Free-radical cyclization approach to polyheterocycles containing pyrrole and pyridine rings

• Ivan P. Mosiagin,
• Olesya A. Tomashenko,
• Dar’ya V. Spiridonova,
• Mikhail S. Novikov,
• Sergey P. Tunik and
• Alexander F. Khlebnikov

Beilstein J. Org. Chem. 2021, 17, 1490–1498, doi:10.3762/bjoc.17.105

• heteroaromatics available for various applications. Fused polyheteroarenes, containing a pyrrole moiety, are widely present in natural products and pharmacologically important agents and have a significant importance in the development of new materials useful for bioimaging applications and chemosensor systems [3

A new glance at the chemosphere of macroalgal–bacterial interactions: In situ profiling of metabolites in symbiosis by mass spectrometry

• Marine Vallet,
• Filip Kaftan,
• Veit Grabe,
• Fatemeh Ghaderiardakani,
• Simona Fenizia,
• Aleš Svatoš,
• Georg Pohnert and
• Thomas Wichard

Beilstein J. Org. Chem. 2021, 17, 1313–1322, doi:10.3762/bjoc.17.91

• multicellular host and bacteria interactions can characterise natural products in symbiotic interactions. Algal growth and morphogenesis-promoting factors (AGMPFs) are required for the development of the model organism U. mutabilis [7]. They are provided by a combination of two essential bacteria, Maribacter sp

• mass deviation equal to or lower than five ppm, which suggested several known natural products such as ectoine [49]. To confirm the identity of the significant features, mass spectral information was compared with analytical standards analysed with the AP-SMALDI-HRMS (DMSP, chlorophyll-a, ectoine

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

Heterogeneous photocatalytic cyanomethylarylation of alkenes with acetonitrile: synthesis of diverse nitrogenous heterocyclic compounds

• Guanglong Pan,
• Qian Yang,
• Wentao Wang,
• Yurong Tang and
• Yunfei Cai

Beilstein J. Org. Chem. 2021, 17, 1171–1180, doi:10.3762/bjoc.17.89

• photocatalysis; recyclable; Introduction Nitrogenous heterocyclic compounds, such as indolines [1][2][3][4], oxindoles [5][6][7], isoquinolinones [8][9][10], and isoquinolinediones [11][12], are pivotal structural motifs in numerous pharmaceuticals, agrochemicals, and bioactive natural products. The oxidative

• in 41% yield (Scheme 6c). Furthermore, the tricyclic indoline 14, a structural motif in diverse natural products [4], could be obtained in 60% yield through a reductive cyclization reaction (Scheme 6d). To investigate the mechanism of the cyanomethylarylation of alkenes, a series of control

N-tert-Butanesulfinyl imines in the asymmetric synthesis of nitrogen-containing heterocycles

• Joseane A. Mendes,
• Paulo R. R. Costa,
• Miguel Yus,
• Francisco Foubelo and
• Camilla D. Buarque

Beilstein J. Org. Chem. 2021, 17, 1096–1140, doi:10.3762/bjoc.17.86

• Joseane A. Mendes Paulo R. R. Costa Miguel Yus Francisco Foubelo Camilla D. Buarque Department of Chemistry, Pontifical Catholic University of Rio de Janeiro Puc-Rio, CEP 22435-900, Brazil Laboratory of Bioorganic Chemistry, Institute of Research of Natural Products, Health Science Center, Federal

• -butanesulfinyl imines as reaction intermediates, including the synthesis of several natural products. The synthesis of nitrogen-containing heterocycles in which the nitrogen atom is not provided by the chiral imine will not be considered in this review. The sections are organized according to the size of the

• heterocycles. The present work will comprehensively cover the most pertinent contributions to this research area from 2012 to 2020. We regret in advance that some contributions are excluded in order to maintain a concise format. Keywords: asymmetric synthesis; chiral auxiliary; natural products; nitrogen

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

• important reaction nowadays. For illustration, the addition products are very promising in medicinal chemistry research [1][2][3][4][5][6][7] and in natural products total syntheses [8][9][10][11][12][13][14][15][16]. Chiral complexes of Rh [17][18][19][20][21][22][23][24] and Pd usually catalyse the

• syntheses of the natural products (−)-caesalpinnone A and (−)-caesalpinflavan B [9]. Plausible catalytic cycle for the addition of phenylboronic acid to 3-methyl-2-cyclohexenone catalysed by L9/Pd(TFA)2 [48][49]. Total syntheses of naturally occurring terpenoids [10][11]. Use of the L9/Pd(TFA)2 catalytic

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

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

• multiple natural products [1][2] and have broad applications in areas ranging from medicinal chemistry [1][2][3][4][5][6][7][8][9][10] to materials science [11]. Figure 1 presents a few examples of dibenzofuran-containing molecules. Benzofurocoumarin analogues of 1 have antiproliferative effects on human

Prins cyclization-mediated stereoselective synthesis of tetrahydropyrans and dihydropyrans: an inspection of twenty years

• Asha Budakoti,
• Pradip Kumar Mondal,
• Prachi Verma and
• Jagadish Khamrai

Beilstein J. Org. Chem. 2021, 17, 932–963, doi:10.3762/bjoc.17.77

• important building blocks and ubiquitous scaffolds in many natural products and active pharmaceutical ingredients (API). Among various established methods, the Prins reaction has emerged as a powerful technique in the stereoselective synthesis of the tetrahydropyran skeleton with various substituents, and

• the strategy has further been successfully applied in the total synthesis of bioactive macrocycles and related natural products. In this context, hundreds of valuable contributions have already been made in this area, and the present review is intended to provide the systematic assortment of diverse

• Prins cyclization strategies, covering the literature reports of the last twenty years (from 2000 to 2019), with an aim to give an overview on exciting advancements in this area and designing new strategies for the total synthesis of related natural products. Keywords: asymmetric; natural products

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

Synthetic reactions driven by electron-donor–acceptor (EDA) complexes

• Zhonglie Yang,
• Yutong Liu,
• Kun Cao,
• Xiaobin Zhang,
• Hezhong Jiang and
• Jiahong Li

Beilstein J. Org. Chem. 2021, 17, 771–799, doi:10.3762/bjoc.17.67

• corresponding borated products, with only a coordinating solvent, DMA. Furthermore, functionalization of natural products and drug molecules has been accomplished smoothly with excellent yields. In 2018, Aggarwal and colleagues [17] proposed a method for preparing alkyl borate derivative 150 by employing

Total synthesis of pyrrolo[2,3-c]quinoline alkaloid: trigonoine B

• Takashi Nishiyama,
• Erina Hamada,
• Daishi Ishii,
• Yuuto Kihara,
• Nanase Choshi,
• Natsumi Nakanishi,
• Mari Murakami,
• Kimiko Taninaka,
• Noriyuki Hatae and
• Tominari Choshi

Beilstein J. Org. Chem. 2021, 17, 730–736, doi:10.3762/bjoc.17.62

• could prevent the cytopathic effects of HIV-1IIIB in C8166 cells. Notably, it was found that both natural products exhibited anti-HIV activity. In addition to trigonoine B, aplidiopsamine A (2) [2] and marinoquinolines 3 [3] are natural products that possess the pyrrolo[2,3-c]quinoline skeleton (Figure

• heterocyclic compounds by constructing fused pyridine ring systems based on a thermal electrocyclization of an azahexatriene moiety [14][15]. It has been hoped that the development of compounds with enhanced biological activity would be possible using these natural products and their derivatives [16][17][18

• the synthesis of various N-substituted 4-aminopyrroloquinolines. The investigation of the biological activity of trigonoine B and its derivatives is under evaluation. Natural products possessing the pyrrolo[2,3-c]quinoline skeleton. Total synthesis of marinoquinolines and the failure of the

Synthesis of dibenzosuberenone-based novel polycyclic π-conjugated dihydropyridazines, pyridazines and pyrroles

• Ramazan Koçak and
• Arif Daştan

Beilstein J. Org. Chem. 2021, 17, 719–729, doi:10.3762/bjoc.17.61

• considerable attention as they are widespread in natural products, as well as in pharmaceuticals, agrochemicals, and organic materials. Among the π-CPHs, pyridazines and pyrroles have important roles [17][18][19][20][21][22]. Although there are very few pyridazine ring-containing compounds isolated from nature

• ], and self-assembled supramolecular architectures [48]. On the other hand, many natural compounds that contain a pyrrole core, such as bilirubin, hemoglobin, chlorophyll a, and vitamin B12, are very important for life. In addition to being common in natural products and biological systems, the active

Stereoselective syntheses of 3-aminocyclooctanetriols and halocyclooctanetriols

• Emine Salamci and
• Yunus Zozik

Beilstein J. Org. Chem. 2021, 17, 705–710, doi:10.3762/bjoc.17.59

• stereospecifically new chlorocyclooctanetriols. Keywords: aminocyclitols; aminocyclooctanetriol; chlorocyclooctanetriol; cyclic sulfate; cyclitols; Introduction The synthesis of aminocyclitols has attracted attention because they contain substructures of many biologically active natural products [1][2][3]. They

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

• ] are central fragments in various natural products, which are often synthesized from lactams by reduction. This makes them important building blocks in the total syntheses of alkaloids and their non-natural analogs [17][18][19][20][21]. However, the γ-lactam substructure itself is a central fragment of

• synthesis of functionalized γ-lactams, which can be used as building blocks for the synthesis of natural products or biologically active compounds. Experimental Tandem nucleophilic epoxide opening/Brook rearrangement/α-oxygenation (general procedure) In a similar manner as described in [74]: LiCl (252 mg, 6

Designed whole-cell-catalysis-assisted synthesis of 9,11-secosterols

• Marek Kõllo,
• Marje Kasari,
• Villu Kasari,
• Tõnis Pehk,
• Ivar Järving,
• Margus Lopp,
• Arvi Jõers and
• Tõnis Kanger

Beilstein J. Org. Chem. 2021, 17, 581–588, doi:10.3762/bjoc.17.52

• and the increasing importance of methods of sustainable chemistry have brought chemoenzymatic approaches for obtaining natural products, or derivatives thereof, with complex structure into focus [1]. Various enzymatic or semisynthetic methods have also been exploited in the synthesis of steroids [2][3

• ][9][10][15]. Biochemical characterization of 9,11-secosterols has so far mainly relied on the identification and purification of natural products from marine invertebrates. The intriguing profile of biological properties has prompted synthetic studies of this class of secosterols. The majority of

Metal-free visible-light-enabled vicinal trifluoromethyl dithiolation of unactivated alkenes

• Xiaojuan Li,
• Qiang Zhang,
• Weigang Zhang,
• Jinzhu Ma,
• Yi Wang and
• Yi Pan

Beilstein J. Org. Chem. 2021, 17, 551–557, doi:10.3762/bjoc.17.49

• in natural products, drug molecules, biologically active molecules, and functional materials. However, the highly selective incorporation of two different sulfur-bearing moieties across double bonds remains challenging [42]. Herein, we describe a visible-light-enabled cascade radical

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

• interesting that the (2R)-isomer is neuronally active because the (2S)-isomer is generally neuroactive for glutamic acid and some natural products with a glutamate motif, dysiherbaine [27] and kainic acid [28]. Since the (2R)-isomer is the neuronally active enantiomer in these analogs (Figure 1), our future

Synthesis of N-perfluoroalkyl-3,4-disubstituted pyrroles by rhodium-catalyzed transannulation of N-fluoroalkyl-1,2,3-triazoles with terminal alkynes

• Olga Bakhanovich,
• Viktor Khutorianskyi,
• Vladimir Motornov and
• Petr Beier

Beilstein J. Org. Chem. 2021, 17, 504–510, doi:10.3762/bjoc.17.44

• -disubstituted pyrroles (minor products). The observed selectivities in the case of the reactions with aliphatic alkynes were high. Keywords: pyrrole; transannulation; rhodium carbene; triazole; Introduction Pyrroles are known to be important structural moieties appearing in natural products, synthetic drugs

• transannulation/carboxylation process was demonstrated for the construction of the functionalized pyrrole 2-carboxylic acid with an N-trifluoromethyl functionality. Thus, this work improves the synthetic access to N-perfluoroalkyl-3,4-disubstituted pyrroles. Selected pyrrole-containing natural products, drugs

Deoxygenative C2-heteroarylation of quinoline N-oxides: facile access to α-triazolylquinolines

• Geetanjali S. Sontakke,
• Rahul K. Shukla and
• Chandra M. R. Volla

Beilstein J. Org. Chem. 2021, 17, 485–493, doi:10.3762/bjoc.17.42

• simplicity of the developed protocol. The current transformation was also found to be compatible for the late-stage modification of natural products. Keywords: amination; heteroarylation; quinoline N-oxides; regioselective; triazoles; Introduction Quinoline is a key heterocyclic moiety found in many

• natural products [1][2][3][4], agrochemicals and pharmaceuticals having potent biological activities, such as antimalarial, antibacterial and anticancer activities [5][6][7][8][9][10][11]. Due to their wide range of applications, selective functionalization of quinolines at various positions has gained

• transformation for late-stage modification of complex natural products was explored, and as shown in Scheme 4, the protocol was tested with various natural-product-derived triazoles. Novel C2-triazolyl products 4a–c were synthesized in good yield of 61–70% from triazoles derived from thymol, cholesterol and

Unexpected rearrangements and a novel synthesis of 1,1-dichloro-1-alkenones from 1,1,1-trifluoroalkanones with aluminium trichloride

• Beatrice Lansbergen,
• Catherine S. Meister and
• Michael C. McLeod

Beilstein J. Org. Chem. 2021, 17, 404–409, doi:10.3762/bjoc.17.36

• bond alkynylations of heteroarenes [9]. The 1,1-dichloro-1-alkenyl moiety is found in a number of pyrethroid insecticides including permethrin and marine natural products such as caracolamide A [10] (Figure 1). 1,1-Dichloro-1-alkenes 2 are commonly prepared from the corresponding aldehydes 1 in one

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

• , generated in the first instance so that the producing organism is protected from its deleterious effects, and can be activated outside the cell by glucosidases. Fluorinated natural products via precursor-directed biosynthesis The modification of known antibiotics and other natural products is an important

Progress in the total synthesis of inthomycins

• Bidyut Kumar Senapati

Beilstein J. Org. Chem. 2021, 17, 58–82, doi:10.3762/bjoc.17.7

• polyene chiral allylic β-hydroxycarbonyl fragments and significant biological activities. The full structural motif of the inthomycins is found in several more complex natural products including the oxazolomycins, 16-methyloxazolomycin, curromycins A and B, and KSM-2690. This review summarises the

• very low, this work certainly established the basis for the future enantioselective syntheses of inthomycins and related natural products. In 2002, Moloney et al. described an efficient synthetic route using the Stille coupling reaction as the key step to accomplish the synthesis of phenyl analogues of

• protocol for the construction of the stereogenic center of inthomycins, respectively [22][24]. Despite these recent advances, the development of novel methods for the regio- and stereocontrolled synthesis of inthomycins, inthomycin-embedded natural products, and their synthetic analogues with better

Recent progress in the synthesis of homotropane alkaloids adaline, euphococcinine and N-methyleuphococcinine

• Dimas J. P. Lima,
• Antonio E. G. Santana,
• Michael A. Birkett and
• Ricardo S. Porto

Beilstein J. Org. Chem. 2021, 17, 28–41, doi:10.3762/bjoc.17.4

• examples include cocaine, atropine, and scopolamine. These compounds are 8-azabicyclo[3.2.1]octane derivatives and belong to a large class of natural products known as tropane alkaloids [7][8][9]. In contrast to tropane alkaloids, the higher homologs homotropanes (9-azabicyclononanes) are less common in

• , Spino et al. firstly made the quaternary center, followed by cyclization. Furthermore, Spino's synthesis involved key reactions such as Claisen rearrangement, olefin metathesis, and the Curtius rearrangement that allowed both natural products in good yields. Davis synthesis – 2010 Davis and Edupuganti

• provide enantiomerically pure alkaloids. Therefore, homotropane-based compounds continue to attract the attention of researchers involved in the progress for new synthetic methodologies to reproduce these natural products and synthesize their analogs, improving existing methods. Homotropane

An atom-economical addition of methyl azaarenes with aromatic aldehydes via benzylic C(sp³)–H bond functionalization under solvent- and catalyst-free conditions

• Divya Rohini Yennamaneni,
• Vasu Amrutham,
• Krishna Sai Gajula,
• Rammurthy Banothu,
• Murali Boosa and
• Narender Nama

Beilstein J. Org. Chem. 2020, 16, 3093–3103, doi:10.3762/bjoc.16.259

• to be developed [14]. The formation of new C–C bonds through direct C–H bond functionalization in organic chemistry is attractive [15]. Such methodologies are omnipresent and facilitate sustainable organic transformations for the synthesis of complex natural products and pharmaceuticals. In the past

• [41][42]. However, to develop advantageous eco-friendly, atom-economical, simple, and efficient synthetic-organic processes under solvent- and catalyst-free conditions in order to synthesize highly demanding pharmaceuticals or natural products can be quite backbreaking [43][44][45]. From this