Mass spectra of 3,3-difluoro-1-halo-2-arylcyclopropenes

The electron ionization (EI) mass spectra of a series of 3,3-difluoro-1-halo-2-arylcyclo- propenes (1, 2) give the fragments [M-X](+) (X: Br, Cl) as the base peaks. A comparison of tandem mass spectrometry (MS/MS) profiles of the m/z 151 ions recorded from compounds 1 and 2 and 3-bromo-3,3-difluoro-1-phenylcyclopropyne (5), 1,1,2,2-tetrafluoro-3-phenyl- cyclopropane (6), 1,1,2,2-tetrafluoroindane (7), and 2,3,3-trifluoroindene (8) suggested that the structure of the derived [M-X](+) fragment ion is more likely that of a substituted cyclopropenium ion. The results from calculations using the density functional theory (DFT) method support this MS/MS analysis.     

Differentiation of diasteromeric α-sulfanyl-β-amino acid derivatives by electrospray ionization tandem mass spectrometry

A set of diastereomeric α-sulfanyl-β-amino acid derivatives, which are important building blocks for pharmaceuticals with potent biological activity, are studied by electrospray ionization tandem mass spectrometry. The collision induced dissociation (CID) spectra of [M+H](+), [M+NH(4)](+), [M+Na](+) and [M+Li](+) of the diastereomers were studied, among them the CID of [M+Na](+) and [M+Li](+) showed consistent differences in the relative abundance of characteristic ions that enabled distinction of the anti isomers from syn isomers. The decomposition pathways for the diagnostic ions were arrived at based on high-resolution mass spectrometry data, multiple mass spectrometry data, deuterium labeling experiments and the mass shift in accordance with the substituents located at different places. Loss of (R(1)-C(6)H(4)-CH=NH) and (Cat-NH-SO(2)R(2)) from [M+Cat](+), where Cat=Na and Li, and the product ions as a results of McLafferty rearrangement involving either >S=O or >C=O group were found to be diagnostic. The McLafferty rearrangement product ions involving >S=O group were more abundant in syn isomers while those involving >C=O group were more abundant in anti isomer. The selectivity observed in the decomposition of [M+Li](+) ions was found to be similar to that of [M+Na](+) ions, but in few cases the differences are marginal in the decomposition [M+Li](+) ions.     

Differentiation of the diastereomeric synthetic precursors of isofebrifugine and febrifugine by electrospray ionization tandem mass spectrometry

Febrifugine is an alkaloid with potent antimalarial activity isolated from Dichroa febrifuga and Hydrangea umbellate, and it exists naturally with its diastereomeric component, isofebrifugine. Here we report the differentiation of diastereomeric synthetic precursors of isofebrifugine (1, cis) and febrifugine (2, trans) and a structurally similar model diastereomeric pair without a halogen substituent (3 and 4) by electrospray ionization (ESI) tandem mass spectrometry. Compounds 1-4 contain a tert-butoxycarbonyl (BOC) substituent, and the collision-induced dissociation (CID) spectra of the [M+H](+), [M+Na](+) and [M+Li](+) ions of 1-4 include the expected product ions corresponding to the loss of C(4)H(8) (isobutene) and of C(5)H(8)O(2) (BOC-H). Loss of C(5)H(8)O(2) is dominant in cis isomers (1 and 3) and/or loss of C(4)H(8) ions is dominant in trans isomers (2 and 4). The decomposition of [M+H](+) ions shows stereoselectivity in the formation of the [M+H-(BOC-H)-C(3)H(5)OBr](+) and [M+H-(BOC-H)-C(6)H(5)CH(2)OH](+) ions. The [M+Cat](+) ions (where Cat = Na or Li) additionally show loss of NaBr and HBr from [M+Cat-(BOC-H)](+), and these product ions are constantly more abundant in cis isomers than in trans isomers. The stereoselectivity for the product ion corresponding to the loss of [(BOC-H)+C(3)H(5)OBr] from [M+H](+) ions differs from that from [M+Cat](+) ions.     

Mass spectra of some new 3,4-dihydro-2[H]-pyridones

Electrospray ionization (ESI) and tandem mass spectrometry (MS/MS) experiments, as well as electronic impact (EI) and chemical ionization (CI) techniques, have been applied to the title compounds 1a-h. The observation of different fragmentation pathways in the three sets of spectra is in accord with different degrees of internal excitation of the investigated precursors. In ESI (methanol as solvent) and CI (methane as reagent gas) spectra, the MH(+) ion represents the most important peak, while the fragments [M - OH](+) and [M - SO](+) are either the base peak or a very abundant peak in the EI mass spectra of these compounds. ESI-MS/MS experiments on the parent ions [MH](+) show that the loss of a fragment of 140 Da corresponding to p-toluenesulfenic acid is common from all the precursors. As well as competitive pathways, the second generation ions have also been elucidated to allow some observations to be made concerning the relationships between structure type and mass spectrometric characteristics.     

Novel benzyl rearrangements in electrospray ionization multistage tandem mass spectra of benzyl 2',3'- didehydro-2',3'-dideoxythymidin-5'-yl H-phosphonate

Several alkyl 2',3'-didehydro-2',3'-dideoxythymidin-5'-yl H-phosphonates were synthesized and analyzed by electrospray ionization multistage tandem mass spectrometry (ESI-MS(n)). Two kinds of novel benzyl rearrangement reactions were observed in ESI - MS(2) of [M + H](+), [M + Na](+) and [M + K](+) of benzyl 2',3'-didehydro-2',3'-dideoxythymidin-5' yl H-phosphonate. Results from tandem mass spectrometry, high-resolution mass spectrometry and control experiments showed that the benzyl migration could undergo a four-membered cyclic rearrangement reaction, and benzyl was essential in the process.     

Using non-covalent complexes to direct the fragmentation of glycosidic bonds in the gas phase

An investigation of the gas phase chemistry of proton bound oligosaccharide (S)-ligand (L) non-covalent complexes, [S + H + L](+) has been carried out using electrospray ionization (ESI) and tandem mass spectrometry in a quadrupole ion trap. When subjected to collision-induced dissociation (CID), these [S + H + L](+) complexes undergo a range of reactions that can be broadly classified into three main types: (1) Simple dissociation into the individual monomers; (2) cleavage of the oligosaccharide to form B-type sequence ions; (3) cleavage of the ligand species. The second type of reaction is particularly interesting as it can produce a "ladder series" of [B(x) + L](+) ions via ligand induced oligosaccharide bond cleavage. This novel gas phase reaction greatly simplifies the sequencing of oligosaccharides. Both the oligosaccharide and ligand were found to influence the type of reaction pathway observed, with the "ladder series" of [B(x) + L](+) ions being favored for permethylated oligosaccharides and for bifunctional ligands. Cytosine is a particularly good ligand at facilitating the formation of [B(x) + L](+) ions. Analogies with condensed phase chemistry of sugars is made and a potential mechanism for ligand induced oligosaccharide bond cleavage is proposed.     

Observation of Na(+)-bound oligomers of quercetin in the gas phase

While developing a liquid chromatography/tandem mass spectrometry method for the analysis of the flavonoid quercitin, it was observed that quercetin (3,3',4',5,7-pentahydroxyflavone) exhibited clustering in both the positive and negative ion mode. Two series of positive ion clusters were observed; the first series corresponds to singly charged [2M + Na](+) at m/z 627.2 to [13M + Na](+) at m/z 3947.5, while the second series corresponds to doubly charged [7M + 2Na](2+) at m/z 1080.4 to [25M + 2Na](2+) at m/z 3798.5. In the negative ion mode, the behavior of quercetin parallels that of apigenin (4',5,7-trihydroxyflavone) in that [M + NO(3)](-), [2M + NO(3)](-), and [3M + NO(3)](-) were observed at m/z 364.1, 666.0, and 968.9, respectively; in addition, quercitin clusters with chloride ions ([2M + Cl](-) at m/z 638.9 and [3M + Cl](-) at m/z 940. 9) were observed. The results of tandem mass spectrometric examination of several cluster ions are reported.     

Characterization of the glycosidic linkage of underivatized disaccharides by interaction with Pb(2+) ions

Electrospray ionization in combination with tandem mass spectrometry and lead cationization is used to characterize the linkage position of underivatized disaccharides. Lead(II) ions react mainly with disaccharides by proton abstraction to generate [Pb(disaccharide)(m)-H](+) ions (m = 1-2). At low cone voltages, an intense series of doubly charged ions of general formula [Pb(disaccharide)(n)](2+) are also observed. Our study shows that MS/MS experiments have to be performed to differentiate Pb(2+)-coordinated disaccharides. Upon collision, [Pb(disaccharide)-H](+) species mainly dissociate according to glycosidic bond cleavage and cross-ring cleavages, leading to the elimination of C(n)H(2n)O(n) neutrals (n = 2-4). The various fragmentation processes allow the position of the glycosidic bond to be unambiguously located. Distinction between glc-glc and glc-fru disaccharides also appears straightforward. Furthermore, for homodimers of D-glucose our data demonstrate that the anomericity of the glycosidic bond can be characterized for the 1 --> n linkages (n = 2, 4, 6). Consequently, Pb(2+) cationization combined with tandem mass spectrometry appears particularly useful to identify underivatized disaccharides.     

Fragmentation patterns of novel dispirocyclopiperazinium dibromides with strong analgesic activity under electrospray ionization tandem mass spectrometry conditions

The fragmentation patterns of a series of dispirocyclopiperazinium dibromides with strong analgesic activity are analyzed by positive ion electrospray ionization mass spectrometry in conjunction with tandem mass spectrometry (ESI-MS(n)). Instead of the parent molecular ions, the fragment ions [M-Br](+) are detected as characteristic double peaks and usually the base peaks. Meanwhile, the fragment ions [M-2Br](2+) are unique for this series of diquaternary ammonium dibromides and show high intensity. Besides the common fragmentation patterns around the carbonyl group, elimination of hydrogen bromide from [M--Br](+) ions is another important pathway. Following the elimination, an interesting rearrangement takes place in the unsaturated spirocyclopiperazine and transforms it into a dihydropyrrole structure, whose fragmentations are similar to its precursor ion in the succeeding steps.     

Analysis of triacetone triperoxide (TATP) and TATP synthetic intermediates by electrospray ionization mass spectrometry

The explosive triacetone triperoxide (TATP) has been analyzed by electrospray ionization mass spectrometry (ESI-MS) on a linear quadrupole instrument, giving a 62.5 ng limit of detection in full scan positive ion mode. In the ESI interface with no applied fragmentor voltage the m/z 245 [TATP + Na](+) ion was observed along with m/z 215 [TATP + Na - C(2)H(6)](+) and 81 [(CH(3))(2)CO + Na](+). When TATP was ionized by ESI with an applied fragmentor voltage of 75 V, ions at m/z 141 [C(4)H(6)O(4) + Na](+) and 172 [C(5)H(9)O(5) + Na](+) were also observed. When the precipitates formed in the synthesis of TATP were analyzed before the reaction was complete, a new series of ions was observed in which the ions were separated by 74 m/z units, with ions occurring at m/z 205, 279, 353, 427, 501, 575, 649 and 723. The series of evenly spaced ions is accounted for as oligomeric acetone carbonyl oxides terminated as hydroperoxides, [HOOC(CH(3))(2){OOC(CH(3))(2)}(n)OOH + Na](+) (n = 1, 2 ... 8). The ESI-MS spectra for this homologous series of oligoperoxides have previously been observed from the ozonolysis of tetramethylethylene at low temperatures. Precipitates from the incomplete reaction mixture, under an applied fragmentor voltage of 100 V in ESI, produced an additional ion observed at m/z 99 [C(2)H(4)O(3) + Na](+), and a set of ions separated by 74 m/z units occurring at m/z 173, 247, 321, 395, 469 and 543, proposed to correspond to [CH(3)CO{OOC(CH(3))(2)}(n)OOH + Na](+) (n = 1,2 ... 5). Support for the assigned structures was obtained through the analysis of both protiated and perdeuterated TATP samples.     

Copper-induced oligomerization of peptides: a model study

In this work, copper-binding of the tetraglycine peptide (Gly-Gly-Gly-Gly) was studied by electrospray ionization mass spectrometry. Experiments were performed under alkaline conditions, in the presence of ethanolamine (pH 10.95). We observed that the presence of copper(II) ions induces the aggregation of the peptide and the formation of copper-bound complexes with higher molecular mass is favored, such as the oligomer complexes [3M+2Cu-3H](+) and [4M+3Cu-5H](+). At 1:1 peptide-copper(II) ion ratio, the singly charged [3M+2Cu-3H](+) oligomer complex is the base peak in the mass spectrum. Metal ion-induced oligomer-ization of neurotoxic peptides is well known in the literature; however, there are very few examples in which such oligomerization was directly observed by mass spectrometry. Our results show that application of short peptides can be useful to study the -mechanism of metal ion binding and metal ion-induced oligomerization of peptides.     

Study of the fragmentation pathway of α-aminophosphonates by chemical ionization and fast atom bombardment mass spectrometry

The diastereoisomers of α-aminophosphonates are key intermediates in the synthesis of enantiomerically pure α-aminophosphonic acids, which are analogs of α-amino acids. Although several methods have been reported for the diastereoselective synthesis of α-aminophosphonates, their mass spectrometry (MS) fragmentation patterns have not yet been fully investigated. The work described here involved a detailed study of the fragmentation of enriched α-aminophosphonate diastereoisomers by chemical ionization (CI-MS) and fast atom bombardment (FAB)-MS. The complete characterization of the different conventional MS fragmentation pathways is represented and this intriguing exercise required the use of tandem mass spectrometry (MS/MS) experiments and high-resolution accurate mass measurements. All α-aminophosphonates gave prominent pseudomolecular ions, protonated molecules [MH](+) , and their fragmentations mainly showed a loss of dimethyl phosphite to give the corresponding iminium ions as base peaks for α-aminophosphonates bearing methylbenzyl and 2,2-dimethylbutyl fragments. The loss of the chiral fragment from the iminium ions bearing the (S)-1-(1-naphthyl)ethyl group gave rise to a base peak due to aryl cations. The nature of all fragment ions were confirmed by high-resolution mass spectrometry (HRMS).     

Mass spectral study of Boc-carbo-beta3-peptides: differentiation of two pairs of positional and diastereomeric isomers

A mass spectral study of a series of new Boc-C-linked carbo-beta(3)-peptides prepared from C-linked carbo-beta(3)-amino acids (Caa) was carried out using liquid secondary ion mass spectrometry (LSIMS), electrospray ionization (ESI) and tandem mass spectrometry. Using the nomenclature of Roepstorff and Fohlman, the positive ion high- and low energy collision-induced dissociation (CID) of [M + H - Boc + H](+) ions of the peptides produce both N- and C-terminus ions, y(n) (+) and b(n) (+) ions, with high abundance and other ions of low abundance. Further, characteristic fragment ions of carbohydrate moiety are observed. In contrast to the CID of protonated peptide acids, the CID of [M - H](-) ions of the beta(3)-peptide acids do not give b(n)(-) ions and show abundant z(n)(-) and c(n) (-) ions which are insignificant in the former. Two pairs of positionally isomeric Boc-carbo-beta(3)-dipeptides were differentiated by the CID of [M + H](+) ions in LSIMS and ESIMS. The fragment ion [M + H - C(CH(3))(3) + H](+) formed from [M + H](+) by the loss of 2-methylprop-2-ene is relatively more abundant in the dipeptide Boc-NH-beta-hGly-Caa(S)-OCH(3) (14) containing the sugar moiety at the C-terminus whereas it is insignificant in Boc-NH-Caa(S)-beta-hGly-OCH(3) (13), which has the sugar moiety at the N-terminus. Similarly, two pairs of diastereomeric dipeptides were distinguished by the high- and low-energy CID of [M + H](+) ions. The loss of 2-methylprop-2-ene is more pronounced for Boc-NH-Caa(R)-beta-hGly-OCH(3) (17) and Boc-NH-Caa(R)-Caa(S)-OCH(3) (18) isomers whereas it is insignificant for Boc-NH-Caa(S)-beta-hGly-OCH(3) (13) and Boc-NH-Caa(S)-Caa(S)-OCH(3) (2) isomers. This was attributed to a favorable configuration of the carbohydrate moiety favoring the 'H' migration involved in the loss of 2-methylprop-2-ene from the [M + H](+) ions of isomers 17 and 18 compared with the unfavorable configuration of the carbohydrate moiety in isomers 13 and 2.     

Molecular ions of ionic liquids in the gas phase

Ionic liquids form neutral ion pairs (CA) upon evaporation. The softness of the gas-phase ionization of field ionization has been used to generate "molecular ions," CA(+*), of ionic liquids, most probably by neutralization of the anion. In detail, 1-ethyl-3-methylimidazolium-thiocyanate, [C(6)H(11)N(2)](+) [SCN](-), 1-butyl-3-methylimidazolium-tricyanomethide, [C(8)H(15)N(2)](+) [C(4)N(3)](-), N-butyl-3-methylpyridinium-dicyanamide, [C(10)H(16)N](+) [C(2)N(3)](-), and 1-butyl-1-methylpyrrolidinium-bis[(trifluormethyl)sulfonyl]amide, [C(9)H(20)N](+) [C(2)F(6)NO(4)S(2)](-) were used. The assignment as CA(+*) ions, which has been confirmed by accurate mass measurements and misassignments due to thermal decomposition of the ionic liquids, has been ruled out by field desorption and electrospray ionization mass spectrometry of the residues.     

Structural characterization of hexoses and pentoses using lead cationization. An electrospray ionization and tandem mass spectrometric study

The analytical potential of the complexation of isomeric underivatized hexoses (D-glucose, D-galactose, D-mannose, D-talose, D-fructose), methylglycosides (1-O-methyl-alpha-D-glucose and 1-O-methyl-beta-D-glucose) and pentoses (D-ribose, D-xylose, D-arabinose and D-lyxose) by Pb(2+) ions, was investigated by electrospray ionization and tandem mass spectrometry (MS/MS). Pb(2+) ions react mainly with monosaccharides by proton abstraction to generate [Pb(monosaccharide)(m) - H](+) ions (m = 1-3). At low cone voltage, a less abundant series of doubly charged ions of general formula [Pb(monosaccharide)(n)](2+) is also observed. The maximum number n of monosaccharides surrounding a single Pb(2+) ion depends on the metal : monosaccharide ratio. Our study shows that MS/MS experiments have to be performed to differentiate Pb(2+)-coordinated monosaccharides. Upon collision, [Pb(monosaccharide) - H](+) species mainly dissociate according to cross-ring cleavages, leading to the elimination of C(n)H(2n)O(n) neutrals. The various fragmentation processes observed allow the C(1), C(2) and C(4) stereocenters of aldohexoses to be characterized, and also a clear distinction aldoses and fructose. Furthermore, careful analysis of tandem mass spectra also leads to successful aldopentose distinction. Lead cationization combined with MS/MS therefore appears particularly useful to identify underivatized monosaccharides.     

Linear free energy relationships in C-N bond dissociations in molecular ions of 4-substituted N-(2-furylmethyl)anilines in the gas phase

The substituent effect on the reactivity of the C-N bond of molecular ions of 4-substituted N-(2-furylmethyl)anilines toward two dissociation pathways was studied. With this aim, six of these compounds were analyzed by mass spectrometry using electron ionization with energies between 7.8 and 69.9 eV. Also, the UB3LYP/6-31G (d,p) and UHF/6-31G (d, p) levels of theory were used to calculate the critical energies (reaction enthalpies at 0 K) of the processes that lead to the complementary ions [C(5)H(5)O](+) and [M - C(5)H(5)O](+), assuming structures that result from the heterolytic and homolytic C-N bond cleavages of the molecular ions, respectively. A kinetic approach proposed in the 1960s was applied to the mass spectral data to obtain the relative rate coefficients for both dissociation channels from ratios of the peak intensities of these ions. Linear relationships were obtained between the logarithms of the relative rate coefficients and the calculated critical energies and other thermochemical properties, whose slopes showed to be conditioned by the energy provided to the compounds within the ion source. Moreover, it was found that the dissociation that leads to [C(5)H(5)O](+) is a process strongly dependent upon the electron withdrawing or donating properties of the substituent, favored by those factors that destabilize the molecular ion. On the contrary, the dissociation that leads to [M - C(5)H(5)O](+) is indifferent to the polar electronic effects of the substituent. The abundance of both products was governed by the rule of Stevenson-Audier, according to which the major ion is the one of less negative electronic affinity.     

Analysis of triacylglycerols with non-aqueous reversed-phase liquid chromatography and positive ion electrospray tandem mass spectrometry

A non-aqueous reversed-phase liquid chromatographic method coupled to electrospray ionisation (ESI) tandem mass spectrometry was developed for the analysis of triacylglycerols (TGs). The synthetic TGs studied were separated according to their equivalent carbon number with a gradient of methanol (containing 0.01% (v/v) formate adjusted to pH 5.3 with ammonia) and chloroform. ESI mass spectra of TGs yielded positive ion current signals for [M + NH(4)](+) and [M + NH(4)-RCOONH(4)](+). The mass spectra also showed signals believed to arise from [M + K](+). Collision-induced dissociation (CID) of the [M + NH(4)](+) precursor ion yielded [M + NH(4) - RCOONH(4)](+), [RCO + 74](+) and [RCO](+) product ions as aids for the structural elucidation of the TGs. In addition, [RCO - 18](+) and small amounts of [RCO - 2](+) product ions were also found. The latter ions were observed only for TGs containing unsaturated fatty acids. CID of ammoniated 1-stearoyl-2-oleoyl-3-linoleoyl-glycerol (18:0/18:1/18:2) indicated that neutral loss of the sn-2 fatty acid was energetically less favourable than loss of the fatty acid from the sn-1 or sn-3 position.     

Characterization of a phosphorylated peptide and peptoid and peptoid-peptide hybrids by mass spectrometry

Nano-electrospray tandem mass spectrometry (nano-ES-MS/MS) was used to record collision-induced dissociation (CID) spectra of a set of peptoid-peptide hybrids and the complete peptoid derived from the phosphopeptide Ac-pTyr-Glu-Thr-Leu-NH(2) (1). The presence of B and Y'-type fragment ions in the tandem mass spectra of the protonated molecular ions [M + H](+) allowed confirmation of sequence similar to mass spectrometric sequence analysis in peptides. In the isomeric peptoid compounds studied, one or several amino acid residues were replaced by peptoid residues (N-substituted glycine residues), which resulted in characteristic tandem mass spectra with differently increased relative abundances of Y'-and B-type fragment ions. The increment of a particular Y'-ion was directly correlated to the position of a peptoid residue present. In addition to these increased peak intensities, other characteristic peaks were also observed compared with the spectrum of reference peptide 1. When a peptoid phosphotyrosine was incorporated, the presence of this residue was apparent from the occurrence of a relatively intense peak at m/z 187 representing the positively charged side-chain of phosphotyrosine, which was almost absent in the spectrum of the reference peptide 1. Since the threonine side-chain had to be translated into the homo peptoid analog this substitution was apparent from the presence of [M + H](+) and fragment ions 14 mass units higher than observed in the spectrum of the reference phosphopeptide 1. The presence of an NLeu peptoid residue could be confirmed by the specific fragmentation of the immonium ion showing an intense peak in its tandem mass spectrum at m/z 57, which results from the loss of an neutral imine molecule leading to a positively charged [C(4)H(9)](+) ion. By means of these mass spectrometric characteristics, all isomeric peptoid compounds could be distinguished from each other and characterized. The methods used appear to be very useful in future studies of peptoids and peptoid-peptide hybrids.     

Elimination of isocyanate and isothiocyanate molecules at the electrospray ionization ion trap, electrospray ionization quadrupole time-of-flight and matrix-assisted laser desorption/ionization time-of-flight tandem mass spectrometry fragmentation of sodium cationized brassitin, brassinin and their glycosides

Fragmentation mechanisms of phytoalexin analogs, including brassitin and brassinin and their glucosylated analogs, have been studied by electrospray (ESI) ion trap (IT) multistage (MS(n), n = 1-4) mass spectrometry, matrix-assisted laser desorption/ionization time-of-flight (MALDI ToF/ToF) and ESI-Q/ToF tandem mass spectrometry techniques. At the fragmentation of sodium adducts a hitherto not described process has been elucidated The proposed mechanism of this process includes cyclization of the brassitin and brassinin cationized adducts through a six-membered cycle of the molecules and the elimination of isocyanate or isothiocyanate from the thio- or dithiocarbamate moiety, giving rise to [M + Na - 43](+) or [M + Na - 59](+) adducts. The elimination of NH=C=O or NH=C=S molecules has been confirmed by the high resolution measurement of the elemental composition of the ions produced and quantum-chemical calculations of the six-membered transition state. Other fragmentation routes include cleavage of an alkane linker, while numerous characteristic hexopyranose pathways are taking place in the glucosylated compounds. The presented theoretical data on the ESI and MALDI behavior of the saccharidic, as well as of the indole aglycon parts, can facilitate structural elucidation of the analogous compounds.     

Structural determination of lysophosphatidylcholines extracted from marine sponges by fast atom bombardment tandem mass spectrometry

A series of lysophosphatidylcholines were isolated from the marine sponge Spirastrella abata by reversed-phase high performance liquid chromatography (HPLC) and analyzed by fast atom bombardment mass spectrometry (FAB-MS). Their structural elucidation was carried out with fast atom bombardment tandem mass spectrometry (FAB-MS/MS). The collision-induced dissociation (CID) of protonated and sodiated molecular ions produced diverse product ions via a series of dissociative processes. Because of the positive charge of the amine group at the end of the molecules, charge-remote fragmentation patterns of specific ions, [M + H](+) or [M + Na](+), were very helpful for the identification of product ions which are characteristic for choline and long hydrocarbon chains substituted at the glycerol back bone. Moreover, the CID-MS/MS spectra of sodium adducted molecular ions for lysophosphatidylcholines yielded common characteristic fragment ions for the choline moiety and characteristic ions [M + Na-103](+), [M + Na-85](+) and [M + Na-59](+) in the higher mass region.