Molecular basis for the plasticity of aromatic prenyltransferases in hapalindole biosynthesis

• Takayoshi Awakawa and
• Ikuro Abe

Beilstein J. Org. Chem. 2019, 15, 1545–1551, doi:10.3762/bjoc.15.157

• structures. The indole of HU, W117, and Y168 formed a cation shield [27][28], which stabilizes the cation intermediate after the removal of the phosphate from DMAPP in the HU structure, and Y225 was substituted with Y168 in the HA structure (Figure 5). The orientation of W117 changed in accordance with the

• orientation of the indole in HU and HA. As expectedly, W117 was shown to be important for the reaction through a point mutation study, in which W117A and W117F completely lost the catalytic activity. In the HU structure, the distance between C-2 of HU and C-3 of DMSPP (Figure 5A, a: 3.6 Å) is shorter than

Superelectrophilic carbocations: preparation and reactions of a substrate with six ionizable groups

• Sean H. Kennedy,
• Makafui Gasonoo and
• Douglas A. Klumpp

Beilstein J. Org. Chem. 2019, 15, 1515–1520, doi:10.3762/bjoc.15.153

• in the Brønsted superacid CF3SO3H, the substrate undergoes two types of reactions. In the presence of only the superacid, the highly ionized intermediate(s) provide a double cyclization product having two pyrido[1,2-a]indole rings. With added benzene, an arylation product is obtained. A mechanism is

• studies of tri-, tetra-, and pentacationic systems [11][12]. This product, 10, is the result of charge migration involving the carbocation center and the phenyl group (vide infra). When compound 9 is treated with only superacid, the bis(pyrido[1,2-a]indole) 11 is formed as the major product. Likewise, the

• tri-, tetra-, and pentacationic systems 3–5 provide the pyrido[1,2-a]indole ring system. Interestingly, there was no evidence of the cyclization product 11 (NMR analysis) when compound 9 reacts with superacid in the presence of benzene – product 10 is formed as the major product. These products may be

Multicomponent reactions (MCRs): a useful access to the synthesis of benzo-fused γ-lactams

• Edorta Martínez de Marigorta,
• Jesús M. de Los Santos,
• Ana M. Ochoa de Retana,
• Javier Vicario and
• Francisco Palacios

Beilstein J. Org. Chem. 2019, 15, 1065–1085, doi:10.3762/bjoc.15.104

• (Scheme 4). In this case, copper catalyst and alkynes are also used but, unlike the above method, alkynes 18 are monosubstituted. The third component is an indole or pyrrole derivative 19 and the result of the reaction is a 3,3-disubstituted isoindolinone derivative 20, which contains a newly formed

• quaternary centre [79]. The reaction takes places in water, even in the presence of air, and with nanodomain cuprous oxide as an inexpensive and reusable catalyst. The scope includes aryl, alkyl and carboxyl groups at 2- and 3-positions of the lactam ring. Pyrrole reacts across the 2-carbon while indole

• similar way to that described in Scheme 3. In this case, the coupled alkyne moiety is again activated by Cu(I) and then base-promoted cyclization occurs. A new copper complex formation with the alkene analogue to 13 (see Scheme 3) facilitates the aromatic nucleophilic substitution by indole or pyrrole

Novel (2-amino-4-arylimidazolyl)propanoic acids and pyrrolo[1,2-c]imidazoles via the domino reactions of 2-amino-4-arylimidazoles with carbonyl and methylene active compounds

• Victoria V. Lipson,
• Tetiana L. Pavlovska,
• Nataliya V. Svetlichnaya,
• Anna A. Poryvai,
• Nikolay Yu. Gorobets,
• Erik V. Van der Eycken,
• Irina S. Konovalova,
• Svetlana V. Shiskina,
• Alexander V. Borisov,
• Vladimir I. Musatov and
• Alexander V. Mazepa

Beilstein J. Org. Chem. 2019, 15, 1032–1045, doi:10.3762/bjoc.15.101

• aminoazole fragments. In all earlier described experiments with participation of different α-aminoazoles as binucleophiles the reaction cascade readily accomplished by the formation of fused heterocyclic systems [25]. An analogous three-component reaction involving indole or imidazo[1,2-a]pyridine

• 2-amino-4-arylimidazoles are more reactive substrates for these syntheses leading to the stable Michael-type adducts with aldehydes and Meldrum’s acid than the previously investigated indole and imidazo[1,2-a]pyridine. Moreover, as it has been shown that their further transformations may result in

The LANCA three-component reaction to highly substituted β-ketoenamides – versatile intermediates for the synthesis of functionalized pyridine, pyrimidine, oxazole and quinoxaline derivatives

• Tilman Lechel,
• Roopender Kumar,
• Mrinal K. Bera,
• Reinhold Zimmer and
• Hans-Ulrich Reissig

Beilstein J. Org. Chem. 2019, 15, 655–678, doi:10.3762/bjoc.15.61

• polyphosphoric acid to undergo a Fischer indole reaction to 5-indolyl-substituted oxazole OX20. To demonstrate the versatility of the route to new oxazole derivatives, typical palladium-catalyzed processes are compiled in Scheme 27. First, the acetyl moiety was converted into a vinyl or an ethynyl substituent

Catalyst-free assembly of giant tris(heteroaryl)methanes: synthesis of novel pharmacophoric triads and model sterically crowded tris(heteroaryl/aryl)methyl cation salts

• Rodrigo Abonia,
• Luisa F. Gutiérrez,
• Braulio Insuasty,
• Jairo Quiroga,
• Kenneth K. Laali,
• Chunqing Zhao,
• Gabriela L. Borosky,
• Samantha M. Horwitz and
• Scott D. Bunge

Beilstein J. Org. Chem. 2019, 15, 642–654, doi:10.3762/bjoc.15.60

• ][14][15][16][17][18][19][20][21][22]. Although, “Yonemitsu-type” three-component reactions have been employed for the synthesis of indole-based triarylmethanes [23][24][25][26] (Scheme 2), there still exists a need for the development of new approaches for easy access to libraries of triarylmethanes

• new structure. This concept has recently received attention by the pharmaceutical industry because it provides new options to develop more specific drugs for the treatment of persistent and challenging pathologies [27][28] (Scheme 1). The indole, coumarin, quinoline, chromone and fluorene moieties are

• . [52] and by Mousavizadeh et al. [53] through the three-component reactions of indole and coumarin, but in all cases, ordinary aliphatic and aromatic aldehydes as the third partner, mediated by a catalyst or by a biphasic system as solvent, respectively, were used. The lack of structural diversity in

Synthesis and SAR of the antistaphylococcal natural product nematophin from Xenorhabdus nematophila

• Frank Wesche,
• Hélène Adihou,
• Thomas A. Wichelhaus and
• Helge B. Bode

Beilstein J. Org. Chem. 2019, 15, 535–541, doi:10.3762/bjoc.15.47

• described as a potent inhibitor of various proteases, in particular trypsin and thrombin [17][18][19]. Hereby, the α-keto amide covalently binds to the serine oxygen in the active site under formation of a stable tetrahedral hemiketal. Furthermore, substitution of the indole hydrogen by alkyl, aryl or

• benzyl improves the in vitro antistaphylococcal activity. In contrast, the incorporation of smaller heterocycles like pyridine and imidazole as well as isosteric benzimidazole instead of the indole moieties lead to a loss of antibacterial activity. Kennedy et al. could synthesize a 2-phenyl derivative

• could not be avoided. However, we were interested in expanding the aforementioned structure–activity studies regarding the substitution of the indole moiety by different aromatic systems as well as substitution of side chains in the α-keto carboxylic acids to generate more derivatives of this

Design of indole- and MCR-based macrocycles as p53-MDM2 antagonists

• Constantinos G. Neochoritis,
• Maryam Kazemi Miraki,
• Eman M. M. Abdelraheem,
• Ewa Surmiak,
• Tryfon Zarganes-Tzitzikas,
• Beata Łabuzek,
• Tad A. Holak and
• Alexander Dömling

Beilstein J. Org. Chem. 2019, 15, 513–520, doi:10.3762/bjoc.15.45

• synthesis was accomplished by a rapid, one-pot synthesis of indole-based macrocycles based on Ugi macrocyclization. The reaction of 12 different α,ω-amino acids and different indole-3-carboxaldehyde derivatives afforded a unique library of macrocycles otherwise difficult to access. Screening of the library

• for p53-MDM2 inhibition by fluorescence polarization and 1H,15N HSQC NMR measurements confirm MDM2 binding. Keywords: 1H,15N HSQC NMR; indole; macrocycles; multicomponent; p53-MDM2; Ugi reaction; Introduction Macrocycles are the chemical entities that are consisting of a 12-membered or even bigger

• ]. Herein, an indole-based macrocycle synthesis is reported in a one-pot fashion based on Ugi macrocyclization with readily available α,ω-amino acids. Moreover, in continuation of our efforts in the design and synthesis of macrocycles targeting the p53–MDM2 interaction demonstrating the potential of these

Annulation of 1H-pyrrole-2,3-diones by thioacetamide: an approach to 5-azaisatins

• Aleksandr I. Kobelev,
• Ekaterina E. Stepanova,
• Maksim V. Dmitriev and
• Andrey N. Maslivets

Beilstein J. Org. Chem. 2019, 15, 364–370, doi:10.3762/bjoc.15.32

• heterocycles; thioamides; Introduction Omnipresent among natural compounds and drugs, the indole core is a privileged scaffold for library design and drug discovery [1]. Its dioxo derivative, isatin (1H-indole-2,3-dione), is an important building block for the construction of diverse indole-based compounds

Oxidative radical ring-opening/cyclization of cyclopropane derivatives

• Yu Liu,
• Qiao-Lin Wang,
• Zan Chen,
• Cong-Shan Zhou,
• Bi-Quan Xiong,
• Pan-Liang Zhang,
• Chang-An Yang and
• Quan Zhou

Beilstein J. Org. Chem. 2019, 15, 256–278, doi:10.3762/bjoc.15.23

• indole moiety to afford the target product 64 along with the regenerated Rh(III) catalyst. A silver-catalyzed intramolecular cascade amination/ring-opening/cyclization of a variety of substituted MCPs 69 was proposed by Fan and co-workers, which provided a simple and efficient way for the building of

• and vinyl azides 92 for the synthesis of azaheterocyles 93 (Scheme 20) [98]. This strategy could also be applied to the synthesis of the quaternary indole alkaloid and melinonine-E. Quinones play an important role in organic chemistry because of their unique structure. In 2013, Malayappasamy and co

Mn-mediated sequential three-component domino Knoevenagel/cyclization/Michael addition/oxidative cyclization reaction towards annulated imidazo[1,2-a]pyridines

• Olga A. Storozhenko,
• Alexey A. Festa,
• Delphine R. Bella Ndoutoume,
• Alexander V. Aksenov,
• Alexey V. Varlamov and
• Leonid G. Voskressensky

Beilstein J. Org. Chem. 2018, 14, 3078–3087, doi:10.3762/bjoc.14.287

• diverse substitution patterns in the aldehyde component (Scheme 2). According to the literature [47][48][49][50][51][52], the introduction of an indole core into a chromene moiety is an appealing task, which prompted us to investigate the possibility to use this nucleophile in the discovered process. The

• previously optimized conditions worked nicely for the reaction of N-(cyanomethyl)pyridinium chloride, o-hydroxybenzaldehyde and indole, producing the desired compound 6a with good 77% yield (Scheme 3, footnote a). Unfortunately, the employment of N-methylindole resulted in the formation of the inseparable

Ring-closing-metathesis-based synthesis of annellated coumarins from 8-allylcoumarins

• Christiane Schultze and
• Bernd Schmidt

Beilstein J. Org. Chem. 2018, 14, 2991–2998, doi:10.3762/bjoc.14.278

• work by Arisawa et al. [75], who reported a synthesis of indoles by RCM of sterically less encumbered enamides, we investigated the RCM of 20. Unfortunately, no conversion to the indole 22 could be observed under various conditions. Ring-closing metathesis of 19 was, in contrast, successful and

• attempted synthesis of indole 22. Synthesis of 8-allyl-7-hydroxycoumarins 8. Synthesis of oxepino- 11 and furanocoumarins 3 from a common precursor 9. Synthesis of acrylates 12. Optimization of RCM conditions and synthesis of annellated coumarins 13. Synthesis of pyran-2-one-annellated coumarins 15 via

Synthesis of indole–cycloalkyl[b]pyridine hybrids via a four-component six-step tandem process

• Muthumani Muthu,
• Rakkappan Vishnu Priya,
• Abdulrahman I. Almansour,
• Raju Suresh Kumar and
• Raju Ranjith Kumar

Beilstein J. Org. Chem. 2018, 14, 2907–2915, doi:10.3762/bjoc.14.269

• condensation–nucleophilic addition to carbonyl–Michael addition–N-cyclization–elimination–air oxidation sequence to afford structurally intriguing indole–cycloalkyl[b]pyridine-3-carbonitrile hybrid heterocycles in excellent yields. Keywords: cycloalkyl[b]pyridine-3-carbonitrile; cyclododecanone; 3-(1H-indol-3

• four-component reaction of cyclic/acyclic ketones, malononitrile, aromatic aldehyde and ammonium acetate affording 2-amino-3-cyanopyridine derivatives have been explored extensively [45][46][47][48][49][50][51][52][53][54][55]. However, syntheses of pyridine scaffolds bearing an indole side chain have

• received less attention. For instance, the multicomponent reactions of aldehydes, 3-(1H-indol-3-yl)-3-oxopropanenitriles and 5-aminopyrazol or naphthylamine afforded indole substituted fused pyridine derivatives [56]. 2-Indole substituted pyridine derivatives have also been prepared through AlCl3-induced C

Protein–protein interactions in bacteria: a promising and challenging avenue towards the discovery of new antibiotics

• Laura Carro

Beilstein J. Org. Chem. 2018, 14, 2881–2896, doi:10.3762/bjoc.14.267

• -based design built on the indoloquinolizinone 35 (Figure 8), afforded the chimeric molecule indole 36 (Figure 8) as an inhibitor of the ZipA/FtsZ interaction with an improved, but still modest, IC50 of 192 μM. The antibacterial activity of all the target compounds was also evaluated against a panel of

• library of small molecules whose inhibition properties were measured by a fluorescence polarization competition assay [89]. Derivatization of the indole nitrogen atom of lead compound 36 (Figure 8) returned the interesting indole analogue 37 (Figure 8). The authors then confirmed that the compounds were

• . catarrhalis, and E. coli (imp). Unfortunately, the most active compound, indole 37, exhibited an IC50 = 296 μM and a dissociation constant of 105 μM which undoubtedly make it a too weak inhibitor. Excitingly, the results are consistent with the inhibition of the ZipA/FtsZ interaction measured by FP and

An overview on recent advances in the synthesis of sulfonated organic materials, sulfonated silica materials, and sulfonated carbon materials and their catalytic applications in chemical processes

• Hashem Sharghi,
• Pezhman Shiri and
• Mahdi Aberi

Beilstein J. Org. Chem. 2018, 14, 2745–2770, doi:10.3762/bjoc.14.253

• (57). Two peaks due to C=C and C=N were observed at 1680 and 1540 cm−1. The bands at the range of 1200–1000 cm−1 are due to SO2 asymmetric and symmetric vibrations. A variety of aryl or heterocyclic aldehydes 7, 38, and 58 were reacted with indole or 5-bromo-1H-indole (6a) to synthesize the desired

Targeting the Pseudomonas quinolone signal quorum sensing system for the discovery of novel anti-infective pathoblockers

• Christian Schütz and
• Martin Empting

Beilstein J. Org. Chem. 2018, 14, 2627–2645, doi:10.3762/bjoc.14.241

• conformation of the PqsR-DNA binding domain, whereas the LBD is not affected extensively. Aryloxyacetindoles Spero Therapeutics further optimized M64 (42), firstly by changing the phenoxyphenylamide into a carbonyl-linked indole containing a hetarylether (43) [80]. Afterwards they varied the linkage of the

Synthesis of 3-aminocoumarin-N-benzylpyridinium conjugates with nanomolar inhibitory activity against acetylcholinesterase

• Nisachon Khunnawutmanotham,
• Cherdchai Laongthipparos,
• Patchreenart Saparpakorn,
• Nitirat Chimnoi and
• Supanna Techasakul

Beilstein J. Org. Chem. 2018, 14, 2545–2552, doi:10.3762/bjoc.14.231

• . Hybrid compounds such as huperzine A–tacrine hybrids [5], donepezil–tacrine hybrid related derivatives [6][7] and tacrine–indole hybrids [8] with dual-binding site properties exhibit potent AChE inhibition activities. In addition, coumarin compounds linked with various side chain moieties [9][10][11] as

Cobalt- and rhodium-catalyzed carboxylation using carbon dioxide as the C1 source

• Tetsuaki Fujihara and
• Yasushi Tsuji

Beilstein J. Org. Chem. 2018, 14, 2435–2460, doi:10.3762/bjoc.14.221

• diverse alkenyl triflates was also examined. As a result, the desired carboxylic acids 4a–k were obtained in good-to-high yields, as shown in Scheme 5. Notably, the ester and p-toluenesulfonate functionalities in 4c and 4d, respectively, were tolerated. An indole-functionalized substrate 3f was converted

• in good TON. Benzofuran (32h) and indole (32i) also gave the carboxylic acids, which were isolated as their methyl esters. Li and co-workers reported the Rh-catalyzed site-selective C(sp2)–H carboxylation reaction using 2-arylphenols as the substrates (Scheme 31) [62]. The desired reactions proceeded

Synthesis of indolo[1,2-c]quinazolines from 2-alkynylaniline derivatives through Pd-catalyzed indole formation/cyclization with N,N-dimethylformamide dimethyl acetal

• Antonio Arcadi,
• Sandro Cacchi,
• Giancarlo Fabrizi,
• Francesca Ghirga,
• Antonella Goggiamani,
• Antonia Iazzetti and
• Fabio Marinelli

Beilstein J. Org. Chem. 2018, 14, 2411–2417, doi:10.3762/bjoc.14.218

• related to hinckdentine A received increasing attention as a source of new and useful pharmaceuticals. One well-established approach is based on the elaboration of a preformed indole ring, for example through cyclocondensation of 2-(o-aminophenyl)indoles with 2-cyanobenzothiazoles [14], aldehydes [9] and

• -(o-aminophenyl)indole derivatives followed by further cyclization [19][20][21][22]. Our interest in this field led to the development of an original approach to 6-trifluoromethyl-12-aryl(vinyl)indolo[1,2-c]quinazolines 4 through sequential Pd-catalyzed reactions of bis(o-trifluoroacetamidophenyl

• )acetylene (1) with aryl or vinyl halides and triflates followed by cyclization reactions (Scheme 1) [19]. The reaction, which tolerates a variety of important functional groups, likely involves the formation of the indole intermediates 2 (through aminopalladation/reductive elimination) [20][21] followed by

Correction: Varioloid A, a new indolyl-6,10b-dihydro-5aH-[1]benzofuro[2,3-b]indole derivative from the marine alga-derived endophytic fungus Paecilomyces variotii EN-291

• Peng Zhang,
• Xiao-Ming Li,
• Xin-Xin Mao,
• Attila Mándi,
• Tibor Kurtán and
• Bin-Gui Wang

Beilstein J. Org. Chem. 2018, 14, 2394–2395, doi:10.3762/bjoc.14.215

Hydroarylations by cobalt-catalyzed C–H activation

• Rajagopal Santhoshkumar and
• Chien-Hong Cheng

Beilstein J. Org. Chem. 2018, 14, 2266–2288, doi:10.3762/bjoc.14.202

• . Indoles also efficiently participated in intra- and intermolecular hydroarylation reactions to access useful organic skeletons [70][71][72][73]. Thus, the reaction of indole bearing an aldimine and homoallyl group 29 in the presence of CoBr2, SIMes·HCl and Me3SiCH2MgCl gave dihydropyrroloindoles 30

• in the presence of CoCp*(CO)I2 and AgNTf2 (Scheme 38) [98]. The reaction tolerated various pyrimidine containing arenes, such as indole, phenyl, and pyrrole with different ketenimines to form enaminylation products 61. Subsequently, the hydroarylation products 61 were further converted into bioactive

Applications of organocatalysed visible-light photoredox reactions for medicinal chemistry

• Michael K. Bogdos,
• Emmanuel Pinard and
• John A. Murphy

Beilstein J. Org. Chem. 2018, 14, 2035–2064, doi:10.3762/bjoc.14.179

• benzofused heterocycles (indole etc.) – such as benzimidazoles or tetrazolopyridines are often seen in medicinal chemistry. Singh et al. reported a method for preparing 3-arylnitrobenzimidazoles from 2-aminopyridines and nitroalkanes, using green LED Eosin Y photocatalysis, with molecular oxygen as the

Anomeric modification of carbohydrates using the Mitsunobu reaction

• Julia Hain,
• Patrick Rollin,
• Werner Klaffke and
• Thisbe K. Lindhorst

Beilstein J. Org. Chem. 2018, 14, 1619–1636, doi:10.3762/bjoc.14.138

• ]. In spite of the fact that parent indole is too weak an acid to undergo Mitsunobu conversions, a model maleimide–indole hybrid was investigated by Ohkubo and colleagues to pave the way for the synthesis of indolo[2,3-a]pyrrolo[3,4-c]carbazole compounds with anticancer activity [90][91]. N-Glycosides

• of indole derivatives were also approached by Zembower et al. employing 2,3,4,6-tetra-O-benzyl glucopyranose in a Mitsunobu reaction [92]. In the same period, Prudhomme’s group followed closely related approaches for the N-glycosylation of indolic structures. Various rebeccamycin analogues were

Hypervalent organoiodine compounds: from reagents to valuable building blocks in synthesis

• Gwendal Grelier,
• Benjamin Darses and
• Philippe Dauban

Beilstein J. Org. Chem. 2018, 14, 1508–1528, doi:10.3762/bjoc.14.128

• ligands, and tolerates a variety of substituents on both the indole and the iodonium salt. However, the atom-economy of the reaction is limited by the need to use the iodonium salts in slight excess (1.5 equivalents). Another multicomponent reaction has been designed for the preparation of

• indoles with diaryl-λ3-iodanes (Scheme 36) [75]. The reaction first involves the use of 20 mol % of CuI and 1.1 equivalents of di-tert-butylpyridine (dtbpy) to convert the indole to the C3–H arylated product. The released Ar–I building block, then, can be engaged in the subsequent step of N–H arylation by

Hyper-reticulated calixarene polymers: a new example of entirely synthetic nanosponge materials

• Alberto Spinella,
• Marco Russo,
• Antonella Di Vincenzo,
• Delia Chillura Martino and
• Paolo Lo Meo

Beilstein J. Org. Chem. 2018, 14, 1498–1507, doi:10.3762/bjoc.14.127

• (bromocresol green, 8), a bis-indole (indigo carmine, 9) and a naphthalene-bis-diazoic (naphthol blue-black, 10), in order to evaluate the outcome of molecular size, shape and electric charge. Dyes can be considered suitable and easily detectable models of pollutants [43][44][45][46][47], for the removal of