Steroid diversification by multicomponent reactions

• Leslie Reguera,
• Cecilia I. Attorresi,
• Javier A. Ramírez and
• Daniel G. Rivera

Beilstein J. Org. Chem. 2019, 15, 1236–1256, doi:10.3762/bjoc.15.121

• displaying biological activities such as antimicrobial, antiviral and anti-inflammatory, among others. Scheme 3 exemplifies the reaction of cholestan-6-one 7 with 2-aminopyridine and phenyl isocyanide to afford the heterocycle–steroid hybrid 8 in good yield and diastereoselectivity, whereas different

• paraformaldehyde and benzyl isocyanide to form hybrid 11 in good yield. Similarly, the spirostanic lactone 12 was transformed into spirostanic acid 13 and amine 14, which were next ligated to alanine methyl ester and Boc-histidine leading to the amino acid–steroid conjugates 15 and 16, respectively. This approach

• bonds in one-pot, leading to a remarkably complex amino acid–steroid hybrid 27 in very good yield [29]. After the pioneering work of Wessjohann and co-workers, other groups relied on the functionalization of steroids with isocyanide groups for their subsequent derivatization by isocyanide-based MCRs

Mechanochemical synthesis of hyper-crosslinked polymers: influences on their pore structure and adsorption behaviour for organic vapors

• Sven Grätz,
• Sebastian Zink,
• Hanna Kraffczyk,
• Marcus Rose and
• Lars Borchardt

Beilstein J. Org. Chem. 2019, 15, 1154–1161, doi:10.3762/bjoc.15.112

• variety of these materials [1]. While inorganic materials such as activated carbons, porous metal oxides, and zeolites have been investigated for decades, hybrid materials such as metal-organic frameworks [2], purely organic frameworks such as crystalline covalent-organic frameworks [3], and amorphous

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

• ]. Besides, several hybrid molecules containing, inter alia the oxindole moiety, have been discovered and they demonstrated diverse therapeutic activities, for example, against breast [46] and colon cancer cells [47] and drug-resistant bacteria [48]. Among the many excellent recent reviews on the preparation

Catalytic asymmetric oxo-Diels–Alder reactions with chiral atropisomeric biphenyl diols

• Chi-Tung Yeung,
• Wesley Ting Kwok Chan,
• Wai-Sum Lo,
• Ga-Lai Law and
• Wing-Tak Wong

Beilstein J. Org. Chem. 2019, 15, 955–962, doi:10.3762/bjoc.15.92

• supramolecular helices or dimers through intermolecular hydrogen bonding of two axially chiral biphenyl hybrid diols (1 and 2 in Scheme 1) which contain point chirality at the side arms and axial chirality at the biphenyl backbone [37]. We envisage the structural similarity and the ability of our scaffold to

• other biphenyl hybrid diols with different steric bulky substituents were incorporated (3 and 4). Since it is known that the catalyst acidity has significant influence on hydrogen-bond-catalyzed reactions [32], we also incorporated a CF3 group in our molecular scaffold to investigate how it would affect

Synthesis of (macro)heterocycles by consecutive/repetitive isocyanide-based multicomponent reactions

• Angélica de Fátima S. Barreto and
• Carlos Kleber Z. Andrade

Beilstein J. Org. Chem. 2019, 15, 906–930, doi:10.3762/bjoc.15.88

• approach provided the synthesis of steroid-biaryl ether hybrid macrocycles 117 and 118 with up to 68 members by the MiBs strategy. Another representative example of MiBs is the synthesis of the biaryl ether-containing macrocycles 123a–f (Scheme 23) [39]. The synthetic strategy involved the mixing of three

• [41] performed the first use of the diamine/diacid combination of bidirectional Ugi-MiBs in the synthesis of novel steroid–peptoid hybrid macrocycles. Scheme 25 shows two examples using this combination for the synthesis of cholane–peptoid hybrid macrocycles. Another application of the MiBs approach

• -based macrocyclization yielded steroid-aryl hybrid macroheterocycles 151 and 152, which after ester hydrolysis, acted as trifunctional building blocks for consecutive 3-fold Ugi-4CR-based macrocyclizations with triisocyanide 153. The cross-linked igloo-shaped skeletons of cages 154 and 155 were obtained

Azologization of serotonin 5-HT₃ receptor antagonists

• Karin Rustler,
• Galyna Maleeva,
• Piotr Bregestovski and
• Burkhard König

Beilstein J. Org. Chem. 2019, 15, 780–788, doi:10.3762/bjoc.15.74

• hybrid biomolecule. In this context, various photochromic scaffolds including dithienylethenes, fulgi(mi)des, and azobenzenes are investigated [31][42]. The latter ones were already discovered in 1834 by E. Mitscherlich [43] but it took around another 100 years till G. S. Hartley [44] revealed their

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

• a set of “privileged structural motifs” that are present in both synthetic and naturally occurring compounds of practical and biological interest [29][30][31][32][33][34][35][36]. Consequently, there have been many attempts to produce hybrid structures with interesting properties by combining two

Polyaminoazide mixtures for the synthesis of pH-responsive calixarene nanosponges

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

Beilstein J. Org. Chem. 2019, 15, 633–641, doi:10.3762/bjoc.15.59

• -sensitive functionalities in the highly hydrophobic nanoporous environment provided by the fully synthetic calixarene-based polymer, might open interesting perspectives for applicative purposes, in particular in the fields of organocatalysis and of hybrid organic-inorganic materials, such as in the emerging

Synthesis and fluorescent properties of N(9)-alkylated 2-amino-6-triazolylpurines and 7-deazapurines

• Andrejs Šišuļins,
• Jonas Bucevičius,
• Yu-Ting Tseng,
• Irina Novosjolova,
• Kaspars Traskovskis,
• Ērika Bizdēna,
• Huan-Tsung Chang,
• Sigitas Tumkevičius and
• Māris Turks

Beilstein J. Org. Chem. 2019, 15, 474–489, doi:10.3762/bjoc.15.41

• , steepest descent algorithm) and systematic conformational analysis as implemented in Avogadro 1.1.1 software. The minimum energy conformers found by molecular mechanics were further optimized with the Gaussian 09 program package [57] by the means of DFT using B3LYP exchange–correlation hybrid functional

Aqueous olefin metathesis: recent developments and applications

• Valerio Sabatino and
• Thomas R. Ward

Beilstein J. Org. Chem. 2019, 15, 445–468, doi:10.3762/bjoc.15.39

• shock protein from M. Jannaschii (MjHSP) [71]. The authors reported a HG-II-type catalyst modified on its NHC backbone with an α-bromoacetyl unit (68) that is reacted with the unique cysteine of the modified MjHSP variant (G41C) to afford ArM 4 (Scheme 15). The hybrid catalyst ArM 4 was then tested for

• (NB4exp). The coupling reaction in aqueous buffer at pH 7.5 finally affords ArM 5, ArM 6 and ArM 7, respectively (Scheme 16). The obtained hybrid catalysts were tested for the RCM with substrates 21 and 64 (Table 9). Overall, ArM 6 and ArM 7 are comparable and perform best in both reactions with 35

• % conversion of substrate 21 and quantitative conversion of substrate 64. The water-soluble catalyst 9 was compared to the hybrid catalysts, displaying a higher TON in the RCM of 21 (Table 9, entry 4). Interestingly, the activity of catalyst 9 is inhibited in the presence of NB4exp (Table 9, entries 5 and 10

Application of olefin metathesis in the synthesis of functionalized polyhedral oligomeric silsesquioxanes (POSS) and POSS-containing polymeric materials

• Patrycja Żak and
• Cezary Pietraszuk

Beilstein J. Org. Chem. 2019, 15, 310–332, doi:10.3762/bjoc.15.28

• edges, chemically bonded with eight different or similar organic substituents so that it represents a truly hybrid architecture. The cubic silsesquioxane unit is characterized by a three-dimensional nanoscopic size structure with approximate Si–Si distance equal to 0.5 nm and an approximate R–R distance

• to 11033 Da and polydispersity index (PDI) = 1.5. Ring-opening metathesis polymerization (ROMP) of POSS-functionalized monomers The chemistry of inorganic–organic hybrid materials has emerged as a fascinating new field of modern nanotechnology. The inclusion of POSS cages into the polymeric material

• are the subject of numerous reviews [30][31][32][33][34][35][36][37]. From among the methods for preparation of organic–inorganic hybrid materials, polymerization or copolymerization is particularly convenient to incorporate POSS units into polyolefins. Ring-opening metathesis polymerization (ROMP) is

Adhesion, forces and the stability of interfaces

• Robin Guttmann,
• Johannes Hoja,
• Christoph Lechner,
• Reinhard J. Maurer and
• Alexander F. Sax

Beilstein J. Org. Chem. 2019, 15, 106–129, doi:10.3762/bjoc.15.12

Fabrication of supramolecular cyclodextrin–fullerene nonwovens by electrospinning

• Hiroaki Yoshida,
• Ken Kikuta and
• Toshiyuki Kida

Beilstein J. Org. Chem. 2019, 15, 89–95, doi:10.3762/bjoc.15.10

• , 380, and 475 nm) are observed. These results clearly suggest the successful preparation of β-CD (γ-CD) fiber materials with molecularly dispersed C60 (C70). The preparation of hybrid materials of a polymer and a CD–fullerene inclusion complex might be interesting to enhance material integrity and

Synthesis, biophysical properties, and RNase H activity of 6’-difluoro[4.3.0]bicyclo-DNA

• Sibylle Frei,
• Adam K. Katolik and
• Christian J. Leumann

Beilstein J. Org. Chem. 2019, 15, 79–88, doi:10.3762/bjoc.15.9

• oligonucleotides hybridized to complementary DNA or RNA disclosed a significant destabilization of both duplex types (ΔTm/mod = −1.6 to −5.5 °C). However, in the DNA/RNA hybrid the amount of destabilization could be reduced by multiple insertions of the modified unit. In addition, CD spectroscopy of the

• cleavage of the RNA strand of an AON/RNA hybrid structure by the endonuclease RNase H [9][18]. Both, the F–ANA and the F–RNA, are appealing modifications for several oligonucleotide-based silencing applications [8][19][20][21][22][23][24][25]. Also evaluated on their antisense properties were the 3

• (ΔTm/mod = −5.4 °C and −4.5 °C for complementary DNA and RNA, respectively). Interestingly, the DNA/RNA hybrid structure better accommodated multiple 6’-diF-bc4,3-Ts than a single insertion. Additionally, the hybrid structure also better tolerated multiple 6’-diF-bc4,3-T units than the DNA/DNA duplex

6’-Fluoro[4.3.0]bicyclo nucleic acid: synthesis, biophysical properties and molecular dynamics simulations

• Sibylle Frei,
• Andrei Istrate and
• Christian J. Leumann

Beilstein J. Org. Chem. 2018, 14, 3088–3097, doi:10.3762/bjoc.14.288

• RNase H1 which selectively cleaves the RNA strand of a DNA/RNA hybrid duplex [8]. To activate this process, fully modified DNA-like oligonucleotides (ONs) or gapmer AONs are used [9][10]. However, the widespread use of oligonucleotide-based therapeutics is limited by several factors amongst which the

• unit and possibly positively impact the duplex stability. Here we report on the synthesis of the two 6’F-bc4,3 pyrimidine analogs with the base T and C, their incorporation into DNA, their biophysical properties, as well as a structural analysis by molecular dynamics simulations of hybrid DNA and RNA

• that of the corresponding natural duplexes (Figure S1, Supporting Information File 1). All seven modified oligonucleotides exhibited a B-type pattern when paired to DNA, indicating B-form helices. All modified oligonucleotides duplexed to RNA disclosed a similar pattern than the natural hybrid

MoO₃ on zeolites MCM-22, MCM-56 and 2D-MFI as catalysts for 1-octene metathesis

• Hynek Balcar,
• Martin Kubů,
• Naděžda Žilková and
• Mariya Shamzhy

Beilstein J. Org. Chem. 2018, 14, 2931–2939, doi:10.3762/bjoc.14.272

• –Grubbs type hybrid catalysts active in metathesis of long-chain unsaturated esters [24]. Results and Discussion Catalyst preparation and characterization XRD patterns and texture properties (Table 1, Figure 1 A,B,C,D) of prepared MCM-22, MCM-56 and 2D-MFI zeolites proved a high quality of these supports

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

• green chemical protocols widely employed for the synthesis of myriad of natural products and hybrid heterocycles [4][5][6][7][8][9][10][11][12][13]. These reactions are one-pot processes involving several bond forming steps under identical reaction conditions affording the desired product in a single

• -oxopropanenitriles, aromatic aldehydes, cycloalkanones and ammonium acetate. This work also stems from our continuous effort in synthesizing novel cycloalkyl[b]pyridine-3-carbonitrile hybrid heterocycles via tandem/domino reaction [71][72]. Results and Discussion Initially the precursors viz. 3-(1H-indol-3-yl)-3

Pd-Catalyzed microwave-assisted synthesis of phosphonated 13α-estrones as potential OATP2B1, 17β-HSD1 and/or STS inhibitors

• Rebeka Jójárt,
• Szabolcs Pécsy,
• György Keglevich,
• Mihály Szécsi,
• Réka Rigó,
• Csilla Özvegy-Laczka,
• Gábor Kecskeméti and
• Erzsébet Mernyák

Beilstein J. Org. Chem. 2018, 14, 2838–2845, doi:10.3762/bjoc.14.262

• , only 2-regioisomers displayed substantial inhibitory action, which did not depend on the hybrid state of carbon attached to C-2 [22]. Phan et al. described that halogenation of ring A of estrone is a powerful strategy in the synthesis of effective STS inhibitors [25]. Certain 4-halogenated estrone

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

• sulfated solid supports are: sulfonated organic compounds [21], sulfonated silica materials [22][23], sulfonated carbon materials [5], sulfated zirconia [24], sulfated hybrid materials [25], sulfonated magnetic materials [26], sulfonated polymeric materials [27][28], sulfonated MOFs materials [29], and so

Learning from B₁₂ enzymes: biomimetic and bioinspired catalysts for eco-friendly organic synthesis

• Keishiro Tahara,
• Ling Pan,
• Toshikazu Ono and
• Yoshio Hisaeda

Beilstein J. Org. Chem. 2018, 14, 2553–2567, doi:10.3762/bjoc.14.232

• Ru@MOF, as was confirmed through ESR measurements. The resultant heterogeneous hybrid catalyst B12-Ru@MOF successfully mediated the photochemical carbon-skeleton arrangement. Previous studies had demonstrated that the hemolytic cleavage of the Co(III)–C bond of the alkylated complex of 1 generated Co

• terms of both catalytic activity and visible-light harvesting. In relation to the reactivity of 1 with DDT, interesting reactions of trichlorinated organic compounds have recently been investigated [100][114]. The B12-TiO2 hybrid catalyst converted trichlorinated organic compounds into esters and amides

• to those of simple reduced products significantly increased in PhCN, a poor hydrogen radical donor solvent, compared with those in EtOH and CH3CN. Similar phenyl migration was achieved in the UV-light-driven system of the B12-TiO2 hybrid catalyst [96][97][98]. The involvement of a radical species was

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

The enzymes of microbial nicotine metabolism

• Paul F. Fitzpatrick

Beilstein J. Org. Chem. 2018, 14, 2295–2307, doi:10.3762/bjoc.14.204

• pyridine ring. The pyrrolidine pathway, which begins with oxidation of a carbon–nitrogen bond in the pyrrolidine ring, was subsequently characterized in a number of pseudomonads. Most recently, a hybrid pathway has been described, which incorporates the early steps in the pyridine pathway and ends with

• metabolism of nicotinic acid by P. putida KT25440, which begins with the hydroxylation of nicotinic acid by the molybdopterin enzyme NicAB to form 6-hydroxynicotinic acid and its subsequent conversion to 2,5-dihydroxypyridine by the NADH- and FAD-dependent hydroxylase NicC [63][64]. The hybrid pathway While

• the pyridine and pyrrolidine pathways are the best understand reactions by which bacteria degrade nicotine, additional pathways continue to be discovered. The best-characterized is a hybrid of the pyridine and pyrrolidine pathways (Scheme 11). Based on phylogenetic analysis, the pathway is more

Selective formation of a zwitterion adduct and bicarbonate salt in the efficient CO₂ fixation by N-benzyl cyclic guanidine under dry and wet conditions

• Yoshiaki Yoshida,
• Naoto Aoyagi and
• Takeshi Endo

Beilstein J. Org. Chem. 2018, 14, 2204–2211, doi:10.3762/bjoc.14.194

• only in the field of organic and catalyst chemistry but also in inorganic and polymer chemistry. Especially the adsorbent and the catalyst for CO2 fixation are of interest [1][2][3][4][5]. In particular, the inorganic, organic–inorganic hybrid, dendrimeric catalysts have been developed for chemical

Graphitic carbon nitride prepared from urea as a photocatalyst for visible-light carbon dioxide reduction with the aid of a mononuclear ruthenium(II) complex

• Kazuhiko Maeda,
• Daehyeon An,
• Ryo Kuriki,
• Daling Lu and
• Osamu Ishitani

Beilstein J. Org. Chem. 2018, 14, 1806–1812, doi:10.3762/bjoc.14.153

• phase. Keywords: artificial photosynthesis; heterogeneous photocatalysis; hybrid material; metal complexes; solar fuels; Introduction Carbon nitride is one of the oldest synthetic polymers [1], and has several allotropes. Among them, graphitic carbon nitride (g-C3N4) is the most stable form and is an

• capable of photocatalyzing CO2 reduction into formate with high selectivity under visible light irradiation, as confirmed by isotope tracer experiments with 13CO2 [8][9][10][11][12]. After the first report of a metal complex/C3N4 hybrid for CO2 reduction, several groups have presented similar reports

• light [10]. Our previous study also indicated that the amount of a molecular cocatalyst is very important in this kind of mononuclear-complex/C3N4 hybrid photocatalyst for visible-light CO2 reduction [8]. To eliminate any other effects other than heating temperature of urea, we fixed the amount of RuP

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