Studies on the mass spectra of diterpene orthoesters isolated from Thymelaeaceae species

The mass spectral fragmentation mechanism of diterpene orthoesters (1–12) isolated from Thymelaeaceae species has been elaborated by the aid of high resolution data and metastable measurement. On the basis of the mass-spectral correlations so far established, the structures of three unknown substances have been proved to be tanguticacine (5), daphnegiraldin (6), and 15,16-dihydrodaphnetoxin (13), respectively.     

Electrospray-Ionization Mass Spectrometry. Part III. Acid-Catalyzed Isomerization of N,N′-Bis[(E)-3-(4-hydroxyphenyl)prop-2-enoyl]spermidines by the Zip Reaction

The electrospray tandem mass spectra (ESI-MS/MS) of the three N,N′-bis[(E)-3-(4-hydroxyphenyl)prop-2-enoyl]spermidines 1–3 displayed the same fragment-ion signals. These isomers could not be differentiated by ESI-MS/MS, since their fragmentation patterns are similar. (E,E)-N-(3-[¹⁵N]Aminopropyl)-3,3′-bis(4- hydroxyphenyl)-N,N′-(butane-1,4-diyl)bis[prop-2-enamide] ([¹⁵N(1)])-( 1 ) was synthesized in order to get further information about the fragmentation mechanisms. The comparison of the ESI-MS/MS of 1 and [¹⁵N(1)]- 1 revealed a transamidation, the Zip reaction, under mass-spectral conditions of the [ 1 + H]⁺ ions. Because of this reaction, the three isomers 1–3 could not be distinguished.     

Mass-spectral behavior of 2-azatriptycene and its derivatives

The mass-spectral behavior of 11 aromatic and partially hydrogenated 2-azatriptycenes was investigated. It was established that the principal fragmentation pathway for these compounds is the formation of [M-nH] ⁺ and [M-nH]²⁺ ions (n = 1–6), as well as pseudoretrodiene fragmentation of the heterocyclic ring with the elimination of the atoms in the 2 and 3 positions.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1399–1402, October, 1981.     

Features of the mass spectra of lycoctonine bases with 7,8-methylenedioxy groups

The mass-spectral properties of 21 lycoctonine bases with 1-methyoxy-7,8-methyl-enedioxy groups have been studied and generalized. An influence of a methyl-enedioxy group of the nature of the substituents at C-6 and C-10, and of a ¹⁰⁽¹²⁾ bond on the fragmentation of the alkaloids and their derivatives has been found.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR, Tashkent. Abu Ali ibn Sina [Avicenna] Tadzhik State Medical Institute, Dushanbe. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 389–397, May–June, 1987.     

Generalized characteristics of mass spectra of aromatic compounds and their correlation with the constants of substituants

A scheme for calculating generalized mass-spectral characteristics (indices) is suggested. The indices were formed by using a set of parameters determined experimentally: mass numbers (m/z) and intensities of ion peaks (I). Linear correlations of mass-spectral indices with Hammett constants are established for several classes of aromatic and heteroaromatic compounds (azo compounds, azomethines, amides, triazenes).Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2073–2077, December, 1993.This work was supported by the Russian Foundation for Basic Research (Grant 93-03-4424).     

Mass spectrometry of biologically active substances

The mass spectra of 2- and 4-iminobarbituric acid derivatives were studied in relation to the mass spectra of their oxygen analogs. It is shown that the pathways of fragmentation of the investigated compounds depend on the type of substituent attached to the C₅ atom, the position of the imino and oxo groups in the ring, and the specific mass-spectral properties. The fragmentation was studied by means of low-voltage mass spectrometry and deuterium labeling.See [1] for communication I.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 813–817, June, 1978.     

Unimolecular and collision induced fragmentations of molecular ions of polycyclic aromatic hydrocarbons

The unimolecular and collision induced fragmentation reactions of 19 polycyclic aromatic hydrocarbons have been investigated, using B/E linked scans, accelerating voltage scans, and measurements of appearance energies. From the point of view of simple analytical fingerprinting within isomeric series, B/E linked scans without collision gas offered the best compromise. Attempts to correlate trends observed in fragmentation intensities with various molecular parameters were generally unsuccessful, although some tentative conclusions have been drawn. The evidence concerning fragmentation mechanisms and ion structures is also discussed.     

Quaternary 7-oxo-4,5,6,6a-tetrahydrohomoproaporphine alkaloids ofCochicum kesselringii

On the basis of additional information obtained by PMR and mass-spectral methods and chemical transformations, the structures of regelinone and isoregelinone, isolated fromCochicum kesselringii Rgl., have been established as quarternary 7-oxotetradehydrohomoproaporphine alkaloids.V. I. Lenin Tashkent State University. M. I. Kalinin Turkmen Agricultural Institute. Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 81–84, January–February, 1985.     

Syntheses and Mass Spectral Studies of (E)-1-Alkanesulfonylpropenes and (E)-1-Alkanesulfinylpropenes

(E)-1-Alkanesulfonylpropenes and (E)-1-Alkanesulfinylpropenes have been synthesized in good to excellent yields. Studies correlating molecular structure and fragmentation patterns upon electron impact have been carried out. Double hydrogen rearrangements with the elimination of alkenyl radicals are the most facile fragmentations for (E)-1-alkanesulfonylpropenes. Single hydrogen rearrangement with alkene elemination is however the most important fragmentation for (E)-1-alkanesulfinylpropenes. In this case the hydrogen atom only migrates to the sulfinyl oxygen. These differences in fragmentation patterns between the (E)-styryl-alkyl-sulfones/sulfoxides and the (E)-propenyl-alkyl-sulfones/sulfoxides are attributed to the fact that different ionization sites are involved.     

Electron impact mass spectra of some enols and their alkyl ethers

The mass spectra of α-arylamino-β-hydroxycrotonic acid anilides and their O-methyl and O-ethyl ethers have been determined and the characteristic fragmentation pathways are discussed. The proposed fragmentation patterns are supported by the appropriate metastables and deuterium labelling.     

Electron impact induced cyclizations in 4-chioro-3-(N-aryliminomethyl) (2H) benzopyrans and benzothiopyrans

Intramolecular substitutions leading to cyclizations with the ejection of chlorine have been noticed during mass spectral fragmentation of 4-chloro-3-(N-aryliminomethyl) (2H) benzopyrans and benzothiopyrans. Very interesting ortho effects involving intramolecular substitutions have also been observed in 6-methyl-4-diloro-3-[N-(2-methoxyphenyliminomethyl)] (2H) benzopyran and 6-methyl-4-chloro-3-[N-(2-chlorophenyliminomethyl)]-(2H) benzopyran. The proposed fragmentation mechanisms have been supported by the accurate mass measurements and linked scan studies.     

Conjugated Schiff's bases 16—Substituent effect on electron impact fragmentation of some 1-oxa-4-azabutadienes1

The electron impact fragmentation patterns of some 1-oxa-4-azabutadienes have been determined and supported by the corresponding metastables. The effect of substituents on this fragmentation has been investigated. Satisfactory correlation of intensity ratios of the peaks characterizing the primary fragmentation versus the Brown and Okamoto σ⁺ substituent parameters has been found. The relationship between the substituent parameters and the dissociation energy E_D,C(3)-C(5), estimated with the help of appearance energies has been considered.     

Gas chromatography/electron impact mass spectrometry applied to the differentiation of the positional isomers of long-chain n-alkylcyclohexanones

The influence of n-butyl group position upon the fragmentation behavior of the three isomeric n-butylcyclohexanones was studied. The different fragmentation processes are described and have been applied to the differentiation of the positional isomers of long-chain n-alkylcyclohexanones. In the case of the 4-n-alkyl isomers, an interesting mechanism involving a recyclization is proposed and substantiated by deuterium labelling.     

Understanding the Fragmentation Pathways of Carbocyclic Derivatives of Amino Acids by Using Electrospray Ionization Tandem Mass Spectrometry

Aminoacyl derivatives of aminoadamantanes amantadine and rimantadine have been investigated in regard to their antiviral properties. So far, few studies on the mass spectrometric fragmentation pathway of these compounds have been reported using high-resolution mass spectrometry (HRMS). Two major fragmentation pathways have been observed. For the rimantadine derivatives, losses of rimantadine and N-(1-adamantyl) ethylformamide were described. Similarly, in case of amantadine derivatives, there were losses of amantadine and N-(1-adamantyl) formamide. The loss of the aminoacyl group was common to all of the studied compounds. Understanding the fragmentation mechanism can bring new insight into the characterization of these compounds.     

A mass spectrometric study of dimethyl ester trimethylsilyl ether derivatives of some 3-hydroxydicarboxylic acids

The fragmentation pathways for the dimethyl ester trimethylsilyl ether derivatives of some 3-hydroxydicarboxylic acids have been found by using B/E 2nd B²/E linked scans and isotope substitution techniques. Most of the fragments are due to ionization at silicon, which induces a fragmentation pattern that intimately reflects the structure of the compounds.     

A mass spectrometric study of the dimethyl ester trimethylsilyl enol ether derivatives of some 3-oxodicarboxylic acids

The fragmentation pathways for the dimethyl ester trimethylsilyl enol ether derivatives of some 3-oxodicarboxylic acids have been found by using B/E and B²/E linked scans, collisional activated decomposition and isotope substitution techniques. The trimethylsilyloxy group strongly directs the decomposition processes, and induces a fragmentation pattern that intimately reflects the structure of the compounds.     

Mass Spectral Fragmentation Patterns of 11-(o- and p-R-Anilino)-5H-dibenzo[b,e][1,4]diazepines. IV

The mass spectral fragmentation patterns of eleven 11-(o- and p-R-anilino)-5H-dibenzo[b,e][1,4]diazepines obtained by electron impact have been studied. All the spectra analyzed contain molecular ions, which are base peak for para isomers and the principal fragmentation routes takes place either from the molecular ion, or from (M⁺ - 1) ion. There are, however, some deviations from the general fragmentation pattern in the case of 1,4-dibenzodiazepines with o-amino and p-methoxy substituents caused by direct interaction of these groups with the dibenzodiazepine ring.     

3-(indolylamino)vinyl ketones

The reaction of 5- and 6-aminoindoles with 1,3-diketones leads to 3-(indolylamino)vinyl ketones, which have an enamino ketone structure. A study of the mass-spectral fragmentation of the enamino ketones makes it possible to unambiguously determine the direction of the reaction and also to distinguish and identify isomeric pairs.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 73–78, January, 1977.     

Substituent effects in the mass spectral fragmentation of aryl esters

The mass spectra of m- and p-substituted phenyl acetates, phenyl propionates, phenyl chloroacetates and phenyl fluoroacetates have been determined. The fragmentation of aryl esters is affected by acyl substituents as well as by aryl substituents. Esters having acyl groups of low ionization potential show greater changes in fragmentation because of aryl substituents than those having acyl groups of high ionization potential. Each series has a fairly definite crossover point where fragmentation changes from predominant rearrangement to predominant cleavage.     

Mass spectra of substituted 1,2,3,4-tetrahydro-γ-carbolines

The mass-spectral behavior of substituted 1,2,3,4-tetrahydro--carbolines has been investigated. For the 4-unsubstituted or 4-monosubstituted compounds a characteristic process is the primary retrodiene decomposition of the molecular ion. More characteristic for 4,4-disubstituted compounds is the primary loss of a substituent from position 4.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1047–1049, August, 1973.