Application of the computer program GENOA and two-dimensional NMR spectroscopy to structure elucidation

The effectiveness and utility of the combined use of the interactive computer program GENOA and two-dimensional double quantum coherence ¹³C NMR spectroscopy to solve structure elucidation problems are demonstrated with three examples. The substructural information inferred from the ¹H NMR and ¹³C NMR spectra was insufficient to identify the structures of the example compounds. However, with the additional substructural information available from the two-dimensional NMR experiment (which identifies directly bonded carbon atoms), the problems were solved in an extremely efficient manner.     

Modern NMR Spectroscopy of Organolithium Compounds

Modern methods of NMR spectroscopy, in particular the two-dimensional techniques, offer new chances for structure determinations in the field of organolithium compounds, where the combination of ¹H-, ¹³C-, and ⁶⁽⁷⁾Li-NMR spectroscopy is an especially useful feature. Chemical shift correlations which also include the lithium nuclei allow a complete assignment of the ¹H-, ¹³C-, and ⁶Li-NMR spectra and thereby a better characterization of the various aggregates and complexes present in solution. Spatial proximities of ⁶Li and ¹H can be detected by nuclear Overhauser experiments, and ⁶⁽⁷⁾Li-NMR exchange spectroscopy can provide new information with regard to the mechanisms and energetics of dynamic processes like aggregate interchange and complexation. After a short resumé of the experimental aspects of the NMR spectroscopy of organolithium compounds and a discussion of the NMR parameters of these systems, new experimental techniques are presented. Areas of application of these newly conceived one- and two-dimensional NMR experiments are illustrated with selected examples. The results show that even more detailed information about the structure and reactivity of organolithium compounds, which are so important for organic synthesis, can be expected in the future.     

Structure of hyper-branched polyester polyol BOLTORN H2O-COOH. NMR data

The methods of one- and two-dimensional ¹H and ¹³C NMR spectroscopy have been used to study the structure of hyper-branched polyester polyol BOLTORN H2O-COOH and complex Co₁₂[BH20(COOH)] on its basis. It was shown that both compounds have non-stereoregular structure. Paramagnetic ions Co(II) are coordinated both on the surface of the molecule and near the core.     

Detection and quantification of phenolic compounds in olive oil by high resolution H nuclear magnetic resonance spectroscopy

High resolution ¹H NMR spectroscopy has been employed as a versatile and rapid method to analyze the polar fraction of extra virgin olive oils containing various classes of phenolic compounds. The strategy for identification of phenolic compounds is based on the NMR chemical shifts of a large number of model compounds assigned by using two-dimensional (2D) NMR spectroscopy. Furthermore, 2D NMR was applied to phenolic extracts in an attempt to discover additional phenolic compounds. The ¹H NMR methodology was successful in detecting simple phenols, such as p-coumaric acid, vanillic acid, homovanillyl alcohol, vanillin, free tyrosol, and free hydroxytyrosol, the flavonols apigenin and luteolin, the lignans (+) pinoresinol, (+) 1-acetoxypinoresinol and syringaresinol, two isomers of the aldehydic form of oleuropein and ligstroside, the dialdehydic form of oleuropein and ligstroside lacking a carboxymethyl group, and finally total hydroxytyrosol and total tyrosol reflecting the total amounts of free and esterified hydroxytyrol and tyrosol, respectively. The absolute amount of each phenolic constituent was determined in the polar fraction by using anhydrous 1,3,5-triazine as an internal standard.     

Synthesis and structure of nitroethylpyrrolidone carboxylates

3-Methoxycarbonyl-4-phenyl- and 4-(3-pyridyl)-2-pyrrolidones react with 2-aryl(heteryl)-1-nitroethenes to form C³-adducts as one or two diastereomers. Their structure was characterized by the IR, ¹H, and ¹³C NMR spectroscopy, using the two-dimensional correlation spectroscopy.     

Synthesis of 8,16-diarylacridino[4,3-<Emphasis Type="Italic">c</Emphasis>]acridine-1,9-dione derivatives

A number of new acridino[4,3-c]acridinedione derivatives have been synthesized for the first time by condensation of N¹,N⁵-bis(arylmethylidene)naphthalene-1,5-diamines with cyclic 1,3-diketones (cyclohexane-1,3-dione and dimedone). The product structure has been determined by two-dimensional NMR spectroscopy, and a probable reaction mechanism has been proposed.     

Trimethylsilylation - Aid in NMR Analysis of Oligosaccharides. Assigment of 29Si and 13C NMR Spectra of Trimethylsilylated Methyl β-D-Xylobiosides by 2D NMR

The ¹H, ¹³C and ²⁹Si NMR spectra of methyl β-D-xylopyranoside and three methyl β-D-xylopyranosyl-β-D-xylopyranosides have been measured and assigned by two-dimensional NMR spectroscopy. According to the determined proton-proton coupling constants, the ring conformer ratio is essential ly the same in the studied compounds. The assigned chemical shifts provide correct substituent chemical shifts for assignments in the spectra of higher trimethylsilylated xylooligosaccharides. Heteronuclear chemical shift correlated 2D NMR spectroscopy is proven to be a usable experimental method for ²⁹Si NMR line assignment in carbohydrates. The assigned silicon shifts identify the site of glycosidation.     

Correlation NMR spectroscopy of 1,1-dichloro-2,3,4,5-tetraphenyl-1-germacyclopenta-2,4-diene

Assignment of all of the signals in the¹H and¹³C NMR spectra of 1,1-dichloro-2,3,4,5-tetraphenyl-l-germacyclopenta-2,4-diene has been carried out using two-dimensional NMR spectroscopy. Translated fromIzvestiya Akademii Nauk Seriya Khimicheskaya, No. 3, pp. 623–625, March, 1997.     

Synthesis of condensed pregnano[17,16-<Emphasis Type="Italic">d</Emphasis>]triazolines under high pressure

Condensed pregnano[17,16-d]triazolines were produced in 1,3-dipolar cycloaddition of 16-dehydropregnenolone acetate with organic azides at 10 kbar. The structure of the synthesized compounds was determined by using two-dimensional NMR spectroscopy (¹H—¹H COSY, NOESY, HSQC, and HMBC).     

Data of one- and two-dimensional NMR spectroscopy in the study of structure and nature of associations of hyperbranched polyester polyol Boltorn H20-OH

Structure of the hyperbranched polyester of the polyol BOLTORN H20-OH was studied by one- and two-dimensional ¹H and ¹³C NMR spectroscopy in combination with the IR spectroscopy and semiempirical quantum-chemical calculations (method AM1). The polyol structure was shown not to be stereoregular. Three basic types of H-bonding interactions of intra- or intermolecular nature were revealed: C=O...HO, OH...OH, and C=O...HO...HO.     

Identification of modified natural porphyrin isomers: 1H and 13C NMR assignments by NOESY and reverse heteronuclear shift correlation

The efficiency of two-dimensional homonuclear ¹H ¹H NOE spectroscopy in characterizing and fully assigning the ¹H NMR spectra of several isomers of meso- or ring-substituted deuteroporphyrins is demonstrated. The carbon resonances of the skeleton and the substituents were fully assigned using two-dimensional reverse heteronuclear shift correlation spectroscopy.     

Phosphate Derivatives of Natural Lactones. II. Synthesis of Novel Dialkylphosphonates of Arteannuin B

Novel dialkylphosphonates of arteannuin B were synthesized in 45-47% yields by reaction of this cadinanolide with dialkylphosphites. Their structures were established using IR, PMR, ¹³C and ³¹P NMR spectroscopy, and two-dimensional ¹H-¹H NMR (COSY) spectroscopy. The reaction of arteannuin B and dialkylphosphites is highly stereoselective.     

The effect of added alcohols on the micellization process of sodium 8-phenyloctanoate

¹H NMR chemical shifts were examined for mixtures of sodium 8-phenyloctanoate (Na-ω-PhOct) in deuterated aqueous solutions of varying compositions of ethoxylated alcohols. In addition, diffusion-oriented spectroscopy experiments (DOSY) were performed on selected compositions to obtain the diffusion coefficients of the ethoxylated alcohols in the mixed micelles. As expected, the alcohol/surfactant systems exhibit behavior typical to that of an anionic surfactant/alcohol system, in that the critical micellar concentrations and aggregation numbers decrease with increasing alcohol concentration in the mixed solvent. The ¹H NMR aromatic solute induced shifts (ASIS effects) on the alcohol and surfactant protons give significant information on the locations of the alcohol groups in the mixed micelle. All these results are interpreted in terms of the structure of the alcohol/surfactant systems as a function of their composition.     

Synthesis of 14,16-dien-17-yl acetates of androstane series. NMR and mass spectrometry data

On the basis of dehydroepiandrosterone through the Δ¹⁴- and Δ¹⁵-androst-17-ones a series of androsta-14,16-dienyl acetates was obtained, the key compounds in the synthesis of 14-substituted steroids. By the methods of two-dimensional NMR spectroscopy the structure of compounds was proved and a full assignment of signals in the ¹H and ¹³C NMR spectra was performed. With the use of tandem mass spectrometry the main directions of fragmentation of protonated molecules of the synthesized ketones and dienyl acetates were studied.     

Synthesis,structural and conformational study of selected <Emphasis Type="Italic">N</Emphasis>-substituted phthalimides

This paper synthesizes N-substituted phthalimides derived from nitrogen heterocycles as potential 5-HT₄ ligands by using the Mitsunobu reaction. Conformational studies of some of the new compounds have been conducted using ¹H and ¹³C-NMR spectroscopy. Proton and carbon resonances were achieved through the application of one-dimensional selective NOE, two-dimensional NMR techniques-homonuclear COSY-45, NOESY and heteronuclear ¹H-¹³C HMQC correlated spectroscopy- and double resonance experiments. The crystal structure of compound 1 was determined by X-ray diffraction.     

Reaction of Pyridoxal with Hydrophosphoryl Compounds

The products of carbonyl phosphonylation of pyridoxal with dialkylphosphinous acid, alkylphosphinic acid ethyl esters, and phosphorous acid dialkyl (or diphenyl) esters have been obtained for the first time. In some cases, the products of addition are hydrolytically unstable and stabilized by forming internal betaine structures. The reaction of pyridoxal with phosphorous acid in alcohol solutions gives alkoxyfuropyridines possessing the iminium nitrogen atom. The structure and composition of the prepared compounds have been established by ³¹P and ¹H NMR spectroscopy, mass spectrometry (MALDI‐TOF), and X‐ray analysis.     

<Superscript>13</Superscript>C NMR and mass spectrometry of soil organic matter

Liquid state, high resolution ¹³C NMR spectroscopy and mass spectrometry were used to study the composition and structure of soil organic matter (SOM) using soil extracts from two long-term experiments at the Rothamsted Experimental Station. Both one- and two-dimensional NMR techniques were applied. ¹³C NMR sub-spectra of the CH _n (n=0...3) groups, obtained by the Distortionless Enhancement by Polarisation Transfer (DEPT) technique, were used for the elucidation of the qualitative and quantitative composition of humic and fulvic acids in the soils. The chemical structure of SOM was further analysed at the molecular level through Fast Atom Bombardment Mass Spectrometry (FABMS) and Gas Chromatography-Mass Spectrometry (GC/MS). Humic and fulvic extract results were not only compared to each other, but also to the solid state ¹³C NMR results for the complete soil sample.     

Phosphorus Derivatives of Natural Lactones. Synthesis of New Grosshemin Dialkylphosphonates

New phosphorus-containing derivatives of grosshemin were synthesized in 68-70% yield by reacting this guaianolide with dialkylphosphites. Their structures were established by IR, PMR, ¹³C NMR, and ³¹P NMR spectroscopies and two-dimensional ¹H-¹H NMR spectroscopy (COSY). The reaction of grosshemin with dialkylphosphites was found to be highly stereoselective.     

1H and13C spectra of biologically active compounds X. Two-dimensional HH COSY 45° and CH HET CORR spectra of the 18α- and 18β-isomers of glycyrrhetic acid 3-acetate

An assignment of¹H and¹³C NMR signals has been made by the methods of homonuclear two-dimensional spectroscopy, HH COSY (45°), and heteronuclear correlation spectroscopy, CH HET CORR. It has been shown that the range of diastereomeric effects in the¹³C NMR spectra substantially exceeds the effects due to solvents, in contrast to the proton spectra in which these ranges overlap.Institute of Chemistry, Bashkir Scientific Center, Urals Branch, Academy of Sciences of the USSR, Ufa. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 363–368, May–June, 1991.