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

• conformations is an outward directed NH residue. Solution-state NMR data suggests that the surrounding tetralactam in these [2]rotaxanes undergoes rapid exchange between these different conformations, a dynamic process that has been called macrcocyle breathing, and that there is also simultaneous co

Mechanistic investigations on multiproduct β-himachalene synthase from Cryptosporangium arvum

• Jan Rinkel and
• Jeroen S. Dickschat

Beilstein J. Org. Chem. 2019, 15, 1008–1019, doi:10.3762/bjoc.15.99

• with (E)- and (Z)-(4-13C,4-2H)IPP, DMAPP, FPPS and HcS targeting the positions C-3 and C-7 (Figure S11, Supporting Information File 1), using published NMR data for 7 [44]. The stereochemical fate for the hydrogens at C-1 was then targeted by the incubation of (1R)- and (1S)-(1-13C,1-2H)FPP [28] with

• situation like a 1,11-cyclisation. Intriguingly, the stereochemical course of the initial cyclisation step can even be substrate dependent. The 1,6-cyclisation towards the monoterpenes 10, 11 and 13 as investigated by the incubation of (1S)- and (1R)-(1-13C,1-2H)GPP with HcS and comparison to the NMR data

• expression, protein purification, incubation experiments with isotopically labelled precursors, preparative scale incubation and synthesis of (2-13C)DMAPP. The amino acid sequence of HcS, a phylogenetic tree of bacterial terpene synthases, SDS-PAGE analysis of the recombinant protein, listed NMR data for 1

New terpenoids from the fermentation broth of the edible mushroom Cyclocybe aegerita

• Frank Surup,
• Florian Hennicke,
• Nadine Sella,
• Maria Stroot,
• Steffen Bernecker,
• Sebastian Pfütze,
• Marc Stadler and
• Martin Rühl

Beilstein J. Org. Chem. 2019, 15, 1000–1007, doi:10.3762/bjoc.15.98

• m/z 519.2718 in the HRESIMS spectrum. 1H and 1H,13C-HSQC NMR data (Table 1) indicated the presence of four methyls and twelve methylenes, three of them oxomethylene groups. A database search with this data within the Chapman & Hall Dictionary of Natural Products on DVD suggested its identity as

• bovistol, which was confirmed by the elucidation of the structure by COSY and HMBC NMR data [5]. In the course of the isolation of 1 the minor metabolites 2 and 3 accrued. Metabolite 2 was analysed for a molecular weight of 478 Da. Its molecular formula C30H38O5, deduced from HRESIMS data, indicated the

• formal loss of one molecule of water. 1H and HSQC NMR data (Table 1) of 2 were very similar to those of 1, with the exception of the replacement of methyl CH3-12 by an exomethylene group. HMBC correlations from both exo-methylene protons 12-H2 to C-2, C-3, C-4, in addition to those from both 1-H2 and 10

Coordination chemistry and photoswitching of dinuclear macrocyclic cadmium-, nickel-, and zinc complexes containing azobenzene carboxylato co-ligands

• Jennifer Klose,
• Tobias Severin,
• Peter Hahn,
• Alexander Jeremies,
• Jens Bergmann,
• Daniel Fuhrmann,
• Jan Griebel,
• Bernd Abel and
• Berthold Kersting

Beilstein J. Org. Chem. 2019, 15, 840–851, doi:10.3762/bjoc.15.81

• protons [C(CH3)3] appear as singlets. The remaining six signals can be assigned to the methylene protons of the linking diethylenetriamine chains (two doublets for the benzylic CH2 and four multiplets for linking CH2 groups). The 1H NMR data are indicative of a C2v symmetric structure of the [Cd2L]2

Stereochemical investigations on the biosynthesis of achiral (Z)-γ-bisabolene in Cryptosporangium arvum

• Jan Rinkel and
• Jeroen S. Dickschat

Beilstein J. Org. Chem. 2019, 15, 789–794, doi:10.3762/bjoc.15.75

• origin in FPP. Supporting Information Experimental details of culture conditions, gene cloning, protein purification, incubation experiments, isolation of 5 and HPLC purifications, the amino acid sequence of BbS, a phylogenetic tree with the location of BbS, SDS-PAGE analysis, listed NMR data of 5

New sesquiterpenoids from the South China Sea soft corals Clavularia viridis and Lemnalia flava

• Qihao Wu,
• Yuan Gao,
• Meng-Meng Zhang,
• Li Sheng,
• Jia Li,
• Xu-Wen Li,
• Hong Wang and
• Yue-Wei Guo

Beilstein J. Org. Chem. 2019, 15, 695–702, doi:10.3762/bjoc.15.64

• indicated the existence of a trisubstituted double bond. All the above evidence suggested the laurane nature of this molecule, and literature research revealed that 1 should be an isomer of a known laurane-type terpenoid bromolaurenisol (1a) [16][17] due to their extremely similar NMR data and the same

• the same laurane skeleton. In fact, compound 2 differed from 1 only by the debromonation at the C-15 position, which was in agree with the lack of 78/80 units in its mass compared to that of 1. The planar structure of 2 was further confirmed by its 2D NMR data (Figure 2). The relative configurations

• optically active colorless oil. The molecular formula, C15H19OBr, was deduced by HR-EIMS ion peak at m/z 294.0617, [M]+ (calcd for C15H19OBr, 294.0619). The 1H and 13C NMR data (Table 1) of 3 were found to be identical to those of laurenisol (3a), a halogenated sesquiterpenoid previously isolated from the

Influence of per-O-sulfation upon the conformational behaviour of common furanosides

• Alexey G. Gerbst,
• Vadim B. Krylov,
• Dmitry A. Argunov,
• Maksim I. Petruk,
• Arsenii S. Solovev,
• Andrey S. Dmitrenok and
• Nikolay E. Nifantiev

Beilstein J. Org. Chem. 2019, 15, 685–694, doi:10.3762/bjoc.15.63

• . Lomonosov Moscow State University, Moscow, 119991, Russia 10.3762/bjoc.15.63 Abstract The studies on the recently discovered pyranoside-into-furanoside rearrangement have led us to conformational investigations of furanosides upon their total sulfation. Experimental NMR data showed that in some cases

• ). NMR data of furanosides 1–3 and 1s–3s 1H and 13C NMR spectra of parent monosaccharides 1–3 and their per-O-sulfated derivatives 1s–3s were recorded in D2O. The signal assignment was performed using 2D COSY and HSQC. J coupling constants were measured directly from 1D 1H NMR spectra. In case of

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

• Supporting Information File 1). Assignments of the quaternary carbons including the formal carbocation centers were made by HMBC correlations. NMR data suggest that the positive charge is more effectively delocalized into the indole rings. The GIAO-NMR data show the same general trend, as evidenced by the

Syntheses and chemical properties of β-nicotinamide riboside and its analogues and derivatives

• Mikhail V. Makarov and
• Marie E. Migaud

Beilstein J. Org. Chem. 2019, 15, 401–430, doi:10.3762/bjoc.15.36

• anomeric purity were best improved with liquid SO2; the yields of 8a ( −44.7°) and 8b ( −36.8°) were 96% and 90%, respectively, with the isolated product 8b containing no α-anomer (according to 1H NMR data), as specifically emphasized by the authors. The deprotection of 8b conducted at −18 °C in cold

• synthesis may be partially explained by the fast mutarotation of 2′,3′-O-isopropylidene-D-ribofuranosylamine and its tosylate. This mutarotation is solvent-dependent. For example, according to 1H NMR data presented in the work of Cusack et al. [40], compound 23 exists essentially as the pure β-anomer in

Chemical structure of cichorinotoxin, a cyclic lipodepsipeptide that is produced by Pseudomonas cichorii and causes varnish spots on lettuce

• Hidekazu Komatsu,
• Takashi Shirakawa,
• Takeo Uchiyama and
• Tsutomu Hoshino

Beilstein J. Org. Chem. 2019, 15, 299–309, doi:10.3762/bjoc.15.27

• moiety had clear correlations with the double bond carbons (δc 132.8, s, αC and δc 123.3, d, βC), and the βH exhibited clear HMBC correlations with the αC and carbonyl carbon (δc 168.8, s, CO). These NMR data clearly indicate the presence of a dhThr moiety (Figure 3), and the strong NOE between the γCH3

• cichorinotoxin (Figure 1). We then determined the presence of three dhThr residues in the cichorinotoxin (Figure 6) by analyzing the NMR data; the βCH protons (olefinic protons) of the three dhThr moieties are found at δH 6.37 (q, J = 7.0 Hz), δH 6.24 (q, J = 7.0 Hz) and δH 5.89 (q, J = 7.0 Hz) in the 1H NMR

• was acetylated under basic conditions to afford the monoacetate of cichorinotoxin (Figure 6). This basic amino acid was determined to be 2,4(α,γ)-diaminobutanoic acid (Dab-20) by detailed analyses of the NMR data. In the COSY and TOCSY spectra of the acetate, the αNH proton (δH 8.61) was correlated

First synthesis of cryptands with sucrose scaffold

• Patrycja Sokołowska,
• Michał Kowalski and
• Sławomir Jarosz

Beilstein J. Org. Chem. 2019, 15, 210–217, doi:10.3762/bjoc.15.20

• this first sucrose cryptand, suggested by HRMS analysis [m/z = 1285.6803 which corresponds to (C74H97N2O17 + H+)], was confirmed by the NMR data. In the 13C NMR spectrum of the final compound, six characteristic signals at δ ≈ 50–60 ppm were observed. They can be assigned to the methylene groups

• NMR data. In the spectrum recorded in acetone-d6, three signals at δ ≈ 60 ppm were seen. These signals were assigned (by HSQC experiments) to the benzyl groups connected to nitrogen atoms (-NCH2Ph), thus finally confirming the presence of a tripodal unit in the structure of the cryptand. Conclusion We

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

• deprotected derivatives in moderate to good yields. The structures of these compounds were confirmed by NMR and mass spectrometry. NMR data were in good agreement with those reported in the literature for similar CS oligosaccharides. The perfluorinated tag of acceptor 2 may strongly influence on the chemical

Systematic synthetic study of four diastereomerically distinct limonene-1,2-diols and their corresponding cyclic carbonates

• Hiroshi Morikawa,
• Jun-ichi Yamaguchi,
• Shun-ichi Sugimura,
• Masato Minamoto,
• Yuuta Gorou,
• Hisatoyo Morinaga and
• Suguru Motokucho

Beilstein J. Org. Chem. 2019, 15, 130–136, doi:10.3762/bjoc.15.13

• oxide) and conditions, the desired diastereomers were synthesised in moderate to high yields with, in most cases, high stereoselectivity. Comparison of the NMR data of the obtained diols and carbonates revealed that the four different diastereomers of each compound could be distinguished by reference to

• Sharpless AD-mix-β to afford a 2a-type main product (Scheme 1b) [22]. Hao et al. also reported the synthesis of 2a and 2d using OsO4 (Scheme 1a) [23]. However, the NMR data of 2a and 2d were not consistent with those [16] reported by Wang. Moreover, they referred to a published paper [24] for the assignment

• analysis. In particular, the NMR data for 2b and 2d exhibit rather similar values. The assignments of 1H and 13C NMR signals were found to provide a means of differentiating the respective diastereomers for the first time. These fundamental studies will contribute to the organic, bioorganic and

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

• spectrometry and NMR data. Acknowledgements The authors are grateful to Russian Science Foundation (project No. 14-50-00131) for financial support of this work.

Generation of 1,2-oxathiolium ions from (arysulfonyl)- and (arylsulfinyl)allenes in Brønsted acids. NMR and DFT study of these cations and their reactions

• Stanislav V. Lozovskiy,
• Alexander Yu. Ivanov,
• Olesya V. Khoroshilova and
• Aleksander V. Vasilyev

Beilstein J. Org. Chem. 2018, 14, 2897–2906, doi:10.3762/bjoc.14.268

• , the behavior of allenes 1a,b and 2a–h in Brønsted acids (TfOH, D2SO4) was studied by means of NMR (Table 1). Dissolving these allenes in TfOH or D2SO4 directly in NMR tubes at room temperature gave intensively colored red solutions of cationic species, which were stable for a long time. The NMR data

• calculations confirm the experimental NMR data (Table 1) and prove that C5 does have a large positive charge 0.25 e, which should make this carbon a highly reactive electrophilic center. Another electrophilic center is the sulfur atom, which also bears a large positive charge (1.21–2.06 e). Apart from that

• the corresponding thiochromenes, due to oligomerization under the harsh reaction conditions. Other allenes 2g,h gave the corresponding heterocycles 5 in very poor yields (<4%, by GC–MS and 1H NMR data). As it was mentioned above, unsubsituted allenes 2i,j did not react with TfOH at room temperature

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

• at 400 MHz; 13C NMR at 101 MHz) or a JEOL–ECA500 spectrometer (19F NMR at 471 MHz). Chemical shifts are reported in ppm relative to the internal standard signal (0 ppm for Me4Si in CDCl3) for 1H NMR and the solvent signal (77.16 ppm for CDCl3) for 13C NMR. Data are presented as follows: chemical

Synthesis of a tyrosinase inhibitor by consecutive ethenolysis and cross-metathesis of crude cashew nutshell liquid

• Jacqueline Pollini,
• Valentina Bragoni and
• Lukas J. Gooßen

Beilstein J. Org. Chem. 2018, 14, 2737–2744, doi:10.3762/bjoc.14.252

• × 0.25, 100/2.3-30-300/3) and a time program beginning with 2 min at 60 °C, heating rate 30 °C/min, 3 min at 300 °C. NMR spectra were measured at ambient temperature using CDCl3 as solvent, with proton, and carbon resonances at 300 MHz/400 MHz and 75 MHz, respectively. All NMR data are reported in ppm

Synthesis and biological evaluation of 1,2-disubstituted 4-quinolone analogues of Pseudonocardia sp. natural products

• Stephen M. Geddis,
• Teodora Coroama,
• Suzanne Forrest,
• James T. Hodgkinson,
• Martin Welch and
• David R. Spring

Beilstein J. Org. Chem. 2018, 14, 2680–2688, doi:10.3762/bjoc.14.245

• used as starting material, E/Z ratio = 29:71 based on 1H NMR data. b13bb used as starting material, E/Z ratio = 15:85 based on 1H NMR data. Use of an excess of DMEDA in the Cu-catalysed cyclisation of 13bb resulted in the generation of 14bg as a side-product, alongside 14bb. Optimisation of conditions

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

• peptide coupling procedures. 1H and 13C NMR data were recorded using a Bruker AV 400 MHz NMR spectrometer with TMS (tetramethylsilane) as internal reference. Mass spectra were recorded on a Brukermicro TOF-Q II spectrometer in positive mode and negative mode electrospray ionization methods. Reactions were

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

• trituration with methanol that was determined to be exclusively compound 12 by NMR. The formation of either regioisomer 11 (via b) or 12 (via a) results from 6-exo-trig cyclization of the common nucleophilic acyl substitution intermediate 13. The 13C NMR data of the product has a singlet at δ 199 ppm that

Synthesis of eunicellane-type bicycles embedding a 1,3-cyclohexadiene moiety

• Alex Frichert,
• Peter G. Jones and
• Thomas Lindel

Beilstein J. Org. Chem. 2018, 14, 2461–2467, doi:10.3762/bjoc.14.222

• replaced by a methoxy group (Scheme 4, obtained by ethoxycarbonylation of 28) [25]. In agreement with the NMR data, cyanohydrin 30 adopts a chair conformation in the crystal. The 1H NMR spectra of diastereomers 29 and 30 differ characteristically regarding the chemical shift of the hydroxy proton which

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

Stereoselective total synthesis and structural revision of the diacetylenic diol natural products strongylodiols H and I

• Pamarthi Gangadhar,
• Sayini Ramakrishna,
• Ponneri Venkateswarlu and
• Pabbaraja Srihari

Beilstein J. Org. Chem. 2018, 14, 2313–2320, doi:10.3762/bjoc.14.206

• found to be [α]D25 = −43.8 (c 0.35, CHCl3) [10]. Having identical spectral data (see Table 1 for comparative 1H and 13C NMR data for the synthetic and natural strongylodiol H), but with the opposite sign of rotation, and based on the outcome of our synthesis, we unambiguously revise the structure of the

• found to be comparable with the previously reported data of the isolated product {[α]D25 = −30.2 (c 1.7, CHCl3)}; Lit. {[α]D25 = −33.4 (c 0.35, CHCl3)} [10] (see Table 2 for comparative 1H and 13C NMR data for the synthetic and natural strongylodiol I). Thus, our synthesis has led us to revise the

• ) TBDPSCl, imidazole, CH2Cl2, 0 °C to rt, 1 h, 96%; (ii) PPTS, MeOH, 0 °C to rt, 2 h, 87%; (iii) IBX, DMSO/THF 1:1, 0 °C to rt, 1 h, 98%; (b) 16, n-BuLi, THF, −78 °C to rt, 2 h, 81%; (c) TBAF, THF, 0 °C to rt, 2 h, 82%. Comparison of 1H and 13C NMR data of strongylodiol H (isolated natural product vs

Determining the predominant tautomeric structure of iodine-based group-transfer reagents by ¹⁷O NMR spectroscopy

• Nico Santschi,
• Cody Ross Pitts,
• Benson J. Jelier and
• René Verel

Beilstein J. Org. Chem. 2018, 14, 2289–2294, doi:10.3762/bjoc.14.203

• isotropic shift values (δiso) in tandem with experimental 17O NMR data (δobs) lends credence to the aforementioned structural assignment. Specifically, for the "unassigned" compounds mentioned above, the best R2-value for a linear relationship δobs ~ δiso is obtained when 5 and 6 are assigned as 5b and 6a

• minimum reminiscent of the pictographic representation of 4c with an intact but significantly elongated I–O bond of 2.55 Å (Figure 3) and qualitatively, the NMR data are in support of this notion. From a quantitative point of view, the data points (δiso, δobs) for 1, 4b, and 4c afforded a perfect linear

• then subjected to spectroscopic analysis. A 19F NMR chemical shift of −23.2 ppm was obtained, thereby confirming the presence of 4c. However, under these strongly acidic and activating conditions, the compound is unstable over a prolonged period of time (12 h). During the acquisition of the 17O NMR

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

• + H]+ corresponding to a formula of C25H45N2 (requires 373.3577). NMR data further supported such a structure, with pyrrole signals observed at [δH 6.57–6.55, m, H-1" and H-4"; 6.06, br s, H-3"; δC 120.6 (C-2" and C-4"); 118.5 (C-1"); 106.8 (C-3")] and pentylamine substitution at C-1 [δH 3.50–3.46, m