Nanangenines: drimane sesquiterpenoids as the dominant metabolite cohort of a novel Australian fungus, Aspergillus nanangensis

• Heather J. Lacey,
• Cameron L. M. Gilchrist,
• Andrew Crombie,
• John A. Kalaitzis,
• Daniel Vuong,
• Peter J. Rutledge,
• Peter Turner,
• John I. Pitt,
• Ernest Lacey,
• Yit-Heng Chooi and
• Andrew M. Piggott

Beilstein J. Org. Chem. 2019, 15, 2631–2643, doi:10.3762/bjoc.15.256

• , supported by key ROESY correlations between H3-13 and H-11, and between H-5 and 9-OH (Table S10 in Supporting Information File 1). HRESI(+)MS analysis of nanangenine G (9) revealed an adduct ion ([M + Na]+ m/z 407.2406) indicative of a molecular formula C21H36O6. The NMR data for 9 (Table 3) were very

• . Key HMBC correlations (Table S12 in Supporting Information File 1) from H-7 to C-12 and from 12-OMe to C-12 positioned the methoxy group and acetal proton on C-12. Thus, the structure of 10 was assigned as shown in Figure 1. The configuration of 10 at C-12 was determined to be 12R based on a key ROESY

Complexation of chiral amines by resorcin[4]arene sulfonic acids in polar media – circular dichroism and diffusion studies of chirality transfer and solvent dependence

• Bartosz Setner and
• Agnieszka Szumna

Beilstein J. Org. Chem. 2019, 15, 1913–1924, doi:10.3762/bjoc.15.187

• molecules (Figure 2a–g). For 1(LysOMe)2 the most upfield shifted signal is for the δ-CH2 group, that may indicate incorporation of this hydrophobic fragment in the aromatic cavity. ROESY spectra for all complexes show correlation signals between β-CH2 groups of the guest and CH2SO3− of 1 (Figure 2h–j). The

• (bs, 12H), 0.96 (d, J = 6.6 Hz, 24H). Figure S61 (Supporting Information File 1). Structures of the compounds used in this study and labelling scheme for NMR spectra. Spectra of complexes [1(LysOMe)2], [1(ArgOMe)2], [1(HisOMe)2]: 1H NMR (a–g) and ROESY (h–j) in methanol at 298 K, 600 MHz (NMR). CD (a

Synthesis and conformational preferences of short analogues of antifreeze glycopeptides (AFGP)

• Małgorzata Urbańczyk,
• Michał Jewgiński,
• Joanna Krzciuk-Gula,
• Jerzy Góra,
• Rafał Latajka and
• Norbert Sewald

Beilstein J. Org. Chem. 2019, 15, 1581–1591, doi:10.3762/bjoc.15.162

• the NOESY/ROESY spectra. Based on the intensity of the correlation peaks, proton–proton distances were calculated. The most important structural information was gained from the nontrivial inter-residual correlation signals. These experimental data were essential for the calculation of the

• conformational preferences of the examined glycopeptides. Based on the NOESY/ROESY experiments we obtained 6, 27, 10 and 50 distance constrains for peptide 1, 2, 3, and 4, respectively (see Supporting Information File 1). For each of the investigated peptides optimization of 1 000 stable conformers have been

• and SPARKY software [40]. For 2D ROESY, if it was possible, the separation between two geminal protons in −CH2− group was used as a reference in distance calculations, otherwise interatomic distances were calculated from the intensity of the cross and diagonal peaks. In both cases calculated distances

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

• allows to correlate the exchanging signals in both slow and fast exchange regimes. The measured ROESY spectrum featured both NOE interactions of the opposite phase and EXSY peaks of the same phase as diagonal peaks. The EXSY cross-peaks indicate the chemical exchange between methylene protons (H4), the

• ) level of theory. 1H NMR spectrum of 1a in MeCN-d3 measured at −40 °C. #Signal of water. *Signal of acetonitrile. 2D EXSY spectra (ROESY cross-peaks in blue, EXSY cross-peaks in red) measured in MeCN-d3 at −40 °C. a) Zoom of the methylene and methine region, b) zoom of methyl signals, c) zoom of aromatic

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

• spectrometry and NMR spectroscopy. The relative configurations of 2–4 were assigned by ROESY correlations, and 3JH,H coupling constants in the case of 4. Applying quantitative PCR for gene expression validation, we linked the production of bovistol and its derivatives to the respective biosynthesis gene

• methoxy was connected to C-3 due to its HMBC correlation to this carbon atom, along to the ones from 1-H2, 10-H2 and 12-H3 to C-3. Compared to 1, the Δ2,3 double bond is shifted to Δ2,9, explaining the high field shift of the conjugated ketone C-8 (δC 197.2). A ROESY correlation between 3-OCH3 and 13-Ha

• -H2 to C-6/C-7 and 8-H to C-6/C-7/C-13. The strong ROESY correlation between 2-H and 9-H indicated a cis configuration between these protons, and the large coupling constant between 8-H and 9-H, observed in the signal of 8-H, a trans configuration of 8-H/9-H. Finally, the ROESY correlation between 12

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

• to 8.16 ppm of H-14' of triazole) and 126.13 ppm of C-14' triazole is correlated to the signal at 4.57 ppm of the quinidine part. Additional 2D NMR spectra (COSY, HSQC, HMBC, ROESY) are included in Supporting Information File S2 and Supporting Information File S3. Moreover, we also investigated a

• possible inclusion of the cinchona alkaloid substituent in the CD cavity in the case of cinchonine–β-CD 5a in D2O. The 2D ROESY spectrum showed cross-peaks between the substituent (hydrogen atoms of the double bond of the quinuclidine skeleton) and the inner H-3 atoms of the β-CD cavity. However, the low

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

• the cavity is preferred. In all cases, however, the tosyl groups display ROESY cross-peaks with the CD cavity protons (Supporting Information File 1, Figure S11). The cross-peaks indicate the formation of intermolecular as well as intramolecular (self-inclusion) complexes in situ in D2O. This

• conclusion was confirmed by the addition of 1-adamantanecarboxylic acid into a solution of 6A,6D-ditosyl-β-CD. The 2D-ROESY spectra obtained (Supporting Information File 1, Figure S12) show absence of the formerly observed correlation signals between cavity and tosyl protons and emergence of new such signals

6’-Fluoro[4.3.0]bicyclo nucleic acid: synthesis, biophysical properties and molecular dynamics simulations

• Sibylle Frei,
• Andrei Istrate and
• Christian J. Leumann

Beilstein J. Org. Chem. 2018, 14, 3088–3097, doi:10.3762/bjoc.14.288

• the nucleobase was conducted by 1H,1H-ROESY experiments (Supporting Information File 1). The β-anomer 7β then was subjected to Luche reduction [55][56] producing selectively the desired S-configuration at the C(5’) position due to hydride delivery from the less hindered exo-side of the carbonyl group

• . The relative configuration at C(5’) could be assigned by 1H,1H-ROESY experiments (Supporting Information File 1). Tritylation of allylic alcohol 8 with 4,4-dimethoxytrityl chloride (DMTr-Cl) afforded intermediate 9 which was subsequently phosphitylated with 2-cyanoethyl N,N

• -ROESY experiments (Supporting Information File 1). The gem-difluorinated tricyclic nucleoside 12β was then converted into the bicyclic fluoroenone 13 via desilylation and ring-enlargement by short exposure to HF-pyridine. During the following Luche reduction of derivative 13 the benzoyl protecting group

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

• ROESY and 2D NOESY/EXSY experiments. General procedure for the preparation of 2+ and 3+·TFPB− salts Derivative 4 (or 5, 2.2 mmol) was dissolved at 60 °C in liquid (Me3Si)2NH (0.71 g, 4.4 mmol, 0.92 mL), LiClO4 (0.02 g, 2.2 mmol) was added and the reaction was kept under stirring at 60 °C until a white

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

• acid-base stimuli has been confirmed. To further demonstrate the binding mode of the functional macrocycle with the axle, 2D ROESY NMR spectra of rotaxane R1 before and after the deprotonation in CDCl3 were obtained. As shown in Figure 3a, the cross-peaks of phenyl protons H10 (peak A), H14 (peak B

• DB24C8 macrocycle and axle, respectively, was prepared and well characterized. The shuttling movement of the functionalized DB24C8 macrocycle between the DBA recognition site and amide moiety could be realized by stimuli of external acid-base and was investigated by 1H NMR and 2D ROESY NMR spectroscopy

• . Partial 1H NMR spectra (400 MHz, CDCl3, 298 K). (a) [2]Rotaxane R1, (b) deprotonation by the addition of 2.0 equiv of DBU to (a), (c) reprotonation with addition of 3.0 equiv of TFA to (b). Partial 2D ROESY NMR spectra (500 MHz, CDCl3, 298 K). (a) [2]Rotaxane R1, (b) deprotonation with addition of 2.0

Lanyamycin, a macrolide antibiotic from Sorangium cellulosum, strain Soce 481 (Myxobacteria)

• Lucky S. Mulwa,
• Rolf Jansen,
• Dimas F. Praditya,
• Kathrin I. Mohr,
• Patrick W. Okanya,
• Joachim Wink,
• Eike Steinmann and
• Marc Stadler

Beilstein J. Org. Chem. 2018, 14, 1554–1562, doi:10.3762/bjoc.14.132

• double bonds Δ10,11 and Δ12,13 was recognized from their large coupling constants of about 15 Hz while 1H,1H-ROESY correlations between H-3 and H-5 as well as between methyl-37 and both methyl-38 and methoxy-36 suggested the E configuration of the substituted Δ2,3,Δ4,5-diene. Likewise, the E

• configuration of the substituted Δ17,18 double bond was derived from the ROESY correlations between methyl-41 and methylene protons 16a and 16b and between methine-17 and methylenes H-20a and H-20b. The latter simultaneously indicated the s-trans configuration of the enone and explained the observation of a

• ROESY correlation between H-17 and H-21. For confirmation, NMR spectra in DMSO-d6 were measured (Supporting Information File 1, Table S3). At the beginning of the NMR experiments isomer 1 was the major component. Later both were present in equal amounts. The 1H doublets in the 1H NMR spectrum at 8.64

The use of 4,4,4-trifluorothreonine to stabilize extended peptide structures and mimic β-strands

• Yaochun Xu,
• Isabelle Correia,
• Tap Ha-Duong,
• Nadjib Kihal,
• Jean-Louis Soulier,
• Julia Kaffy,
• Benoît Crousse,
• Olivier Lequin and
• Sandrine Ongeri

Beilstein J. Org. Chem. 2017, 13, 2842–2853, doi:10.3762/bjoc.13.276

• bond network. Methanol was used because of the limited solubility of these compounds in aqueous solutions. The 1H and 13C chemical shifts of these pentapeptides were assigned using 1D 1H, 2D 1H,1H-TOCSY, 2D 1H,1H-ROESY, 2D 1H,13C-HSQC, and 2D 1H,13C-HMBC spectra. The 1H and 13C chemical shift

• heterogeneity involved in particular the t-Bu protons of the Boc group and the amide proton of the residue Ala1. The chemical shift set of weaker intensity was assigned more easily by cooling down to 271 K because of significant broadening near room temperature. Exchange peaks were observed on ROESY spectra at

¹⁵N-Labelling and structure determination of adamantylated azolo-azines in solution

• Sergey L. Deev,
• Alexander S. Paramonov,
• Tatyana S. Shestakova,
• Igor A. Khalymbadzha,
• Oleg N. Chupakhin,
• Julia O. Subbotina,
• Oleg S. Eltsov,
• Pavel A. Slepukhin,
• Vladimir L. Rusinov,
• Alexander S. Arseniev and
• Zakhar O. Shenkarev

Beilstein J. Org. Chem. 2017, 13, 2535–2548, doi:10.3762/bjoc.13.250

• -1H and 1H-13C NMR correlation experiments (COSY and HMBC, respectively) or nuclear Overhauser effect spectroscopy (NOESY or ROESY). The selective incorporation of 15N-labelled atoms in different positions of the heterocyclic core allowed for the use of 1H-15N (JHN) and 13C-15N (JCN) coupling

• ROESY) also did not provide unequivocal structures of the N-adamantylated derivatives [13][14]. For example, the attachment of an adamantyl group to the N1 or N3 atom in the azole ring of compounds 5 and 6 could not be distinguished by NOE data. Similar problems with the unambiguous determination of the

Synthesis and supramolecular properties of regioisomers of mononaphthylallyl derivatives of γ-cyclodextrin

• Markéta Bláhová,
• Sergey K. Filippov,
• Lubomír Kováčik,
• Jiří Horský,
• Simona Hybelbauerová,
• Zdenka Syrová,
• Tomáš Křížek and
• Jindřich Jindřich

Beilstein J. Org. Chem. 2017, 13, 2509–2520, doi:10.3762/bjoc.13.248

• worth noting, that while the distance between signals B and C increased (by about 0.07 ppm), the area of aromatic protons A narrowed (about 0.21 ppm). For all of the above cases, the changes of chemical shifts and shapes of signals in the CD hydrogens’ area were minimal. Also, NOESY and ROESY

• CD/NA in NOESY and ROESY experiments with NA inclusion into CD is more difficult. Nevertheless, the change in chemical shifts was observed also for the allyl hydrogens which indicates that the allyl group might be also inserted into the CD cavity which would increase the distance between CD and NA

Structural diversity in the host–guest complexes of the antifolate pemetrexed with native cyclodextrins: gas phase, solution and solid state studies

• Magdalena Ceborska,
• Magdalena Zimnicka,
• Aneta Aniela Kowalska,
• Kajetan Dąbrowa and
• Barbara Repeć

Beilstein J. Org. Chem. 2017, 13, 2252–2263, doi:10.3762/bjoc.13.222

• conformation of the guest molecule as well as its possible interactions with host CDs. All experiments were done in D2O, and also in DMSO-d6 which enabled tracking of the changes of chemical shifts of acidic protons. The architecture of the formed complexes was then studied by 2D ROESY NMR. UV–vis titration

• observed. It is also consistent with literature data regarding another structurally related antifolate – methotrexate, where β-CD formed stable complexes [21][22], whereas for γ-CD weak binding was observed [21]. Studies of native CDs/PTX complexes in solution by the means of 1H NMR and 2D ROESY NMR The

• supramolecular complexes of PTX with native CDs were studied in solution by the means of 1H NMR and 2D ROESY NMR (Supporting Information File 1, Figures S6–S23). α-CD/PTX and its comparison with α-CD/FA: In the 1H NMR spectra of an equimolar mixture of α-CD and PTX in D2O only marginal changes in chemical shifts

β-Cyclodextrin- and adamantyl-substituted poly(acrylate) self-assembling aqueous networks designed for controlled complexation and release of small molecules

• Liang Yan,
• Duc-Truc Pham,
• Philip Clements,
• Stephen F. Lincoln,
• Jie Wang,
• Xuhong Guo and
• Christopher J. Easton

Beilstein J. Org. Chem. 2017, 13, 1879–1892, doi:10.3762/bjoc.13.183

• and MO in the analogous systems.) Equimolar D2O solutions of β-CD and each of the three dyes show 2D 1H ROESY NMR cross-peaks arising from dipolar interactions between the β-CD annular H3,5,6 protons and those of the dye (Figures S23–S25, Supporting Information File 1) consistent with dye complexation

• determined from their 1H NMR spectra to be 8.8 ± 0.2%, 3.3 ± 0.1%, 3.0 ± 0.1% and 2.9 ± 0.1%, respectively. NMR spectroscopy A Varian Inova 600 spectrometer operating at 599.96 MHz was used to run 1D, 2D NOESY and 2D ROESY 1H NMR spectra using standard pulse sequences with a mixing time of 0.3 s in the last

Molecular recognition of N-acetyltryptophan enantiomers by β-cyclodextrin

• Spyros D. Chatziefthimiou,
• Mario Inclán,
• Petros Giastas,
• Athanasios Papakyriakou,
• Konstantina Yannakopoulou and
• Irene M. Mavridis

Beilstein J. Org. Chem. 2017, 13, 1572–1582, doi:10.3762/bjoc.13.157

• . Moreover, it is observed that the magnitude of the shifts of the L-enantiomer are always larger and the slopes of the Job plots steeper than those of the D-enantiomer, suggesting stronger binding of β-CD with L- than with D-NAcTrp. 2D ROESY spectra of each enantiomer with β-CD at a 1:1 mole ratio in D2O

• carried out on a 500 MHz Bruker Avance instrument at 300 K using a BBI probe, the library pulse sequences and 300 ms mixing time for the 2D ROESY runs. The compounds were dissolved in unbuffered D2O. The data was processed with Topspin. X-ray crystallography Crystallisation of β-CD–L-NAcTrp. In an aqueous

The effect of cyclodextrin complexation on the solubility and photostability of nerolidol as pure compound and as main constituent of cabreuva essential oil

• Joyce Azzi,
• Pierre-Edouard Danjou,
• David Landy,
• Steven Ruellan,
• Lizette Auezova,
• Hélène Greige-Gerges and
• Sophie Fourmentin

Beilstein J. Org. Chem. 2017, 13, 835–844, doi:10.3762/bjoc.13.84

• employed using a competition method. The solubility of cabreuva EO rich in trans-Ner was also assessed with HP-β-CD using the total organic carbon method developed in our laboratory [17]. In addition, 1H and 2D ROESY NMR experiments and molecular modelling were performed to investigate the orientations of

• trans-Ner within the CD cavity, NMR spectroscopy was used. Because HP-β-CD is a heterogeneous mixture of isomers, NMR was conducted only with β-CD. 1H NMR and ROESY spectra were recorded for β-CD and β-CD/trans-Ner solutions in D2O. The induced shift (∆δ) which is the difference between chemical shifts

• hydrophobic interactions and that Ner penetrates the cavity from the wider side [28]. Furthermore, a ROESY experiment was performed to gain further insight into the dynamic structure of the β-CD/trans-Ner inclusion complex. The two-dimensional spectrum indicates a strong intermolecular cross-peaks between H3

Inclusion complexes of β-cyclodextrin with tricyclic drugs: an X-ray diffraction, NMR and molecular dynamics study

• Franca Castiglione,
• Fabio Ganazzoli,
• Luciana Malpezzi,
• Andrea Mele,
• Walter Panzeri and
• Giuseppina Raffaini

Beilstein J. Org. Chem. 2017, 13, 714–719, doi:10.3762/bjoc.13.70

• 7, 20131 Milano, Italy 10.3762/bjoc.13.70 Abstract Tricyclic fused-ring cyclobenzaprine (1) and amitriptyline (2) form 1:1 inclusion complexes with β-cyclodextrin (β-CD) in the solid state and in water solution. Rotating frame NOE experiments (ROESY) showed the same geometry of inclusion for both 1

• the corresponding 1/β-CD complex, thus showing the formation of two diastereomeric inclusion complexes. Similar behaviour can be reported for 2. The geometry of inclusion can be inferred by analysis of intermolecular NOEs obtained from ROESY spectra (Figure 3). The signals of H9, H10 and H11 of 1 show

• experiments in the rotating frame (ROESY) were acquired on 4 mM solutions by using a suitable pulse sequence with two different transmitter offsets for spin-lock and pulse [14] in order to minimize artefacts due to the J-coupling magnetization transfer (HOHAHA). The typical experimental set-up was as follows

Novel β-cyclodextrin–eosin conjugates

• Gábor Benkovics,
• Damien Afonso,
• András Darcsi,
• Szabolcs Béni,
• Sabrina Conoci,
• Éva Fenyvesi,
• Lajos Szente,
• Milo Malanga and
• Salvatore Sortino

Beilstein J. Org. Chem. 2017, 13, 543–551, doi:10.3762/bjoc.13.52

• , Supporting Information File 1) and the in-depth analysis of the DEPT-edited HSQC spectra supported by COSY data (Figures S23 and S31, Supporting Information File 1), allowed the complete assignment of the aromatic resonances. Additional 2D NMR spectra (HMBC and ROESY) for the eosin–β-CD conjugates are also

Secondary metabolome and its defensive role in the aeolidoidean Phyllodesmium longicirrum, (Gastropoda, Heterobranchia, Nudibranchia)

• Alexander Bogdanov,
• Cora Hertzer,
• Stefan Kehraus,
• Samuel Nietzer,
• Sven Rohde,
• Peter J. Schupp,
• Heike Wägele and
• Gabriele M. König

Beilstein J. Org. Chem. 2017, 13, 502–519, doi:10.3762/bjoc.13.50

• D) was thus suggested. A ROESY experiment showed a distinct correlation of the resonances H-26 and H-30 (see conformational fragment structure, Figure 10). The lack of an ROE correlation between H-26 and the resonance of the vicinal methyl group CH3-39, as well as the different 13C NMR shift of C-30

• correlation could be observed between the latter and the α-oriented H-30. H3-40 has a ROESY interaction with H-29b, since the latter has a 1H-coupling to H-30 of 13.9 Hz it must be axial and β and this way proves the β and axial orientation of CH3-40. A ROE correlation between the resonance of H-32 and the H3

• between H-2 and H-21 indicating the β-orientation of both protons and the configuration change at C-21 from S to R. The related biscembranoid 15 was isolated as an amorphous solid with a specific optical rotation of [α]D20 −14.0 (c 0.2 in MeOH). The NMR data (1H NMR, 13C NMR, COSY, HSQC, HMBC and ROESY

Facile synthesis of a 3-deazaadenosine phosphoramidite for RNA solid-phase synthesis

• Elisabeth Mairhofer,
• Elisabeth Fuchs and
• Ronald Micura

Beilstein J. Org. Chem. 2016, 12, 2556–2562, doi:10.3762/bjoc.12.250

• -bis(trimethylsilyl)acetamide and trimethylsilyl trifluoromethanesulfonate in toluene. No protection of the 4-amino group of compound 3 was required. The reaction proceeded in high yields and gave the tribenzoylated c3A nucleoside 4. This compound was analysed by 1H ROESY NMR spectroscopy which was

Radical polymerization by a supramolecular catalyst: cyclodextrin with a RAFT reagent

• Kohei Koyanagi,
• Yoshinori Takashima,
• Takashi Nakamura,
• Hiroyasu Yamaguchi and
• Akira Harada

Beilstein J. Org. Chem. 2016, 12, 2495–2502, doi:10.3762/bjoc.12.244

• in water was significantly low, leading to the formation of precipitates. β-CD-CTA forms a self-inclusion complex or a supramolecular dimer complex, which was characterized using 2D ROESY NMR (Supporting Information File 1, Figure S4). We focused on the polymerization activity of α-CD-CTA because the

Reactivity studies of pincer bis-protic N-heterocyclic carbene complexes of platinum and palladium under basic conditions

• David C. Marelius,
• Curtis E. Moore,
• Arnold L. Rheingold and
• Douglas B. Grotjahn

Beilstein J. Org. Chem. 2016, 12, 1334–1339, doi:10.3762/bjoc.12.126

• other half of the dimer, which would be expected to shield the NH and cause a significant upfield chemical shift. Moreover, a ROESY experiment on 6-Pt (Figure S6, Supporting Information File 1) confirms that the NH (N5’, Figure 2) has a through-space interaction with the proton on the imidazole ring (C3

Elucidation of a masked repeating structure of the O-specific polysaccharide of the halotolerant soil bacteria Azospirillum halopraeferens Au4

• Elena N. Sigida,
• Yuliya P. Fedonenko,
• Alexander S. Shashkov,
• Nikolay P. Arbatsky,
• Evelina L. Zdorovenko,
• Svetlana A. Konnova,
• Vladimir V. Ignatov and
• Yuriy A. Knirel

Beilstein J. Org. Chem. 2016, 12, 636–642, doi:10.3762/bjoc.12.62

• enabled suggestion of the general OPS structure (Scheme 1). This structure was confirmed by NMR spectroscopy, including assignment of the 1H and 13C NMR spectra (Table 2) as described above for compounds 1 and 2 and sequence analysis by two-dimensional 1H–1H ROESY and 1H–13C HMBC experiments. The

• of an unsubstituted residue in the β-anomeric form [19] and thus confirmed that β-Glc occupied the terminal position in the side chain. The ROESY spectrum (Supporting Information File 1) showed the following cross-peaks between the anomeric protons and the protons at the linkage carbon atoms: Rha2Me

• calibration. Two-dimensional NMR experiments were performed using standard Bruker software. Spin lock time in TOCSY experiments and mixing time in ROESY experiments were set to 60 and 200 ms, respectively. The HMBC spectrum was recorded with a 60-ms delay for evolution of long-range couplings. Samples were