Catalyzed and uncatalyzed procedures for the syntheses of isomeric covalent multi-indolyl hetero non-metallides: an account

• Ranadeep Talukdar

Beilstein J. Org. Chem. 2021, 17, 2102–2122, doi:10.3762/bjoc.17.137

• hit compound 160. As discussed earlier, bis(indolyl)amines possess electroluminescent properties [41][109]. In 2009, Yagi and co-workers synthesized a large library of bis(indol-5-yl)amines 163 for studying their efficiency in organic electroluminescent devices, where 5-bromoindoles and 5-aminoindoles

• the strong base led to the formation of the over-aminated product 168 (Scheme 22b) [110]. Alzheimer’s disease is caused by the β-amyloid-42 aggregation in brain tissue [111][112]. In 2017, Sreenivasachary synthesized a library of 6,5’- and 6,6’-bis(indolyl)amines and other similar 7-azaindole

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

• long-acting vitamin K antagonist (Figure 1) [8]. This scaffold has also been reported as anti-Alzheimer’s disease [9], such as the natural product decursinol, isolated from Angelica gigas [10]. In this sense, our research group has synthesized and evaluated a library of coumarin derivatives as

Regioselective N-alkylation of the 1H-indazole scaffold; ring substituent and N-alkylating reagent effects on regioisomeric distribution

• Ryan M. Alam and
• John J. Keating

Beilstein J. Org. Chem. 2021, 17, 1939–1951, doi:10.3762/bjoc.17.127

• an improved and cost-effective approach to N-1 substituted indazole precursors as part of drug discovery and development campaigns. Results and Discussion Working towards the synthesis of a library of novel 1,3-disubstituted indazole derivatives necessitated us to develop a regioselective method that

On the application of 3d metals for C–H activation toward bioactive compounds: The key step for the synthesis of silver bullets

• Renato L. Carvalho,
• Amanda S. de Miranda,
• Mateus P. Nunes,
• Roberto S. Gomes,
• Guilherme A. M. Jardim and
• Eufrânio N. da Silva Júnior

Beilstein J. Org. Chem. 2021, 17, 1849–1938, doi:10.3762/bjoc.17.126

Cationic oligonucleotide derivatives and conjugates: A favorable approach for enhanced DNA and RNA targeting oligonucleotides

• Mathias B. Danielsen and
• Jesper Wengel

Beilstein J. Org. Chem. 2021, 17, 1828–1848, doi:10.3762/bjoc.17.125

• injected before the plasmid, and no inhibition could be observed when the plasmid was injected first. This indicated that a competition between the cationic TFOs and the histones for DNA binding had a large impact [111]. The library of phosphoramidate variants was expanded when the aminobutyl

Volatile emission and biosynthesis in endophytic fungi colonizing black poplar leaves

• Christin Walther,
• Pamela Baumann,
• Katrin Luck,
• Beate Rothe,
• Peter H. W. Biedermann,
• Jonathan Gershenzon,
• Tobias G. Köllner and
• Sybille B. Unsicker

Beilstein J. Org. Chem. 2021, 17, 1698–1711, doi:10.3762/bjoc.17.118

• library was prepared, and PolyA enrichment was performed before sequencing on an IlluminaHiSeq 3000 sequencer (Max Planck Genome Centre, Cologne, Germany) with 25 Mio reads, 150 base pairs, paired end. Trimming of the obtained Illumina reads and de novo assembly were both performed with the program CLC

Icilio Guareschi and his amazing “1897 reaction”

• Gian Cesare Tron,
• Alberto Minassi,
• Giovanni Sorba,
• Mara Fausone and
• Giovanni Appendino

Beilstein J. Org. Chem. 2021, 17, 1335–1351, doi:10.3762/bjoc.17.93

• , moved his interests first to technology and history and next to nutrition and war gases. The first event was the fire at the Turin Biblioteca Nazionale Universitaria (BNU, National University Library) in 1904 and the second one was WWI. The Turin BNU was one of the major Italian libraries, hosting

• manuscripts hosted in the library, including the only copy of Très Belles Heures de Notre-Dame by Jean de Berry, illustrated by Jan van Eyck. It was a veritable “European cultural tragedy”, as commented by contemporaries. The books and manuscripts on paper recovered from the fire could be restored, but the

A comprehensive review of flow chemistry techniques tailored to the flavours and fragrances industries

• Guido Gambacorta,
• James S. Sharley and
• Ian R. Baxendale

Beilstein J. Org. Chem. 2021, 17, 1181–1312, doi:10.3762/bjoc.17.90

• reoptimised the Schürt’s process for a more general library of molecules (28 compounds were screened) and they managed to overcome the catalyst deactivation enabling a process to be operated continuously for more than 5 days (TOF = 0.09 h−1 and STY = 354 g (L day−1) using a mixture toluene/EtOH 9:1, noticing

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

• -substituted porphyrins In the CSD database, there are a few other notable examples which whilst they are interesting, they do not constitute a significant library to support a complete discussion (compounds 20–24, Figure 21) [37][38][39]. Other examples do exist in the CSD, such as strapped systems [40], but

• increasing the library of simulated data and use this as a model to predict the most appealing structures for generating halogen bonded supramolecular networks followed by targeted synthesis and crystallization of such compounds. Experimental General information All commercial chemicals used were of

Recent advances in palladium-catalysed asymmetric 1,4–additions of arylboronic acids to conjugated enones and chromones

• Jan Bartáček,
• Jan Svoboda,
• Martin Kocúrik,
• Jaroslav Pochobradský,
• Alexander Čegan,
• Miloš Sedlák and
• Jiří Váňa

Beilstein J. Org. Chem. 2021, 17, 1048–1085, doi:10.3762/bjoc.17.84

• of the boronic acid to Pd. This enhanced catalytic system showed a great turnover number (TON) up to 9,900. The authors described additions to cyclic substrates with high yields (90–99%) and enantioselectivities (89–94% ee; entries 1–5, Table 2). Also, a library of linear enones was tested giving

• , Table 22) [51]. According to these findings, Stoltz and co-workers tested the catalytic system with a library of different chromones for the addition of various boronic acids. The substituted flavanones were obtained with moderate to good yields (36–96%) and usually very high levels of

Synthetic accesses to biguanide compounds

• Oleksandr Grytsai,
• Cyril Ronco and
• Rachid Benhida

Beilstein J. Org. Chem. 2021, 17, 1001–1040, doi:10.3762/bjoc.17.82

• alkylbiguanides with yields up to 97%, despite great variability in the case of alkylbiguanides (Scheme 8A) [24]. Recently, Zhou et al. reported similar conditions applied for the synthesis of anticancer biguanides [25]. The conditions chosen for the synthesis of a small library of pyrazole‐containing biguanide

• intermediate in the synthesis of substituted cyanoguanidines on the route to non-symmetrical N1,N5-disubstituted biguanides. After the first report of Rose for the synthesis of chlorhexidine, another application has been described by Rembarz et al. in 1964 [57]. The authors synthesized a small library of

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

• , POB 35, 40351 Jyväskylä, Finland Stereochemistry Research Group of the Hungarian Academy of Sciences, H-6720 Szeged, Eötvös u. 6, Hungary, Interdisciplinary Centre of Natural Products, University of Szeged, Szeged, Hungary 10.3762/bjoc.17.80 Abstract A library of pinane-based 2-amino-1,3-diols was

• transformations of pinane-based 2-amino-1,3-diols To obtain a library of pinane-based 2-amino-1,3-diols, the oxazolidine-2-ones 9 and 12 were applied as starting materials. The alkaline hydrolysis of both 9 and 12 resulted in the same primary aminodiol 13 [38]. According to the NMR spectra and other physical and

• -diols was recently reported [31]. When compound 21A or 21B were treated in less protic solvents such as DMSO-d6 or CD3OD, tautomerization was not observed. Conclusion A small library of pinane-based 2-amino-1,3-diols was synthesized in a stereoselective manner starting from (1R)-(−)-myrtenol and

Application of the Meerwein reaction of 1,4-benzoquinone to a metal-free synthesis of benzofuropyridine analogues

• Rashmi Singh,
• Tomas Horsten,
• Rashmi Prakash,
• Swapan Dey and
• Wim Dehaen

Beilstein J. Org. Chem. 2021, 17, 977–982, doi:10.3762/bjoc.17.79

• expand the library of derivatives containing core structure 13, electrophilic aromatic substitution of this compound was explored (Scheme 2). Nitration of 13 using 70% nitric acid in glacial acetic acid gave the corresponding regioisomers 14 and 15 in 53% and 41% isolated yield, respectively. The 1H NMR

Enhanced target cell specificity and uptake of lipid nanoparticles using RNA aptamers and peptides

• Roslyn M. Ray,
• Anders Højgaard Hansen,
• Maria Taskova,
• Bernhard Jandl,
• Jonas Hansen,
• Citra Soemardy,
• Kevin V. Morris and
• Kira Astakhova

Beilstein J. Org. Chem. 2021, 17, 891–907, doi:10.3762/bjoc.17.75

• exponential enrichment (SELEX) [30]. SELEX is an iterative process that begins with a large oligonucleotide library that, through a process of negative and positive selections, ends with a few candidates that are specific for a particular protein [30][31]. Using HIV-1 as our model, we explored the use of two

Microwave-assisted multicomponent reactions in heterocyclic chemistry and mechanistic aspects

• Shivani Gulati,
• Stephy Elza John and
• Nagula Shankaraiah

Beilstein J. Org. Chem. 2021, 17, 819–865, doi:10.3762/bjoc.17.71

• longer reaction time (3 h) with lower yields (60%) as compared to microwave (20 min with 91% yield). The library of molecules synthesized was found to be active against SKOV-3 cancer cells with 9a emerging as a promising molecule with IC50 = 0.24 ± 0.05 μM (Scheme 3). The protocol surfaces the efficiency

• of MWA-MCR in the construction of fused polycycles with functional diversity for the generation of a library of pharmacologically active molecules. The construction of fused annulated rings are seldomly reported often achieved by a sequential addition approach [40]. Contributing to the same and

• co-workers [50] demonstrated an aqueous phase, diastereoselective, multicomponent reaction involving substituted isatins 35, β-nitrostyrene 36 and benzylamine (20) or α-amino acids 37 using microwave irradiation to afford a library of spirooxindoles 38 in good yields under catalyst-free conditions

Effective microwave-assisted approach to 1,2,3-triazolobenzodiazepinones via tandem Ugi reaction/catalyst-free intramolecular azide–alkyne cycloaddition

• Maryna O. Mazur,
• Oleksii S. Zhelavskyi,
• Eugene M. Zviagin,
• Svitlana V. Shishkina,
• Vladimir I. Musatov,
• Maksim A. Kolosov,
• Elena H. Shvets,
• Anna Yu. Andryushchenko and
• Valentyn A. Chebanov

Beilstein J. Org. Chem. 2021, 17, 678–687, doi:10.3762/bjoc.17.57

• complex scaffold in just two steps. Unusually, the azide–alkyne cycloaddition for both terminal and non-terminal alkynes was effective under catalyst-free conditions while normally for non-terminal alkynes a ruthenium-based catalysis is required. Using the developed method, a library of 22 target

• compounds was obtained. Currently, we are working on testing some library representatives for their biological activity. Benzodiazepine-based azolo-containing drugs. Novel potential 1,2,3-triazolobenziadiazepine drugs. Code legend for Ugi products 6 and molecular structure (X-ray analysis) of compound 6aaa

Synthesis of (Z)-3-[amino(phenyl)methylidene]-1,3-dihydro-2H-indol-2-ones using an Eschenmoser coupling reaction

• Lukáš Marek,
• Lukáš Kolman,
• Jiří Váňa,
• Jan Svoboda and
• Jiří Hanusek

Beilstein J. Org. Chem. 2021, 17, 527–539, doi:10.3762/bjoc.17.47

• the present paper, we want to describe an optimized procedure avoiding the intermediary thiazoles and to demonstrate the usefulness and wide group tolerability of our new synthetic approach for the preparation of a library of substituted phenyl and amino derivatives (Table 1). A number of the

The synthesis of chiral β-naphthyl-β-sulfanyl ketones via enantioselective sulfa-Michael reaction in the presence of a bifunctional cinchona/sulfonamide organocatalyst

• Deniz Tözendemir and
• Cihangir Tanyeli

Beilstein J. Org. Chem. 2021, 17, 494–503, doi:10.3762/bjoc.17.43

•  1). This new organocatalyst was employed in the model asymmetric sulfa-Michael reaction of naphthalene-1-thiol and trans-chalcone, in addition to the amino-substituted DMAP and quinine-based organocatalysts (6, 7a–c and 8a–c) in our library (Figure 1), as well as previously reported quinine derived

Synthetic strategies of phosphonodepsipeptides

• Jiaxi Xu

Beilstein J. Org. Chem. 2021, 17, 461–484, doi:10.3762/bjoc.17.41

• and oxidation with sodium periodate, benzyl 2-azido-3-(((benzyloxy)(2-oxoethyl)phosphoryl)oxy)-2-methylpropanoate (69) was obtained. The latter was further transformed to the final phosphonodepsipeptide library 64 after the reductive amination with pyrrolidine derivatives 70 and acylation with a

• library of carboxylic acids 72 in the presence of coupling reagents (Scheme 11) [27]. Alternatively, the 1,3-protected glycerol 73 was first converted into various 2,3-protected glycerols 74, which were further transformed to methyl 2-alkoxy-3-hydroxypropanoates 75. Following a similar strategy as above

• , another library of phosphonodepsipeptides 78 was prepared (Scheme 12) [27]. Synthesis of γ-phosphonodepsipeptides γ-Phosphonodepsipeptides 79 have been prepared from N-Cbz-ʟ-glutamic acid (80) and diethyl 2-hydroxyglutarate (84). To prepare phosphorus analogues of γ-glutamyl peptide, the starting N-Cbz-ʟ

Identification of volatiles from six marine Celeribacter strains

• Anuj Kumar Chhalodia,
• Jan Rinkel,
• Dorota Konvalinkova,
• Jörn Petersen and
• Jeroen S. Dickschat

Beilstein J. Org. Chem. 2021, 17, 420–430, doi:10.3762/bjoc.17.38

• mass spectra to library spectra and of retention indices [38] to tabulated literature data (Table 1), or by a direct comparison to authentic standards. The structures of the identified compounds are shown in Figure 2. While the headspace extracts from C. marinus, C. neptunius and C. manganoxidans were

• 41 showed strong similarities to the library mass spectrum of 2-mercaptobenzothiazole that has a molecular weight of 167 Da. The isotope pattern of the molecular ion at m/z = 213 indicated the presence of three sulfur atoms. The strong base peak at m/z = 167 in the mass spectrum of 41 suggested a

Coupling biocatalysis with high-energy flow reactions for the synthesis of carbamates and β-amino acid derivatives

• Alexander Leslie,
• Thomas S. Moody,
• Megan Smyth,
• Scott Wharry and
• Marcus Baumann

Beilstein J. Org. Chem. 2021, 17, 379–384, doi:10.3762/bjoc.17.33

• library of these versatile carbamate building blocks (3, ca. 1 mmol scale), we decided to apply a scavenger column to perform in-line purification. This was achieved as previously reported [22] based on a mixture of Amberlyst A21 (a tertiary amine, ca. 2 equiv) and Amberlyst A15 (a sulfonic acid, ca. 2

• purification of a small library of valuable Cbz-carbamates (see Figure 1). Furthermore, the CALB column was effectively used over several days after purging with toluene to prevent cross contamination. The scale-up of this flow process was demonstrated on a 100 mmol scale showcasing the robust nature of this

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

• , protein folding, and potentially small-molecule library screening, as it can broaden the accessibility of quantitative NMR spectroscopy to a wider range of laboratories. Ligand-observed protein binding interactions In addition to protein-observed fluorine (PrOF) NMR spectroscopy, ligand-observed fluorine

• ] which is a binding assay, and fluorine atoms for biochemical screening (n-FABS) methodology which is a functional assay [39][40]. Both of these methods have been successfully used for ligand-based screening, fragment-based functional screening and dynamic library screening, and have been recently

A sustainable strategy for the straightforward preparation of 2H-azirines and highly functionalized NH-aziridines from vinyl azides using a single solvent flow-batch approach

• Michael Andresini,
• Leonardo Degannaro and
• Renzo Luisi

Beilstein J. Org. Chem. 2021, 17, 203–209, doi:10.3762/bjoc.17.20

• corresponding 2H-azirines in a microfluidic reactor, overcoming the hazards associated with this transformation under batch conditions. A small library of functionalized aryl and alkyl-substituted NH-aziridines has been created under operationally simple conditions. Notably, the addition reaction was found to

1,2,3-Triazoles as leaving groups in S_NAr–Arbuzov reactions: synthesis of C6-phosphonated purine derivatives

• Kārlis-Ēriks Kriķis,
• Irina Novosjolova,
• Anatoly Mishnev and
• Māris Turks

Beilstein J. Org. Chem. 2021, 17, 193–202, doi:10.3762/bjoc.17.19

• hours in neat P(OEt)3 at 160 °C. With the experimental conditions in hand, the SNAr–Arbuzov reaction between 2,6-bistriazolylpurines 6a–i and P(OEt)3 provided a library of novel purine phosphonates 4a–i in 27–82% yield (Table 3). The products 4a, 4d, 4e, and 4i were easily precipitated from hexane left

Novel library synthesis of 3,4-disubstituted pyridin-2(1H)-ones via cleavage of pyridine-2-oxy-7-azabenzotriazole ethers under ionic hydrogenation conditions at room temperature

• Romain Pierre,
• Anne Brethon,
• Sylvain A. Jacques,
• Aurélie Blond,
• Sandrine Chambon,
• Sandrine Talano,
• Catherine Raffin,
• Branislav Musicki,
• Claire Bouix-Peter,
• Loic Tomas,
• Gilles Ouvry,
• Rémy Morgentin,
• Laurent F. Hennequin and
• Craig S. Harris

Beilstein J. Org. Chem. 2021, 17, 156–165, doi:10.3762/bjoc.17.16

• investment in route scouting and optimization. This full paper focuses on the synthesis issues that we encountered during our route exploration and the original solutions we found that helped us to identify two optimized library-style processes to prepare our large kinase inhibitor library. Keywords: 7

• -azabenzotriazole; hinge-binder; ionic hydrogenation; library; pyridine-2(1H)-one; Introduction During a recent medicinal chemistry program targeting a kinase to treat skin disorders, we identified the 4-amino-3-carboxamide disubstituted pyridine-2(1H)-one motif (1) as an interesting starting point. Recently, both

• library building block acid chloride 2. The libraries were prepared in a 3-step manner: 1) amide coupling; 2) deprotection of the 2-methoxypyridine through hydrolysis at elevated temperatures; and 3) the final SNAr or Ullman step to introduce the amine vector with variable yields and chromatographic