Identification of the new prenyltransferase Ubi-297 from marine bacteria and elucidation of its substrate specificity

• Jamshid Amiri Moghaddam,
• Huijuan Guo,
• Karsten Willing,
• Thomas Wichard and
• Christine Beemelmanns

Beilstein J. Org. Chem. 2022, 18, 722–731, doi:10.3762/bjoc.18.72

• farnesylation of quinoline derivatives, such as 8-hydroxyquinoline-2-carboxylic acid (8-HQA) and quinaldic acid. The results of this study provide new insights into the abundance and diversity of Ptases in marine Flavobacteria and beyond. Keywords: Flavobacteria; prenylation; Saccharomonospora; UbiA-like

• obtained after washing and ultracentrifugation. Substrate specificity of UbiA-297 Based on our in silico analysis and previous mass-spectrometry-guided metabolomic analysis of marine Flavobacteria and members of the genus Saccharomonospora [29][30], we anticipated hydroxylated aromatic or even quinoline

• ). As depicted in Figure 5, farnesylated products were detectable for six out of 14 tested aromatic acceptor substrates by HRMS/MS (Figures S4–S8 in Supporting Information File 1). In particular, quinoline-type substrates, such as 8-HQA and quinaldic acid, were transformed, while only moderate

Chemistry of polyhalogenated nitrobutadienes, 17: Efficient synthesis of persubstituted chloroquinolinyl-1H-pyrazoles and evaluation of their antimalarial, anti-SARS-CoV-2, antibacterial, and cytotoxic activities

• Viktor A. Zapol’skii,
• Isabell Berneburg,
• Ursula Bilitewski,
• Melissa Dillenberger,
• Katja Becker,
• Stefan Jungwirth,
• Aditya Shekhar,
• Bastian Krueger and
• Dieter E. Kaufmann

Beilstein J. Org. Chem. 2022, 18, 524–532, doi:10.3762/bjoc.18.54

• -(1H-1,2,4-triazol-1-yl)-1H-pyrazol-1-yl)quinoline (3b) and 7-chloro-4-(3-((4-chlorophenyl)thio)-5-(dichloromethyl)-4-nitro-1H-pyrazol-1-yl)quinoline (9e) inhibited the growth of the chloroquine-sensitive Plasmodium falciparum strain 3D7 with EC50 values of 0.2 ± 0.1 µM (85 ng/mL, 200 nM) and 0.2

• , such as 7-chloro-4-(4-trimethylsilylethynyl-1-pyrazolyl)quinoline at 100 ppm which gave a 100% curative effect in barley infected with barley powdery mildew [23]. A statistical model to predict the structural requirement of 4-(5-trifluoromethyl-1H-pyrazol-1-yl)chloroquine derivatives to inhibit

1,2-Naphthoquinone-4-sulfonic acid salts in organic synthesis

• Ruan Carlos B. Ribeiro,
• Patricia G. Ferreira,
• Amanda de A. Borges,
• Luana da S. M. Forezi,
• Fernando de Carvalho da Silva and
• Vitor F. Ferreira

Beilstein J. Org. Chem. 2022, 18, 53–69, doi:10.3762/bjoc.18.5

• give 1-amino-4-butylaminoanthraquinone. Similarly, quinoline-5,8-diones react with amines under catalysis with Ni(II) ions to selectively give substituted amino derivatives [101][102]. The same group demonstrated that the reactions between β-NQS 18 and N,N’-dialkylanilines or 1,1-bis[p(dimethylamino

A photochemical C=C cleavage process: toward access to backbone N-formyl peptides

• Haopei Wang and
• Zachary T. Ball

Beilstein J. Org. Chem. 2021, 17, 2932–2938, doi:10.3762/bjoc.17.202

• aqueous photocleavage in the presence of triethylamine, and the resulting reaction mixture was purified by reversed-phase HPLC (Figure 2). We isolated a nitroso product 3, in addition to two other major identifiable components of the crude reaction: quinoline N-oxide (4) and quinolinone (5). The compounds

Photophysical, photostability, and ROS generation properties of new trifluoromethylated quinoline-phenol Schiff bases

• Inaiá O. Rocha,
• Yuri G. Kappenberg,
• Wilian C. Rosa,
• Clarissa P. Frizzo,
• Nilo Zanatta,
• Marcos A. P. Martins,
• Isadora Tisoco,
• Bernardo A. Iglesias and
• Helio G. Bonacorso

Beilstein J. Org. Chem. 2021, 17, 2799–2811, doi:10.3762/bjoc.17.191

• more polar solvents (DMSO; 65–150 nm and MeOH; 65–130 nm) than in CHCl3 (59–85 nm). Compounds 3 presented good stability under white-LED irradiation conditions and moderate ROS generation properties were observed. Keywords: photophysical properties; photostability; quinoline; ROS generation; Schiff

• literature by our research group [14]. With the quinolines 1a–f at hands we initially selected quinoline 1b and salicylaldehyde (2a) to optimize the reaction conditions leading to Schiff bases 3. Hence, the reaction solvent and molar ratio between the precursors were evaluated. The reactions were carried out

• ). Based on these results, we selected acetonitrile as the best solvent for further optimization. When changing the molar ratio of the reactants to a 1:2 molar ratio of quinoline 1b and salicylaldehyde (2a), the yield of the desired product 3ba increased to 90%. The best result was obtained when quinoline

Recent advances in the asymmetric phosphoric acid-catalyzed synthesis of axially chiral compounds

• Alemayehu Gashaw Woldegiorgis and
• Xufeng Lin

Beilstein J. Org. Chem. 2021, 17, 2729–2764, doi:10.3762/bjoc.17.185

• (Brønsted acidity/basicity, hydrogen-bonding units, and counter-anions toward metals) [48][49]. In 2019, Shi, Lin, and co-workers achieved an enantioselective synthesis of axially chiral quinoline-derived biaryl atropisomers via Pd-catalyzed C–H olefination of 8-phenylquinoline (11) using a novel chiral

• spirophosphoric acid (CPA 4). A wide range of quinoline-derived biaryls 13 with various substituents was synthesized in good to excellent yields (up to 99%) with excellent enantioselectivities (up to 98% ee) (Scheme 5). A working model for the origin of enantioselectivity in C–H olefination was provided by

• -naphthol derivatives. Enantioselective synthesis of multisubstituted biaryls. Enantioselective synthesis of axially chiral quinoline-derived biaryl atropisomers mediated by chiral spirophosphoric acid catalyst CPA 4. Pd-Catalyzed atroposelective C–H olefination of biarylamines. Palladium-catalyzed directed

Copper-catalyzed monoselective C–H amination of ferrocenes with alkylamines

• Zhen-Sheng Jia,
• Qiang Yue,
• Ya Li,
• Xue-Tao Xu,
• Kun Zhang and
• Bing-Feng Shi

Beilstein J. Org. Chem. 2021, 17, 2488–2495, doi:10.3762/bjoc.17.165

• in 2020, an enantioselective C–H annulation of ferrocenylformamides with alkynes was achieved by the Ye group enabled by Ni-Al bimetallic catalysis and a chiral secondary phosphine oxide (SPO) ligand [35]. Hou et al. also reported the asymmetric C−H alkenylation of quinoline- and pyridine-substituted

Synthesis and investigation on optical and electrochemical properties of 2,4-diaryl-9-chloro-5,6,7,8-tetrahydroacridines

• Najeh Tka,
• Mohamed Adnene Hadj Ayed,
• Mourad Ben Braiek,
• Mahjoub Jabli and
• Peter Langer

Beilstein J. Org. Chem. 2021, 17, 2450–2461, doi:10.3762/bjoc.17.162

• and, as expected, the cyclohexane ring is not involved. In all cases, the electron densities of HOMO were localized in the π-bonding orbitals between the carbon backbone of the quinoline ring and its two external phenyls. The LUMO electron densities were mainly located in the π* antibonding orbitals

• surfaces around the phenyl groups leading to a significant decrease in their electronic densities. However, thanks to the π-donating effect of two methoxy groups for 4b and 4d, yellow-red regions are present in the phenyl groups and quinoline core. The electrochemical behavior of compound 4c was studied by

Base-free enantioselective S_N2 alkylation of 2-oxindoles via bifunctional phase-transfer catalysis

• Mili Litvajova,
• Emiliano Sorrentino,
• Brendan Twamley and
• Stephen J. Connon

Beilstein J. Org. Chem. 2021, 17, 2287–2294, doi:10.3762/bjoc.17.146

• , the reactions were carried out under base-free conditions. It was found that urea-based catalysts outperformed squaramide derivatives, and that the installation of a chlorine atom adjacent to the catalyst’s quinoline moiety aided in avoiding selectivity-reducing complications related to the production

• to the ability of squaramides to bind anionic species more strongly than ureas. The moderate enantiocontrol observed thus far prompted us to posit that the nitrogen atom on the quinoline moiety of the catalyst could participate to the deprotonation of 5a, therefore, leading to less selective

• alkylation. In order to test this hypothesis, we designed novel dihydroquinine-derived catalysts of general type 9 bearing an electron-withdrawing substituent at the C-2' position with the intent of lowering the basicity of the quinoline ring. In addition, we prepared a C-2'-phenyl-substituted dihydroquinine

Halides as versatile anions in asymmetric anion-binding organocatalysis

• Lukas Schifferer,
• Martin Stinglhamer,
• Kirandeep Kaur and
• Olga García Macheño

Beilstein J. Org. Chem. 2021, 17, 2270–2286, doi:10.3762/bjoc.17.145

• activation proposal was later on reported from the Takemoto group in 2007, where the less reactive quinoline derivatives 23 were employed in a thiourea-catalyzed Reissert reaction (Scheme 5b) [37]. In both cases, however, the binding mode of the catalyst can rather be described by the formation of a close

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

• catalyst to perform a regioselective scandium-catalyzed alkylation of 2-phenylquinoline derivatives (Scheme 3B) [38]. It is important to highlight the biological importance of quinoline derivatives, since several quinolines are known to present valuable biological activities, such as anti-HIV (5) [48

Chemical approaches to discover the full potential of peptide nucleic acids in biomedical applications

• Nikita Brodyagin,
• Martins Katkevics,
• Venubabu Kotikam,
• Christopher A. Ryan and
• Eriks Rozners

Beilstein J. Org. Chem. 2021, 17, 1641–1688, doi:10.3762/bjoc.17.116

• thiazole and quinoline, TO fluorescence is almost completely quenched in ssPNA, but increases significantly upon hybridization to the complementary DNA [150]. The intercalation of TO in PNA–DNA duplex restricts rotation around the methine bond enforcing planarity of the two TO’s aromatic system, which

• base pairs in dsRNA [153][154]. Replacement of thiazole in TO with another quinoline gives bis-quinoline (BisQ, Figure 10), a red-shifted PNA nucleobase analogous to TO [155]. Although binding of BisQ with all four natural DNA nucleobases has not been explored in detail, BisQ-modified FIT PNAs showed

2,4-Bis(arylethynyl)-9-chloro-5,6,7,8-tetrahydroacridines: synthesis and photophysical properties

• Najeh Tka,
• Mohamed Adnene Hadj Ayed,
• Mourad Ben Braiek,
• Mahjoub Jabli,
• Noureddine Chaaben,
• Kamel Alimi,
• Stefan Jopp and
• Peter Langer

Beilstein J. Org. Chem. 2021, 17, 1629–1640, doi:10.3762/bjoc.17.115

• the quinoline core and its two arylethynyl groups. As shown in Figure 2, the unsubstituted derivative 4a exhibited wide bands with two maxima at 346 and 365 nm. A methyl group at the ortho position have a minor impact and derivative 4b showed similar optical transitions with a slight red shift. While

• attributed to intermolecular charge transfer between the oxygen lone pair electrons and the quinoline core. The unsubstituted derivative 4a presents an onset of absorption (λonset) at 389 nm and its optical band gap was deduced to be around 3.18 eV. Tetrahydroacridines 4e and 4f showed approximately the same

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

• -amidinopyrazole under the same reaction conditions. Edmont et al. extended this method using hydrazides as nucleophiles to produce potential hypoglycemic quinoline carboxyguanidine derivatives (Scheme 33) [70]. In this case, the “biguanidylation” reagent could convert the hydrazide into the desired compound

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

• ). Abonia and co-workers [85] established a catalyst-free construction of quinoline-based pyridopyridines 97 by employing a microwave-assisted three-component reaction of 3-formyl-2-oxoquinoline derivatives 95, 2,4,6-triaminopyrimidine (96) and a cyclic 1,3-diketone such as dimedone (6a) in DMF. The

• opening resulting in imine intermediate E. A consecutive intramolecular cyclization and tautomerization yields azepino[5,4,3-cd]indoles 143b. 9 Quinolines Quinolines are bicyclic aromatic heterocycles consisting of a fused pyridine and benzene ring. Quinoline and its derivatives are important both from

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

• phenanthridine 38 (also including quinoline products, Scheme 12). In this way, a nitrogen-centered radical was given via the EDA complex that was initiated by single-electron transfer, accomplishing the synthesis of a variety of highly functionalized nitrogen-containing aromatics with excellent yield. In 2019

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

• , Yokohama University of Pharmacy, 601 Matano, Totsuka-ku, Yokohama 245-0066, Japan 10.3762/bjoc.17.62 Abstract The first total synthesis of the pyrrolo[2,3-c]quinoline alkaloid trigonoine B (1) was accomplished via a six-step sequence involving the construction of an N-substituted 4-aminopyrrolo[2,3-c

• ]quinoline framework via electrocyclization of 2-(pyrrol-3-yl)benzene containing a carbodiimide moiety as a 2-azahexatriene system. The employed six-step sequence afforded trigonoine B (1) in 9.2% overall yield. The described route could be employed for the preparation of various N-substituted 4

• -aminopyrroloquinolines with various biological activities. Keywords: 2-azahexatiriene system; carbodiimide; electrocyclization; pyrrolo[2,3-c]quinoline; trigonoine B; Introduction In 2011, two novel alkaloids, namely trigonoine A and B, were isolated from the leaves of Trigonostemon lii by Hao and co-workers [1]. The

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

• ][37][38][39][40][41][42][43][44][45]. For example, Yin and co-workers developed a protocol for the deoxygenative C2-amination of pyridine/quinoline N-oxides using t-BuNH2 and Ts2O/TFA in 2007 (Scheme 1a) [48]. Later, Londregan and co-workers were successful in achieving C2-amination employing

• derivatives is highly desired. The continuous interest and efforts of our group for the derivatization of quinoline moieties [57] and use of N-sulfonyl-1,2,3-triazoles as heterocyclic precursors encouraged us to develop a new strategy for the regioselective C2-triazolylation of quinoline N-oxide under mild

CF₃-substituted carbocations: underexploited intermediates with great potential in modern synthetic chemistry

• Anthony J. Fernandes,
• Armen Panossian,
• Bastien Michelet,
• Agnès Martin-Mingot,
• Frédéric R. Leroux and
• Sébastien Thibaudeau

Beilstein J. Org. Chem. 2021, 17, 343–378, doi:10.3762/bjoc.17.32

• , affording biaryl species 161. Using this strategy, several trifluoromethyl ketones 162 and alcohols 163 bearing heteroaryl substituents (i.e., benzothiazole, quinoline, isoquinoline, benzimidazole, or imidazole) prone to be protonated were elegantly converted into the corresponding alcohols 163 and biphenyl

Decarboxylative trifluoromethylthiolation of pyridylacetates

• Ryouta Kawanishi,
• Kosuke Nakada and
• Kazutaka Shibatomi

Beilstein J. Org. Chem. 2021, 17, 229–233, doi:10.3762/bjoc.17.23

• gave the desired products 2e–g in moderate yields. The method could also be applied to substrates with quinoline and isoquinoline backbones to afford the corresponding products 2h and 2i. In addition, the reaction of α-monosubstituted 2-pyridylacetate 8 was performed to yield the corresponding mono

Synthesis of imidazo[1,5-a]pyridines via cyclocondensation of 2-(aminomethyl)pyridines with electrophilically activated nitroalkanes

• Dmitrii A. Aksenov,
• Nikolai A. Arutiunov,
• Vladimir V. Maliuga,
• Alexander V. Aksenov and
• Michael Rubin

Beilstein J. Org. Chem. 2020, 16, 2903–2910, doi:10.3762/bjoc.16.239

• -(bromomethyl)quinoline (21c) was prepared from commercially available 6-bromo-2-methylquinoline (22c, via radical bromination in the presence of NBS and dibenzoyl peroxide [51]. To this end, the methylquinoline 22c (3.33 g, 15 mmol) was dissolved in carbon tetrachloride (30 mL), and N-bromosuccinimide (2.94 g

• was concentrated in vacuum. The crude product was purified by flash column chromatography eluting with EtOAc/petroleum ether 1:6. Then, the amine was afforded via a Gabriel synthesis using a modified protocol described in the literature [52]. To a stirred solution of 6-bromo-2-(bromomethyl)quinoline

• , 118.5, 113.5; ATR-FTIR (ZnSe) νmax: 3066, 1749, 1676, 1603, 1473, 1458, 1433, 1358, 1305, 1251, 1267, 1120 cm−1; HRESIMS (TOF) m/z: [M + H]+ calcd for C13H11N2, 195.0917; found, 195.0918. 6-Bromo-7-methoxyimidazo[1,5-a]quinoline (19de) The title compound was obtained via the typical procedure 2

Synthesis and characterization of S,N-heterotetracenes

• Astrid Vogt,
• Florian Henne,
• Christoph Wetzel,
• Elena Mena-Osteritz and
• Peter Bäuerle

Beilstein J. Org. Chem. 2020, 16, 2636–2644, doi:10.3762/bjoc.16.214

• -substituted thienopyrrole 26, saponification to carbonic acid 27, and subsequent Cu-mediated decarboxylation in quinoline resulted in thienopyrrole 28 in more than 80% yield over three steps. Lithiation of 28 with n-BuLi and reaction with TIPS chloride selectively occurred at the thiophene α-position to give

Recent synthesis of thietanes

• Jiaxi Xu

Beilstein J. Org. Chem. 2020, 16, 1357–1410, doi:10.3762/bjoc.16.116

Copper-based fluorinated reagents for the synthesis of CF₂R-containing molecules (R ≠ F)

• Louise Ruyet and
• Tatiana Besset

Beilstein J. Org. Chem. 2020, 16, 1051–1065, doi:10.3762/bjoc.16.92

• ). The reaction was efficient (65 examples, up to 97% yield), showed a good functional group tolerance (i.e., cyano, ester, ketone) and even heteroarenes such as pyridine, quinoline and quinoxaline were functionalized with the four fluorinated moieties (Scheme 17). In situ-generated copper-based

Fluorinated phenylalanines: synthesis and pharmaceutical applications

• Laila F. Awad and
• Mohammed Salah Ayoup

Beilstein J. Org. Chem. 2020, 16, 1022–1050, doi:10.3762/bjoc.16.91

• other hand, when the quinoline-based ligand 162 was used, it was shown to promote the palladium-catalyzed direct electrophilic fluorination of β-methylene C(sp3)–H bonds. Thus, fluorinations of ʟ-phenylalanine 4-trifluoromethylphenylamides 161a–l carrying a range of functional groups such as fluoro

• -fluorinated Phe derivatives using quinoline-based ligand 162 in the Pd-catalyzed direct fluorination of β-methylene C(sp3)–H bonds. Synthesis of β,β-difluorophenylalanine derivatives from 2,2-difluoroacetaldehyde derivatives 164a,b. Synthesis of β,β-difluorophenylalanine derivatives via an imine chiral