Solid-phase synthesis of N-labeled acylpentamines as reference compounds for the MS/MS investigation of spider toxins

A solid-phase route for synthesis of ¹⁵N-labeled acylpolyamines is described. Utilizing alkylation at benzylic N-atom as a key step, ¹⁵N-atoms are incorporated by stepwise construction of the polyamine framework on the solid support. The derivatives were used as reference compounds for the investigation of the MS/MS behavior of spider toxins.     

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.     

Possibilities of multinuclear NMR in the chemistry of heteroorganic compounds

Results of multinuclear NMR studies of some heteroorganic compounds have been presented.According to a report at the conference «Current problems of organometallic chemistry» (May 8–13,1994, Moscow).Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 614–616, April, 1994.     

15N NMR spectral parameters of compounds of the N-methylpyrazole series

The¹⁵N NMR chemical shifts and¹⁵N-¹H SSCCs are presented for substituted N-methylpyrazoles with substituents such as CH₃, NO₂, Br, Cl, NH₂, O=CNH₂, O=CPh, and COOH at the carbon atoms. The¹⁵N chemical shifts of the cyclic atoms of nitrogen and the nitro groups are discussed as well as the geminal and vicinal SSCCs of the ring nitrogen atoms with the hydrogen atoms of the CH and CH₃ fragments.N. D. Zelinskii Institute of Organic Chemistry, Russian Academy of Sciences, 117334 Moscow. D. I. Mendeleev Chemico-Technological Institute, Moscow, Translated fromIzvestiya Akademii Nauk, Seriya Khimicheskaya, No. 11, pp. 2554–2561, November, 1992.     

The Molecular Structure and NMR Properties of P-Phosphinoylmethyl Aminophosphonium Salts

The molecular structures of two aminophosphonium salts (bromide and tetrafluoroborate) have been determined by X-ray analysis. They have similar conformations and hydrogen bond (HB) networks: the N–H acid proton is bonded to the anion and, in the case of the fluoroborate, to the oxygen atom of the phosphine oxide, forming a pseudo six-membered ring closed by a weak N–HO intramolecular hydrogen bond (IMHB). These compounds have been studied by multinuclear NMR in solution, including the ¹⁵N-labeled derivatives, to determine a complete set of coupling constants. A coupling of 1.5 Hz between the ¹⁵N and the ³¹P nuclei, separated by three bonds, was observed experimentally for the bromide in CDCl₃ solution, which appears to be a classical ³ J _N-P across the covalent bonds and not a ^3h J _N-P across the IMHB.     

2-Polyfluoroalkylchromones. 13. Synthesis and nitration of 6,8-dibromo-2-trifluoromethylchromone

The nitration of 6,8-dibromo-2-trifluoromethylchromone depends on the reaction conditions and affords 6,8-dibromo-5-nitro- or 3,6,8-tribromo-5-nitro-2-trifluoromethylchromones. The structures of these compounds were determined from the ¹H and ¹³C NMR spectroscopic data.     

Hypervalent triphenyl and diphenyl tin coordination compounds derived from 2-(1H-benzimidazol-2-yl)phenol

Reactions of 2-(1H-benzimidazol-2-yl)phenol (1) and SnPh₃Cl, SnPh₂Cl₂ and SnCl₄ were investigated. One tetracoordinated triphenyltin(IV) compound: triphenyltin-2-(1H-benzimidazol-2-yl)phenolate] (3) and its adducts: [O → Sn] dimethylsulfoxide triphenyltin-[2-(1H-benzimidazol-2-yl)phenolate] (4), [O → Sn] aqua triphenyltin-[2-(1H-benzimidazol-2-yl)phenolate] (5) [O → Sn] ethanol triphenyltin-[2-(1H-benzimidazol-2-yl)phenolate] (6), [N → Sn] pyridine triphenyltin-[2-(1H-benzimidazol-2-yl)phenolate] (7), where 1 acts as a monodentate ligand bound through the phenol oxygen, were obtained. In the pentacoordinated compounds 4-7, the tin atom has tbp geometry. The three phenyl groups are in equatorial positions, whereas the benzimidazole and the Lewis base are in apical positions. Two hexacoordinated tin compounds: diphenyltin-bis[2-(1H-benzimidazol-2-yl-κN)phenolate-κO] (8), dichlorotin-bis[2-(1H-benzimidazol-2-yl-κN)phenolate-κO] (9) bearing two bidentate ligands are reported. The coplanar ligands in 8 and 9 form six membered rings by oxygen and nitrogen coordination. The tin geometry is all-trans octahedral. In 8 the two phenyl groups, and in 9 the two chlorine atoms are perpendicular to the plane of the ligands. Compounds were identified in solution mainly by ¹H, ¹³C and ¹¹⁹Sn NMR and in the solid state by X-ray diffraction analysis.     

H,C, Pt NMR study on platinum(II) interaction with sulphur containing Amadori compounds

The NMR study on the interaction of Pt(II) with Amadori compounds is performed. The Amadori compounds are derived from the reaction of β-d-glucose with l-cystine leading to N,N′-di-(1-deoxy-β-fructos-1-yl)-l-cystine [FruCyscys], and with l-methionine leading to N-(1-deoxy-β-fructos-1-yl)-l-methionine [FruMet].     

Calorimetric study of polymerizing complexes of acrylamide with cobalt(ii) nitrate

Thermal polymerization of complexes of acrylamide with Co^II nitrate has been investigated by differential scanning calorimetry. The conditions of the synthesis of the samples and their treatment have been found to affect the thermal and polymerization properties of the complexes. The existence of several structural modifications of the complex differing noticeably in their polymerization ability has been revealed.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1414–1417, August, 1993.     

Ionic liquid promoted regioselective monobromination of aromatic substrates with N-bromosuccinimide

Aromatic substrates were monobrominated regioselectively with NBS in the ionic liquid 1,3-di-n-butylimidazolium tetrafluoroborate [bbim]BF₄ in 5 min at 28°C in excellent isolated yields (80-98%) in the absence of a catalyst.     

Simple and regioselective oxyiodination of aromatic compounds with ammonium iodide and Oxone

A simple method for the iodination of aromatic compounds using NH₄I as the iodine source and Oxone^® as the oxidant is described.     

Microwave assisted synthesis of an unusual dinitro phytochemical

A novel dinitro secondary metabolite, 2-nitro-4-(2^′-nitroethenyl)phenol from a marine source, has been prepared via highly accelerated, microwave assisted, nitration reactions using mild reagents. ipso-Substitution of a carboxy group by a nitro group is discussed.     

p-Toluenesulfonic acid catalyzed regiospecific nitration of phenols with metal nitrates

Highly regiospecific mononitration of phenols and substituted phenols is accomplished employing a metal nitrate and a catalytic amount of p-toluenesulfonic acid in acetone. An exclusive ortho-selectivity was observed with excellent yields. A variety of metal nitrates were used to obtain o-nitrophenols exclusively in good to excellent yields. The use of p-toluenesulfonic acid is key for the selectivity observed.     

Evaluation of the reactivity of new activated difluoroaromatic compounds

To evaluate the reactivity of new difluroroaromatic compounds in nucleophilic substitution, the positive charges on carbon atoms of C−F bonds were calculated using the quantum-chemical semiempirical PM3 method. A correlation between the charges calculated and the chemical shifts in the¹⁹F NMR spectra was established. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 623–625, April, 1998.     

New unsymmetrical difluoroaromatic compounds and estimation of their reactivities in nucleophilic substitution

A series of previously unknown unsymmetrical difluoroaromatic compounds, viz., p-fluorobenzoylphenyl(p-fluorophenyl)-substituted imidazoles, pyrazines, and quinoxalines, were synthesized according to multistep procedures with the use of chloral as the key compound. The reactivities of the resulting difluoroaromatic compounds were estimated based on ¹⁹F and ¹³C NMR spectral data and the results of quantum-chemical calculations. The calculated charge densities on the C_ipso atoms correlate linearly with the experimental chemical shifts in the ¹⁹F and ¹³C NMR spectra. Difluoroaromatic compounds, which are characterized by _F > –110 and _C > 163 and by the charge density on the C_ipso atom higher than 0.08 e, are sufficiently activated to be used for the preparation of high-molecular-weight polyethers.     

A set of triple-resonance nuclear magnetic resonance experiments for structural characterization of organophosphorus compounds in mixture samples

The ¹H, ¹³C correlation NMR spectroscopy utilizes J_CH couplings in molecules, and provides important structural information from small organic molecules in the form of carbon chemical shifts and carbon-proton connectivities. The full potential of the ¹H, ¹³C correlation NMR spectroscopy has not been realized in the Chemical Weapons Convention (CWC) related verification analyses due to the sample matrix, which usually contains a high amount of non-related compounds obscuring the correlations of the relevant compounds. Here, the results of the application of ¹H, ¹³C, ³¹P triple-resonance NMR spectroscopy in characterization of OP compounds related to the CWC are presented. With a set of two-dimensional triple-resonance experiments the J_HP, J_CH and J_PC couplings are utilized to map the connectivities of the atoms in OP compounds and to extract the carbon chemical shift information. With the use of the proposed pulse sequences the correlations from the OP compounds can be recorded without significant artifacts from the non-OP compound impurities in the sample. Further selectivity of the observed correlations is achieved with the application of phosphorus band-selective pulse in the pulse sequences to assist the analysis of multiple OP compounds in mixture samples. The use of the triple-resonance experiments in the analysis of a complex sample is shown with a test mixture containing typical scheduled OP compounds, including the characteristic degradation products of nerve agents sarin, soman, and VX. The viability of the approach in verification analysis is demonstrated in the analysis of the 30th OPCW Proficiency Test sample.     

Reaction of η-enone and enal-platinum(0) complexes with Lewis acidic compounds

Reaction of η²-enone and enal-platinum(0) complexes Pt(CH₂CHCOR)(PPh₃)₂ (R=H, Me) with Lewis acidic compounds BX₃ (X=F, C₆F₅) afforded adducts formed by coordination of boron to oxygen of the carbonyl group. The X-ray structure determination of the adduct formed from B(C₆F₅)₃ and η²-methylvinylketone complex showed no strong interaction between Pt and carbonyl carbon. In contrast to the inability of the palladium(0) η²-enone complexes to form any Me₃Al adduct, η²-cyclohexenoneplatinum(0) complex formed an isolable adduct with Me₃Al, the structure of which was also confirmed by X-ray analysis. The NMR spectral parameters (Pt-C, Pt-P and P-P coupling constants) of these adducts were compared with those of the original η²-enone or enal-platinum(0) complexes as well as the ordinary η³-allylplatinum cation [Pt(PPh₃)₂(MeCHCHCH₂)]⁺.     

Silica-supported perchloric acid and potassium bisulfate as reusable green catalysts for nitration of aromatics under solvent-free microwave conditions

Silica-supported perchloric acid and bisulfate (SiO₂/HClO₄ and SiO₂/KHSO₄) have been developed as reusable green catalysts for nitration of aromatic compounds using NaNO₂ in acetonitrile medium under conventional and solvent-free microwave conditions. The reaction times under microwave irradiation are significantly shorter than conventional method even though the yields obtained in microwave-assisted reactions are comparable with those obtained under reflux conditions.     

Synthesis and extraction properties of oxathiacrown compounds containing benzyl groups

8-Benzyl-1.4-dioxa-7,10-dithiacyclododecane and 11-benzyl-1,4,7-trioxa-10,13-dithiacyclopentadecane were obtained by the interaction of (2,3-dibromo-1-propyl)benzene with 1,8-dimercapto-3,6-dioxaoctane and 1,11-dimercapto-3,6,9-trioxaundecane. The extracting ability of the obtained compounds has been studied in relation to Sr²⁺ and Pb²⁺ ions from aqueous solutions in the presence of anions of various degrees of hardness with determination of the metal content by a radiometric method. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 244–249, February, 2006.