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This study aims to evaluate the robustness of clinical and metabolic phenotyping through, for the first time, the identification of differential responsiveness to dietary strategies in the improvement of cardiometabolic risk conditions. Clinical phenotyping of 57 volunteers with cardiovascular risk factors was achieved using k-means cluster analysis based on 69 biochemical and anthropometric parameters. Cluster validation based on Dunn and Figure of Merit analysis for internal coherence and external homogeneity were employed. k-Means produced four clusters with particular clinical profiles. Differences on urine metabolomic profiles among clinical phenotypes were explored and validated by multivariate orthogonal signal correction partial least-squares discriminant analysis (OSC-PLS-DA) models. OSC-PLS-DA of (1)H-NMR data revealed that model comparing "obese and diabetic cluster" (OD-c) against "healthier cluster" (H-c) showed the best predictability and robustness in terms of explaining the pairwise differences between clusters. Considering these two clusters, distinct groups of metabolites were observed following an intervention with wine polyphenol intake (WPI; 733 equivalents of gallic acid/day) per 28days. Glucose was significantly linked to OD-c metabotype (P

Amyloid fibrils are thread-like protein aggregates with a core region formed from repetitive arrays of beta-sheets oriented parallel to the fibril axis. Such structures were first recognized in clinical disorders, but more recently have also been linked to a variety of non-pathogenic phenomena ranging from the transfer of genetic information to synaptic changes associated with memory. The observation that many proteins can convert into similar structures in vitro has suggested that this ability is a generic feature of polypeptide chains. Here we have probed the nature of the amyloid structure by monitoring hydrogen/deuterium exchange in fibrils formed from an SH3 domain using a combination of nuclear magnetic resonance spectroscopy and electrospray ionization mass spectrometry. The results reveal that under the conditions used in this study, exchange is dominated by a mechanism of dissociation and re-association that results in the recycling of molecules within the fibril population. This insight into the dynamic nature of amyloid fibrils, and the ability to determine the parameters that define this behaviour, have important implications for the design of therapeutic strategies directed against amyloid disease.

Cis and trans proline conformers are often associated with dramatic changes in the biological function of peptides. A slow equilibrium between cis and trans Ile–Pro amide bond conformers occurs in constrained derivatives of the native marine cyclic heptapeptide stylostatin 1 (cyclo-(NSLAIPF)), a potential anticancer agent. In this work, four cyclopeptides, cyclo-(NSTAIPF), cyclo-(KSTAIPF), cyclo-(RSTAIPF) and cyclo-(DSTAIPF), which are structurally related to stylostatin 1, are experimentally and computationally examined in order to assess the effect of residue mutations on the cis–trans conformational ratio and the apparent capacity to form dimeric aggregates. Primarily, cyclo-(KSTAIPF) and cyclo-(RSTAIPF) showed specific trends in circular dichroism, MALDI-TOF and HPLC purification experiments, which suggests the occurrence of peptide dimerization. Meanwhile, the NMR spectrum of cyclo-(KSTAIPF) indicates that this cyclopeptide exists in the two slow-exchange families of conformations mentioned above. Molecular dynamics simulations combined with quantum mechanical calculations have shed light on the factors governing the cis/trans conformational ratio. In particular, we have found that residue mutations affect the internal hydrogen bond pattern which ultimately tunes the cis/trans conformational ratio and that only trans conformers are capable of aggregating due to the shape complementarity of the two subunits.

This article is licensed under a Creative Commons Attribution 3.0 Unported Licence.-- et al., A new class of guest-induced, bi-radical self-assembled organic capsules is reported. They are formed by the inclusion of a tetramethylammonium (TMA) cation between two monomers of the stable trityl radical OX63. OX63 is extensively used in dissolution dynamic nuclear polarization (DNP) where it leads to NMR sensitivity enhancements of several orders of magnitude. The supramolecular properties of OX63 have a strong impact on its DNP properties. An especially relevant case is the polarization of choline-containing metabolites, where complex formation between choline and OX63 results in faster relaxation., This work was supported in part by funds from the Spanish government (BIO2010-15683, BIO2013-45793R, MAT2012-38318-C03-01 and Juan de la Cierva), the Catalan government (2009SGR1352 and Beatriu de Pinós), the European Commission (BioNMR contract 261863) and the COST action (TD1103). The Hypersense instrument and project BIO2013-45793R are co-financed by structural funds (FEDER) from the EU.

The applied interaction of synthetic molecules with defined regions of protein surfaces is an emerging strategy for the modulation of protein activity and/or stability. In spite of recent advances, the design of these molecules is not trivial. Among the most challenging aspects in designing these compounds is that they must compete with water molecules for interaction with polar patches of protein surfaces. Herein is reported the preparation of an arginine-rich peptide that interacts in aqueous solution with a very hydrophilic patch at the surface of the tetramerization domain of the tumor suppressor protein p53. The interaction has been studied by several complementary techniques. By using this peptide as a template, a library of peptides has been prepared and evaluated in order to examine the different factors that contribute to the recognition event. The conclusions extracted from this work could be useful for the design of ligands directed at highly hydrophilic protein surface patches.

Electron beam-irradiated peeled almonds (dose rate

With the aim of studying the contribution of the beta II turn conformation at the side chain of didemnins to the bioactive conformation responsible for their antitumoral activity, conformationally restricted analogues of aplidine and tamandarin A, where the side chain dipeptide Pro8-N-Me-d-Leu7 is replaced with the spirolactam beta II turn mimetic (5R)-7-[(1R)-1-carbonyl-3-methylbutyl]-6-oxo-1,7-diazaspiro[4.4]nonane, were prepared. Additionally, restricted analogues, where the aplidine (pyruvyl9) or tamandarin A [(S)-Lac9] acyl groups are replaced with the isobutyryl, Boc, and 2-methylacryloyl groups, were also prepared. These structural modifications were detrimental to cytotoxic activity, leading to a decrease of 1-2 orders of magnitude with respect to that exhibited by aplidine and tamandarin A. The conformational analysis of one of these spirolactam aplidine analogues, by NMR and molecular modeling methods, showed that the conformational restriction caused by the spirolactam does not produce significant changes in the overall conformation of aplidine, apart from preferentially stabilizing the trans rotamer at the pyruvyl9-spirolactam amide bond, whereas in aplidine both cis and trans rotamers at the pyruvyl9-Pro8 amide bond are more or less equally stabilized. These results seem to indicate a preference for the cis form at that amide bond in the bioactive conformation of aplidine. The significant influence of this cis/trans isomerism upon the cytotoxicity suggests a possible participation of a peptidylprolyl cis/trans isomerase in the mechanism of action of aplidine.

Dehydrodidemnin B (DDB or aplidine), a potent antitumoral natural product currently in phase II clinical trials, exists as an approximately 1:1 mixture of two slowly interconverting conformations. These are sufficiently long-lived so as to allow their resolution by HPLC. NMR spectroscopy shows that this phenomenon is a consequence of restricted rotation about the Pyr-Pro(8) terminal amide bond of the molecule's side chain. The same technique also indicates that the overall three-dimensional structures of both the cis and trans isomers of DDB are similar despite the conformational change. Molecular dynamics simulations with different implicit and explicit solvent models show that the ensembles of three-dimensional structures produced are indeed similar for both the cis and trans isomers. These studies also show that hydrogen bonding patterns in both isomers are alike and that each one is stabilized by a hydrogen bond between the pyruvyl unit at the terminus of the molecule's side chain and the Thr(6) residue situated at the junction betwen the macrocycle and the molecule's side chain. Nevertheless, each conformational isomer forms this hydrogen bond using a different pyruvyl carbonyl group: CO(2) in the case of the cis isomer and CO(1) in the case of the trans isomer.

To investigate the effect of temperature (0 versus 37 degrees C) in the high-resolution magic angle spinning spectroscopy (HRMAS) pattern of human brain tumor biopsies and its influence in recognition-based tumor type prediction. This proof-of-principle study addressed the bilateral discrimination between meningioma (MM) and glioblastoma multiforme (GBM) cases.Forty-three tumor biopsy samples were collected (20 MM and 23 GBM), kept frozen and later analyzed at 0 degrees C and 37 degrees C by HRMAS. Post-HRMAS histopathology was used to validate the tumor type. Time-course experiments (100 min) at both temperatures were carried out to monitor HRMAS pattern changes. Principal component analysis and linear discriminant analysis were used for classifier development with a training set of 20 biopsies.Temperature-dependent, spectral pattern changes mostly affected mobile lipids and choline-containing compounds resonances and were essentially reversible. Incubation of 3 MM and 3 GBM at 37 degrees C during 100 minutes produced irreversible pattern changes below 13% in a few resonances. Classification performance of an independent test set of 7 biopsies was 100% for the pulse-and-acquire, CPMG at echo times (TE) of 30 ms and 144 ms and Hahn Echo at TE 30 ms at 0 degrees C and 37 degrees C. The performance for Hahn Echo spectra at 136 ms was 83.3% at 0 degrees C and 100% at 37 degrees C.The spectral pattern of mobile lipids changes reversibly with temperature. HRMAS demonstrated potential for automated brain tumor biopsy classification. No advantage was obtained when acquiring spectra at 37 degrees C with respect to 0 degrees C in most of the conditions used for the discrimination addressed.

Polychlorinated trityl radicals bearing carboxylate substituents are water soluble persistent radicals that can be used for dynamic nuclear polarization. In contrast to other trityl radicals, the polarization mechanism differs from the classical solid effect. DFT calculations performed to rationalize this behaviour support the hypothesis that polarization is transferred from the unpaired electron to chlorine nuclei and from these to carbon by spin diffusion. The marked differences observed between neutral and anionic forms of the radical will be discussed.

Activation of the pro-drug isoniazid (INH) as an anti-tubercular drug in Mycobacterium tuberculosis involves its conversion to isonicotinyl-NAD, a reaction that requires the catalase-peroxidase KatG. This report shows that the reaction proceeds in the absence of KatG at a slow rate in a mixture of INH, NAD+, Mn2+, and O2, and that the inclusion of KatG increases the rate by >7 times. Superoxide, generated by either Mn 2+- or KatG-catalyzed reduction of O2, is an essential intermediate in the reaction. Elimination of the peroxidatic process by mutation slows the rate of reaction by 60% revealing that the peroxidatic process enhances, but is not essential for isonicotinyl-NAD formation. The isonicotinyl-NAD.+ radical is identified as a reaction intermediate, and its reduction by superoxide is proposed. Binding sites for INH and its co-substrate, NAD+, are identified for the first time in crystal complexes of Burkholderia pseudomallei catalase-peroxidase with INH and NAD + grown by co-crystallization. The best defined INH binding sites were identified, one in each subunit, on the opposite side of the protein from the entrance to the heme cavity in a funnel-shaped channel. The NAD+ binding site is ∼20 Å from the entrance to the heme cavity and involves interactions primarily with the AMP portion of the molecule in agreement with the NMR saturation transfer difference results. © 2010 by The American Society for Biochemistry and Molecular Biology, Inc., This work was supported by a Discovery Grant 9600 from the Natural Sciences and Engineering Research Council (NSERC) of Canada (to P. C. L.) and by the Canada Research Chair Program (to P. C. L.). This work was supported by Grants BFU2005-08686-C02-01 (to I. F.), BIO2007-63458 (to M. P.), both from the Spanish Ministry of Science and Innovation, and SGR2009-1352 (to M. P.) from the Generalitat de Catalunya.

Polychlorinated trityl radicals (see structure: C black, Cl green, Na gray, O red) used for dynamic nuclear polarization (DNP) showed a new transfer mechanism involving quadrupolar chlorine nuclei. The observation of positive or negative enhancements, depending on the substrate, highlights the supramolecular character of the initial polarization‐transfer process

Malaysiatin (1), the first homodetic cycloheptapeptide from a marine source, has been isolated from the cytotoxic and antimicrobial extracts of the marine sponge Pseudaxinyssa sp., collected in Borneo. The unusual structure of malaysiatin, which contains homodipeptide and homotripeptide fragments, was elucidated by extensive spectroscopic analysis that suggests an all-L stereochemistry. © 1992.

The proton nmr spectra of bacitracin A in H2O and DMSO-d6 have been assigned and the conformational behavior of the peptide in the two solvents has been compared. Although bacitracin A shows a conformational equilibrium between at least two conformations differing in the relative position of the cyclic and linear domains of the molecule, the spectra in water can be interpreted in terms of a preferred conformation in which the linear part is folded over the cyclic moiety and a turn is present around Ile(8)-DPhe(9).

Fast 2D NMR-based screening can be achieved using Hadamard encoded spectroscopy to focus on the signals of interest (e.g., enzyme active or ligand recognition sites). By recording a set of Hadamard spectra (a “Hadamard constellation”) with relative offsets comparable to the excitation bandwidth, quantitative ligand-induced shifts can be obtained from peak intensities.

Aplidine (dehydrodidemnin B), a natural product with potent antitumor activity currently in multicenter phase II clinical trials, exists in DMSO as a mixture of four slowly interconverting conformations in a ratio of 47:33:13:7. NMR spectroscopy shows that these arise as a consequence of cis/trans isomerization about the NMe-Leu(7)-Pro(8) and Pro(8)-Pyr amide bonds of the molecule's side chain. Two major conformations account for 47% and 33% of the total population, a ratio of 60:40 between the two. They correspond to the cis- and trans-isomers, respectively, about the Pro(8)-Pyr amide bond. Two minor conformers arise as a consequence of similar isomerism about the Pro(8)-Pyr amide bond, but in structures in which the NMe-Leu(7)-Pro(8) amide bond is cis rather than trans. These account for approximately 13% and 7% of the total population, corresponding to a ratio of 65:35 cis/trans, respectively. Molecular dynamics simulations show that the three-dimensional structures of all four conformational isomers are similar in the macrocycle and that all are essentially unchanged with respect to the macrocycle of didemnin B. Significant differences in the conformation of the molecule's side chain are, however, observed between major and minor pairs. Analysis of hydrogen-bonding patterns shows that each major conformer exhibits a beta-turn like structure and is stabilized by hydrogen bonding between a different carbonyl group of the pyruvyl unit of the molecule's side chain and the NH of the Thr(6) residue. The minor isomers have a cis-amide bond between the NMe-Leu(7) and Pro(8) residues that obliges the side chain to adopt an extended disposition where hydrogen bonding to the macrocycle is absent. These results suggest that the ability of the molecule's side chain to adopt a beta-turn-like conformation may not be a prerequisite for biological activity in the didemnins and that conformations having an extended side-chain may play a role in the biological activity of aplidine.

A cinchona alkaloid having extraordinary chiral discriminatory powers (alpha = 32.6 for dinitrobenzoyl leucine) is developed as a chiral stationary phase (CSP) for chromatography. An explanation of how chiral discrimination takes place is presented. Using a soluble analogue of the CSP, we found that NMR spectrometry indicates that 1:1 complexes exist for both optical isomers interacting with the CSP, that the free base form of the CSP exists in an open/closed ratio of 35/65 but that the protonated, bound-state form is exclusively in the anti-open conformation, and that significant intermolecular NOEs exist for the more stable diastereomeric complex but not for the less stable complex. Stochastic molecular dynamics simulations were carried out in solvents of low and high dielectric. The chromatographic retention orders and free energy differences of analyte binding to CSP were reproduced computationally as were the observed intra- and intermolecular NOEs. Data from the simulation were used to evaluate the intermolecular forces responsible for analyte binding as well as to discern fragments of the CSP doing most of the work of holding the complexes together. The enantiodifferentiating forces and the parts of the CSP most responsible for chiral discrimination are described. Moments of distributions of key dihedral angles and distances between centroids were used to assess the relative rigidity of the competing diastereomeric complexes. Simultaneous multiple-contact ion-pairing, hydrogen bonding, and pi-stacking are possible for the longer retained enantiomer only. An X-ray crystallographic study of the more stable complex confirms the conclusions derived from chromatography, NMR spectroscopy, and molecular modeling.

The tautomeric equilibria and H−N proton transfer taking place in the nonsymmetrically substituted water-soluble 2-sulfonato-5,15-bis(4-sulfonatophenyl)porphyrin (1) and in its 10-bromo-substituted derivative (2) were analyzed by NMR methods: 1H and 13C spectroscopies and heteronuclear multiple bond correlation (HMBC) and heteronuclear single quantum coherence (HSQC) 1H−13C and 1H−15N techniques. The existence of preferred pathways of H−N transfer was detected. The conclusions are rationalized by taking into account the effect partial meso-substitution exerts on the relative energies of the different cis-tautomer intermediates involved in the tautomerism. These results underline the experimental consequences stemming from the nonequivalence in porphyrins between the ‘tautomeric interconversion' and ‘proton transfer' terms, when observed by NMR techniques, as a consequence of the existence of two pairs of degenerate tautomers and transformation pathways.

Fragment-based drug discovery is widely applied both in industrial and in academic screening programs. Several screening techniques rely on NMR to detect binding of a fragment to a target. NMR-based methods are among the most sensitive techniques and have the further advantage of yielding a low rate of false positives and negatives. However, NMR is intrinsically slower than other screening techniques; thus, to increase throughput in NMR-based screening, researchers often assay mixtures of fragments, rather than single fragments. Herein we present a fast and straightforward computer-aided method to design mixtures of fragments taken from a library that have minimized NMR signal overlap. This approach enables direct identification of one or several active fragments without the need for deconvolution. Our approach entails encoding of NMR spectra into a computer-readable format that we call a fingerprint, and minimizing the global signal overlap through a Monte Carlo algorithm. The scoring function used favors a homogenous distribution of the global signal overlap. The method does not require additional experimental work: the only data required are NMR spectra, which are generally recorded for each compound as a quality control measure before its insertion into the library.

The stereochemical assignment of cis- and trans-2-amino-1,2,3,4-tetrahydro-1-naphthalenols (1) can be performed by means of their conformationally restrained tricyclic tetrahydronaphtho[2,1-d]oxazol-2-one derivatives 2–6. Thus, 1H and 13C nuclear magnetic resonance data of compounds 2–6 reveal differences between the cis and trans stereoisomers that are independent of the nature and number of the aromatic substituents. Conformational analysis of compounds 2–6 has been performed from the LAOCOON/3 analysis of their nuclear magnetic resonance spectra and MNDO theoretical results, through the use of the Karplus–Altona equation. Whereas the trans compounds exist in a rigid half-chair conformation, a 1:1 equilibrium of two interconverting half-chair conformers is found for the cis derivatives.

Structural assignments of all possible diastereoisomers of 1-chloro- 2-ethoxy-1-fluoro-alkylcyclopropanes have been achieved through their 19 F NMR spectra. The previously unreported effect of an ethoxyl group on the fluorine signal has been studied and found to promote in most cases a shielding effect in the vicinal cis -fluorine and a deshielding effect when trans to this halogen.

The presence of repeated proline-rich sequences constitutes a common trend in several cereal storage proteins. The protected hexapeptide Boc-Val-His-Leu-Pro-Pro-Pro-OH (1), with the sequence of the repeated region of glutelin-2 (28 kD) from maize, has been studied by proton and 13C NMR in D2O, DMSO-d6, CDCl3 and CDCl3-CD3OD at different temperatures. Spectra were assigned mainly by using 2D correlation techniques. The spectra in D2O and DMSO-d6 suggest that peptide 1 has a random coil, all-trans conformation. In CDCl3 1 presents a folded conformation, stabilized by hydrogen bonds, with one of the methyl groups of the valine residue situated over the histidine ring. In CDCl3-CD3OD 1 is present as a mixture of different conformations. The spectral data are discussed taking as a reference the known conformation of polyproline.

Bile pigments covalently anchored to beads of a polystyrene-based resin show in gel-phase 13C NMR spectroscopy hydrogen-bond interactions between the anchored groups. Such interactions are similar to those observed in homogeneous solution: attached 5(1 H)-pyrromethenones in aprotic solvents show dimer formation analogously to what happens in homogeneous solution.

The1H NMR spectra of Biliverdin IXα and Mesobiliverdin XIIIα were studied in order to explain their low resolution in CDCl3/CD3OD solvent mixtures. The smallT 2 andT 1 values of these1H NMR spectra are probably due to aggregate formation promoted by the presence of the free propionic acid substituents.

The reaction of 3-oxabicyclo[3.3.0]oct-l(5)ene-2,4-dione, 2, with cyclopentadiene, 3, 5,5-diethoxycyclopentadiene, 4, and 6,6-dimethylfulvene, 5, is studied. Reaction of 2 and 3 yields the expected endo-adduct, while reaction of 2 and 5 gives a mixture of the endo- and exo-adducts whose ratio is slightly dependent on the reaction conditions. Attractive electrostatic interactions in the transition state leading to the exo-adduct can explain the absence of endo stereoselectivity in the last reaction. Steric factors seem to be responsible for the absence of reaction between 2 and 4. The analysis of the 13C NMR spectra of these adducts and some derived compounds confirms the tentative configuration assignment carried out on the basis of PMR data. Also, the synthesis of dimethyl(1R,2S,6R,7S)-10-oxotricy-clo [5.2.1.02.6]decane2,6-decarboxylate, 1, from the endo-adduct of the reaction of 2 and 5, is described

The aerial part of Narcissus requienii (Amaryllidaceae) was found to contain pseudolycorine as the major alkaloid, and two new phenolic bases: 2-O-acetylpseudolycorine and 1-O-acetylpseudolycorine. The present communication reports the complete assignments of the NMR spectra of pseudolycorine, and the structure elucidation of the other comnounds by means of 2D 1H-1H and 1H-13C NMR chemical shift correlation experiments.

We report the isolation of haemanthamine, galanthamine, pretazettine and the new alkaloid N-formylgalanthamine from Narcissus confusus plants. Structural determination was carried out by spectroscopic analyses and application of two-dimensional NMR spectroscopy.

The synthesis of cis- and trans-2-amino-1-arylcyclohexanols 1–8, conformationally restricted analogues of the α-adrenergic drugs norephedrine 9, methoxamine 10, and isopropylmethoxamine 11, is described. trans-Aminoalcohols were obtained through reaction of epoxides 12 or 13 with isopropylamine (to afford 4 and 8) or with sodium azide followed by lithium aluminum hydride reduction (to afford 2 and 6), whereas cis-aminoalcohols 1 and 5 were obtained by condensation of 2-aminocyclohexanone hydrobromide 26 with the appropriate organometallic reagent. Treatment of 1 and 5 with acetone followed by sodium borohydride reduction gave isopropylaminoalcohols 3 and 7. Configurational and conformational assignments of aminoalcohols 1–8 have been carried out on the basis of their 1H nmr and 13C nmr data and by comparison with reference diols 18 and 30. The major or exclusive chair conformation observed for all the compounds has an equatorial aryl group.

The stereoselective synthesis of esters 5a, 6, 7, 8, 12b, 12c, and 13 and dicarboxylic acids 5, 12, and 12a by KMnO4 oxidation, and, in the case of esters, diazomethane esterification, of the known tricyclic ketones 1, 2, 3, and 4 or their derivatives 9, 9a, 9b, 10, 10a, 11, and 11a, is described. Conformational analyses of these compounds have been carried out by 200-MHz 1H-NMR and 13C-NMR spectroscopy at room temperature with the aid of theoretical calculations (MM2 program). Also, a 1H-NMR study of compound 5a at temperatures between 21 and 119°C is presented. In general, a good agreement has been found among experimental and calculate average vicinal proton/proton coupling constant values. Compounds 5 and 5a, in [D6]DMSO and CDCl3 solutions, respectively, exist mainly as boat-chair conformers, while compounds 6, 7, 8, and 13 exist mainly as chair conformers with respect to the bis(methoxycarbonyl)-substituted cyclohexane or oxane ring. Compounds 12, 12a, 12b, and 12c show similar proportions for boat-chair and chair-chair conformers. Konformationsanalyse von Bicyclo [3.3.1]nonan-exo-2,exo-4-dicar-bonsaure-Derivaten und strukturell verwandten Verbindungen Die stereoselektive Synthese der Ester 5a, 6, 7, 8, 12b, 12c und 13 sowie der Dicarbonsauren 5, 12 und 12a, durch Oxidation mit KMnO4 und, im Fall der Ester, durch Veresterung mit Diazomethan, ausgehend von den bekannten tricyclischen Ketonen 1, 2, 3 und 4 oder ihren tricyclischen Derivaten 9, 9a, 9b, 10, 10a, 11 und 11a wird beschrieben. Konformationsanalysen dieser Verbindungen wurden mittels 200-MHz-1H-NMR- und 13C-NMR-Spektroskopie bei Raumtemperatur und mit Hilfe theoretischer Berechnungen (MM2-Programm) durchgefuhrt. Zusatzliche 1H-NMR-Studien an Verbindung 5a zwischen 21 und 119°C werden ebenso beschrieben. In der Regel wurde eine gute Ubereinstimmung zwischen experimentellen und berechneten Mittelwerten der vicinalen Proton/Proton-Kopplungskonstanten gefunden. Verbindungen 5 und 5a in [D6]DMSO bzw. CDCl3 befinden sich bevorzugt in der Wannen-Sessel-Konformation, wahrend Verbindungen 6, 7, 8 und 13 bevorzugt in der Sessel-Form relativ zum Bis(methoxycarbonyl)-substituierten Cyclohexan- oder Oxan-Ring existieren. Verbindungen 12, 12a, 12b und 12c nehmen sowohl die Wannen-Sessel- als auch die Sessel-Sessel-Konformation ein.

A single alkaloid, dubiusine, has been isolated from Narcissus dubius growing in Candasnos (Spain). The structure 2α-acetoxy-9-(3-hydroxybutyryl)homolycorine is proposed for the compound from spectroscopic analysis and chemical correlation.

13 C-NMR spectra of fluorinated molecules are difficult to observe under conventional broad-band proton decoupling. The large coupling constants involved make polarization transfer between fluorine and carbon, using INEPT or DEPT experiments very effective while broad band fluorine decoupling collapses the multiplet pattern.

The first total synthesis of the indole alkaloid vinoxine and the reassignment of the relative configuration at carbon-16 in this alkaloid is reported.

The green parts of Artemisia rehan , Chiov (Asteraceae) were found to contain vulgarin. The 1 H and 13 C NMR spectra of vulgarin and 4- epi vulgarin were unambiguously assigned based on COSY and 1 H- 13 C correlation experiments and an X-ray investigation settled the configuration. Furthermore, the compounds barrelin and judaicin were proved to be identical with vulgarin.

A synthesis of dimethyl tetracyclo[5.2.1.02,6.03,8]decane-7,8-dicarboxylate, 3, whose key step implies the formation of the C1—C2 bond by regioselective intramolecular C—H insertion of a carbene generated from dimethyl (1R,2S,6R,7S)-10-oxotricyclo[5.2.1.02,6]decane-2,6-dicarboxylate, 1 via its tosylhydrazone, is described. Attempts to synthesize diester 3 or compounds containing its carbon skeleton, by forming the same C—C bond, starting from dimethyl (1R,2S,6R,7S)-4-oxotricyclo[5.2.1.02,6]decane-2,6-dicarboxylate, 2, or the corresponding anhydride, 13, are also included.

Acid cyclization of 4-(indol-1- and -3-ylmethyl)-2-cyanopiperidines 5 led to the bridged tetracyclic indole- systems 1 and 2. The required 2-cyanopiperidines 5 were prepared by catalytic hydrogenation of 2-cyano-1,2,3,6-tetrahydropyridines 4 and by DIBAL reduction of lactams 7 followed by cyanide ion addition to the intermediate enamine.