Nucleoside macrocycles formed by intramolecular click reaction: efficient cyclization of pyrimidine nucleosides decorated with 5'-azido residues and 5-octadiynyl side chains

• Jiang Liu,
• Peter Leonard,
• Sebastian L. Müller,
• Constantin Daniliuc and
• Frank Seela

Beilstein J. Org. Chem. 2018, 14, 2404–2410, doi:10.3762/bjoc.14.217

• functionalized at the 5-position of the nucleobase with octadiynyl side chains and with azido groups at the 5’-position of the sugar moieties were synthesized. The macrocycles display freely accessible Watson–Crick recognition sites. The conformation of the 16-membered macrocycle was deduced from X-ray analysis

• new lead for a diversity of molecules. From the cyclic molecule a single crystal X-ray analysis was obtained. The sugar conformation was studied in solution and in solid state. Results and Discussion The octadiynyl derivative 1 of dC [32][33][34][35] was the starting material for the synthesis of 5

• decrease. Next, a X-ray analysis was performed from the dU macrocycle 8, which was crystallized from methanolic solution containing traces of water. Colorless needles with a melting point of 260–265 °C (decomp.) were obtained. The solid state structure of the macrocycle is displayed in Figure 2. The X- ray

Some mechanistic aspects regarding the Suzuki–Miyaura reaction between selected ortho-substituted phenylboronic acids and 3,4,5-tribromo-2,6-dimethylpyridine

• Piotr Pomarański,
• Piotr Roszkowski,
• Jan K. Maurin,
• Armand Budzianowski and
• Zbigniew Czarnocki

Beilstein J. Org. Chem. 2018, 14, 2384–2393, doi:10.3762/bjoc.14.214

• determined on the basis of HT NMR and thermal epimerisation experiments. The structure of most presented atropisomeric derivatives of 2,6-dimethylpyridine was confirmed by single-crystal X-ray analysis. Racemic chiral, differently substituted atropisomers were also examined by 1H NMR spectroscopy in the

• chromatography using a specialist high-purity grade silica gel type H (10–40 µm). The structure of (syn)-10 was also confirmed by the single-crystal X-ray analysis (see Supporting Information File 1 for details). We also carried out a series of the cross-coupling reactions using 3,4-dibromo-5-(2-methoxyphenyl

• possible by careful crystallization from methanol. The structure and configuration of the products 12–14 were established by NMR as well as the single-crystals X-ray analysis (see Supporting Information File 1 for details). The data presented in Table 4 clearly indicate that the substituent change from

Novel photochemical reactions of carbocyclic diazodiketones without elimination of nitrogen – a suitable way to N-hydrazonation of C–H-bonds

• Liudmila L. Rodina,
• Xenia V. Azarova,
• Jury J. Medvedev,
• Dmitrij V. Semenok and
• Valerij A. Nikolaev

Beilstein J. Org. Chem. 2018, 14, 2250–2258, doi:10.3762/bjoc.14.200

• ][39]. The structures of diazodiketones 1a–g were established using a standard set of spectroscopic methods (1Н and 13С NMR, IR and UV; for details, see Supporting Information File 1, Table S1) and in the case of the tricyclic diazodiketone 1с the structure was also confirmed by means of X-ray analysis

• % (Table 1, entries 1 and 3). The irradiation of tricyclic diazodiketone 1b in the presence of 1 equiv of benzophenone in THF solution led to the formation of hydrazone 2b in a yield of 32% (Table 1, entry 4), whose structure was unambiguously established by X-ray analysis (Figure 2). To increase the

• tetrahydrofuran used in the project. Molecular structure of hydrazone 2b as determined by X-ray analysis data (Olex2 plot with 50% probability level of ellipsoids). Photochemical cycloelimination of furans from hydrazones 2d,e. Different pathways of diazodiketones 1 light-induced reactions in the singlet

Synthesis of 1,4-imino-L-lyxitols modified at C-5 and their evaluation as inhibitors of GH38 α-mannosidases

• Maroš Bella,
• Sergej Šesták,
• Ján Moncoľ,
• Miroslav Koóš and
• Monika Poláková

Beilstein J. Org. Chem. 2018, 14, 2156–2162, doi:10.3762/bjoc.14.189

• absolute configuration of carbamate 20 was confirmed by single-crystal X-ray analysis (Figure 2) [36]. Basic hydrolysis of carbamate 20 with 10% NaOH in refluxing EtOH provided aminoalcohol 21 which was subsequently N-benzylated with the corresponding benzyl bromides to yield pyrrolidines 22. Final

D-Fructose-based spiro-fused PHOX ligands: synthesis and application in enantioselective allylic alkylation

• Michael R. Imrich,
• Jochen Kraft,
• Cäcilia Maichle-Mössmer and
• Thomas Ziegler

Beilstein J. Org. Chem. 2018, 14, 2082–2089, doi:10.3762/bjoc.14.182

• molecular structure is shown in Figure 2, detailed crystal data and structure refinements of the X-ray analysis are given in Supporting Information File 1. The configuration at the anomeric center is β and the fructose ring adopts 5C2 conformation. To confirm that the configuration of the major product of

Water-soluble SNS cationic palladium(II) complexes and their Suzuki–Miyaura cross-coupling reactions in aqueous medium

• Alphonse Fiebor,
• Richard Tia,
• Banothile C. E. Makhubela and
• Henok H. Kinfe

Beilstein J. Org. Chem. 2018, 14, 1859–1870, doi:10.3762/bjoc.14.160

• representative X-ray crystal structure of 17d is shown in Figure 3 [38]. Single crystals suitable for X-ray analysis of complexes 17d were obtained by slow evaporation of a mixture of dichloromethane and diethyl ether at about −4 °C. Crystallographic data and structure refinement parameters for 17d are

Preparation and X-ray structure of 2-iodoxybenzenesulfonic acid (IBS) – a powerful hypervalent iodine(V) oxidant

• Irina A. Mironova,
• Pavel S. Postnikov,
• Rosa Y. Yusubova,
• Akira Yoshimura,
• Thomas Wirth,
• Viktor V. Zhdankin,
• Victor N. Nemykin and
• Mekhman S. Yusubov

Beilstein J. Org. Chem. 2018, 14, 1854–1858, doi:10.3762/bjoc.14.159

• -iodosylbenzenesulfonic acid as confirmed by X-ray diffraction analysis [17]. In the present work, we report the preparation and isolation of IBS (as potassium or sodium salts) and its structural study by X-ray analysis. Furthermore, we have developed a new method for the preparation of the IBS reduced form, 2

• , which probably has a noncyclic (or pseudocyclic) structure of 2-OIC6H4SO2ONa. Indeed, X-ray analysis of 2-iodosylbenzenesulfonic acid (4) indicated a cyclic structure with a I–O bond length of 2.38 Å in the benziodoxathiole ring [18], while in the anionic iodine(V) benziodoxathiole ring in aggregate 6

• impossible in the cyclic structure of 2-iodosylbenzenesulfonic acid. Conclusion In conclusion, we have reported a selective preparation of IBS (as potassium or sodium salts) and investigated its structure by X-ray analysis. Furthermore, we have developed a new method for the preparation of the reduced form

Synthesis of new tricyclic 5,6-dihydro-4H-benzo[b][1,2,4]triazolo[1,5-d][1,4]diazepine derivatives by [3⁺ + 2]-cycloaddition/rearrangement reactions

• Lin-bo Luan,
• Zi-jie Song,
• Zhi-ming Li and
• Quan-rui Wang

Beilstein J. Org. Chem. 2018, 14, 1826–1833, doi:10.3762/bjoc.14.155

• -jian Lin for structural confirmation of 10k and 13e by single-crystal X-ray analysis.

Synthesis of spirocyclic scaffolds using hypervalent iodine reagents

• Fateh V. Singh,
• Priyanka B. Kole,
• Saeesh R. Mangaonkar and
• Samata E. Shetgaonkar

Beilstein J. Org. Chem. 2018, 14, 1778–1805, doi:10.3762/bjoc.14.152

• ). Furthermore, the absolute configuration of 88 was assigned by its single crystal X-ray analysis. 3.3. Application of spirolactams in natural product synthesis In 2001, Ciufolini and co-workers [103] employed PIDA (15) as an electrophile during the synthesis of naturally occurring tricyclic azaspirane

An unusual thionyl chloride-promoted C−C bond formation to obtain 4,4'-bipyrazolones

• Gernot A. Eller,
• Gytė Vilkauskaitė,
• Algirdas Šačkus,
• Vytas Martynaitis,
• Ashenafi Damtew Mamuye,
• Vittorio Pace and
• Wolfgang Holzer

Beilstein J. Org. Chem. 2018, 14, 1287–1292, doi:10.3762/bjoc.14.110

• racemic mixture or the meso-form came into consideration. The single crystal X-ray analysis disclosed that the molecule of the newly obtained compound 3a consists of two pyrazolone residues, which are directly connected to each other by a single covalent carbon–carbon bond between the asymmetric sp3

• ) for performing the X-ray analysis and to one of the referees for assistance with the proposed reaction mechanism.

Novel unit B cryptophycin analogues as payloads for targeted therapy

• Eduard Figueras,
• Adina Borbély,
• Mohamed Ismail,
• Marcel Frese and
• Norbert Sewald

Beilstein J. Org. Chem. 2018, 14, 1281–1286, doi:10.3762/bjoc.14.109

• research group. Docking and modelling of cryptophycin derivatives There is no X-ray analysis of cryptophycin–tubulin complexes available to provide information on the binding site. Based on biochemical evidence, binding close to the vinca-alkaloid binding site of β-tubulin, the so called “peptide-site

Stereoselective nucleophilic addition reactions to cyclic N-acyliminium ions using the indirect cation pool method: Elucidation of stereoselectivity by spectroscopic conformational analysis and DFT calculations

• Koichi Mitsudo,
• Junya Yamamoto,
• Tomoya Akagi,
• Atsuhiro Yamashita,
• Masahiro Haisa,
• Kazuki Yoshioka,
• Hiroki Mandai,
• Koji Ueoka,
• Christian Hempel,
• Jun-ichi Yoshida and
• Seiji Suga

Beilstein J. Org. Chem. 2018, 14, 1192–1202, doi:10.3762/bjoc.14.100

• Centre via http://www.ccdc.cam.ac.uk/data_request/cif. X-ray analysis of 1a–f. Acknowledgements This work was supported in part by JSPS KAKENHI (No. 16H01155, No. 16K05777), and by JST, ACT-C, Japan.

One hundred years of benzotropone chemistry

• Arif Dastan,
• Haydar Kilic and
• Nurullah Saracoglu

Beilstein J. Org. Chem. 2018, 14, 1120–1180, doi:10.3762/bjoc.14.98

Fluorocyclisation via I(I)/I(III) catalysis: a concise route to fluorinated oxazolines

• Felix Scheidt,
• Christian Thiehoff,
• Gülay Yilmaz,
• Stephanie Meyer,
• Constantin G. Daniliuc,
• Gerald Kehr and
• Ryan Gilmour

Beilstein J. Org. Chem. 2018, 14, 1021–1027, doi:10.3762/bjoc.14.88

• conformations around the two respective torsion angles [37][38]. In this case, it is also highly probable that hydrogen bonding will reinforce these conformational preferences. Whilst it was not possible to isolate crystals of 3 that were suitable for X-ray analysis, it was possible to unambiguously establish

Methyl isocyanide as a convertible functional group for the synthesis of spirocyclic oxindole γ-lactams via post-Ugi-4CR/transamidation/cyclization in a one-pot, three-step sequence

• Amarendar Reddy Maddirala and
• Peter R. Andreana

Beilstein J. Org. Chem. 2018, 14, 875–883, doi:10.3762/bjoc.14.74

• cyclization product 7a and not the 4-exo-dig-cyclization compound 7a' (Scheme 3). We rationalized, as per Baldwin’s rules, that the 5-endo-dig cyclization of a 1,4-Michael addition was more favorable than the 4-exo-dig-cyclization [50][51]. The structure of compound 7a was definitively confirmed by X-ray

• analysis (Figure 1). We then elected to carry out yield optimization studies of the cyclization reaction using a number of solvents, reagents and reaction temperatures (Table 1) and also to explore the possibility of a possible 4-exo-dig outcome. The study validated that all the reaction conditions, with

An air-stable bisboron complex: a practical bidentate Lewis acid catalyst

• Longcheng Hong,
• Sebastian Ahles,
• Andreas H. Heindl,
• Gastelle Tiétcha,
• Andrey Petrov,
• Zhenpin Lu,
• Christian Logemann and
• Hermann A. Wegner

Beilstein J. Org. Chem. 2018, 14, 618–625, doi:10.3762/bjoc.14.48

• EtOAc/BrPh 1:1 (v/v). The X-ray analysis revealed a triptycene-type arrangement (Figure 2) which was similar to a pyridazine complex of 9,10-dihydro-9,10-diboraanthracene reported by Wagner and co-workers [19] as well as the phthalazine complex of 5,10-dimethyl-5,10-dihydroboranthrene [17]. The 11B NMR

Diastereoselective auxiliary- and catalyst-controlled intramolecular aza-Michael reaction for the elaboration of enantioenriched 3-substituted isoindolinones. Application to the synthesis of a new pazinaclone analogue

• Romain Sallio,
• Stéphane Lebrun,
• Frédéric Capet,
• Francine Agbossou-Niedercorn,
• Christophe Michon and
• Eric Deniau

Beilstein J. Org. Chem. 2018, 14, 593–602, doi:10.3762/bjoc.14.46

• X-ray analysis of a single crystal allowed us to assert the (2R,3S) configuration of 3a (Figure 5). This result allowed for the determination of the absolute configurations of all isolated isoindolinones. Asymmetric synthesis of a new pazinaclone analogue With this handful methodology in hands, we

An alternative to hydrogenation processes. Electrocatalytic hydrogenation of benzophenone

• Cristina Mozo Mulero,
• Alfonso Sáez,
• Jesús Iniesta and
• Vicente Montiel

Beilstein J. Org. Chem. 2018, 14, 537–546, doi:10.3762/bjoc.14.40

• for the electrocatalytic hydrogenation of Ph2CO. Characterisation of Pd/C electrocatalyst. a) TEM micrograph. b) Energy dispersive X-ray analysis (EDX). c) Thermogravimety analysis in N2/O2 (4/1) atmosphere at a heating slope of 10 K min−1 from 298 K to 1023 K. SEM images of (a) Pd0.02/C/T and (b

Oxidative cycloaddition of hydroxamic acids with dienes or guaiacols mediated by iodine(III) reagents

• Hisato Shimizu,
• Akira Yoshimura,
• Keiichi Noguchi,
• Victor N. Nemykin,
• Viktor V. Zhdankin and
• Akio Saito

Beilstein J. Org. Chem. 2018, 14, 531–536, doi:10.3762/bjoc.14.39

• X-ray analysis [24]. Next, we investigated the oxidative cycloaddition reactions of hydroxamic acids 1a–c with various dienes 2 under the optimal conditions (Table 2). Similarly to the benzoyl derivative 1a, the carbamate analogues 1b (R1 = OBn) and 1c (R1 = Ot-Bu) reacted with 1,3-cyclohexadiene

• -alkylammonium periodates. To our delight, the sole use of DIB in a mixed solvent of DCM and methanol gave the endo-cycloadduct 6aa as a single regioisomer in 84% yield starting from hydroxamic acid 1a and guaiacol (5a, Scheme 2). The structure of 6aa was determined by single crystal X-ray analysis [24]. It

Nucleophilic dearomatization of 4-aza-6-nitrobenzofuroxan by CH acids in the synthesis of pharmacology-oriented compounds

• Alexey M. Starosotnikov,
• Dmitry V. Shkaev,
• Maxim A. Bastrakov,
• Ivan V. Fedyanin,
• Svyatoslav A. Shevelev and
• Igor L. Dalinger

Beilstein J. Org. Chem. 2017, 13, 2854–2861, doi:10.3762/bjoc.13.277

• with β-dicarbonyl compounds. Selected NMR parameters of the ANBF-CH-acid adducts (in DMSO-d6)a. Supporting Information Supporting Information File 426: Experimental section, NMR spectra, HRMS and X-ray analysis data. Acknowledgements This work was supported by the Russian Science Foundation (grant no

• -ray analysis [28] (Figure 3). Compound 15 crystallizes as a solvate with one DMSO molecule connected to the hydrogen atom of the amino fragment by an intermolecular H-bond. Bond lengths and angles in the dearomatized 4-aza-6-nitrobenzofuroxan ring are very similar to those observed in the crystal of

• the chirality of carbon atom C7, the protons HA and HB of the methylene group are diastereotopic and therefore have different chemical shifts (3.34 and 3.74 ppm). The geminal protons and H7 represent a well-resolved AMX system, Figure 2. The structure of compound 15 was additionally studied using X

Ring-size-selective construction of fluorine-containing carbocycles via intramolecular iodoarylation of 1,1-difluoro-1-alkenes

• Takeshi Fujita,
• Ryo Kinoshita,
• Tsuyoshi Takanohashi,
• Naoto Suzuki and
• Junji Ichikawa

Beilstein J. Org. Chem. 2017, 13, 2682–2689, doi:10.3762/bjoc.13.266

• characterization of 6 was achieved by X-ray analysis using a single crystal of 6a (Figure 2), and it was found that the iodoarylation products 6 have a seven-membered carbocycle bearing adjacent difluoromethylene and iodomethylene units. In addition, a selective HI elimination from 6a could be achieved by the

A Brønsted base-promoted diastereoselective dimerization of azlactones

• Danielle L. J. Pinheiro,
• Gabriel M. F. Batista,
• Pedro P. de Castro,
• Leonã S. Flores,
• Gustavo F. S. Andrade and
• Giovanni W. Amarante

Beilstein J. Org. Chem. 2017, 13, 2663–2670, doi:10.3762/bjoc.13.264

• diastereomer was assigned by X-ray analysis. Finally, one of the products was selectively reduced to provide a functionalized analogue of streptopyrrolidine, a marine natural product isolated from Streptomyces sp. As shown in Table 1, our studies started with the synthesis of dimer 2a using azlactone 1a in the

• -position relative to both the benzyl substituents [32]. The relative stereochemistry of 6 was assigned by X-ray analysis (Figure 5). Conclusion In summary, we have demonstrated the first diastereoselective dimerization of azlactones mediated by a combination of acetonitrile and potassium or sodium

• trichloroacetate salts, which provides a straightforward and practical access to azlactone dimers with good to excellent yields and good diastereoselectivities. In addition, the relative stereochemistry of major azlactone dimer was assigned as being trans by X-ray analysis. A plausible mechanism was proposed by 1H

Rh(II)-mediated domino [4 + 1]-annulation of α-cyanothioacetamides using diazoesters: A new entry for the synthesis of multisubstituted thiophenes

• Jury J. Medvedev,
• Ilya V. Efimov,
• Yuri M. Shafran,
• Vitaliy V. Suslonov,
• Vasiliy A. Bakulev and
• Valerij A. Nikolaev

Beilstein J. Org. Chem. 2017, 13, 2569–2576, doi:10.3762/bjoc.13.253

• also confirmed by X-ray analysis (Figure 2). In the 1H NMR spectra of these compounds, the characteristic signals of NH protons are observed in the range of 9.84–9.68 and 7.96–7.80 ppm for 3a–e and 4a–e, respectively. The signals of thiophene H-4 and C-4 atoms in the 1H and 13C NMR spectra of compounds

• diazocyanoester 2d with the thioamides 1a–e gave rise to thiophenes 5b–e in the yields of up to 51%. The structure of the isolated thiophenes 5a–e was established by a regular set of spectroscopic data, whereupon the structure of compound 5c was in addition confirmed by X-ray analysis (Figure 3). In the 1H NMR

• )4 and Rh2(Oct)4 was studied (Scheme 3). The reaction was carried out in methylene chloride at room temperature using a 2-fold excess of thioacetamides 1. It produced almost quantitatively dark green adducts 6a–e, 6b’–e’, which structure was confirmed by analytical methods, X-ray analysis for complex

Pyrene–nucleobase conjugates: synthesis, oligonucleotide binding and confocal bioimaging studies

• Artur Jabłoński,
• Yannic Fritz,
• Hans-Achim Wagenknecht,
• Rafał Czerwieniec,
• Tytus Bernaś,
• Damian Trzybiński,
• Krzysztof Woźniak and
• Konrad Kowalski

Beilstein J. Org. Chem. 2017, 13, 2521–2534, doi:10.3762/bjoc.13.249

• pyrenyl–thymine 2 was confirmed by single-crystal X-ray analysis. Crystal structure Crystals of 2 suitable for X-ray diffraction analysis were obtained by slow diffusion of pentane into a chloroform solution of 2. The oak ridge thermal-ellipsoid plot (ORTEP) with the atom labelling scheme is shown in

Dialkyl dicyanofumarates and dicyanomaleates as versatile building blocks for synthetic organic chemistry and mechanistic studies

• Grzegorz Mlostoń and
• Heinz Heimgartner

Beilstein J. Org. Chem. 2017, 13, 2235–2251, doi:10.3762/bjoc.13.221

• yields. The X-ray analysis showed that products 53 obtained with primary amines are Z-configured whereas those derived from secondary amines, 54, display E-configuration [58] (Scheme 18). The observed different configurations demonstrate the importance of the intramolecular hydrogen-bond between the NH