Synthesis and antimicrobial activity of 1H-1,2,3-triazole and carboxylate analogues of metronidazole

• Satya Kumar Avula,
• Syed Raza Shah,
• Khdija Al-Hosni,
• Muhammad U. Anwar,
• Rene Csuk,
• Biswanath Das and
• Ahmed Al-Harrasi

Beilstein J. Org. Chem. 2021, 17, 2377–2384, doi:10.3762/bjoc.17.154

• -Wittenberg, Kurt-Mothes-Str. 2, d-06120, Halle (Saale), Germany 10.3762/bjoc.17.154 Abstract Herein, a series of novel 1H-1,2,3-triazole and carboxylate derivatives of metronidazole (5a–i and 7a–e) were synthesized and evaluated for their antimicrobial activity in vitro. All the newly synthesized compounds

• inhibiting effects compared to the activity of the parent compound. Amongst the tested compounds 5b, 5c, 5e, 7b and 7e displayed excellent potent antimicrobial activity. The current study has demonstrated the usefulness of the 1H-1,2,3-triazole moiety in the metronidazole skeleton. Keywords: antimicrobial

• agents; carboxylate analogues; 1H-1,2,3-triazole analogues; metronidazole; synthesis; Introduction Metronidazole (1) is an important antimicrobial agent which has been clinically used successfully for a long time. It was originally used for the treatment of infections caused by Trichomonas varginalis

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

• , but also to cation–H or π–π interactions. Some of the advantages of multidentate, supramolecular anion-binding catalysis were recently exploited by the Feringa group, who designed an anion-binding catalyst 86 that fuses the known triazole binding properties with a light-switchable molecular motor. In

• this way, they were not only able to control the folding of the triazole units through successive irradiation and thermal excitation, but they could also selectively control the stereochemical outcome of the benchmark reaction of 1-chloroisochromane (73) with silylketene acetals (Scheme 19) [92]. Such

(Phenylamino)pyrimidine-1,2,3-triazole derivatives as analogs of imatinib: searching for novel compounds against chronic myeloid leukemia

• Luiz Claudio Ferreira Pimentel,
• Lucas Villas Boas Hoelz,
• Henayle Fernandes Canzian,
• Frederico Silva Castelo Branco,
• Andressa Paula de Oliveira,
• Vinicius Rangel Campos,
• Floriano Paes Silva Júnior,
• Rafael Ferreira Dantas,
• Jackson Antônio Lamounier Camargos Resende,
• Anna Claudia Cunha,
• Nubia Boechat and
• Mônica Macedo Bastos

Beilstein J. Org. Chem. 2021, 17, 2260–2269, doi:10.3762/bjoc.17.144

• )pyrimidine-pyridine (PAPP) group as a pharmacophoric fragment, and these compounds were biologically evaluated. The synthesis of twelve new compounds was performed in three steps and assisted by microwave irradiation in a 1,3-dipolar cycloaddition to obtain 1,2,3-triazole derivatives substituted on carbon C

• -4 of the triazole nucleus. All compounds were evaluated for their inhibitory activities against a chronic myeloid leukemia cell line (K562) that expresses the enzyme tyrosine kinase BCR-Abl-1 and against healthy cells (WSS-1) to observe their selectivity. Three compounds showed promising results

• in the docking studies. Keywords: chronic myeloid leukemia; 1,3-dipolar cycloaddition; imatinib; (phenylamino)pyrimidine-pyridine; 1,2,3-triazole; Introduction Changes in tyrosine kinase proteins (TKPs), either by mutation or chromosomal translocation, can turn them into potent oncogenes

Chemical syntheses and salient features of azulene-containing homo- and copolymers

• Vijayendra S. Shetti

Beilstein J. Org. Chem. 2021, 17, 2164–2185, doi:10.3762/bjoc.17.139

• (146) and triazole-containing azulene methacrylate 150, whose synthesis is outlined in Scheme 25. The azulene-2-yl methacrylate (146) was synthesized in 75% yield from 2-hydroxyazulene (145) by treating it with methacryloyl chloride in chloroform (Scheme 25A). The 2-hydroxyazulene (145) was converted

• to 2-bromoazulene (147) and subsequently to the TMS acetylene derivative 148 suitable for the ‘click’ reaction [46] to obtain the triazole 149, which was eventually transformed into the triazole-containing azulene methacrylate monomer 150 (Scheme 25B). The monomers 146 and 150 were then subjected to

• -2-yl methacrylate (146) and (B) the triazole-containing azulene methacrylate 150. Synthesis of (A) azulene methacrylate polymer 151 and (B) triazole-containing azulene methacrylate polymer 152. Synthesis of azulene methyl methacrylate polymers 154, 155 (A and B) and azulene-sulfobetaine methacrylate

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

• commercially available 3’-phosphoramidite derivative of 5’-O-dimethoxytrityl-2’-O-methyluridine could be converted into an N4-triazole-modified 2’-OMe-cytidine phosphoramidite [60]. This concept was later used to prepare spermine-functionalized 2’-OMe and 2’-O-((2-methoxy)ethyl) (MOE)cytidine phosphoramidites

• complementary RNA [61]. In general, the study showed that the modifications had a positive effect on Tm for the formed ON/RNA duplex for all ONs substituted with cytidine monomers 26 or 27. These findings were also in agreement with an earlier study where the conjugation of a spermine-substituted triazole group

• -toluenesulfonyl-5’-O-dimethoxytrityl-2’-deoxycytidine followed by ON synthesis [63]. A less investigated strategy is the anchoring of amine functionalities onto purines. Beginning with adenine, the N6 position has been the most explored attachment point. For example, a 2’-deoxy-N6-triazole-substituted adenosine

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

• synthesis of a wide variety of relevant 1,4,5-trisubstituted 1,2,3-triazole molecules are reported. The synthesis of this category of diverse fully functionalized 1,2,3-triazoles has become a necessary and unique research subject in modern synthetic organic key transformations in academia, pharmacy, and

• -triazoles; N-containing heterocycles; 1,4,5-trisubstituted 1,2,3-triazoles; Introduction A high number of N-heterocycles [1][2][3][4] are identified, and this number is increasing very quickly [5][6][7][8]. Among them, the small heterocyclic ring of the 1,2,3-triazole is present in a broad variety of

• compounds with not only biological but also industrial significance [9][10][11]. It possesses a cyclic scaffold with carbon and three nitrogen elements in the ring [12][13][14][15]. An immense versatility of biological properties is possessed by 1,2,3‐triazole heterocyclic systems, and many strategies are

Double-headed nucleosides: Synthesis and applications

• Vineet Verma,
• Jyotirmoy Maity,
• Vipin K. Maikhuri,
• Ritika Sharma,
• Himal K. Ganguly and
• Ashok K. Prasad

Beilstein J. Org. Chem. 2021, 17, 1392–1439, doi:10.3762/bjoc.17.98

• . The heterocyclic structures which were found to be attached to these double-headed nucleosides include triazolophthalazine [11], 4,6-di-tert-butylbenzoxazole [12], mesitylisoxazole [13], 5-trimethylsilyl-1,2,3-triazole [14], 1-pivaloyloxymethyl-1H-1,2,3-triazole [15], 1,3,4-oxadiazino[6,5-b]indole [16

• ], 6,7-dihydro-6-oxo-5H-1,2,4-triazolo[3,4-b][1,3,4]thiadiazine [17], 1,2,4-triazino[5,6-b]indole [18], 1,3,4-thiadiazoline [19], 1,3,4-oxadiazoline [19], 1,2,4-triazoline [19], 3-mercapto-1H-1,2,4-triazole [20], 1,3,4-oxadiazole-2(3H)-thione [20], 4-amino-5-mercapto-4H-1,2,4-triazole [20], and 1,2,4

• ]. Nielsen and co-workers [43] synthesized 2′-(4-(thymin-1-ylmethyl)-1,2,3-triazole-1-yl)- and 2′-(4-(N6-benzoyladenine-9-ylmethyl)-1,2,3-triazole-1-yl)-substituted double-headed nucleosides of 2′-deoxy-5′-O-(4,4′-dimethoxytrityl)uridine (14 and 15) from the nucleoside azide 12 which in turn was obtained by

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

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

• ). It is interesting to note that heterocyclic nitrogen atoms can also react with cyanoguanidine. For example, Zeng et al. reported the conversion of 1,2,4-triazole derivatives into their related biguanide products in good 70% yield by simple reflux heating in ethanol (Scheme 10). The resulting

Beyond ribose and phosphate: Selected nucleic acid modifications for structure–function investigations and therapeutic applications

• Christopher Liczner,
• Kieran Duke,
• Gabrielle Juneau,
• Martin Egli and
• Christopher J. Wilds

Beilstein J. Org. Chem. 2021, 17, 908–931, doi:10.3762/bjoc.17.76

• (suNA) (Figure 7J) [167], 2'-Me LNAs (Figure 7K) [168][169], 6'-Me-2'-O,4'-C-ethylene-bridged (6'-Me-ENA) (Figure 7L) [170], and various triazole-linked LNA (Figure 7M) [171][172] that have all shown the ability to modulate LNA properties. Arabinose and fluoroarabinose nucleic acids Arabino nucleic

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

Synthesis of β-triazolylenones via metal-free desulfonylative alkylation of N-tosyl-1,2,3-triazoles

• Soumyaranjan Pati,
• Renata G. Almeida,
• Eufrânio N. da Silva Júnior and
• Irishi N. N. Namboothiri

Beilstein J. Org. Chem. 2021, 17, 762–770, doi:10.3762/bjoc.17.66

• compounds and N-tosyl triazole in moderate to high yields. Our synthesis takes place with complete regioselectivity as confirmed by crystallographic analysis which is rationalized by a suitable mechanistic proposal. This method provides an efficient, versatile and straightforward strategy towards the

• precursors in denitrogenative transannulation reactions under metal-catalysed conditions to form other heterocycles such as functionalized pyrroles, imidazoles and pyridines (Scheme 1b) [11][12][13]. The traditional method for the synthesis of triazole unit is the Huisgen 1,3-dipolar cycloaddition between

• -arylation [32], NIS-mediated N2-arylation [33], etc. Although these are significant advances towards metal-free functionalization of triazoles, many of them suffer from poor regioselectivity. Therefore, a new method for N1-selective alkylation of the triazole moiety under simple, mild and metal-free

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

• molecular frameworks in medicinal chemistry. Of these, 1,4-benzodiazepines fused with pyrazole or triazole cycles are the base for many drugs (Figure 1) [1]. The spectrum of their biological activity includes tranquilizing, muscular relaxant, anticonvulsant, and sedative effects [2]. The general application

• receptor (CCK1R) located in the gastrointestinal tract. It is a potential target for treating obesity and diabetes [5]. Although derivatives of 1,2,3-triazolobenzodiazepines are less studied as to their 1,2,4-triazole fused analogs, 1,2,3-triazolobenzodiazepinone A (Figure 2) has already reached clinical

• signal rising at 8.45 ppm (chemical shift is close to triazole proton value), that can indicate the transformation of the alkyne moiety to the triazole ring. The signals of the aromatic ring also significantly change: the aromatic multiplets observed in the 1H NMR spectrum of the starting material turn

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

• , conveniently prepared by [3 + 2] cycloadditions of terminal alkynes with sulfonyl azides, have been used as the precursors to N-sulfonylindoles by transition-metal-catalyzed transannulation reactions. In the presence of Rh(II) or Ni(0) catalysts the triazole ring-opening takes place and intermediate highly

• incomplete conversion. Reducing the reaction temperature to 80 °C afforded a full conversion of the starting triazole, but no reaction took place at 60 °C. The optimized conditions are presented in Table 1, entry 8; however, for the following reaction scope study, a temperature of 100 °C and 20 min reaction

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

• triazolylation of various heterocyclic N-oxides using sulfuryldiimidazole and 1,2,4-triazole, respectively. However, their protocol affords a mixture of C2- and C4-heteroarylated products [52][53]. More recently, Muthusubramanian and co-workers further expanded the scope of Keith’s protocol to a variety of

• reaction conditions (Scheme 1b) [58][59][60][61][62]. Results and Discussion We initiated our trials employing easily accessible quinoline N-oxide (1a) and 1-tosyl-4-phenyl-1,2,3-triazole (2a) as model substrates. Subjecting the reaction mixture to 100 °C in the presence of DIPEA in 1,2-dichloroetane (DCE

• and observed that triazoles bearing electron-donating groups on the aromatic ring, such as alkyl or methoxy moieties, were well tolerated, furnishing the corresponding products 3b–h in 83–95% yield. For electron-poor substituents (CF3 and F) on the aryl ring of the triazole, the corresponding products

1,2,3-Triazoles as leaving groups: S_NAr reactions of 2,6-bistriazolylpurines with O- and C-nucleophiles

• Dace Cīrule,
• Irina Novosjolova,
• Ērika Bizdēna and
• Māris Turks

Beilstein J. Org. Chem. 2021, 17, 410–419, doi:10.3762/bjoc.17.37

• (triazole)), 7.93 (s, 1H, H-C(8)), 7.91 (d, 3J = 7.6 Hz, 2H, Ar), 7.39 (t, 3J = 7.6 Hz, 2H, Ar), 7.30 (t, 3J = 7.6 Hz, 1H, Ar), 4.65 (t, 3J1’’,2’’ = 6.7 Hz, 2H, H2C(1’’)), 4.26 (t, 3J1’,2’ = 7.2 Hz, 2H, H2C(1’)), 1.96 (tq, 3J1’’,2’’= 6.7 Hz, 3J2’’-3’’= 7.4 Hz, 2H, H2C(2’’)), 1.93‒1.82 (m, 2H, H2C(2’)), 1.35

• 9.38 (s, 1H, H-C(triazole)), 8.70 (s, 1H, H-C(8)), 8.02 (d, 3J = 7.6 Hz, 2H, Ar), 7.50 (t, 3J = 7.6 Hz, 2H, Ar), 7.39 (t, 3J = 7.6 Hz, 1H, Ar), 6.06 (d, 3J1’,2’ = 5.8 Hz, 1H, H-C(1’)), 4.65 (dd, 3J1’,2’ = 5.8 Hz, 3J2’,3’ = 4.8 Hz, 1H, H-C(2’)), 4.29 (s, 3H, (-OCH3)), 4.22 (dd, 3J2’,3’ = 4.8 Hz, 3J3’,4

• , 1H, H-C(triazole)), 8.02 (s, 1H, H-C(8)), 7.94 (d, 3J = 7.5 Hz, 2H, Ar), 7.47 (d, 3J = 7.5 Hz, 2H, Ar), 7.37 (t, 3J = 7.5 Hz, 1H, Ar), 4.28 (t, 3J1’,2’ = 7.2 Hz, 2H, H2C(1’)), 1.96‒1.83 (m, 2H, H2C(2’)), 1.40‒1.32 (m, 4H, H2C(3’), H2C(4’)), 1.31‒1.23 (m, 4H, H2C(5’), H2C(6’)), 0.86 (t, 3J6’,7’ = 6.9

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

• leaving group in SNAr reactions with S- and N-nucleophiles [19][20][21]. It is worth to note that 2/6-amino-6/2-triazolylpurines possess high levels of fluorescence [19][22][23][24]. Herein, we describe an extension for SNAr reactions that makes use of the 1,2,3-triazole leaving group of 2,6

• -bistriazolylpurines. This led to a discovery of novel C–P bond formations from C–N bonds in SNAr–Arbuzov reactions (I→J, Scheme 1). The obtained series of compounds combines three structural motifs that are important in terms of medicinal chemistry in one molecule: purine, triazole, and phosphonate. Results and

• crude reaction mixtures revealed the presence of the products 7a and 8a (Scheme 3). When the latter mixture was submitted to CuAAC with phenylacetylene (CuI/Et3N/AcOH/EtOH (or DCM), CuSO4∙5H2O/sodium ascorbate/EtOH (or DMF)), no triazole formation at the purine C2 position was observed. We briefly tried

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

• -opening of the triazole moiety through a Dimroth rearrangement process affording 20 (reaction becomes instantly bright red); c) reduction of diazonium species to afford intermediate 21, observed by UV-LC–MS; and finally d) reductive cleavage of the -O–NH- bond, usually carried out under catalytic

Chiral anion recognition using calix[4]arene-based ureido receptors in a 1,3-alternate conformation

• Tereza Horáčková,
• Jan Budka,
• Vaclav Eigner,
• Wen-Sheng Chung,
• Petra Cuřínová and
• Pavel Lhoták

Beilstein J. Org. Chem. 2020, 16, 2999–3007, doi:10.3762/bjoc.16.249

• triazole functional groups (to name at least some of them) has appeared during the last two decades [19][20][21]. Due to well-established functionalisation approaches, calix[4]arenes [22][23][24] are frequently used as molecular platform in the design of more complex receptor systems. The existence of four

Regioselective synthesis of heterocyclic N-sulfonyl amidines from heteroaromatic thioamides and sulfonyl azides

• Vladimir Ilkin,
• Vera Berseneva,
• Tetyana Beryozkina,
• Tatiana Glukhareva,
• Lidia Dianova,
• Wim Dehaen,
• Eugenia Seliverstova and
• Vasiliy Bakulev

Beilstein J. Org. Chem. 2020, 16, 2937–2947, doi:10.3762/bjoc.16.243

• , Department of Chemistry, KU Leuven, Celestijnenlaan 200F, 3001 Leuven, Belgium 10.3762/bjoc.16.243 Abstract N-Sulfonyl amidines bearing 1,2,3-triazole, isoxazole, thiazole and pyridine substituents were successfully prepared for the first time by reactions of primary, secondary and tertiary heterocyclic

• thioamides with alkyl- and arylsulfonyl azides. For each type of thioamides a reliable procedure to prepare N-sulfonyl amidines in good yields was found. Reactions of 1-aryl-1,2,3-triazole-4-carbothioamides with azides were shown to be accompanied with a Dimroth rearrangement to form 1-unsubstituted 5

• -arylamino-1,2,3-triazole-4-N-sulfonylcarbimidamides. 2,5-Dithiocarbamoylpyridine reacts with sulfonyl azides to form a pyridine bearing two sulfonyl amidine groups. Keywords: amidines; Dimroth rearrangement; isoxazoles; sulfonyl thiazoles; thioamides; 1,2,3-triazoles; Introduction The biological activity

Synthesis and investigation of quadruplex-DNA-binding, 9-O-substituted berberine derivatives

• Jonas Becher,
• Daria V. Berdnikova,
• Heiko Ihmels and
• Christopher Stremmel

Beilstein J. Org. Chem. 2020, 16, 2795–2806, doi:10.3762/bjoc.16.230

• not provide evidence for a significant effect of the adenine unit on the binding affinity of the ligands, for example, by additional association with the loops, presumably because the adenine residue is sterically shielded by the neighboring triazole unit. Keywords: berberine alkaloids; DNA ligands

• contributed significantly to the binding affinity depending on their spacing from the π-stacking unit. In the case of 4a–e, however, the position of the triazole and adenine unit relative to the berberine does not appear to be highly relevant for the overall binding affinity. It may be concluded that the

• binding constants, selectivities or optical responses should have been observed with the variation of the linker length. It may be concluded that the triazole ring, used as a synthetically convenient connection unit, imposes too much steric hindrance and restricted conformational flexibility in the

Water-soluble host–guest complexes between fullerenes and a sugar-functionalized tribenzotriquinacene assembling to microspheres

• Si-Yuan Liu,
• Xin-Rui Wang,
• Man-Ping Li,
• Wen-Rong Xu and
• Dietmar Kuck

Beilstein J. Org. Chem. 2020, 16, 2551–2561, doi:10.3762/bjoc.16.207

• , the 1H NMR spectrum of TBTQ-(OAcG)6 exhibits two singlet resonances at δ = 8.62 and δ = 8.58 ppm, each of which indicates three equivalent protons of the six triazole rings. Likewise, two singlets at δ = 7.33 and δ = 7.30 ppm are due to two sets of three equivalent arene protons of the TBTQ core [40

• ]. The acetyl protons of the protected glucose residues appear as eight distinct resonances. The 13C NMR spectrum shows a similar splitting. The triazole carbons resonate at δ = 123.71 and δ = 123.69 ppm and at δ = 143.88 and δ = 143.79 ppm, indicating two sets of magnetically nonequivalent linkers. This

• of the resonances did not shift significantly, the triazole pair of singlets was shifted to higher field by Δδ = −0.14 ppm (see Figure S2 in Supporting Information File 1). All these observations reflect the molecular C3-symmetry of TBTQ-(OAcG)6 in solution and the presence of two diastereotopic sets

Conformational preferences of fluorine-containing agrochemicals and their implications for lipophilicity prediction

• Daniela Rodrigues Silva,
• Joyce K. Daré and
• Matheus P. Freitas

Beilstein J. Org. Chem. 2020, 16, 2469–2476, doi:10.3762/bjoc.16.200

• geometry is quite similar among the three conformers. Only for Iga, where the gauche fluorine atom points to the opposite direction of the amine group, the triazole ring was farther away from the 1,2-disubstituted ethane moiety. Note that the gas-phase relative conformational energy ΔE increases, i.e

Design and synthesis of a bis-macrocyclic host and guests as building blocks for small molecular knots

• Elizabeth A. Margolis,
• Rebecca J. Keyes,
• Stephen D. Lockey IV and
• Edward E. Fenlon

Beilstein J. Org. Chem. 2020, 16, 2314–2321, doi:10.3762/bjoc.16.192

• of 6 with an excess of known (see Supporting Information File 1) dialkyne 10 under several of the most common conditions produced triazole 11 in only modest yields (Scheme 2). The best conditions involved using Cu(MeCN)4PF6 as the copper(I) source, tris(2-benzimidazolylmethyl)amine as a ligand, and

• ascorbic acid to provide a 42% yield of triazole 11. Alkylation of diethyl 2,5-dihydroxyterephthalate (12) with 11 under standard conditions provided low yields (12–18%) of the core diester 13, which contains all the atoms of host 1. The yields for this route were disappointingly low, so it was hoped that

• exhibit this behavior. Two separate triazole peaks were observed (8.19 and 8.38 ppm), consistent with a new triazole ring being formed. The mass spectrum of the product showed peaks for the expected mass of the TLC product(s) and various cation adducts: (peak mass, assignment, relative intensity): 1563.9

Automated high-content imaging for cellular uptake, from the Schmuck cation to the latest cyclic oligochalcogenides

• Rémi Martinent,
• Javier López-Andarias,
• Dimitri Moreau,
• Yangyang Cheng,
• Naomi Sakai and
• Stefan Matile

Beilstein J. Org. Chem. 2020, 16, 2007–2016, doi:10.3762/bjoc.16.167

• reported cell-penetrating streptavidin, in which four asparagusic acids are covalently bound to the protein through irreversible triazole linkages [59]. The CP50 value of 7.3 ± 0.5 µM of 25 was not far above the CP50 value of 3.1 ± 0.5 µM of HIV Tat, the original CPP [55]. As the uptake efficiency