Host–guest interactions between p-sulfonatocalix[4]arene and p-sulfonatothiacalix[4]arene and group IA, IIA and f-block metal cations: a DFT/SMD study

• Valya K. Nikolova,
• Cristina V. Kirkova,
• Silvia E. Angelova and
• Todor M. Dudev

Beilstein J. Org. Chem. 2019, 15, 1321–1330, doi:10.3762/bjoc.15.131

• ., acetaldehyde – ethanal, CH3CHO) are required in condensation reactions with resorcinol and pyrogallol [1]. Thiacalixarenes are macrocycles (or cyclic oligomers) based on a condensation of the same phenol derivatives and sulfur [2]. They are characterized by a larger cavity size than the conventional

Bambusuril analogs based on alternating glycoluril and xylylene units

• Tomáš Lízal and
• Vladimír Šindelář

Beilstein J. Org. Chem. 2019, 15, 1268–1274, doi:10.3762/bjoc.15.124

• reaction yielded a mixture of two (n = 2) to five (n = 5)-membered macrocycles and acyclic oligomers. The crude mixture of macrocycles was separated by reversed-phase flash silica gel chromatography after normal phase silica and size-exclusion chromatography did not show satisfactory results. The

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

• solution of the pre-formed imine (3 equiv), which avoids formation of higher oligomers. Remarkably, such procedure was undertaken with formation of twelve covalent bonds and the incorporation of eight components in one pot. A few years later, the same authors described the implementation of a sequential

Mechanochemical amorphization of chitin: impact of apparatus material on performance and contamination

• Thomas Di Nardo and
• Audrey Moores

Beilstein J. Org. Chem. 2019, 15, 1217–1225, doi:10.3762/bjoc.15.119

• ] or acidic depolymerization [23][24] and simultaneously during processing [42], yielding oligomers and monomers. Differentiating these regions of impact would be of great value for biomass processing. It is therefore important to understand precisely how to master media selection: finding the right

Molecular recognition using tetralactam macrocycles with parallel aromatic sidewalls

• Dong-Hao Li and
• Bradley D. Smith

Beilstein J. Org. Chem. 2019, 15, 1086–1095, doi:10.3762/bjoc.15.105

• (Scheme 3) [35]. The template molecule favors this step over the alternative intermolecular reaction that leads to larger oligomers. The poor solubility of A prevents the traditional host–guest affinity measurements; however, the [2]rotaxane yield is a useful indicator of template affinity for the

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

• the presence of 1.0 mol % of catalyst 11a,c,d as compared with 0.1 mol % of catalyst (cf. Table 3, entries 9/10, 12/13). Obviously, a high concentration of the catalysts accelerates the formation of undesirable products (oligomers and polymers of styrene). At 40 °C in dichloromethane, excellent yields

• the side cross metathesis (13 and 27). Moreover, sparingly soluble high molecular weight products were isolated from all reactions; according to gel permeation chromatography data, these solids are, presumably, norbornene oligomers (see, for example data for entry 35, Supporting Information File 1 and

Homo- and hetero-difunctionalized β-cyclodextrins: Short direct synthesis in gram scale and analysis of regiochemistry

• Gábor Benkovics,
• Mihály Bálint,
• Éva Fenyvesi,
• Erzsébet Varga,
• Szabolcs Béni,
• Konstantina Yannakopoulou and
• Milo Malanga

Beilstein J. Org. Chem. 2019, 15, 710–720, doi:10.3762/bjoc.15.66

• -difunctionalization; regioselectivity; Introduction Cyclodextrins (CDs) are cyclic oligomers of α-D-glucopyranose (Figure 1 illustrates the heptamer, β-CD) that have attracted worldwide interest in various fields of applied supramolecular chemistry due to their ability to form host–guest inclusion complexes [1]. A

Selectivity in multiple multicomponent reactions: types and synthetic applications

• Ouldouz Ghashghaei,
• Francesca Seghetti and
• Rodolfo Lavilla

Beilstein J. Org. Chem. 2019, 15, 521–534, doi:10.3762/bjoc.15.46

• illustrate a repetitive Ugi 4CR-deprotection-Ugi 4CR protocol to obtain peptide nucleic acid (PNA) oligomers (Scheme 13A) [49], peptidic tetrazoles and hydantoinimides (Scheme 13B) [50], respectively. Incidentally, the later processes take place in solid phase, which enhances their synthetic suitability. The

• sequence. High order MMCRs. A) Ugi/Ugi–Smiles 7C combination; B) imidazoline-N-cyanomethylamide-Ugi union leading to an 8CR. Consecutive Ugi 4CR-deprotection–Ugi 4CR strategy towards A) PNA oligomers and B) peptidic tetrazoles and hydantionimides. Sequential Ugi 4CR-deprotection access to cyclopeptoids

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

• the application of ADMET in the synthesis of oligomers or polymers containing a POSS unit in the main chain. Marciniec disclosed ADMET copolymerization of DDSQ-2SiVi with dienes in the stereoselective synthesis of a new class of vinylene–arylene copolymers containing double-decker silsesquioxanes in

• . Analogous ADMET copolymerization of divinylgermasilsesquioxanes with 4,4'-divinylbiphenyl or 4,4''-divinylterphenyl can be used in the synthesis of stereoregular trans-germasilsesquioxyl–vinylene–phenylene oligomers (Scheme 19) [19]. This method permitted obtaining a polymer with Mw in the range from 9057

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

• temperatures in the ROMP of norbornene and cyclooctene. Oligomers were obtained at room temperature in the presence of 4a and 4d, while 4b and 4c yielded polymers. At 60 °C, ROMP was observed with norbornene (98–100%) and cyclooctene (72–80%) in the presence of 4. We investigated a number of Grubbs 1- and

Unexpected loss of stereoselectivity in glycosylation reactions during the synthesis of chondroitin sulfate oligosaccharides

• Teresa Mena-Barragán,
• José L. de Paz and
• Pedro M. Nieto

Beilstein J. Org. Chem. 2019, 15, 137–144, doi:10.3762/bjoc.15.14

• substitution pattern of GlcA units for the efficient synthesis of CS oligomers. Keywords: carbohydrate chemistry; chondroitin sulfate; glycosylation; oligosaccharide synthesis; stereoselectivity; Introduction Chondroitin sulfate (CS) is a highly heterogeneous polysaccharide, constituted by the repetition of

• ][6][7][8]. For example, Jacquinet, Lopin-Bon and co-workers presented the preparation of CS oligomers with different sulfation motifs, starting from a single GlcA-GalNAc disaccharide precursor easily obtained by depolymerization of the natural product [9][10][11][12][13]. CS tetrasaccharides

• for the synthesis of CS oligomers. A fully deprotected tetrasaccharide was successfully prepared for biological studies. This synthesis involved the [2 + 2] coupling of disaccharide building blocks. The use of a fluorous tag facilitated the isolation of the fluorinated species from the glycosylation

Lectins of Mycobacterium tuberculosis – rarely studied proteins

• Katharina Kolbe,
• Sri Kumar Veleti,
• Norbert Reiling and
• Thisbe K. Lindhorst

Beilstein J. Org. Chem. 2019, 15, 1–15, doi:10.3762/bjoc.15.1

• homodimers, homotrimers, and higher-ordered oligomers, which increases their avidity for multivalent ligands. C-Type lectins play key roles in cell–cell interactions, such as host–pathogen interactions, and phagocytosis [92]. The Mtb gene product of Rv2075c shows partial amino acid sequence similarity to

Degenerative xanthate transfer to olefins under visible-light photocatalysis

• Atsushi Kaga,
• Xiangyang Wu,
• Joel Yi Jie Lim,
• Hirohito Hayashi,
• Yunpeng Lu,
• Edwin K. L. Yeow and
• Shunsuke Chiba

Beilstein J. Org. Chem. 2018, 14, 3047–3058, doi:10.3762/bjoc.14.283

• thiocarbonylthio compounds has also been developed for the synthesis of the sequence-controlled oligomers [41][42][43][44][45]. For example, the group of Boyer and Xu developed fac-Ir(ppy)3 (6)-catalyzed polymerization of xanthate 4 with various vinyl monomers such as vinyl acetate, providing polymers of type 5

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

• in considerable amounts. It is a consequence of the 1-octene double bond isomerization followed by cross metathesis. Moreover, a certain amount of oligomers (mainly dimers) were also observed in the reaction mixtures. Both isomerization and oligomerization are due to the acidic character of the

• Ktot is plotted in Figure 2 in this case. Both Ktot and Kmet for 6MoO3/MCM-22(28) were significantly higher than the total conversion for 6MoO3/SBA-15 (Figure 2). Conversions to oligomers (Kol = Ktot − Kmet) were about 12% (at 2 h) and practically did not change in the further course of the reaction

• accord with this, the conversions fell down in comparison with 6MoO3/MCM-22(28), the selectivity, however, slightly increased: the amount of oligomers was reduced and the selectivity to the tetradecene approximately doubled. It suggests that more acid sites were covered by MoOx species and

Synergistic approach to polycycles through Suzuki–Miyaura cross coupling and metathesis as key steps

• Sambasivarao Kotha,
• Milind Meshram and
• Chandravathi Chakkapalli

Beilstein J. Org. Chem. 2018, 14, 2468–2481, doi:10.3762/bjoc.14.223

• ][20][21][22], oligomers [23][24], polycyclic ethers [25], heterocycles [26], nonbenzenoid aromatics [27], and spirocycles [28][29]) by decreasing the number of steps. Different metathesis catalysts used in this study are shown in Figure 1. Review Annulation Grela and co-workers [30] demonstrated a

Non-metal-templated approaches to bis(borane) derivatives of macrocyclic dibridgehead diphosphines via alkene metathesis

• Tobias Fiedler,
• Michał Barbasiewicz,
• Michael Stollenz and
• John A. Gladysz

Beilstein J. Org. Chem. 2018, 14, 2354–2365, doi:10.3762/bjoc.14.211

• ) consisted of unidentified and/or impure products, or oligomers and polymers. Products that could be characterized are as follows (in order of elution). H3B·P(n-C8H17)3 (4·BH3 [33]; 0.007 g, 0.018 mmol, 1%), colorless oil. Anal. calcd for C24H54BP (384.47): C, 74.98; H, 14.16; found: C, 74.93; H, 14.02; 1H

• ·2BH3 (0.056 g, 0.083 mmol, 5%, minor impurities evident by 13C{1H} NMR), and (in,in/out,out)-2·2BH3 (0.075 g, 0.111 mmol, 7%), along with several fractions consisting of unidentified and/or impure products, or oligomers and polymers. Spectroscopic data for in,out-2·2BH3, (in,in/out,out)-2·2BH3, and 6

Synthesis and post-functionalization of alternate-linked-meta-para-[2ⁿ.1ⁿ]thiacyclophanes

• Wout De Leger,
• Koen Adriaensen,
• Koen Robeyns,
• Luc Van Meervelt,
• Joice Thomas,
• Björn Meijers,
• Mario Smet and
• Wim Dehaen

Beilstein J. Org. Chem. 2018, 14, 2190–2197, doi:10.3762/bjoc.14.192

• the [2 + 2] adduct 6 is the more thermodynamically favoured product and the [3 + 3] adduct 7 is the kinetic product. When the reaction was carried out at higher temperatures, an increase in the formation of open chain oligomers was observed (Supporting Information File 1, Table S1, entries 13 and 14

• -elimination (route B) can easily occur, leading to reversal of the addition reactions. This was observed in a stability experiment where pure [3 + 3] macrocycle 7 in CDCl3 (without adding base) over two weeks’ time converted into a mixture of [3 + 3] macrocycle 7 (9%), acyclic oligomers (50%) and the more

• ] adduct 19. Traces of unidentified oligomers and functionalized [2 + 2] macrocycle were also observed in the reaction mixture. It can be argued that, due to steric hindrance, the alkylation of macrocycle 6 is slow. The less sterically hindered cyclic trimer 7 and the linear oligomers are therefore faster

A hemicryptophane with a triple-stranded helical structure

• Augustin Long,
• Olivier Perraud,
• Erwann Jeanneau,
• Christophe Aronica,
• Jean-Pierre Dutasta and
• Alexandre Martinez

Beilstein J. Org. Chem. 2018, 14, 1885–1889, doi:10.3762/bjoc.14.162

• three imine functions is highly sable [12][13]. Hydrogen bonds between the amide group and the formed imine function could account for the high stability of this intermediate, shifting the equilibrium between the different oligomers and the cage in favor of this latter (vide infra). 1H NMR of cage 1 The

• thermodynamic stability compared to oligomers that could also be formed during the reaction between 4 and 5. Interestingly, one can also see that the CTV with the P configuration (respectively M) imposes a Δ (respectively Λ) propeller-like arrangement of the lateral arms, with a 120° turn around the C3 axis of

Visible light-mediated difluoroalkylation of electron-deficient alkenes

• Vyacheslav I. Supranovich,
• Vitalij V. Levin,
• Marina I. Struchkova,
• Jinbo Hu and
• Alexander D. Dilman

Beilstein J. Org. Chem. 2018, 14, 1637–1641, doi:10.3762/bjoc.14.139

• ). However, some byproducts were observed in amounts of up to 10%, which were tentatively identified as oligomers arising from multiple addition of tert-butyl acrylate to the propagating radical. Fortunately, increase of the amount of borohydride to 2 equiv suppressed the formation of oligomers, and addition

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

• diazide for 18 h at 70 °C in 4.0 mL of DMSO. Unfortunately, we noticed that by applying these conditions only an intractable mixture of unidentifiable oligomers could be isolated. However, we succeeded in obtaining the desired fully reticulated polymers by reducing the amount of solvent (2.0 mL) and

Oligonucleotide analogues with cationic backbone linkages

• Melissa Meng and
• Christian Ducho

Beilstein J. Org. Chem. 2018, 14, 1293–1308, doi:10.3762/bjoc.14.111

• , thus weakening the attraction of the oppositely charged backbones [41]. In order to elucidate the stability of aminoethyl phosphoramidate-linked oligonucleotides to nuclease-catalysed degradation, Letsinger and co-workers described the incubation of such oligomers, the deoxyadenosyl dimer 11 and DNA

• range and its ability to form both intermolecular electrostatic interactions and hydrogen bonds [50]. Letsinger's aminoalkyl phosphoramidate modification was stereogenic at the phosphorus atom, thus leading to complex mixtures of diastereomeric oligomers (with the exception of the aforementioned related

• of DNG oligomers were introduced. They enabled chain elongation either in the 5'→3' [52] or 3'→5' [53] direction, respectively. Starting from protected 3',5'-dideoxy-5'-amino-3'-azidothymidine 21, the 5'→3' route was based on the synthesis of the diamino intermediate 22 and thiourea monomer 23, which

An overview of recent advances in duplex DNA recognition by small molecules

• Sayantan Bhaduri,
• Nihar Ranjan and
• Dev P. Arya

Beilstein J. Org. Chem. 2018, 14, 1051–1086, doi:10.3762/bjoc.14.93

• ). This has been attributed to strong self-association (dimerization) in an antiparallel, head-to-tail orientation in aqueous solution during complex formation with duplex DNA oligomers verified via NOE experiments [61]. They further reported several structurally diverse MGBs, derived from distamycin, in

Enzyme-free genetic copying of DNA and RNA sequences

• Marilyne Sosson and
• Clemens Richert

Beilstein J. Org. Chem. 2018, 14, 603–617, doi:10.3762/bjoc.14.47

• 2',5'-isomers is expected for this reaction. Work on quantifying the ratio of the diastereomers formed is under way in our laboratories. Unlike assays performed with pre-activated monomers, primer extension with in situ activation of ribonucleotides led to significant levels of oligomers that form

• via untemplated polymerization of the nucleotides [63]. This was a welcome side reaction, as it helps to explain how RNA may have been formed and copied under prebiotic conditions. In fact, when oligomerization assays were performed with any of the four natural ribonucleotides, oligomers of mixed

Preparation of trinucleotide phosphoramidites as synthons for the synthesis of gene libraries

• Ruth Suchsland,
• Bettina Appel and
• Sabine Müller

Beilstein J. Org. Chem. 2018, 14, 397–406, doi:10.3762/bjoc.14.28

• proceed by either phosphite triester chemistry or phosphotriester chemistry with the latter being the more robust method. Also H-phosphonate chemistry has been used for assembling short oligomers in solution [34], although not with the aim of generating trinucleotide synthons for gene synthesis. 2

• this strategy the large scale synthesis (5 g) of 3'-unprotected trinucleotides proceeded with a total 75–90% yield [20]. Other strategies with potential for the solid-phase synthesis of protected trinucleotides might rely on a universal solid support, from which oligomers with free 3'-OH function are

Reactivity of bromoselenophenes in palladium-catalyzed direct arylations

• Aymen Skhiri,
• Ridha Ben Salem,
• Jean-François Soulé and
• Henri Doucet

Beilstein J. Org. Chem. 2017, 13, 2862–2868, doi:10.3762/bjoc.13.278

• temperature (110–130 °C), 2-bromoselenophene seems to afford larger amounts of selenophene oligomers as side-products. The use of PdCl2 or PdCl(C3H5)(dppb) as catalysts instead of Pd(OAc)2 or other bases such as K2CO3, Cs2CO3, CsOAc or NaOAc afforded 1 in lower yields (Table 1, entries 4–9). The influence of

• , due to these higher energies of activation for reactions with thiophene or pyrrole, larger amounts of selenophene oligomers were formed in the presence of these less reactive heteroarenes. Then, the reactivity of imidazo[1,2-a]pyridine, which contains a very reactive C–H bond at C3-position was