Deuterium isotope effects in carbohydrates revisited. Cryoprobe studies of the anomerization and NH to ND deuterium isotope induced 13C NMR chemical shifts of acetamidodeoxy and aminodeoxy sugars

Complete ¹H and ¹³C NMR chemical shift assignments have been generated from a series of acetamidodeoxy and aminodeoxy sugar derivatives. For free sugars, the enhanced sensitivity of an NMR cryoprobe allowed simple 1D and 2D NMR spectra to be obtained from essentially single anomers, before significant mutarotation had occurred. The NMR assignments have been used to characterize deuterium isotope effects on ¹³C chemical shifts measured under conditions of slow NH to ND exchange in single solutions. Within a range of 0 to −0.138 ppm, β, γ, δ, and ζ deuterium isotope effects have been observed, thus providing additional reference data for assignment of the ¹³C NMR spectra of nitrogenous saccharides.     

Hydroxycinnamic acid spermidine amides from pollen of corylus avellana L.

Two hydroxyannamic acid amides from the pollen of Corylus avellana L. have been identified as (E)-caffeoyl-(E)-feruloylspermidine and di-(E)-feruloylspermidine on the basis of ¹H NMR, ¹³C NMR and mass spectral data.     

Oriciopsin,a new ring-D cleaved tetranortriterpenoid,and flindersiamine from Oriciopsis glaberrima

A novel ring-D cleaved tetranortriterpenoid, oriciopsin and flindersiamine have been isolated from the whole plant extracts of Oriciopsis glaberrima. The structure of the new limonoid was determined from its ¹H NMR and ¹³C NMR spectra and by mass spectrometry.     

A revision of the structures of three limonoids

Three limonoids, two from Aphanamixis polystacha and one from Trichilia prieuriana, have been found to have ¹³C NMR spectra at variance wit     

Alkaloids of Uncaria attenuata from Thailand

The major alkaloids of a sample of leaves of Uncaria attenuata obtained from Thailand have been identified as the pentacyclic heteroyohimbine alkaloids tetrahydroalstonine, rauniticine and the novel 14-β-hydroxy-3-iso-rauniticine. Evidence for the structure of the new alkaloid was obtained from a study of UV, IR, MS, ¹H NMR and ¹C NMR spectra.     

One-dimensional 13C NMR and HPLC-1H NMR techniques for observing carbon-13 and deuterium labelling in biosynthetic studies

For several decades isotope labelling techniques have been the indispensable tools used to unravel pathways of secondary product biosynthesis. NMR spectroscopy, together with mass spectrometry, is the most effective measuring technique used in the analysis of metabolites enriched with stable isotopes. ²H and ¹³C are the NMR-detectable nuclides which have been most frequently employed in plant secondary metabolite synthesis. Examples from the biosynthesis of phenylpropanoids, phenylphenalenones, and glucosinolates are used when discussing some aspects of one-dimensional NMR analysis of metabolites selectively labelled with ²H and ¹³C. Besides direct NMR detection of ¹³C-enriched metabolites, special emphasis is placed on indirect detection of ¹³C and ²H, especially by HPLC-¹H NMR coupling, to analyse the isotopomer pattern of compounds in low concentration. The examples discussed in this paper were obtained from studies with Anigozanthos preissii (root cultures) (Haemodoraceae) and Eruca sativa (Brassicaceae).     

3-Methoxyflavones and coumarins from Artemisia incanescens

Seven 3-methoxyflavones and three coumarins have been isolated from aerial parts of Artemisia incanescens. Their ¹H NMR spectra in DMSO-d₆ and CDCl₃ are compared and discussed. The hitherto unreported ¹³C NMR spectra of some of these compounds are also discussed.     

Iridoid aglycones from Deutzia scabra

Scabrogenin and deutziogenin, the stable aglycones of known iridoid glucosides scabroside and deutzioside, have been isolated from Deutzia scabra. Their structures and mutarotational equilibria were investigated by detailed analysis of ¹H NMR and ¹³C NMR data.     

Iridoid glycosides from Penstemon richardsonii

Five ester iridoids of the valeriana type have been isolated from dried leaves of Penstemon richardsonii. The structures have been elucidated by FAB MS ¹H NMR and ¹³C NMR spectroscopy and by enzymatic cleavage of the glycosidic linkages. Besides the known iridoids penstemide penstemide-aglucone 8-epi-valerosidatum and serrulatoside a new iridoid penstebioside (penst of an iridoid aglycone attached to cellobiose.     

Argophyllone-B,a sesquiterpene lactone from Helianthus argophyllus

The sesquiterpene lactone, 2-methyl-2-butenoic acid dodecahydro-4-(hydroxymethyl)-10a-methyl-8-methylene-3,7-dioxooxineno[5,6]cyclodeca[1,2-b]furan-9-yl ester [1aR^*-[1aS^*,4R^*,5aS^*,8aR^*,9R^*(E)]], argophyllone-B, was isolated from acetone extracts from the leaves of Helianthus argophyllus. Its structure has been determined by single crystal X-ray analysis. Complete ¹H NMR and ¹³C NMR assignments have been made.     

Two pentacyclic triterpenes from Rubia cordifolia

Rubicoumaric acid and rubifolic acid isolated from Rubia cordifolia have been shown to be 30-hydroxy-3β-p-hydroxycoumaryloxy-urs-12-ene-28-oic acid and 3β,30-dihydroxy-urs-12-ene-28-oic acid(30-hydroxyursolic acid) respectively on the basis of ¹H NMR, ¹³C NMR and mass spectral and chemical evidence.     

Structure of fomitellan A, a mannofucogalactan from the fruiting bodies of Fomitella fraxinea

Chemical structure of fomitellan A, a polysaccharide with a mitogenic effect isolated from the fruiting bodies of Fomitella fraxinea, has been assigned as a mannofucogalactan with a repeating unit of penta-saccharide, which was composed of a (1→6)-linked d-galactopyranosyl backbone having a C-2 position substituted with disaccharide units of 3-O-d-mannopyranosyl-l-fucopyranosyl residue. The ¹H and ¹³C NMR signals of fomitellan A have been completely assigned by extensive NMR experiments.     

Bryonoside and bryoside—new triterpene glycosides from Bryonia dioica

The structures of two new triterpene glycosides from Bryonia dioica have been shown, on the basis of chemical and FDMS and ¹H and ¹³C NMR s     

Wampetin,a furocoumarin from Clausena wampi

A new furocoumarin wampetin has been isolated from Clausena wampi (syn. Clausena lansium). The structure was established from ¹H NMR, ¹³C NMR, MS and chemical data.     

Review of NMR and μSR studies in the molecular nanomagnet Mn12-ac

We present a comprehensive review of the NMR and μSR studies performed in the molecular nanomagnet Mn12 a system characterized and widely studied by Prof. Gatteschi’s group in Florence. The proton (¹H, ²D) NMR, the ⁵⁵Mn NMR and the μSR investigations have yielded important information regarding both static and dynamic magnetic properties of the molecule. The magnetic and quadrupole hyperfine interactions have been extracted from NMR data. The spin dynamics at high and intermediate temperature associated with the zero dimensionality and with the spin–phonon coupling has been studied together with the spin dynamics in the quantum tunneling low temperature regime. The local spin configuration in the giant S = 10 total spin ground state has been determined via ⁵⁵Mn NMR in zero magnetic field and with fields parallel and perpendicular to the anisotropy axis. Finally a novel method is described to monitor the relaxation of the magnetization from the time evolution of the NMR spectrum.     

Synthesis of Ru-Arene complexes of Me-Duphos. X-ray, PGSE NMR diffusion and catalytic studies

Cationic [RuCl(arene)(Me-Duphos)]Cl complexes, arene=η⁶-benzene and η⁶-p-cymene, Me-Duphos=1,2-bis-((2R,5R)-2,5-dimethylphospholano) benzene) have been prepared and studied by X-ray crystallography and NMR spectroscopy. PGSE NMR diffusion studies have been used to recognize (a) ion pairing as a function of solvent and (b) larger molecular volumes. Several arene-Ru-complexes have been shown to be useful catalyst precursors in the hydrolysis of terminal aryl alkynes to afford acetophenones.     

Diterpenoids from sideritis pusilla subsp. flavovirens

Several new 14-hydroxybeyerene acetates have been isolated from the aerial parts of Sideritis pusilla subsp. flavovirens. In addition, an ent-kaur-15-ene (siderol) and a new ent-7α, 18-dihydroxybeyer-15-ene (flavovirol) have been obtained from the same source. The structures of these new acetates have been established by chemical and spectroscopic means and the structure of flavovirol has been confirmed by ¹³C NMR.     

Teupolin III,a furanoid diterpene from Teucrium polium

A new clerodane derivative was isolated from Teucrium polium var. polium. The structure and stereochemistry have been established by detailed studies of the ¹H NMR spectra.     

Three quinicine derived alkaloids from Guettarda trimera

Three alkaloids, isolated from the trunk bark of Guettarda trimera have been identified as derivatives of quinicine on the basis of mass spectrometry, ¹H and ¹³C NMR data.     

Phenolic and acetylenic metabolites from Artemisia assoana

Nine flavones, three coumarins, two flavone glycosides, p-hydroxyacetophenone and methyl caffeate have been isolated from the aerial parts of Artemisia assoana. Six diacetylenic spiroketal enol-ethers, a mixture of n-alkyl p-coumarates and a new phenylpropanoid metabolite, sinapyl alcohol diisovalerate, have been isolated from root extracts of the same plant. ¹H and ¹³C NMR spectra of some of these compounds are given and taxonomic aspects are discussed.