Scope of tetrazolo[1,5-a]quinoxalines in CuAAC reactions for the synthesis of triazoloquinoxalines, imidazoloquinoxalines, and rhenium complexes thereof

• Laura Holzhauer,
• Chloé Liagre,
• Olaf Fuhr,
• Nicole Jung and
• Stefan Bräse

Beilstein J. Org. Chem. 2022, 18, 1088–1099, doi:10.3762/bjoc.18.111

• confirmed via single crystal X-ray crystallography. Several other byproducts, such as the bistriazolo product were isolated (see Supporting Information File 1). The obtained triazoloquinoxaline and TIQ products are promising ligands for complexation with different metals. The formation of organometallic

• prepared by reaction of the ligands with rhenium pentacarbonyl bromide (26) in toluene at 110 °C (see Scheme 6 and Scheme 7) as reported in the literature [12]. The structures of all obtained complexes could be confirmed via single crystal X-ray crystallography, verifying unambiguously the formation of the

• . Five rhenium complexes with 1,2,3-triazoloquinoxalines and a novel TIQ rhenium complex were synthesized, and their structures were confirmed via X-ray crystallography. All complexes were characterized and compared regarding their absorption and electrochemical properties. The TIQ complex could be

Facile and diastereoselective arylation of the privileged 1,4-dihydroisoquinolin-3(2H)-one scaffold

• Dmitry Dar’in,
• Grigory Kantin,
• Alexander Bunev and
• Mikhail Krasavin

Beilstein J. Org. Chem. 2022, 18, 1070–1078, doi:10.3762/bjoc.18.109

• spectrum), mass spectrometry and, in the case of compound 10c, by single-crystal X-ray crystallography (Scheme 2). Using compound 10a as the model substrate, we proceeded to screen for suitable reaction conditions that would allow involving this kind of diazo compounds in the TfOH-promoted benzene C

• characterized). cCompound 14 was identified as the reaction product. Preparation of 4-diazo-3(2H)-isoquinolones 10. aConfirmed by single-crystal X-ray crystallography (see Supporting Information File 1). TfOH-promoted arylation of diazo substrates 10. aStructure confirmed by single-crystal X-ray analysis

Isolation and biosynthesis of daturamycins from Streptomyces sp. KIB-H1544

• Yin Chen,
• Jinqiu Ren,
• Ruimin Yang,
• Jie Li,
• Sheng-Xiong Huang and
• Yijun Yan

Beilstein J. Org. Chem. 2022, 18, 1009–1016, doi:10.3762/bjoc.18.101

• . Furthermore, the absolute configuration of C-4 and C-5 in compound 1 was also confirmed as 4R and 5S by X-ray crystallography (Figure 2). (±)-Daturamycin B (2) was isolated as a white powder, and its molecular formula was determined as C17H14O3 by HRMS–ESI data (m/z 289.0833 [M + Na]+, calcd for C19H16O5Na

• (Figures S14 and S15, Supporting Information File 1) indicated that compound 3 showed strong similarity with 1,4-diphenyl-2,3,5,6-tetramethoxybenzene [19], with two methyl signals were absent in the NMR data of 3. Furthermore, the structure of 3 could be confirmed, as shown in Figure 1, based on X-ray

• crystallography (Figure 2). The known congeners were determined as terferol (4) [20], BTH-II0204-207: D (5) [21], and betulinan A (6) [22] (Figure 1) by comparing their 1H and 13C NMR spectroscopic data (Figures S16–S21, Supporting Information File 1) and specific rotation values with those in the literatures

Synthesis of novel alkynyl imidazopyridinyl selenides: copper-catalyzed tandem selenation of selenium with 2-arylimidazo[1,2-a]pyridines and terminal alkynes

• Mio Matsumura,
• Kaho Tsukada,
• Kiwa Sugimoto,
• Yuki Murata and
• Shuji Yasuike

Beilstein J. Org. Chem. 2022, 18, 863–871, doi:10.3762/bjoc.18.87

• reactions. Transformation from 4aa. One-pot reaction of Se powder with 1a and 3aa. One-pot two-step synthesis of alkynyl imidazopyridinyl selenides 4a. Supporting Information Supporting Information File 76: Characterization data of all new compounds, synthetic procedures for compounds 6–8, X-ray

• crystallography details, and copies of spectra. Supporting Information File 77: X-ray crystal structure of 4aa. Supporting Information File 78: X-ray crystal structure of 8. Funding This research was supported by JSPS KAKENHI (Grant Number JP19K07005) (S. Y.). The authors also thank the research grant from

First series of N-alkylamino peptoid homooligomers: solution phase synthesis and conformational investigation

• Maxime Pypec,
• Laurent Jouffret,
• Claude Taillefumier and
• Olivier Roy

Beilstein J. Org. Chem. 2022, 18, 845–854, doi:10.3762/bjoc.18.85

• solid state by X-ray crystallography (dimer 2), and implicit solvent QM geometry optimizations. N-(Methylamino)peptoids were found to preferentially adopt trans amide bonds with the side chain N–H bonds oriented approximately perpendicular to the amide plane. This orientation is conducive to local

• ) after coupling and TFA-mediated Boc removal. Structural characterization of N-methylamino peptoid oligomers X-ray diffraction analysis of peptoid dimer 2 Peptoid dimer 2 was crystallized by slow evaporation from chloroform, and its high resolution structure was determined by X-ray crystallography. The

Structural basis for endoperoxide-forming oxygenases

• Takahiro Mori and
• Ikuro Abe

Beilstein J. Org. Chem. 2022, 18, 707–721, doi:10.3762/bjoc.18.71

• endoperoxygenase NvfI. Keywords: biosynthesis; endoperoxide; enzyme; natural products; X-ray crystallography; Introduction Endoperoxide-containing compounds form a large group of natural products with cyclic peroxide structures [1][2][3][4][5]. These compounds are widely distributed in nature, and many

• [41][42][43]. Crystal structures of COXs The structural basis for the di-peroxide formation reaction by COXs has been substantially elucidated by electron paramagnetic resonance (EPR), kinetic analysis, X-ray crystallography, and mutagenesis experiments [24][44][45]. The structural analyses of

DDQ in mechanochemical C–N coupling reactions

• Shyamal Kanti Bera,
• Rosalin Bhanja and
• Prasenjit Mal

Beilstein J. Org. Chem. 2022, 18, 639–646, doi:10.3762/bjoc.18.64

• established from the X-ray crystallography data. Various methodologies are available in the literature toward constructing quinazolin-4(3H)-one derivatives [40][45][46]. Quinazolin-4(3H)-ones and its derivatives possess several biological activities such as antibacterial [47], antiviral [48], antitumor [49

• conditions: reactants were milled at 21 Hz in a 25 mL milling jar containing one stainless-steel grinding ball (15 mm in diameter). Optimization of the reaction conditions.a Supporting Information Supporting Information File 46: Experimental details, characterization data, copies of NMR spectra and X-ray

• crystallography details. Funding SKB thank DST (INSPIRE) and RB thank CSIR (India) for fellowships.

Tosylhydrazine-promoted self-conjugate reduction–Michael/aldol reaction of 3-phenacylideneoxindoles towards dispirocyclopentanebisoxindole derivatives

• Sayan Pramanik and
• Chhanda Mukhopadhyay

Beilstein J. Org. Chem. 2022, 18, 469–478, doi:10.3762/bjoc.18.49

• synthesized compound was confirmed by an X-ray crystallography experiment on a Bruker SMART diffractometer. General procedure for the synthesis of compound 3: In a manner similar to [28], 3-phenacylideneoxindole (1 mmol), tosylhydrazine (0.5 mmol) and Et3N (1 equivalent) were added with 6 mL CH3CN in a dry 10

Site-selective reactions mediated by molecular containers

• Rui Wang and
• Yang Yu

Beilstein J. Org. Chem. 2022, 18, 309–324, doi:10.3762/bjoc.18.35

• and fixed orientation of the guests inside the cage A. One of the carbonyl groups of 10 was in close proximity to the methyl group of 11, which was determined by X-ray crystallography. The possible C-coupled 1,2-adduct and other coupling products were not detected. However, in the absence of host A, a

• alkenyl site, producing the final 1,2-reduction product cis-O-hydroxycinnamyl alcohol 19. As a comparison, in the absence of the β-cyclodextrin host, both the 1,2- and 1,4-reduction products were observed. X-ray crystallography determined the host–guest complex of the coumarin and β-cyclodextrin, which

Iridium-catalyzed hydroacylation reactions of C1-substituted oxabenzonorbornadienes with salicylaldehyde: an experimental and computational study

• Angel Ho,
• Austin Pounder,
• Krish Valluru,
• Leanne D. Chen and
• William Tam

Beilstein J. Org. Chem. 2022, 18, 251–261, doi:10.3762/bjoc.18.30

• (15e, 15f, 15h). Sensitive functional groups like alkyl iodides were tolerated in the reaction, although product yields were slightly diminished. The relative stereo- and regiochemistry of the adducts was confirmed through NMR experiments and X-ray crystallography (15h) [67]. We next sought to

Ready access to 7,8-dihydroindolo[2,3-d][1]benzazepine-6(5H)-one scaffold and analogues via early-stage Fischer ring-closure reaction

• Irina Kuznetcova,
• Felix Bacher,
• Daniel Vegh,
• Hsiang-Yu Chuang and
• Vladimir B. Arion

Beilstein J. Org. Chem. 2022, 18, 143–151, doi:10.3762/bjoc.18.15

• , characterization data and 1H and 13C NMR spectra of compounds, NMR numbering schemes and X-ray crystallography data. Acknowledgements We also thank Mr. Alexander Roller and Ms. Natalie Gajic for collection of X-ray diffraction data. Funding Support from the Austrian Science Fund (FWF) (P31293-N37) and Slovak

Synthesis of new pyrazolo[1,2,3]triazines by cyclative cleavage of pyrazolyltriazenes

• Nicolai Wippert,
• Martin Nieger,
• Claudine Herlan,
• Nicole Jung and
• Stefan Bräse

Beilstein J. Org. Chem. 2021, 17, 2773–2780, doi:10.3762/bjoc.17.187

• able to exemplarily determine the molecular structure by X-ray crystallography, proving the regioisomer obtained in the alkylation reaction (Figure 2). While isomer 12 was used for the synthesis of pyrazolo[3,4-d][1,2,3]-3H-triazine derivatives of general structure 5, the isomer 13 was intended to

Asymmetric organocatalyzed synthesis of coumarin derivatives

• Natália M. Moreira,
• Lorena S. R. Martelli and
• Arlene G. Corrêa

Beilstein J. Org. Chem. 2021, 17, 1952–1980, doi:10.3762/bjoc.17.128

• substitution reaction between the coumarin and the activated MBH substrate, it is possible to obtain functionalized coumarins 41 (Scheme 13). Furthermore, the absolute configuration of the stereogenic center was determined by X-ray crystallography. The enantioselective synthesis of cyclopropa[c]coumarins 45

• compared to the one-pot procedure. The obtained products possess a (R)-configuration, determined by X-ray crystallography (Scheme 26). Sebesta and colleagues described an enantioselective Michael/hemiketalization addition of hydroxycoumarins 1 to enones 2 and ketoesters 86 using squaramide 85 [62]. The

• addition in the least hindered Re face, consequently resulting in products of (R)-configurations, which were determined via X-ray crystallography. A stereoselective [3 + 2] cycloaddition with indandione alkylidenes 103 and 3-homoacylcoumarin 70 as the 1,3-dipole precursor, to generate a series of coumarin

Development of N-F fluorinating agents and their fluorinations: Historical perspective

• Teruo Umemoto,
• Yuhao Yang and
• Gerald B. Hammond

Beilstein J. Org. Chem. 2021, 17, 1752–1813, doi:10.3762/bjoc.17.123

• . Deprotection followed by fluorination with FClO3 gave (R)- and (S)-28-3 in good yields. X-ray crystallography was used to determine the structure and confirm the absolute stereochemistry of (S)-28-3. The optically active reagents (R)- and (S)-28-3 were effective in the enantioselective fluorination of cyclic

• reported by Banks when quinuclidine was N-fluorinated with Selectfluor [62] (Scheme 67). Subsequently, in 2001, Shibata et al. presented full details of their studies including the definitive identification of N-fluorinated cinchona alkaloids by X-ray crystallography analysis and further applications [96

A recent overview on the synthesis of 1,4,5-trisubstituted 1,2,3-triazoles

• Pezhman Shiri,
• Ali Mohammad Amani and
• Thomas Mayer-Gall

Beilstein J. Org. Chem. 2021, 17, 1600–1628, doi:10.3762/bjoc.17.114

• one of the products was proved by NMR analysis and X-ray crystallography. A number of different substituents was introduced to the bromotriazole scaffold, where unsubstituted and electron-rich derivatives gave a good yield, while the presence of electron-withdrawing groups decreased the product yield

Breaking paracyclophane: the unexpected formation of non-symmetric disubstituted nitro[2.2]metaparacyclophanes

• Suraj Patel,
• Tyson N. Dais,
• Paul G. Plieger and
• Gareth J. Rowlands

Beilstein J. Org. Chem. 2021, 17, 1518–1526, doi:10.3762/bjoc.17.109

• mixture of starting material 6, the conjugate addition product 14, and a trace of the denitration product 15. The structure of both compounds was confirmed by single X-ray crystallography (Figure 4 and Figure 5). The addition of methanol is stereoselective with only a single diastereomer of 14 being

Co-crystallization of an organic solid and a tetraaryladamantane at room temperature

• Fabian Rami,
• Jan Nowak,
• Felix Krupp,
• Wolfgang Frey and
• Clemens Richert

Beilstein J. Org. Chem. 2021, 17, 1476–1480, doi:10.3762/bjoc.17.103

• evaporation or diffusion. The implications for generating other co-crystals of two solids are briefly discussed. Keywords: adamantanes; crystallization; organic solids; structure elucidation; X-ray crystallography; Introduction Obtaining a crystal suitable for X-ray crystallography can be a challenge for

• X-ray crystallography were collected after more than one week. Table 1 lists the details of the structures observed. In case of the TDA/phenol co-crystals (Figure 2a/c), the asymmetric unit is made up of one host and two guest molecules, so the overall stoichiometric ratio is 1:2 (TDA/phenol). One

• most important methods for purifying organic compounds in industry [19]. It usually produces solids made up of one compound only. It is common knowledge among synthetic chemists that mixtures are difficult to crystallize. In fact, crystallization to obtain single crystals that are suitable for X-ray

Structural effects of meso-halogenation on porphyrins

• Keith J. Flanagan,
• Maximilian Paradiz Dominguez,
• Zoi Melissari,
• Hans-Georg Eckhardt,
• René M. Williams,
• Dáire Gibbons,
• Caroline Prior,
• Gemma M. Locke,
• Alina Meindl,
• Aoife A. Ryan and
• Mathias O. Senge

Beilstein J. Org. Chem. 2021, 17, 1149–1170, doi:10.3762/bjoc.17.88

• has been a topic of strong interest over the past decades. With this in mind we have characterized a series of direct meso-halogenated porphyrins using single crystal X-ray crystallography. This is accompanied by a detailed conformational analysis of all deposited meso-halogenated porphyrins in the

Stereoselective synthesis and transformation of pinane-based 2-amino-1,3-diols

• Ákos Bajtel,
• Mounir Raji,
• Matti Haukka,
• Ferenc Fülöp and
• Zsolt Szakonyi

Beilstein J. Org. Chem. 2021, 17, 983–990, doi:10.3762/bjoc.17.80

• 9 ring system (Scheme 1). The absolute configuration of compound 9 was determined by 2D NMR spectroscopic techniques. Clear NOE signals were observed between the H-7a and Me-10 as well as the Ha-9 and Me-10 protons. Beside NOESY experiments, the structure was also elucidated by X-ray crystallography

• exclusively [41]. The configuration of oxazolidine 17 was determined by 2D NMR spectroscopic techniques. Clear NOE signals were observed between the H-7a and Me-10 as well as the Ha-9 and Me-10 protons. In addition to NOESY experiments, the structure was also elucidated by X-ray crystallography (Figure 3

α,γ-Dioxygenated amides via tandem Brook rearrangement/radical oxygenation reactions and their application to syntheses of γ-lactams

• Mikhail K. Klychnikov,
• Radek Pohl,
• Ivana Císařová and
• Ullrich Jahn

Beilstein J. Org. Chem. 2021, 17, 688–704, doi:10.3762/bjoc.17.58

• oxide ((R)-7b) provided the product (2S,4R)-9i in a much better 8:1 anti/syn coupling diastereoselectivity (Table 2, entry 10). The configuration of the major anti-diastereomer of alkoxyamine 9j was determined by X-ray crystallography after desilylation and hydrochloride formation (see Supporting

• for 12m. However, the coupling diastereoselectivity with TEMPO (3) amounted to 4:1 for the trans diastereomers 12nA,B and exclusive for the cis isomer 12nC. The relative configuration of diastereomer 12nA was unequivocally established by X-ray crystallography of the hydrochloride adduct of the keto

• substituents. One of the minor cis diastereomers of 13j crystallized and its configuration was unequivocally established by X-ray crystallography (Figure 3, vide supra). Lactams 12l–o with cyclic subunits were also subjected to a Dess–Martin oxidation to confirm their relative configuration (Scheme 5). The

Menthyl esterification allows chiral resolution for the synthesis of artificial glutamate analogs

• Kenji Morokuma,
• Shuntaro Tsukamoto,
• Kyosuke Mori,
• Kei Miyako,
• Ryuichi Sakai,
• Raku Irie and
• Masato Oikawa

Beilstein J. Org. Chem. 2021, 17, 540–550, doi:10.3762/bjoc.17.48

• analysis by NMR, conformational calculation, and X-ray crystallography. A mice in vivo assay showed that (2R)-MC-27, with a six-membered oxacycle, is neuroactive, whereas the (2S)-counterpart is inactive. It was also found that TKM-38, with an eight-membered azacycle, is neuronally inactive, showing that

Biochemistry of fluoroprolines: the prospect of making fluorine a bioelement

• Vladimir Kubyshkin,
• Rebecca Davis and
• Nediljko Budisa

Beilstein J. Org. Chem. 2021, 17, 439–460, doi:10.3762/bjoc.17.40

• the fact that alanine mimics the secondary structure preferences of most proteinogenic amino acids, allowing the relative importance of each side chain for the biological function to be determined [23]. Classical X-ray crystallography also employs the polyalanine model for backbone chain tracing to

¹⁹F NMR as a tool in chemical biology

• Diana Gimenez,
• Aoife Phelan,
• Cormac D. Murphy and
• Steven L. Cobb

Beilstein J. Org. Chem. 2021, 17, 293–318, doi:10.3762/bjoc.17.28

• their functional architecture. Such an approach typically includes the use of a variety of high-resolution proteomic tools, cryo-electron microscopy and X-ray crystallography to achieve full molecular characterization at the atomic level. However, macromolecules such as DNA/RNA and proteins are not

Annulation of a 1,3-dithiole ring to a sterically hindered o-quinone core. Novel ditopic redox-active ligands

• Sergey V. Norkov,
• Anton V. Cherkasov,
• Andrey S. Shavyrin,
• Maxim V. Arsenyev,
• Viacheslav A. Kuropatov and
• Vladimir K. Cherkasov

Beilstein J. Org. Chem. 2021, 17, 273–282, doi:10.3762/bjoc.17.26

• electrode (2 mm diameter), platinum wire counter electrode and Ag/AgCl/KCl reference electrode. X-ray crystallography The X-ray data for 6a–d and 7–9 were collected on Rigaku OD Xcalibur (6b–d, 7, 9) and Bruker D8 Quest (6a, 8) diffractometers (Mo Kα radiation, ω-scans technique, λ = 0.71073 Å) using APEX3

Molecular basis for protein–protein interactions

• Brandon Charles Seychell and
• Tobias Beck

Beilstein J. Org. Chem. 2021, 17, 1–10, doi:10.3762/bjoc.17.1

• methods. These methods are summarised in Figure 1. Atomic resolution methods focus on the structure determination of protein complexes and elucidating the PPIs at a near-atomic resolution. Such methods include X-ray crystallography [12], nuclear magnetic resonance (NMR) [13], and cryogenic electron

• microscopy (cryo-EM) [14]. Traditionally, X-ray crystallography was the preferred method to solve the protein structure and determine protein–protein interfaces. However, protein crystallography has the limitation that some protein assemblies have a low diffraction quality and are difficult to crystallise

• Data Bank [16]. The main advantage that cryo-EM has compared to X-ray crystallography is that the former does not require crystals, thus making it easier or sometimes even possible at all to study flexible protein assemblies that do not crystallise. Albeit this, the main limitations of cryo-EM included