unless stated otherwise and were monitored by TLC using 0.25 mm silica gel plates with UV indicator (70F-254). Commercial HiPco (purchased from Carbon Nanotechnologies Inc., with

Phenotellurazine redox catalysts: elements of design for radical cross-dehydrogenative coupling reactions

• Alina Paffen,
• Christopher Cremer and
• Frederic W. Patureau

Beilstein J. Org. Chem. 2024, 20, 1292–1297, doi:10.3762/bjoc.20.112

• enabling the activation of small yet highly relevant organic substrates. For example, Huber and co-authors recently designed a Te-based catalyst in an indole Michael addition reaction [1][2][3][4][5]. Pale and Mamane utilized another Te-based catalyst in an electrophilic bromine-mediated cyclization

Domino reactions of chromones with activated carbonyl compounds

• Peter Langer

Beilstein J. Org. Chem. 2024, 20, 1256–1269, doi:10.3762/bjoc.20.108

• ). Acknowledgements I am grateful to my co-workers who contributed to the work included in this account article. These are (in alphabetical order): Drs Uwe Albrecht, Bettina Appel, Alina Bunescu, Friedrich Erben, Edith Holtz, Muhammad Farooq Ibad, Ilia Freifeld, Viktor O. Iaroshenko, Abid Obaid-ur-Rahman, Muhammad A

Competing electrophilic substitution and oxidative polymerization of arylamines with selenium dioxide

• Vishnu Selladurai and
• Selvakumar Karuthapandi

Beilstein J. Org. Chem. 2024, 20, 1221–1235, doi:10.3762/bjoc.20.105

• FTIR spectroscopy (Figures S1 and S2, Supporting Information File 1). The spectral data were consistent with the emeraldine free base. Further, a characteristic n→π* transition for the CO group was noticed in the UV spectrum of polymer 3, which was absent in the UV spectra of the other two polymers [53

Two-fold addition reaction of silylene to C₆₀: structural and electronic properties of a bis-adduct

• Masahiro Kako,
• Masato Kai,
• Masanori Yasui,
• Michio Yamada,
• Yutaka Maeda and
• Takeshi Akasaka

Beilstein J. Org. Chem. 2024, 20, 1179–1188, doi:10.3762/bjoc.20.100

• eight possible regioisomers for bis-addition reactions. Hirsch and co-workers reported two-fold additions of C60 using the Bingel–Hirsch and the Bamford–Stevens reactions as well as nitrene addition reactions, indicating the formation of regioisomers as anticipated from the possible addition sites in

• Figure 1 [5]. Diederich and co-workers developed a general methodology using tether-directed remote functionalization for the regioselective formation of multiple adducts of fullerenes [6]. In our earlier reports, the reactions of C60 and C70, with silylene Dip2Si (1, Dip = 2,6-diisopropylphenyl), a

• . These results confirm that the two addends in 3 are both silirane structures, which represents the first example of a crystallographic analysis of silirane derivatives of fullerenes. Theoretical calculations Hirsch and co-workers reported the bis-functionalization of C60 using the Bingel–Hirsch, the

Manganese-catalyzed C–C and C–N bond formation with alcohols via borrowing hydrogen or hydrogen auto-transfer

• Mohd Farhan Ansari,
• Atul Kumar Maurya,
• Abhishek Kumar and
• Saravanakumar Elangovan

Beilstein J. Org. Chem. 2024, 20, 1111–1166, doi:10.3762/bjoc.20.98

• results in the co-production of a significant amount of waste or side-products. Borrowing hydrogen (BH) or hydrogen auto-transfer (HA) reactions have emerged as the most elegant and powerful strategy to overcome this drawback [3][4][5]. Furthermore, this method has been considered an environmentally

• been developed for the N-alkylation of amines with alcohols, including methanol (Figure 1). Beller and co-workers introduced the first intriguing manganese-catalyzed BH for the N-alkylation of amines with alcohols in 2016 [34]. The potential Mn(I)-pincer complex Mn1 (3 mol %) catalyzed the coupling of

• hydride. In 2018, the Milstein group demonstrated a partial hydrogen-borrowing reaction with a manganese-pincer complex by coupling alcohols and hydrazine to form N-substituted hydrazones. Benzylic and aliphatic alcohols were studied with hydrazine using Mn(t-Bu-PNN)(CO)2Br (Mn5, 3 mol %) and a catalytic

Kinetically stabilized 1,3-diarylisobenzofurans and the possibility of preparing large, persistent isoacenofurans with unusually small HOMO–LUMO gaps

• Qian Liu and
• Glen P. Miller

Beilstein J. Org. Chem. 2024, 20, 1099–1110, doi:10.3762/bjoc.20.97

• interesting class of organic semiconductors. Hamura and co-workers pioneered the synthesis of large isoacenofurans. They prepared a pair of 1,3-diarylisoanthracenofurans [3] and a pair of 1,3-diphenethynylisoanthracenofurans [4], and impressively utilized the latter as intermediates for the synthesis of

• persistence associated with isoacenofurans is of great concern if these molecules are to be utilized as organic semiconductors. Likewise, Hamura and co-workers’ 1,3-diphenethynylisobenzofurans were fleeting intermediates that could not be isolated, but were instead trapped in situ by a suitable dienophile [4

• ]. Large acenes are prone to photooxidation, especially when dissolved in solution while exposed to ambient light and air. They sensitize singlet oxygen formation, and the same is expected from large isoacenofurans. Indeed, the endoperoxides observed by Hamura and co-workers [3] confirm this expectation

Light on the sustainable preparation of aryl-cored dibromides

• Fabrizio Roncaglia,
• Alberto Ughetti,
• Nicola Porcelli,
• Biagio Anderlini,
• Andrea Severini and
• Luca Rigamonti

Beilstein J. Org. Chem. 2024, 20, 1076–1087, doi:10.3762/bjoc.20.95

• CCl4 to prevent undesired solvent degradation. Furthermore, the direct use of Br2, even if used in low concentration, exhibits limited selectivity towards benzylic bromination, primarily due to co-bromination occurring on the aromatic ring. This side process produces awkward halogenated byproducts that

Novel route to enhance the thermo-optical performance of bicyclic diene photoswitches for solar thermal batteries

• Akanksha Ashok Sangolkar,
• Rama Krishna Kadiyam and
• Ravinder Pawar

Beilstein J. Org. Chem. 2024, 20, 1053–1068, doi:10.3762/bjoc.20.93

• )/Def2TZVP level (Table 1). Also, the energy storage capacity of type-Ia, Ib, Ic and IIa, IIb, and IIc systems is the highest among all the studied photoswitches. This infers that –CH2–, –(CO)–, and –NH– are better elongation units of the studied BBD-based photoswitches for improving energy storage

• BBD-based photoswitches with elongated unsaturated bridges have higher energy storage capacities than the NBD/QC pair. The storage energy is found to be higher for systems whose unsaturated bridge lengths are extended with –CH2–, –(CO)– and –NH– units. Additionally, extension of the unsaturated bridge

• extended using –(CO)– and –NH– units. The calculated λ (λonset) for the dienes of type-Ib, Ic, IIb, and IIc photoswitches are 247.18 (275.00), 249.65 (295.60), 235.86 (261.50), and 251.62 (292.20) nm, respectively (Table 2). These absorption wavelengths are significantly longer than the previously reported