Compounds with bridgehead nitrogen. 44—the conformational analysis of perhydropyrido[1,2-c] [1,3]thiazine

The 270 MHz NMR data on trans- and cis-(H-4a, H-7)-7-ethylperhydropyrido[1,2-c][1,3]thiazine show heavy conformational bias to the trans- and S-inside cis-fused conformations, respectively. Comparison of the ¹³C NMR spectra of these anancomeric systems with the ¹³C NMR spectrum of perhydropyrido[1,2-c][1,3]thiazine indicates a trans-?S-inside cis-conformational equilibrium for the latter compound in CDCl₃ at 25°C, containing ca 75% trans-fused conformer. The ¹³C NMR spectrum of perhydropyrido[1,2-c][1,3]-thiazine at ?75°C showed 64% trans-fused conformer and 36% S-inside cis-conformer.     

1H and 13C NMR study of the effects exerted by an oxirane ring in the epoxybicyclo-[2.2.2]octane series

The ¹H and ¹³C NMR spectra of 2,3-disubstituted exo-5,6- and endo-5,6-bicyclo[2.2.2]octanes, and the corresponding alkanes, have been investigated to determine the effects exerted by an oxirane ring. The ¹H NMR study showed that the anti protons, H-7a and H-8a, are significantly shielded and the syn protons, H-7s and H-8s, are deshielded, although to a smaller extent, by the exo-oxirane. An endo-oxirane has practically no effect on the same protons. The stereochemistry of epoxybicyclo[2.2.2]octanes is, thus, easily deduced from ¹H NMR data. The ¹³C NMR study of the epoxy compounds provided an estimate of the value of α, β, γ syn and γ anti effects (to the epoxide oxygen) of an oxirane ring. In these rigid bicyclic molecules, of known geometry, the γ syn and the γ anti effects are of the same value, even though the dihedral angles are very different (0° and 120°).     

1H and 13C NMR Assignments for a 27-Norolean-13-en-3-hydroxy-28-oic Acid Glycoside from Isertiahaenkeana

A nortriterpene glycoside, pyrocincholic acid 3β-O-β-6-deoxy-D-glucopyranoside-28-O-β-D-glucopyranoside, was isolated from the leaves of Isertia haenkeana and its structure established by ¹H and ¹³C NMR spectral studies. The complete ¹H and ¹³C NMR resonance assignments for this triterpene were confirmed by the conventional 1D NMR methods and 2D shift-correlated NMR techniques: DQF COSY, TOCSY, ROESY and HMQC.     

Complexation of hydroxylated ent-kaurane diterpenoids with boric acid as an aid to the assignment of the 13C NMR spectra

The ¹³C NMR spectra of some hydroxylated ent-kaurane diterpenoids were measured in CDCl₃-Py-d₅ (1:1) solution and also after addition of boric acid. Complexation of ent-3β,18-, ent-7α,15β-, ent-7α,15α-, ent-15β,16β- and ent-16β,17-dihydroxy derivatives with boric acid produced considerable chemical shift changes and marked broadening of the signals of the hydroxy-bearing and neighbouring carbon atoms. This behaviour provides a useful and reliable method for assigning the ¹³C NMR spectra of these compounds.     

13C and 1H NMR investigation of the structure of N″-sulphonyl-N-alkylideneformamidrazones

The ¹³C and ¹H NMR spectra of N″-sulphonyl-N-alkylideneformamidrazones have been recorded and the chemical shifts assigned. The tautomeric structure proved to be an N²- alkylidenehydrazide sulphonylimide. The barrier to rotation around the CN¹ bond was estimated from variable from temperature ¹H NMR measurements, and the Z/E ratio and its solvent dependence was investigated.     

The One Step Synthesis of 2-(2-Bromo-5- methoxyphenyl)-5-(3-arylidene)-1,3-thiazolo[3,2-b]- 1,2,4-triazol-6-(5H)-ones and the Evaluation of the Anticonvulsant Activity

A smooth one-step synthesis of 2-(2-bromo-5-methoxyphenyl)-5-(3-arylidene)-1,3-thiazolo[3,2-b]-1,2,4-triazol-6-(5H)-ones (4a–n) is described. The newly prepared compounds are characterized by analytical and IR, ¹ H NMR, ¹³ C NMR, and FABMS spectral analysis. A few compounds are screened for anticonvulsant activity. Compounds 4i and 4n exhibit promising anticonvulsant activity and are recommended for further studies.     

Carbon-13 NMR study of some isomeric n-nitroindazole derivatives

The ¹³C NMR spectra of 1,5- and 2,x-dinitroindazoles “x=4-7” and 3-bromo-1,x-dinitroindazoles are recorded and discussed. The data on he 2,x-dinitroindazoles confirm our previous structurea assignment based on ¹H NMR spectroscopy. The ¹³C NMR spectra established that in the novel 3-bromo-1,x-dinitroindazoles the N-nitro group is attached at N-1.     

α-氨基膦酸酯衍生物的合成及其表征

合成了一系列N端含有均三唑并噻二唑的α-氨基膦酸酯衍生物, 其结构经过红外、核磁共振氢谱、磷谱、质谱和高分辨质谱等确证.     

Study of alkaloids from the flora of the Siberian and Altai regions. 6. Crystal and molecular structure of songorine Z-oxime

Oximation of songorine afforded a mixture of its Z- and E-oximes. The crystal and molecular structure of the Z-isomer was established by X-ray diffraction analysis. Its structure was also confirmed by the spectral data (2D ¹H—¹H and ¹³C—¹H NMR spectroscopy and mass spectrometry). The structure of isomeric E-oxime was established by comparing its NMR spectroscopic data (¹H and ¹³C) with the data for the Z-isomer.     

Reactions of pentachloro-2-nitrobutadiene with some aliphatic and heterocyclic thiols and a crystallographic study

In this study, S-, S,S- and S,O-substituted novel nitrodiene compounds were synthesized. Cyclization products were formed when difunctional nucleophiles were used. The stereoisomerism of a heterocyclic nitrodiene is discussed with the help of XRD studies. The structures of all compounds were characterized by spectroscopic methods (FT-IR, ¹H NMR, ¹³C NMR, ¹⁹F NMR, MS) and microanalysis.     

Studies in tertiary amine oxides. Part V—carbon-13 nuclear magnetic resonance spectra of some N-aryl tertiary amines,the corresponding N-oxides and the meisenheimer rearrangement products

The carbon-13 NMR spectra of some N-(2- or 4-nitrophenyl) tertiary amines and their corresponding N-oxides have been analysed. These N-oxides undergo thermal rearrangement to O-arylhydroxylamines, for which the ¹³C NMR spectral assignments were also carried out. The N-oxidation effect on the aromatic and aliphatic fragments is calculated.     

Microstructure of polyisoprene produced by cationic polymerization: NMR spectroscopic study

High-resolution ¹H and ¹³C NMR spectroscopy, including two-dimensional heteronuclear experiments, has been used to study the microstructure of polyisoprene produced by cationic polymerization. It is shown that macromolecules resulting from both regular and inverse additions are predominantly composed of trans-1,4-units, while 1,2- and 3,4-units are present in small amounts. NMR spectra demonstrate the absence of cis-1,4-units in the polymer, whereas broad signals (pedestals) are related to the presence of saturated structures. It is proposed to determine the content of trans-1,4-, 1,2-, and 3,4-units in cationic polyisoprene via the combined measurements of intensities of signals in the olefinic regions of ¹H and ¹³C NMR spectra.     

Temperature and solvent variation of the 13C and 1H NMR spectra of r-1,t-2,c-3,t-4-tetrachlorotetralin

Vicinal coupling constants in the ¹H and ¹³C NMR spectra of r-1,t-2,c-3,t-4-tetrachlorotetralin change with temperature and solvent in a manner better explained by conformational equilibration than by intramolecular or solvent-determined distortions.     

Carbon-13 NMR spectra of monosubstituted pyrazines

Carbon-13 NMR chemical shifts and one-bond carbon–hydrogen coupling constants have been obtained at 15·09 MHz. The trends in the carbon chemical shifts obtained for the pyrazines parallel those of monosubstituted benzenes and 2-substituted pyridines, except for the direct effect of substitution where the pyrazines resemble pyridines not benzenes. The substituent effects on the ¹³C NMR spectra are generally quite similar to those in the ¹H NMR spectra. The ¹³C NMR spectrum of the tautomeric hydroxypyrazine has been compared with the ¹³C NMR spectra of 2-, 3- and 4-hydroxypyridines. Hydroxy compounds that can exist as a cyclic amide show a large meta substituent effect on the chemical carbon shift.     

Direct polycondensation of carbon dioxide with xylylene glycols: a new method for the synthesis of polycarbonates

This communication describes the direct polycondensation of carbon dioxide with p- and m-xylylene glycols using the system trisubstituted phosphine/carbon tetrahalide/base as a condensing agent. The polymerization reaction of carbon dioxide with p-xylylene glycol was carried out in the presence of the condensing agent in N,N-dimethylformamide. The yield was at most 81.0% obtained by using the condensing agent tributylphosphine/carbon tetrabromide/N-cyclohexyl-N′,N′,N″,N″-tetramethylguanidine (CyTMG). The structure of the product was determined by means of ¹H NMR, ¹³C NMR, and IR spectroscopy to be that of a polycarbonate. The molecular weight was estimated to be ca. 1 000–2 000 by ¹H NMR analyses.     

A new flavane acid from the fruits of Illicium verum

A new compound, illiciumflavane acid (1), along with 13 known compounds (2–14), were isolated from the fruits of Illicium verum Hook. F. Their structures were elucidated through various spectroscopic methods, including 1D NMR (¹H NMR, ¹³C NMR), 2D NMR (HMQC, HMBC and NOESY) and HRMS. The stereochemistry at the chiral centres was determined using CD spectrum as well as analyses of coupling constants and optical rotation data. Cytotoxicity evaluation of four compounds showed that illiciumflavane acid and (E)-1,2-bis(4-methoxyphenyl)ethene exhibited potential against A549 activities with IC₅₀ values of 4.63 μM and 9.17 μM, respectively.     

Synthesis and Herbicidal Activities of 2-Methylpropan-2-Aminium Methyl 1-(Substituted Phenoxyacetoxy) Alkylphosphonates

Abstract

A series of 2-methylpropan-2-aminium methyl 1-(substituted phenoxyacetoxy) alkylphosphonates were selectively synthesized by reacting the corresponding dimethyl 1-(substitutedphenoxyacetoxy)alkylphosphonates with an excess of 2-methylpropan-2-amine. All the title compounds were identified by IR, ¹H NMR, and ³¹P NMR, some of them were further analyzed by ¹⁹F NMR and ¹³C NMR. Their herbicidal activity was investigated and the results showed that most of the demethylated aminium salts exhibited notable herbicidal activities against Brassica napus L. and Echinochloa crusgalli.

Supplementary materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfer, and Silicon and the Related Elements for the following free supplemental files: Additional text, figures and tables.     

Structural features of a polysaccharide from the leaves of Thea sinensis

A polysaccharide of Thea sinensis, TSA, has been isolated from the fresh leaves as a major fraction of polysaccharides. The mol. wt. was estimated to be 850,000 with [α]_D¹⁵ + 25.5^° (c=0.75, H₂O). The component sugars were determined as L-rhamnose, L-arabinose, and D-galactose in molar ratio of 0.54: 1.0: 0.94. The O-acetyl groups locating on galactose residues position 2 were also identified and the content was 3.8%. The ¹³C NMR spectrum and CrO₃ oxidation of TSA indicated the Rhamnose, Arabinose and Galactose to be in α-, α- and β-configurations, respectively. Methylation analysis, periodate oxidation, partial hydrolysis and ¹³C NMR spectrum showed that TSA is a branched galactoarabinan.     

Regioselective hydrolysis of ketenimines derived from NH-acids and acetylenic esters in the presence of tert -butyl isocyanide under neutral conditions

The regioselective hydrolysis of ketenimines derived from NH-acids, such as 2,2,2-trichloro-N-phenylacetamide or ethyl-2-anilino-2-oxoacetates and acetylenic esters in the presence of tert-butyl isocyanide in a THF/H₂O system (1/1) without any catalysis leads to a diastereomeric mixture of dialkyl 2-[(tert-butylamino)carbonyl]-3-[(2,2,2-trichloroacetyl)anilino]succinates and dialkyl 2-[(tert-butylamino)carbonyl]-3-[2-ethoxy-2-oxoacetyl)anilino]-succinates in good yields. Dynamic NMR effects were observed in the ¹³C NMR spectra of diethyl 2-[(tert-butylamino)carbonyl]-3-[(2,2,2-trichloroacetyl)anilino]succinate as a result of restricted rotation around the N-aryl single bond. The free energy of activation (ΔG ^#) for this process is 37.9 kJ mol⁻¹ which leads to an observable atropisomerism.     

Carbon-13 NMR Spectra of Peracetylated Derivatives of Methyl L-Arabinofuranoside and Oligosaccharides Related to Arabinoxylan

Abstract

The ¹³C NMR signals of methyl tri-O-acetyl-l-arabinofuranosides were assigned on the basis of heteronuclear shift correlated NMR spectra. From the enzymic digest of barley-hull arabinoxylan two oligosaccharides, i.e., α-l-Araf-(1→3)-β-d-xylp-(1→4)-d-xylp and α-l-Araf-(1→3)-β-d-xylp-(1→4)-β-d-xylp-(1→4)-d-xylp were obtained. The NMR spectra of their per-O-acetylated derivatives were assigned, and discussed.