Isolation and characterisation of irinans, androstane-type withanolides from Physalis peruviana L.

• Annika Stein,
• Dave Compera,
• Bianka Karge,
• Mark Brönstrup and
• Jakob Franke

Beilstein J. Org. Chem. 2019, 15, 2003–2012, doi:10.3762/bjoc.15.196

• identities of 22–28%, indicating that no P450 enzymes of these clans exist in P. peruviana. Although enzymes with similar catalytic activity might have evolved convergently in plants, the different substitution pattern in the side chain suggests that a side-chain cleavage mechanism distinct from mammals is

Recent advances on the transition-metal-catalyzed synthesis of imidazopyridines: an updated coverage

• Gagandeep Kour Reen,
• Ashok Kumar and
• Pratibha Sharma

Beilstein J. Org. Chem. 2019, 15, 1612–1704, doi:10.3762/bjoc.15.165

• -benzenedicarboxylate), Puthiaraj and co-workers have unprecedently discovered the catalytic activity of this metal-organic framework (MOF) for the synthesis of imidazo[1,2-a]pyridines [100]. The three-component, one-pot reaction between 1, 3 and nitromethane (10, Scheme 5) involved an intermolecular aza-Michael

• catalytic activity exhibited by Cu(0) NPs Chenglong et al. have reported an efficient, three-component one-pot reaction for the synthesis of imidazo[1,2-a]pyridines [111]. The protocol enjoyed a solvent-free domino reaction between compounds 3, 1 and 2 under nitrogen atmosphere at 120 °C (Scheme 15

• the past few years [57]. Recently, Buchwald and Castillo have reviewed the exceptional utility of Pd-catalyzed C–N cross-coupling reactions for the preparation of anilines and aniline derivatives [58]. In many of the reactions, palladium was used along with a co-catalyst to enhance its catalytic

Enantioselective PCCP Brønsted acid-catalyzed aza-Piancatelli rearrangement

• Gabrielle R. Hammersley,
• Meghan F. Nichol,
• Helena C. Steffens,
• Jose M. Delgado,
• Gesine K. Veits and
• Javier Read de Alaniz

Beilstein J. Org. Chem. 2019, 15, 1569–1574, doi:10.3762/bjoc.15.160

• 65% ee. At lower temperatures (30 °C and 23 °C (rt)) the selectivity increased to 73% and 78% ee, respectively. For consistency the optimization studies were all allowed to run for 48 h with higher temperatures being more efficient (Table 1, entries 1–3). Importantly, the catalytic activity did not

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

• 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

A heteroditopic macrocycle as organocatalytic nanoreactor for pyrroloacridinone synthesis in water

• Piyali Sarkar,
• Sayan Sarkar and
• Pradyut Ghosh

Beilstein J. Org. Chem. 2019, 15, 1505–1514, doi:10.3762/bjoc.15.152

• ][47][48][49][50]. The multifunctional macrocycle BATA-MC (Figure 1) has been successfully applied as a wheel in the molecular rotors fields [51]. Considering its multiple binding sites (π-interactions, H-bonding site, cavity), we investigated the catalytic activity of this macrocycle. BATA-MC was

• is a molecular assembly of BATA-MC single molecules which may provide a suitable organic environment to the starting materials by π-interaction and H-bonding, and inevitably orients them into the necessary reactive positions. To represent the simple catalytic activity, we have chosen a part of the

• . Recyclability of the BATA-MC catalyst The BATA-MC catalyst was recovered by column chromatography and its recyclability was investigated in the synthesis of 4a to demonstrate the eco-friendly nature of the catalyst. The catalytic activity remained nearly unchanged up to five cycles as shown in Figure 7

Phylogenomic analyses and distribution of terpene synthases among Streptomyces

• Lara Martín-Sánchez,
• Kumar Saurabh Singh,
• Mariana Avalos,
• Gilles P. van Wezel,
• Jeroen S. Dickschat and
• Paolina Garbeva

Beilstein J. Org. Chem. 2019, 15, 1181–1193, doi:10.3762/bjoc.15.115

• of type I terpene synthases, including the aspartate-rich motif, the NSE triad, the pyrophosphate sensor and the RY pair [19][20][21]. Both domains have a catalytic activity, the N-terminal domain for the conversion of FPP into the intermediate sesquiterpene alcohol (1(10)E,5E)-germacradien-11-ol (12

Mechanochemistry of supramolecules

• Anima Bose and
• Prasenjit Mal

Beilstein J. Org. Chem. 2019, 15, 881–900, doi:10.3762/bjoc.15.86

• , supramolecular catalysis proposes a much simpler model to understand the catalytic activity of enzymes. In 2010, MacGillivray and co-workers have demonstrated the concept of “supramolecular catalysis” in a hydrogen-bond-assisted self-assembled formation of a [2 + 2]-cycloaddition product. The reaction was found

New α- and β-cyclodextrin derivatives with cinchona alkaloids used in asymmetric organocatalytic reactions

• Iveta Chena Tichá,
• Simona Hybelbauerová and
• Jindřich Jindřich

Beilstein J. Org. Chem. 2019, 15, 830–839, doi:10.3762/bjoc.15.80

• derivatives monosubstituted with cinchona alkaloids (cinchonine, cinchonidine, quinine and quinidine) on the primary rim through a CuAAC click reaction. Subsequently, permethylated analogs of these cinchona alkaloid–CD derivatives also were synthesized and the catalytic activity of all derivatives was

• the primary side. Further characterization data are included in Supporting Information Files 1–3. Catalytic activity of cinchona–CD derivatives Lastly, the activity of all prepared CD derivatives was tested in asymmetric organocatalytic reactions. After unsuccessful application in Morita–Baylis

• afforded on one side lower enantiomer excesses (Table 3, entries 18–28), on the other hand, they showed some catalytic activity in the solvent mixture acetonitrile/H2O, which could be promising for future applications of these catalysts in water. The disubstituted CD derivative 11 was not active in this

Synthesis of acylglycerol derivatives by mechanochemistry

• Karen J. Ardila-Fierro,
• Andrij Pich,
• Marc Spehr,
• José G. Hernández and
• Carsten Bolm

Beilstein J. Org. Chem. 2019, 15, 811–817, doi:10.3762/bjoc.15.78

• nucleophiles [36]. Moreover, salen complexes endure mechanochemical conditions, as proven during their preparation in ball mills [37]. In addition, various related Jacobsen salen complexes have shown catalytic activity under solvent-free conditions [38]. Collectively, these precedents made this synthetic route

Hoveyda–Grubbs catalysts with an N→Ru coordinate bond in a six-membered ring. Synthesis of stable, industrially scalable, highly efficient ruthenium metathesis catalysts and 2-vinylbenzylamine ligands as their precursors

• Kirill B. Polyanskii,
• Kseniia A. Alekseeva,
• Pavel V. Raspertov,
• Pavel A. Kumandin,
• Eugeniya V. Nikitina,
• Atash V. Gurbanov and
• Fedor I. Zubkov

Beilstein J. Org. Chem. 2019, 15, 769–779, doi:10.3762/bjoc.15.73

• possible to overcome this problem [44]. Thus, the pathways described in Schemes 1–3 permit one to vary the steric volume of substituents at the nitrogen atom in a wide range enabling synthesis of selective Grubbs catalysts with different catalytic activity. These styrenes were used in the preparation of

• should have the strongest effect on the catalytic activity. With the increase of the steric volume of substituents at the nitrogen atom, the ruthenium–nitrogen coordinate bond is extended, which makes it weaker. That should, obviously, increase the activity of the catalyst towards metathesis reactions

• process, temperature also exerts a strong influence on the catalytic activity of metallo complexes 11. None of catalysts 11 were active at room temperature (19–23 °С) towards the styrene cross metathesis, meaning that all reactions required temperatures higher than 30–35 °С. After all observations, we

Synthesis of polydicyclopentadiene using the Cp₂TiCl₂/Et₂AlCl catalytic system and thin-layer oxidation of the polymer in air

• Zhargolma B. Bazarova,
• Ludmila S. Soroka,
• Alex A. Lyapkov,
• Мekhman S. Yusubov and
• Francis Verpoort

Beilstein J. Org. Chem. 2019, 15, 733–745, doi:10.3762/bjoc.15.69

• catalytic activity of the Cp2TiCl2/organoaluminum compound is determined by the molar ratio of the components of the catalytic system [15]. The rate of transformation in the system depends both on the Al:Ti molar ratio and on the temperature [16]. UV spectra of toluene solutions of Cp2TiCl2 and AlEt2Cl

Back to the future: Why we need enzymology to build a synthetic metabolism of the future

• Tobias J. Erb

Beilstein J. Org. Chem. 2019, 15, 551–557, doi:10.3762/bjoc.15.49

• point to search for enzyme variants that possess a desired catalytic activity. While existing databases might provide a good resource to find the parts to reconstruct level 3 pathways, this task becomes more challenging in respect to level 4 and level 5 designs that require new-to-nature reactions. How

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

• on the catalytic activity of the reaction. In fact, catalyst and substrate are encapsulated into emulsion droplets formed in the reaction media above the aqueous layer, making the reaction proceed “on water” [21][22]. The introduction of amphiphilic molecules for aqueous micellar catalysis allows

• -metathesis of allyl alcohol (59) and the cis–trans isomerization of cis-butenedienol (Z-58). Metathesis catalysts bearing quaternary ammonium groups provide an attractive alternative to classical ruthenium catalysts. Although they do not represent a great improvement in terms of catalytic activity, they

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

• and do not show catalytic activity in metathesis. The most important consequences of the above-described reactivity in metathesis of vinyl-substituted siloxanes, spherosilicates and silsesquioxanes are presented in Figure 2. It should be indicated that one of the consequences of the described

• allyltrimethoxysilane, ethyl undec-10-enylate, oct-7-enyltrimethoxysilane, 5-bromopentene, pent-4-en-1-ol) and styrene. Moreover, the catalytic activity of the first generation Grubbs’ catalyst (Ru-1) was demonstrated in CM of OVS with pent-4-en-1-ol and 5-bromopentene. It has been found that terminal alkenes undergo

Catalysis of linear alkene metathesis by Grubbs-type ruthenium alkylidene complexes containing hemilabile α,α-diphenyl-(monosubstituted-pyridin-2-yl)methanolato ligands

• Tegene T. Tole,
• Johan H. L. Jordaan and
• Hermanus C. M. Vosloo

Beilstein J. Org. Chem. 2019, 15, 194–209, doi:10.3762/bjoc.15.19

• -quinolinolate Grubbs 2-type derivative, patented by Slugovc and Wappel [15] for use in ROMP reactions, was found to be inactive (<1% conversion) for 1-octene metathesis at 60 °C [12]. Schachner et al. [16] evaluated the catalytic activity of 5b, 5d and related complexes for the ROMP of cyclooctene, CM of hex-5

• precatalyst 6 at 420 min. At 420 min, 1-octene conversion is 98.0% (110 °C), 93.0% (100 °C), 70.5% (90 °C), 19.4% (80 °C), 6.8% (70 °C) and 2.5% (60 °C). This shows the dramatic increase of the catalytic activity upon increasing the temperature. An investigation of the PMPs formation reveals a huge 66

• , on the overall metathesis reaction. During the course of PMPs formation, high catalytic activity for 9 is observed within 200 min at temperatures above 90 °C (ca. 60%), while the activity of the precatalyst showed a dramatic increase from 70 to 90 °C after ca. 500 min, similar to that of 6 (see

Silanediol versus chlorosilanol: hydrolyses and hydrogen-bonding catalyses with fenchole-based silanes

• Falco Fox,
• Jörg M. Neudörfl and
• Bernd Goldfuss

Beilstein J. Org. Chem. 2019, 15, 167–186, doi:10.3762/bjoc.15.17

• )–2.05(2) Å) than with chlorosilanol 8 (OH···2.16(0) Å). Due to its two hydroxy units, the silanediol 9 shows higher catalytic activity as hydrogen bond donor than chlorosilanol 8, e.g., C–C coupling N-acyl Mannich reaction of silyl ketene acetals 11 with N-acylisoquinolinium ions (up to 85% yield and 12

• (Scheme 6). The reactivity and stability of such an ion pair depend on the employed solvent. For this reaction and BIFOXSi(OH)2 (9) as catalyst, several solvents are tested (Table 7). In a nonpolar solvent like n-hexane, no catalytic activity is observed (Table 7, entry 1). In halogenated solvents as

• not show catalytic activity for the reaction of 18 with 11a, as the background reaction is slightly faster (54% vs 58%, Table 10, entries 9 and 13). With increasing of the steric demand of the nucleophilic silyl group, the background reaction slows down and chlorosilanol 8 has a positive influence on

Ammonium-tagged ruthenium-based catalysts for olefin metathesis in aqueous media under ultrasound and microwave irradiation

• Łukasz Gułajski,
• Andrzej Tracz,
• Katarzyna Urbaniak,
• Stefan J. Czarnocki,
• Michał Bieniek and
• Tomasz K. Olszewski

Beilstein J. Org. Chem. 2019, 15, 160–166, doi:10.3762/bjoc.15.16

• Abstract The influence of microwave and ultrasonic irradiation on the performance of ammonium-tagged Ru-based catalysts in olefin metathesis transformations in aqueous media was studied. Differences in the catalytic activity in correlation with the nature of the present counter ion and the size of the N

• only in academia but also in industry [7][8][9][10][11][12]. However, there is still a large interest in improving the catalytic activity of the existing Ru-based metathesis catalysts as there is no universal catalyst for all the metathesis transformations. This is especially true for olefin metathesis

• (e.g., 50 mg mL−1 for 1a or 3a) whereas for those with I− as counter-ion is much lower (e.g., 4.0 mg mL−1 for 1b). In turn catalysts bearing PF6− or BF4− as counter ions are not soluble in water [71]. We have started our study with the comparison of the catalytic activity of complex 4b, having the

Gold-catalyzed ethylene cyclopropanation

• Silvia G. Rull,
• Andrea Olmos and
• Pedro J. Pérez

Beilstein J. Org. Chem. 2019, 15, 67–71, doi:10.3762/bjoc.15.7

• ethyl diazoacetate.a Catalytic activity of IPrAuCl/NaBArF4 in the reaction of ethylene and ethyl diazoacetate.a Acknowledgements Support for this work was provided by the MINECO (CTQ2017-82893-C2-1-R and CTQ2015-73693-JIN).

Asymmetric synthesis of a high added value chiral amine using immobilized ω-transaminases

• Antonella Petri,
• Valeria Colonna and
• Oreste Piccolo

Beilstein J. Org. Chem. 2019, 15, 60–66, doi:10.3762/bjoc.15.6

• excess starting from a commercial substrate. The reaction was carried out by using different commercially available immobilized enzymes, evaluating the catalytic activity and the enantioselectivity under different experimental conditions. Re-use of the most efficient enzyme was performed both in batch

Ruthenium-based olefin metathesis catalysts with monodentate unsymmetrical NHC ligands

• Veronica Paradiso,
• Chiara Costabile and
• Fabia Grisi

Beilstein J. Org. Chem. 2018, 14, 3122–3149, doi:10.3762/bjoc.14.292

• and 4a clearly outperformed GII-SIMes, with catalyst 4a emerging as the most efficient of all (>97% conversion in 9 min). Complex 5a showed a higher initiation rate with respect to GII-SIMes, but eventually was found to be less efficient due to a decrease in its catalytic activity related to

• beneficial effect on the catalytic activity was observed. Indeed complex 22 revealed a very poor olefin metathesis catalyst, likely as a consequence of the excessive steric hindrance of the adamantyl moiety at the ruthenium center. It is worth to underline that the first Z-selective ruthenium catalyst (23

• reported by Blechert and co-workers [21]. In addition to the concept that the presence of more electron-donating alkyl groups on the NHC could lead to enhanced σ-donor properties, and, consequently, to higher catalytic activity, the authors postulated that the unsymmetrical nature of the NHC ligands could

Thermophilic phosphoribosyltransferases Thermus thermophilus HB27 in nucleotide synthesis

• Ilja V. Fateev,
• Ekaterina V. Sinitsina,
• Aiguzel U. Bikanasova,
• Maria A. Kostromina,
• Elena S. Tuzova,
• Larisa V. Esipova,
• Tatiana I. Muravyova,
• Alexei L. Kayushin,
• Irina D. Konstantinova and
• Roman S. Esipov

Beilstein J. Org. Chem. 2018, 14, 3098–3105, doi:10.3762/bjoc.14.289

• phosphoribosyltransferase Thermus thermophilus (TthHPRT), investigated its substrate specificity and optimal conditions for catalytic activity, and determined the kinetic parameters of the enzyme. A comparative study of the substrate specificity of TthAPRT and TthHPRT was performed to determine the usability of

A tutorial review of stereoretentive olefin metathesis based on ruthenium dithiolate catalysts

• Daniel S. Müller,
• Olivier Baslé and
• Marc Mauduit

Beilstein J. Org. Chem. 2018, 14, 2999–3010, doi:10.3762/bjoc.14.279

• introduced by Hoveyda in 2015 [4] showed moderate to good catalytic activity and can therefore be considered as a relatively general catalyst (Figure 1). In 2016 Pederson and Grubbs reported SIPr-based catalyst Ru-4 with increased catalytic activity for Z-alkenes (Figure 1) [3]. Further improvement was made

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

• metathesis catalysts [1]. Albeit typical ill-defined catalysts they are still popular as relatively cheap catalysts finding industrial applications especially in the treatment of low olefins [2][3][4][5]. Their catalytic activity depends on many factors, especially on Mo loading, support acidity, and pre

• -reaction activations. Surface isolated MoO4 tetrahedra were proved as the main precursors of the catalytic species [6][7], thus the perfect dispersion of MoO3 on the surface is a crucial precondition for a high catalytic activity. The mechanisms of transformation of these precursors to the surface Mo

• the parent supports. It may be explained by the formation of some amount of Mo in a lower oxidation state which has been already described for siliceous supports (MCM-41, SBA-15) [9][26]. Catalytic activity MCM-22-based catalysts Na+ forms of zeolites turned out to be unsuitable supports for

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

• inhibition of the catalytic activity of the enzyme [23]. All these drug discovery successes have validated PPIs as a target and, in conjunction with the elucidation and reconstruction of protein–protein interaction networks in bacteria, have paved the way towards the development of novel and promising

Copolymerization of epoxides with cyclic anhydrides catalyzed by dinuclear cobalt complexes

• Yo Hiranoi and
• Koji Nakano

Beilstein J. Org. Chem. 2018, 14, 2779–2788, doi:10.3762/bjoc.14.255

• benzene ring as a linker and their activities in copolymerization reactions. The dinuclear cobalt complexes showed a higher catalytic activity for the copolymerization of propylene oxide with phthalic anhydride than the corresponding mononuclear cobalt–salen complex and achieved one of the highest

• turnover frequencies ever reported. A variety of epoxides and CAs were also found to be copolymerized successfully by the dinuclear cobalt complex with a high catalytic activity. Keywords: cobalt; copolymerization; cyclic anhydrides; epoxides; polyesters; Introduction Aliphatic polyesters have received

• epoxide/CA copolymerization was constricted until recently because of low catalytic activity and poor control over the main chain sequence (formation of ether linkages through consecutive epoxide enchainment) and molecular weight. In 2007, Coates and co-workers reported that β-diiminate zinc complexes