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

• , 21.49, 20.63, 19.33, 19.18; 29Si NMR (60 MHz, CDCl3, 25 °C, TMS) δ −21.93; MS (HRMS ESI) m/z: [M + Na]+ calcd for C32H41O3ClNaSi, 559.2405; found, 559.2404 (−0.1 ppm). Synthesis BIFOXSi(OH)2 (9): In a dried Schlenk flask BIFOXSiCl2 (7, 1 g, 1.8 mmol, 1 equiv) was solved in THF (25 mL) and H2O (25 mL

• ), 0.59 (s, 6H), 0.45 (s, 6H); 13C NMR (75 MHz, CDCl3, 25 °C, TMS) δ 144.28, 141.97, 135.16, 128.80, 124.70, 124.17, 90.24, 55.04, 50.08, 48.11, 43.98, 35.33, 29.01, 23.65, 20.85, 19.76; MS (HRMS ESI) m/z: [M + Na]+ calcd for C32H42O4NaSi, 541.2744; found, 541.2742 (−0.4 ppm); 29Si NMR (60 MHz, CDCl3, 25

Synthesis of a tubugi-1-toxin conjugate by a modulizable disulfide linker system with a neuropeptide Y analogue showing selectivity for hY1R-overexpressing tumor cells

• Rainer Kufka,
• Robert Rennert,
• Goran N. Kaluđerović,
• Lutz Weber,
• Wolfgang Richter and
• Ludger A. Wessjohann

Beilstein J. Org. Chem. 2019, 15, 96–105, doi:10.3762/bjoc.15.11

• conjugate 8 was characterized by ESI–FTICR–MS measurements (see Supporting Information File 1). All signals for [M + nH]n+ with n = 4–8 could be identified. After NPY Y1 receptor-mediated, endocytotic accumulation of the respective peptide–toxin conjugate 8 in the targeted tumor cells, the cytotoxic tubugi

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

• downsizing C60 with bowl milling [26] and high-speed vibration milling [27]. We confirmed that a simple grinding process by an agate mortar is sufficient for the HFIP system (Figure S2 in Supporting Information File 1). ESI mass spectrometry of the purple solution indicates the presence of the γ-CD–C60 (2:1

• detected even after the nonwovens were stored in toluene for three days (Figure S10 in Supporting Information File 1). The other aimed examined the solution of the nonwovens re-dissolved with HFIP. The resulting purple solution clearly provides the same UV–vis absorption and ESI mass results as the

• spectroscopy (V-730, JASCO, Japan), ESI mass spectroscopy (Autoflex III, Bruker), and small sample viscometry (m-VROCTM, RheoSense, USA). γ-CD/HFIP (15 w/v %; 500 μL) and C60/toluene (0, 0.14, 0.29, 0.43, 0.58, 0.72 mM; 25 μL) were mixed and measured by UV–vis spectrometry. The calibration curve was prepared

Mechanistic studies of an L-proline-catalyzed pyridazine formation involving a Diels–Alder reaction with inverse electron demand

• Anne Schnell,
• J. Alexander Willms,
• S. Nozinovic and
• Marianne Engeser

Beilstein J. Org. Chem. 2019, 15, 30–43, doi:10.3762/bjoc.15.3

• charge-tagged proline catalyst. The charge-tagging technique strongly increases the ESI response of the respective species and therefore enables to capture otherwise undetected reaction components. With the first two reaction variants, only small intensities of intermediates were found, but the temporal

• ; L-proline; reaction mechanism; Introduction Electrospray (ESI) mass spectrometry (MS) [1] is well suited for studying reaction mechanisms as it is a soft ionization method leaving most species intact [1][2][3]. In addition, it is a fast analytical method [3] making it possible to study transient

• with liquid or gas chromatography. Further, ESI signal intensities do not directly correlate to concentrations in solution, but to the ESI response of the pertaining molecules [3][22]. The ESI response is influenced by a variety of factors like chargeability and surface activity of a given analyte and

A simple and effective preparation of quercetin pentamethyl ether from quercetin

• Jin Tatsuzaki,
• Tomohiko Ohwada,
• Yuko Otani,
• Reiko Inagi and
• Tsutomu Ishikawa

Beilstein J. Org. Chem. 2018, 14, 3112–3121, doi:10.3762/bjoc.14.291

• the solvent peak for the 1H and 13C NMR spectra. The following abbreviations are used: s = singlet, d = doublet, t = triplet, q = quartet, dd = double doublet. Electron spray ionization time-of-flight mass spectra (ESI–TOF MS) were recorded on a Bruker micrOTOF-05 to give high-resolution mass spectra

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

• sequence). Mass spectra were measured on an Agilent 6224, ESI-TOF, LC/MS (USA) in positive ion mode (ESI), LCQ Fleet ion trap mass spectrometer (Thermo Electron, USA) and Agilent 1100 LC/MSD VL (Agilent Technologies) equipped an APCI and ESI source (positive and negative mode of ionization), 1100 DAD and

• ; 37%) of 9-(β-D-ribofuranosyl)-2-chloroadenine 5'-monophosphate of 99% purity (HPLC). HRMS (ESI+): m/z [M + H]+ calcd for C10H13N5O7P1Cl1: 382.0315; found, 382.0353; [2M + H]+, found, 763.0606; [Base + H]+, found, 170.0244; 1Н NMR (DMSО-d6) δ ppm) 8.52 (s, 1Н, H8), 7.78 (br. s., 2H, NH2), 5.83 (d, J1

• -ribofuranosyl)pyrazolo[3,4-d]pyrimidine-4-one 5'-monophosphate of 97% purity (HPLC). HRMS (ESI+): m/z [M + H]+ calcd for C10H13N4O8P1: 349.0545; found, 349.0520; [2M + H]+, found, 697.0952; [3M + H]+, found, 1045.1374; [Base + H]+ found, 137.0453; 1Н NMR (DMSО-d6) δ 12.44 (br. s, 1H, NH), 8.15 (s, 1H, H3), 8.13

N-Acylated amino acid methyl esters from marine Roseobacter group bacteria

• Hilke Bruns,
• Lisa Ziesche,
• Nargis Khakin Taniwal,
• Laura Wolter,
• Thorsten Brinkhoff,
• Jennifer Herrmann,
• Rolf Müller and
• Stefan Schulz

Beilstein J. Org. Chem. 2018, 14, 2964–2973, doi:10.3762/bjoc.14.276

• and ESI mass spectra revealed fragmentation patterns helpful for the detection of similar compounds derived from other amino acids. Some of these compounds showed antimicrobial activity. The structural similarity of N-acylated amino acid methyl esters and similar lipophilicity to AHLs might indicate a

• :1-NAVME. The extract of Roseovarius sp. D12_1.68 was also investigated by HPLC/ESI+–MS to detect more polar compounds compared to GC. The NAMEs, NABMEs and NAVMEs reported here were detected by MS2 analyses based on their characteristic fragmentation (see below). The only oxygenated derivative

• the three strains. Mass spectrometry The analysis of the mass spectra of NAMEs, NABMEs, NAVMEs, and NAGMEs revealed the typical fragmentation of N-acylated amino acid methyl esters under both EI (Figure 7) and ESI ionization (Figure 8). Detailed structural information can be obtained by EI-MS. A

Olefin metathesis catalysts embedded in β-barrel proteins: creating artificial metalloproteins for olefin metathesis

• Daniel F. Sauer,
• Johannes Schiffels,
• Takashi Hayashi,
• Ulrich Schwaneberg and
• Jun Okuda

Beilstein J. Org. Chem. 2018, 14, 2861–2871, doi:10.3762/bjoc.14.265

• nm indicated the presence of the GH-type catalyst. Finally, the peak for the biohybrid conjugate was observed in ESI–TOF–MS suggesting successful covalent anchoring. Beside ring-closing metathesis (RCM) of 2,2-diallylpropane-1,3-diol to yield the corresponding cyclopentane derivative, the synthesized

Unprecedented nucleophile-promoted 1,7-S or Se shift reactions under Pummerer reaction conditions of 4-alkenyl-3-sulfinylmethylpyrroles

• Takashi Go,
• Akane Morimatsu,
• Hiroaki Wasada,
• Genzoh Tanabe,
• Osamu Muraoka,
• Yoshiharu Sawada and
• Mitsuhiro Yoshimatsu

Beilstein J. Org. Chem. 2018, 14, 2722–2729, doi:10.3762/bjoc.14.250

• with p-methoxybenzenethiol/TBAH, which exclusively produced 9a (the diol 24a was not detected by ESI mass spectroscopy). A similar result was obtained from the reaction of 5a with p-chlorobenzenethiol/TBAH. These results support the hypothesis that the reaction proceeds via the initial formation of the

Domino ring-opening–ring-closing enyne metathesis vs enyne metathesis of norbornene derivatives with alkynyl side chains. Construction of condensed polycarbocycles

• Ritabrata Datta and
• Subrata Ghosh

Beilstein J. Org. Chem. 2018, 14, 2708–2714, doi:10.3762/bjoc.14.248

• (s, 6H); 13C NMR (125 MHz) δ 144.3, 139.8, 136.4, 136.1, 117.0, 113.1, 71.9, 68.6, 63.4, 61.2, 52.2, 52.0, 45.8, 36.8, 36.0, 33.8, 28.8, 26.0 (× 3), 18.4, −5.4, −5.6; HRMS–ESI m/z: [M + Na]+ calcd for C23H38O2SiNa 397.2539; found, 397.2537. Diels–Alder reaction of diene 11. Synthesis of adduct 14. A

• , 9H), 0.08 (s, 6H); 13C NMR (75 MHz) δ 169.0, 168.7, 136.4, 135.8, 133.6, 132.4, 132.2, 117.9, 72.0, 68.8, 63.1, 61.2, 52.3 (× 2), 52.1 (× 2), 45.7, 41.1, 36.8, 33.6, 30.9, 28.9, 28.6, 26.0 (× 3), 18.4, −5.4, −5.6; IR: 2952, 1728, 1471 cm−1; HRMS–ESI m/z: [M + Na]+ calcd for C29H44O6SiNa 539.2805

• , 1249 cm−1; HRMS–ESI m/z: [M + Na]+ calcd for C31H46O7SiNa 581.2911; found, 581.2914. Synthesis of the tetracycle 20. The dienyne 18 (100 mg, 0.25 mmol) in degassed anhydrous toluene (7 mL) was treated with Grubbs’ catalyst G-II (22 mg, 0.025 mmol) at 65 °C for 5 h. On completion of the reaction (TLC

Ring-opening metathesis of some strained bicyclic systems; stereocontrolled access to diolefinated saturated heterocycles with multiple stereogenic centers

• Zsanett Benke,
• Melinda Nonn,
• Márton Kardos,
• Santos Fustero and
• Loránd Kiss

Beilstein J. Org. Chem. 2018, 14, 2698–2707, doi:10.3762/bjoc.14.247

• , CH2), 2.98–3.06 (m, 1H, H-3), 4.33–4.39 (m, 1H, CHN), 4.78–4.84 (m, 1H, H-5), 5.23–5.32 (m, 4H, CH=), 5.66–5.82 (m, 3H, CH= and NH); 13C NMR (CDCl3, 100 MHz) δ 29.0, 29.7, 44.7, 52.5, 79.4, 80.1, 118.7, 119.3, 134.8, 135.1, 155.1, 174.2; MS (ESI, pos) (m/z): 288 [M + 1], 168 [M − Boc]; anal. calcd for

• ), 3.00–3.09 (m, 1H, H-3), 4.48–4.54 (m, 1H, CNH), 4.73–4.85 (m, 2H, H-5 and NH), 5.27–5.33 (m, 3H, CH=), 5.40–5.46 (m, 1H, CH=), 5.77–6.01 (m, 2H, CH=); 13C NMR (CDCl3, 100 MHz) δ 28.9, 29.4, 45.7, 52.0, 79.0, 80.1, 116.8, 118.6, 135.2, 135.7, 155.6, 175.7; MS (ESI, pos) (m/z): 288 [M + 1], 168 [M − Boc

• ; MS (ESI, pos) (m/z): 288 [M + 19], 168 [M – Boc]; anal. calcd for C14H21NO4: C, 62.90; H, 7.92; N, 5.24; found, C, 62.59; H, 7.60; N, 4.86. tert-Butyl ((1R*,2S*,6S*,Z)-8-oxo-7-oxabicyclo[4.2.2]dec-4-en-2-yl)carbamate ((±)-14). White solid; yield 38%; mp 101–102 °C; Rf = 0.50 (n-hexane/EtOAc 2:1); 1H

Novel solid-phase strategy for the synthesis of ligand-targeted fluorescent-labelled chelating peptide conjugates as a theranostic tool for cancer

• Sagnik Sengupta,
• Mena Asha Krishnan,
• Premansh Dudhe,
• Ramesh B. Reddy,
• Bishnubasu Giri,
• Sudeshna Chattopadhyay and
• Venkatesh Chelvam

Beilstein J. Org. Chem. 2018, 14, 2665–2679, doi:10.3762/bjoc.14.244

• , 28.0; HRMS (ESI) m/z: [M + Na]+ calcd for C30H46N2O9, 601.3096; found, 601.3092. Procedure for debenzylation of benzyl tris(tert-butoxy)-protected DUPA precursor 3 to give (S)-5-(tert-butoxy)-4-(3-((S)-1,5-di-tert-butoxy-1,5-dioxopentan-2-yl)ureido)-5-oxopentanoic acid (4): To a solution of benzyl tris

• = 5.0, 5.26, 7.76 Hz, 2H), 2.37–2.21 (m, 4H), 2.10–2.01 (m, 2H), 1.89–1.80 (m, 2H), 1.45 (s, 9H), 1.42 (s, 18H); 13C NMR (100 MHz, CDCl3) δ 176.1, 173.1, 172.5, 171.9, 157.8, 82.5, 82.1, 80.6, 53.3, 53.0, 31.5, 30.3, 28.4, 28.1, 28.0, 27.9, 27.8; HRMS (ESI) m/z: [M + Na]+ calcd for C23H40N2O9, 511.2626

• chromatography (RP-HPLC) tR = 9.8 min. The molecular mass is determined by LCMS. HRMS (+ESI) calcd for [M − Cl]+ (C89H121N14O21S)+: 1753.8546; found, 1753.8557. General procedure for solid-phase peptide synthesis of pteroate rhodamine B conjugate 17, pteroate-NH-(CH2)7CO-Lys(rhodamine B)-DAP-Asp-Cys: H-Cys(Trt

Design and synthesis of C₃-symmetric molecules bearing propellane moieties via cyclotrimerization and a ring-closing metathesis sequence

• Sambasivarao Kotha,
• Saidulu Todeti and
• Vikas R. Aswar

Beilstein J. Org. Chem. 2018, 14, 2537–2544, doi:10.3762/bjoc.14.230

• , 6H), 6.28 (s, 6H), 3.51–3.44 (m, 12H), 1.79 (d, J = 8.8 Hz, 3H), 1.61 (d, J = 8.8 Hz, 3H) ppm; 13C NMR (125 MHz, CDCl3) δ 177.0, 141.8, 141.3, 134.8, 131.4, 128.2, 127.2, 125.7, 52.4, 46.0, 45.7 ppm; HRMS (ESI, Q-ToF) m/z: [M + H]+ calcd for C51H40N3O6, 790.2912; found, 790.2918; IR (neat) max: 2918

• , 175.4, 136.7, 136.2, 136.1, 129.2, 126.5, 116.3, 49.1, 46.4, 35.4, 26.8 ppm; HRMS (ESI, Q-ToF) m/z: [M + Na]+ calcd for C19H19NO3·Na, 332.1257; found, 332.1254; IR (neat) max: 2325, 1671, 1263, 746 cm−1. Synthesis of trimerized compound 12 Based on the earlier procedure of trimerization, compound 13

• , 131.4, 128.1, 126.9, 125.6, 116.1, 49.1, 46.3, 35.5 ppm; HRMS (ESI, Q-ToF) m/z: [M + Na]+ calcd for C57H51N3O6·Na, 896.3670; found; 896.3678; IR (neat) max: 2342, 1709, 1512, 1183, 919, 736 cm−1. Synthesis of trimerized product 19 Based on the earlier procedure of trimerization, compound 18 (500 mg

Quinolines from the cyclocondensation of isatoic anhydride with ethyl acetoacetate: preparation of ethyl 4-hydroxy-2-methylquinoline-3-carboxylate and derivatives

• Nicholas G. Jentsch,
• Jared D. Hume,
• Emily B. Crull,
• Samer M. Beauti,
• Amy H. Pham,
• Julie A. Pigza,
• Jacques J. Kessl and
• Matthew G. Donahue

Beilstein J. Org. Chem. 2018, 14, 2529–2536, doi:10.3762/bjoc.14.229

• (DMSO-d6, 100 MHz) δ 158.8 (s, Ca), 146.7 (s, Cb), 140.6 (s, Cc), 139.3 (d, Cd), 130.5 (d, Ce), 117.6 (d, Cf), 114.5 (s, Cg), 112.4 (s, Ch); HRMS (ESI): calcd for [C8H4BrNO3 + Na]+ 263.926677; found: 263.926475; anal. calcd for C8H4BrNO3: C, 50.34; H, 3.90; found: C, 49.98; H, 3.80. General procedure

• ), 2.39 (s, 3H, Cl-H), 1.27 (t, J = 7.1 Hz, 1H, Cm-H); 13C NMR (DMSO-d6, 100 MHz) δ 172.0 (s, Ca), 166.4 (s, Cb), 149.4 (s, Cc), 138.0 (s, Cd), 134.9 (d, Ce), 127.1 (d, Cf), 126.0 (s, Cg), 120.6 (d, Ch), 116.3 (s, Ci), 115.0 (s, Cj), 60.4 (t, Ck), 18.2 (q, Cl), 14.1 (q, Cm); HRMS (ESI): calcd for

• Infectious Disease for AI127282. Funding for the Bruker UltraShield Plus 400 MHz NMR and ThermoFinnigan LXQ ESI LC–MS used in this research was provided by National Science Foundation Major Research Instrumentation under Grant Numbers 0840390 and 0639208, respectively. NGJ, JDH, and EBC thank the USM

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

• by ESI–TOF mass spectra, 1H and 13C NMR spectroscopy as well as 2D NMR spectra (Supporting Information File 1). The NMR data gave evidence of the structural assignment of the 5’-azido compounds and the macrocycles. A strong upfield shift (≈10 ppm) for the C5’-carbon signal as well as a moderate

• Information File 402: Experimental procedures, analytical data, NMR spectra, conformational analysis and crystallographic data. Acknowledgements We would like to thank Dr. M. Letzel, Universität Münster, Germany, for the ESI–TOF spectra and Prof. Dr. B. Wünsch, Institut für Pharmazeutische und Medizinische

The mechanochemical synthesis of quinazolin-4(3H)-ones by controlling the reactivity of IBX

• Md Toufique Alam,
• Saikat Maiti and
• Prasenjit Mal

Beilstein J. Org. Chem. 2018, 14, 2396–2403, doi:10.3762/bjoc.14.216

• ), multiplicity (s = singlet, d = doublet, t = triplet, q = quartet, brs = broad singlet, m = multiplet), coupling constant (Hz) and integration. High-resolution mass spectra (HRMS) were recorded on an ESI–TOF (time of flight) mass spectrometer. IR (infrared) spectral data are reported in wave numbers (cm−1

A novel and practical asymmetric synthesis of eptazocine hydrobromide

• Ruipeng Li,
• Zhenren Liu,
• Liang Chen,
• Jing Pan,
• Kuaile Lin and
• Weicheng Zhou

Beilstein J. Org. Chem. 2018, 14, 2340–2347, doi:10.3762/bjoc.14.209

• Bruker 400 MHz spectrometer with TMS as an internal standard. Mass spectra were recorded with a Q-TOF mass spectrometer using electrospray positive ionization (ESI+). Enantiomeric ratios were determined by HPLC using a chiral column (Chiralpak AY-H) with hexane/isopropyl alcohol 50:50 as eluents

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

• electrospray ionization (ESI-QTOF). Chemical shifts are reported in ppm, and coupling constants are given in hertz (Hz). All signals in NMR spectra were normalized relative to signals of CНCl3 (δ = 7.26 ppm in 1H NMR) and CDCl3 (δ = 77.0 in 13C NMR spectra). For single crystal X-ray diffraction experiments of

• ), 3.95–3.88 (m, 1H), 2.69–2.60 (m, 4H), 2.33–2.19 (m, 2H), 2.08–1.96 (m, 2H) ppm; 13C NMR (101 MHz, CDCl3, δ) 200.3, 198.7, 130.9, 92.5, 69.2, 33.3, 31.8, 31.2, 24.4 ppm; HRMS–ESI (m/z): [M + Na]+ calcd for C9H12N2O3, 219.0746; found, 219.0746. B. Sensitized photoexcitation of 2-diazo-3a,4,7,7a

• , 68.5, 52.0, 48.8, 45.9, 30.3, 24.4 ppm; HRMS–ESI (m/z): [M + Na]+ calcd for C14H16N2O3, 283.1059; found, 283.1065. C. Sensitized photoexcitation of 2-diazohexahydro-1H-4,7-methanoindene-1,3(2H)-dione (1c). The reaction was performed according to the general procedure with 376 mg (2 mmol, 1 equiv) of

Investigation of the electrophilic reactivity of the biologically active marine sesquiterpenoid onchidal and model compounds

• Melissa M. Cadelis and
• Brent R. Copp

Beilstein J. Org. Chem. 2018, 14, 2229–2235, doi:10.3762/bjoc.14.197

• determined by 1H NMR. Purification of the crude reaction product gave 29 as the free base (15% yield) and as the salt, 30 (also 15% yield, Figure 3). Spectroscopic and spectrometric analysis of 29 confirmed the formation of a diamine adduct, with detection of a protonated molecular ion in the (+)-ESI mass

• deconvoluted (+)-ESI mass spectrum, identifying a total lysozyme modification yield of 15% (Table 1). The presence of a large amount of unmodified lysozyme (85%), even after 72 h, was attributed to the slow reactivity of the enol acetate functionality of onchidal, as observed in the original model studies

Calix[6]arene-based atropoisomeric pseudo[2]rotaxanes

• Carmine Gaeta,
• Carmen Talotta and
• Placido Neri

Beilstein J. Org. Chem. 2018, 14, 2112–2124, doi:10.3762/bjoc.14.186

• stoppering or catenation of such atropoisomeric pseudorotaxanes. Experimental ESI(+)–MS measurements were performed on a Micromass Bio-Q triple quadrupole mass spectrometer equipped with electrospray ion source, using a mixture of H2O/CH3CN (1:1) and 5% HCOOH as solvent. Flash chromatography was performed on

• (respect chloride salt); mp 135–138 °C; ESI(+) MS (m/z): 350.2 (M+); 1H NMR (400 MHz, CD3OD, 298 K) δ 4.34 (s, 4H), 7.37–7.41 (overlapped, 6H), 7.61–7.67 (overlapped, 20H), 7.76 (d, J = 7.8 Hz, 4H); 13C NMR (100 MHz, CD3OD, 298 K) δ 51.7, 118.4, 118.4, 118.5, 121.7, 124.4, 127.1, 128.0, 128.8, 129.0, 130.0

• , 130.1, 130.2, 130.3(2), 130.5(2), 130.6, 131.2, 131.5, 135.8, 141.3, 143.9, 162.1, 162.6, 163.1, 163.6; anal. calcd for C58H36BF24N: C, 57.40; H, 2.99; found: C, 57.39; H, 3.01. Derivative 3+ Light brown solid, 0.57 g, 0.48 mmol, 70 % yield (respect chloride salt); mp 125–128 °C; ESI(+) MS (m/z): 334.1

A switchable [2]rotaxane with two active alkenyl groups

• Xiu-Li Zheng,
• Rong-Rong Tao,
• Rui-Rui Gu,
• Wen-Zhi Wang and
• Da-Hui Qu

Beilstein J. Org. Chem. 2018, 14, 2074–2081, doi:10.3762/bjoc.14.181

• construct stimuli-responsive polymers and smart materials. Experimental General and materials 1H NMR and 13C NMR spectra were measured on a Bruker AV-400 spectrometer. The electronic spray ionization (ESI) mass spectra were tested on a LCT Premier XE mass spectrometer. Chemicals were used as received from

• Acros, Aldrich, Fluka, or Merck. All solvents were reagent grade, which were dried and distilled prior to use according to standard procedures. The molecular structures were confirmed via 1H NMR, 13C NMR and high-resolution ESI mass spectroscopy. The synthesis of compound 1, 2, 6, 7, 9 have already been

• ), 0.87 (t, J = 6.8 Hz, 9H); 13C NMR (CDCl3, 100 MHz, 298 K) δ 169.2, 167.8, 153.1, 141.3, 128.1, 105.6, 73.5, 69.2, 51.2, 44.1, 39.5, 31.9, 30.2, 29.70, 29.68, 29.66, 29.62, 29.56, 29.39, 29.36, 29.34, 29.31, 28.7, 26.4, 26.3, 26.07, 26.05, 22.7, 14.1; HRMS–ESI–TOF (m/z): [M + K]+ calcd for C51H93N5O5K

Synthesis and supramolecular self-assembly of glutamic acid-based squaramides

• Juan V. Alegre-Requena,
• Marleen Häring,
• Isaac G. Sonsona,
• Alex Abramov,
• Eugenia Marqués-López,
• Raquel P. Herrera and
• David Díaz Díaz

Beilstein J. Org. Chem. 2018, 14, 2065–2073, doi:10.3762/bjoc.14.180

• 2.5 instrument. Specific rotation calculations were made in chloroform or acetone employing a Jasco P-1020 polarimeter. ESI ionization method and mass analyzer type MicroTof-Q were used for HRMS measurements. 1H NMR spectra and 13C APT-NMR spectra were recorded at 300 MHz and 75 MHz, respectively

• ) ν: 3269, 2983, 1806, 1736, 1653, 1618, 1610, 1500, 1464, 1378, 1345, 1299, 1263, 1201, 1102, 1024; HRMS (ESI+) m/z: [M + Na]+ calcd for C14H19NNaO7, 336.1054; found, 336.1094. (S)-Diethyl 2-((2-(octadecylamino)-3,4-dioxocyclobut-1-en-1-yl)amino)pentanedioate (3): A solution of n-octadecylamine (8

• , 1203, 1021, 720; HRMS (ESI+) m/z: [M + Na]+ calcd for C31H54N2O6Na, 573.3874; found, 573.3840. (S)-2-((2-(Octadecylamino)-3,4-dioxocyclobut-1-en-1-yl)amino)pentanedioic acid (4): Squaramide 3 (1.2 g, 2.15 mmol) was dissolved in a 1:1 v/v MeOH/H2O mixture (40 mL) containing KOH (0.36 g, 6.45 mmol) at

Coordination-driven self-assembly vs dynamic covalent chemistry: versatile methods for the synthesis of molecular metallarectangles

• Li-Li Ma,
• Jia-Qin Han,
• Wei-Guo Jia and
• Ying-Feng Han

Beilstein J. Org. Chem. 2018, 14, 2027–2034, doi:10.3762/bjoc.14.178

• peaks was found. Again, significant downfield shifts of the pyridyl proton signals were observed, indicating the efficient self-assembly of the rhodium-based assembly (Figure 2a,b). Clear evidence for the formation of a discrete tetranuclear organometallic product was obtained from ESI mass spectrometry

• tetranuclear [4 + 4] condensation products 3a (Figure 1c) and 3b (Figure 2c) was observed, respectively. Complexes 3a and 3b were isolated in good yields, and their structures were confirmed by 1H NMR spectroscopy and ESI mass spectrometry. After establishing that the condensation reaction of 2 with amines is

• mg, 80%).1H NMR (400 MHz, DMSO-d6, ppm) δ 10.09 (s, 2H, -CHO), 8.89 (d, J = 5.0 Hz, 4H), 7.82 (d, J = 5.0 Hz, 4H), 1.55 (s, 30H, Cp*-H); HRMS–ESI (m/z): [2 − 2OTf]2+ calcd for C34H40O12N2F6S2Rh2, 390.0571; found, 390.0541. Synthesis of [Cp*4Rh4(μ-η2-η2-C2O4)2(L1)2](OTf)4 (3a) Method A: AgOTf (36 mg

An amphiphilic pseudo[1]catenane: neutral guest-induced clouding point change

• Tomoki Ogoshi,
• Tomohiro Akutsu and
• Tada-aki Yamagishi

Beilstein J. Org. Chem. 2018, 14, 1937–1943, doi:10.3762/bjoc.14.167

• ), 2.27 (t, 2H, alkyne) ppm; 13C NMR (125 MHz, CDCl3) δ 150.0, 149.8, 149.3, 129.1, 129.0, 128.6, 128.4, 115.6, 115.4, 115.2, 115.1, 71.9, 70.9, 70.8, 70.6, 70.4, 70.3, 68.3, 68.2, 68.1, 68.0, 59.0, 56.5, 29.7, 29.3 ppm; HRMS–ESI (m/z): [M + Na]+ calcd for C97H146NaO34, 1877.9593; found, 1877.9612

• , 149.6, 149.4 129.0, 128.6, 128.3, 124.3, 115.7, 115.0, 71.9, 70.8, 70.7, 70.6, 70.3, 68.4, 68.1, 67.8, 67.6, 59.0, 29.7, 29.0, 28.8, 28.5, 27.3, 24.5 ppm; HRMS–ESI (m/z): [M + 2Na]2+ calcd for C109H170N6Na2O34, 1076.5777; found, 1076.5635. Determination of association constants. In a similar manner as

A pyridinium/anilinium [2]catenane that operates as an acid–base driven optical switch

• Sarah J. Vella and
• Stephen J. Loeb

Beilstein J. Org. Chem. 2018, 14, 1908–1916, doi:10.3762/bjoc.14.165

• , 149.8, 147.6, 146.8, 140.5, 140.2, 129.9, 128.4, 127.9, 127.6, 120.8, 120.4, 113.1, 47.6; HRMS (ESI) m/z: [M + H]+ calcd for [C23H20N3]+, 338.1657; found, 338.1650. Synthesis of [7][OTf]4 [5][OTf]2 (0.400 g, 0.626 mmol) and 6 (2.61 g, 6.26 mmol) were dissolved in CH3CN (75 mL) and stirred at room

• = 6.1 Hz, 4H), 7.91 (s, 2H), 7.86 (d, 3J = 8.2 Hz, 4H), 7.71 (d, 3J = 8.2 Hz, 4H), 7.68 (d, 3J = 7.9 Hz, 2H), 7.67 (d, 3J = 8.2 Hz, 4H), 7.62 (d, 3J = 8.0 Hz, 4H), 7.57 (t, 3J = 7.9, 3J = 8.1 Hz, 2H), 7.54 (d, 3J = 8.2 Hz, 4H), 5.89 (s, 4H), 5.30 (br s, 4H), 4.66 (s, 4H); HRMS (ESI) m/z: [M − OTf

• ) to extract any remaining salts. The CH3NO2 layer was dried with anhydrous MgSO4 and then evaporated to yield [8DB24C8][OTf]6 as a yellow-orange solid. Yield 0.030 g, 12%; mp >210 °C (dec.); HRMS (ESI) m/z: [M − 2OTf]2+ calcd for [C113H103F12N7O20S4]2+, 1116.7969, found, 1116.7972; [M − 3OTf]3+ calcd