Fast atom bombardment mass spectra of keto acid and keto ester phosphoranes

Positive-ion fast atom bombardment mass spectra of 13 keto acid and keto ester phosphoranes were examined. All compounds gave a protonated molecular ion and characteristic peaks at m/z 303, 279, 262 and 201.     

Identification of butyryl derivatives of cyclic nucleotides by positive ion fast atom bombardment mass spectrometry and mass-analysed ion kinetic energy spectrometry

The syntheses of the dibutyryl derivatives of the 3′,5′-cyclic monophosphates of adenosine, guanosine and cytidine are described. The fast atom bombardment mass spectra of these compounds are discussed, together with the mass-analysed ion kinetic energy spectra of their protonated molecular ions and of diagnostic fragments. A protocol for the identification of the derivatives is reported which includes criteria for confirming retention of the cyclic phosphodiester moiety, substitution of both heterocyclic base and ribose ring, and butyrylation of the 2′-O-position. The origins of significant fragments in the spectra are discussed.     

Structural characterization of isomeric triazolocoumarins by high- and low-energy collision spectrometry of M+˙, [M + H]+ and [M − H]− species

Two monometayl- and four dimethyl-triazolocoumarin isomers were characterized by their electron impact mass spectra and by low-energy collision experiments performed on molecular ions M⁺˙ and other fragment ions with an ion-trap mass spectrometer. High-energy collision-activated dissociation measurements were performed on the protonated [M + H]⁺ and deprotonated [M ? H]^? molecular ion obtained by fast atom bombardment and M⁺˙ species produced by electron impact ionization on a double-focusing, reverse-geometry instrument. The data obtained allowed unequivocal structural identification of all the compounds investigated.     

Fast atom bombardment mass spectrometry of salts of substituted methylene bisphosphonic acids and other analogues of pyrophosphoric acid

Fast atom bombardment mass spectra have been obtained of salts of analogues of inorganic pyrophosphoric acid, e.g. substituted methylene bisphonates, and positive ion fast atom bombardment mass spectrometry (FABMS) has proved to be more successful than negative ion FABMS for the analysis of these salts. Owing to the low molecular weight of these analogues, FAMBS of the free acids and the sodium salts does not always give results which are easy to interpret as interference by peaks from the matrix can occur. However, the potassium salts in a 60% glycerol matrix, when bombarded by argon atoms, give good FAB spectra which are relatively free of interfering peaks.     

Soft ionization mass spectrometry of chromanols produces radical cation molecular ions

Several chromanol drug substance candidates exhibit unconventional behavior under the soft ionization conditions of fast atom bombardment and electrospray ionization in the mass spectrometer. Under FAB, these compounds produce radical cation molecular ions rather than protonated molecular ions. Similarly, under acidic mobile phase conditions in an electrospray LC-MS experiment, they produce radial cation molecular ions. Upon changing to a neutral, ammonium acetate-containing mobile phase, the molecular ion species is an ammonium adduct. The two example compounds behave conventionally under negative ion detection, both being free carboxylic acids and forming abundant [M - H](-). Examination of structural analogs indicates that the chromanol, methoxyl and chroman compounds behave this way. Oxidation to a chromanone causes formation of a conventional [M + H](+). Oxidation to a chromene produces even more complex behavior-namely a mixture of [M - H](+), M(+') and [M + H](+). We propose that, for these compounds, elimination of a valence electron to form the radical cation is the more energetically favored reaction than attachment of a proton.     

Mass spectral fragmentation of (S,S)-2-substituted 4,4-diphenyl-3,1-oxazabicyclo[3.3.0]octanes: ring contraction of pyrrolidine and 1,3-oxazolidine in mass spectrometry

The mass spectral behaviour of (S,S)-2-substituted 4,4-diphenyl-3,1-oxazabicyclo[3.3.0]octanes has been studied with the aid of mass-analyzed ion kinetic energy spectrometry and accurate mass measurements under fast atom bombardment (FAB) and electron impact (EI) ionization conditions. Under FAB ionization, all compounds show a tendency to form protonated aldehyde or benzophenone ions and to form protonated 1-azabicyclo[3.1.0]hexane ions, which can further lose an ethylene or cyclopropane from the pyrrolidine ring to produce protonated 1-azabicyclo[1.1.0]butane ions and 3H-azirine ions, respectively. Under EI ionization, a similar fragmentation to that under FAB ionization was observed. The title compounds also show a tendency to yield oxirane ions and oxirenium ions by loss of pyrrolidine and pyrrolidine plus H. Ring contractions of 1,3-oxazolidine by loss of an aldehyde or ketone and of pyrrolidine by loss of an ethylene or cyclopropane were observed under both FAB and EI ionization conditions.     

Fast atom bombardment positive-ion mass spectra of 1,2,2-tris(sulfonyl)hydrazines

Several 1,2,2-tris(sulfonyl)hydrazines, conceived as prodrugs of 1,2-bis(sulfonyl)hydrazines and synthesized as potential antineoplastic and trypanocidal drugs, were analyzed by mass Spectrometry as part of the confirmation of the structure of these compounds. Since these compounds showed activity against several transplanted animal tumors, an understanding of the mass spectral behavior of these agents is important to gain information should clinical trials and metabolic studies be undertaken. In all spectra, protonated molecular ions were observed. Collision activation resulted in considerable fragmentation in the fast atom bombardment spectra. Rearrangement ions formed by elimination of substituted diimides from the middle of the molecule were observed. Other rearrangements involving the alkyl substituent and sulfonyl oxygen also occurred.     

Mass spectral determination of long-chain quaternary amines in mixtures

The analytical utility of several ionization techniques, which are known for their abilities to produce molecular ions of non-volatile/thermally labile compounds, is compared for the determination of the composition of quaternary ammonium salt mixtures derived from beef tallow. The ionization techniques include direct-exposure chemical ionization, field desorption, and fast atom bombardment. While all three techniques produce molecular cations from the salts, fast atom bombardment produces these in greatest relative abundance. Both fast atom bombardment and direct-exposure chemical ionization can be used for characterization of the composition of chain lengths in the mixture. Fast atom bombardment also produces different fragmentation/decomposition ions (imminium ions) than direct-exposure chemical ionization (protonated tertiary amines).     

Hydride abstraction in fast atom bombardment

Under fast atom bombardment conditions, compounds having long alkyl chains may exhibit [M ? H]⁺ as the major quasimolecular ion species, which can lead to incorrect assignment of molecular masses. It is shown that for a long-chain ether the loss of the hydride occurs from the hydrocarbon chain remote from the oxygen. This effect may yield information concerning ionization mechanisms in fast atom bombardment/mass spectrometry.     

Fast atom bombardment mass spectra of O-isopropyl oligodeoxyribonucleotide triesters

The positive and negative fast atom bombardment (FAB) mass spectra of representative dimeric O-isopropyl oligodeoxyribonucleotide triesters were recorded and examined. Features found to be shared among the FAB mass spectra of these compounds yielded important information regarding molecular weight, nucleobase composition and nucleotide sequence.     

Significant differences in site of protonation and extent of fragmentations in chemical ionization and fast atom bombardment mass spectrometry of simple bifunctional compounds. A mechanistic implication for formation of protonated molecules

Chemical ionization (CI) and fast atom bombardment (FAB) mass spectra of simple bifunctional aromatic compounds were compared. Some significant differences were revealed with respect to the site of protonation and extent of fragmentations. Unlike conventional CI ionization, the protonated molecule formation by FAB could not be accounted for by ordinary proton transfer reactions in the gas phase. The observed ions under FAB conditions appear to be regulated by proton exchange reactions through frequent collisions in some particular region between the matrix and the gas phase.     

Fast atom bombardment mass spectra of isobaric/isomeric phosphonium salts

The positive ion fast atom bombardment mass spectra of isobaric/isomeric aryl phosphonium salts typically contain abundant intact cations, which can be used to establish the cationic molecular weight, characteristic ions that can be used to delineate structural subgroups, and fragment ions corresponding to losses of small neutral molecules. Several of the fragmentation pathways were elucidated by parent ion and daughter ion tandem mass spectrometry experiments. Dependence of the fragmentation reactions on functional group substitution suggests that fast atom bombardment mass spectrometry is an excellent method for the differentiation of isobaric/isomeric phosphonium salts used in synthetic organic and industrial catalytic processes.     

FAB-MS/MS法在皂苷结构分析中的应用

皂苷是一类中草药成份中具有生理活性的组份。它们是强极性,热不稳定和较难挥发的化合物。用传统水解法测定其结构手续繁杂,用质谱法测定皂苷的结构近年来日益引起人们的重视[1]。     

甘草次酸及其衍生物的质谱研究

本文通过应用ＥＩ质谱和高分辨质谱对甘草次酸及其衍生物进行研究，阐明了分子离子的各种裂解、重排机理，讨论了主要离子的形成过程以及不同取代基对分子离子峰强度的影响。并用软电离手段──快原子轰击正、负离子（ＰＦＡＢ和ＮＦＡＢ）质谱，使ＥＩ谱上不出现分子离子峰的两个化合物而获得满意结果。     

Charge remote fragmentation of peptides following attachment of a fixed positive charge: A matrix-assisted laser desorption/ionization postsource decay study

A fixed positive charge can be placed at the N-terminus of a peptide by addition of a tris[(2,4,6-trimethoxyphenyl)phosphonium]acetyl group. The usefulness of these charged derivatives has been demonstrated in fast atom bombardment mass spectrometry and in matrix-assisted laser desorption/ionization mass spectrometry. After ion formation and acceleration, these derivatized peptide ions dissociate and their fragment ions can be analyzed in a postsource decay experiment by using a time-of-flight mass spectrometer. The matrix-assisted laser desorption/ionization-postsource decay spectra are very different from what may be expected based on fragment ions observed from protonated peptide molecules. Cleavage of CHR-C(O) bonds dominates to form a series of a type ions. Mechanistic possibilities are evaluated. When aspartic acid residues are encountered, the chemistry radically changes. This appears to be due to the formation of geometrically accessible intermediates that can dissociate via low energy processes. This chargeremote chemistry parallels that for much simpler systems, resulting in spectra that are very easy to interpret.     

Secondary ion mass spectra of organic cationic dyestuffs

Rules for the behavior under fast atom bombardment (FAB) have been established for 15 cationic dyes — quaternary ammonium salts of heterocyclic amines and heterocycles containing quaternary nitrogen atoms with aliphatic substituents. Intense peaks corresponding to the molecular mass of the cationic part of the dyes [M-Hal]⁺ are observed in the spectra of all the derivatives. Fragmentation of the azodyes is determined by the azo group and the heterocyle. The base peaks in the case of compounds containing a quaternary nitrogen atom with aliphatic substituents correspond to the ammonium ion and a fragment of amine type. The results obtained can be used to identify dyes of unknown structure from their secondary ion mass spectra (SIMS).DeceasedTranslated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, 1411–1417, October, 1992     

快原子轰击和电喷雾电离质谱表征烷基苯磺酸盐

用负离子化快原子轰击（ＦＡＢ）和电喷雾电离（ＥＳＩ）质谱并结合碰撞活化解离（ＣＡＤ）质谱方法对烷基苯磺酸盐（ＡＢＳ）进行鉴定。试样在负离子电喷雾电离（ＥＳＩ）过程中不产生碎片峰,但是在ＦＡＢ过程中产生许多碎片、比较这些谱图,就可以区别碎片峰和分子离子峰。线性或支化烷基苯磺酸盐的结构与相对含量可以在离子ＥＳＩ／ＣＡＤ－ＭＳ方法中得到。负离子ＥＳＩ－ＭＳ是快速、有效和可靠的鉴定ＡＢＳ的方法。     

Mass spectrometric study of novel estra derivatives of amino acids and peptides

The mass spectra of novel estra derivatives of amino acids and peptides were studied using electron impact and fast atom bombardment ionization, high-resolution data and mass-analysed ion kinetic energy spectrometry. The characteristic peaks of the basic nucleus of estrogenic steroids, the amino acid sequence of the peptide chain and partial skeletal rearrangement of some of these compounds were observed.     

Fast atom bombardment mass spectrometric study of alkali metal cationized unsaturated C-glycosides

Fast atom bombardment mass spectrometry of alkali metal cationized unsaturated C-glycosides is a useful method for the determination of the molecular masses of these compounds. The mass-analyzed ion kinetic energy and collision-activated dissociation mass-analyzed ion kinetic energy spectra of the pairs of anomers are distinguishable and are characteristic of each anomer.     

Study of structural characteristic features of phenanthriondolizidine alkaloids by fast atom bombardment with tandem mass spectrometry

The mass spectrometric behavior of phenanthroindolizidine alkaloids has been investigated in detail by positive ion fast atom bombardment tandem mass spectrometry (FAB-MS/MS) combined with collision-induced dissociation (CID). The fragmentation has been correlated with the skeleton structure and positions of substituents. The product ions arising from retro-Diels-Alder cleavages differ clearly for compounds with different skeletons. The substituents at C-14 were observed to markedly influence the fragmentation pathway of [M + H](+) ions. A diversity of dissociation behavior initiated by the variation of substituents on the aromatic ring was also observed in the CID spectra. Product ions resulting from loss of CH(4) were obtained for compounds in which both C-6 and C-7 are occupied by methoxy groups. FAB-MS/MS spectra can reflect the connection between the fragmentation behavior and structural features of these phenanthroindolizidine alkaloids rapidly and effectively, and should prove to be a powerful method to determine the structures of related compounds.