Pyrolytic studies of phenoxarsine derivatives

The predicted pyrolyzate of phenoxarsine derivatives from their mass spectra is diphenylene oxide. The prediction is verified by the experiment.     

Mass spectrometric studies on azidomorphine derivatives

The mass spectrometric behaviour of nine azidomorphine derivatives have been studied. These compounds proved to have surprisingly specific and selective fragmentation under electron-impact. For 6-deoxy-6-azido-dihydro-isomorphine derivatives (I to V) the main decomposition pathway involves the loss of an N₂ molecule followed by a very rapid and selective fragmentation process. On the other hand, the molecular ions of 6-deoxy-8-azido-pseudomorphine derivatives (VI to VIII) and 6-deoxy-6-azido-14-hydroxy-isocodein (IX) primarily decompose by loss of the N₃ radical. This is due to the allylic effect of the double bond in ring C, corresponding to the chemical behaviour of these compounds.     

Mass spectrometric and pyrolytic studies of diphenylarsine derivatives

The trivalent diphenylarsine derivatives studied gave molecular ions and diagnostic common fragment ions at m/e 229, 227, 154, 153, 152, 151, 77 and 51. The diphenylarsine odd electron ion, m/e 229, undergoes the “ortho coupling” reaction before splitting off the arsenic atom. The correlation between the ion fragmentation and the pyrolytic decompositions is discussed.     

Mass spectrometric studies of 2-aryl-5-acetylthiazole derivatives

Electron ionisation mass spectrometry was usefully used to characterize structurally 2-aryl-5-acetylthiazole derivatives in the gas phase. The compounds show characteristic fragmentation pathways depending on the chemical nature of the substituent at position 2, consisting mainly in the cleavage of both the 1,2- and 3,4-bonds of the thiazole ring. Liquid secondary ion mass spectrometry was applied to study the effects of protonation on the gas-phase unimolecular reactions of this class of compound. Tandem mass spectrometric experiments, carried out on molecular and protonated molecular ions, and also on fragment ions produced in the source, allowed the elucidation of gas-phase decompositions of low-internal energy ions.     

Mass spectrometric studies on gibberellins

Based on the element maps of twenty-two gibberellin methyl esters fragmentations are discussed, which are characteristic of the common structural features as well as structural modification in gibberellin homologues.     

Mass spectrometric study of derivatives of adamantane

Conclusions The mass spectra of adamantane derivatives, substituted at C-2, possess characteristic features distinguishing them from the mass spectra of adamantane derivatives substituted at C-1.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 2, pp. 337–342, February, 1972.     

Mass spectrometric studies of 2-nitrosophenols

The mass spectra of 2-nitrosophenols are independent of the insertion temperature, suggesting that the compounds either do not exhibit tautomerism in the vapour phase or that the enthalpy of isomerization is low. However, their fragmentation patterns suggest tautomerism in the molecular ion.     

Mass spectrometric studies of benzoxazine resorcarenes

Eleven differently substituted 3,4-dihydro-2H-1,3-benzoxazine resorcarenes were studied by electrospray ionisation (ESI) and matrix-assisted laser desorption/ionisation (MALDI) mass spectrometry, using Fourier transform ion cyclotron resonance (FT-ICR) and time-of-flight (TOF) mass spectrometers, respectively. Under ESI conditions it was possible to transfer the intact resorcarenes from solution to the gas phase, yielding [M + H](+) and [M + 2H](+) ions as the main ions observed. Energy increase of the ions induced ready decomposition through successive eliminations of four CH(2)NR groups. Ion-molecule reactions showed that the ionising proton was situated somewhere inside the molecule and could not be reached with neutral reagent gases. In the host-guest complexation experiments, the benzoxazine resorcarenes studied turned out to be poor hosts for alkali metal and ammonium ions. In MALDI experiments, 2,5-dihydroxybenzoic acid proved to be the best matrix for these compounds. However, the intensity of the [M + H](+) ions was low for all compounds, and extensive fragmentation with consecutive elimination of CH(2)NR groups was observed.     

Mass spectrometric study of apogalanthamine and its derivatives

Conclusions 1. The mass spectra of apogalanthamine, its monomethyl ether, and the acetate of the monomethyl ether have been studied.2. The general nature of the fragmentation of these compounds and of alkaloids of the galanthamine type has been shown and specific features of fragmentation due to the presence of the second aromatic ring have been determined.Khimiya Prirodnykh Soedinenii, Vol. 5, No. 6, pp. 519–521, 1969     

Mass spectrometric studies of anomeric glycopyranosyl azides

We studied the mass spectrometric behaviour of peracetylated and underivatized anomeric hexopyranosyl azides and 5-thioglucopyranosyl azides by means of different mass spectrometric techniques. The unstable molecular ions fragment predominantly by losing either N3 radical or N2 molecule. Loss of N2 molecule and the protonation of the derived nitrene were characteristic of the studied compounds. The presence of BF3.Et2O in the ion source is favorable for producing the protonated nitrene form. The protonated nitrene shows a new type of ring expansion rearrangement. The abundances of the [M + H - N2]+ ion makes it possible to identify the anomeric configuration of the azido group.     

Mass spectrometric studies of some novel sulfonamides

A recent paper described the overall 5-endo cyclisation of homoallylic sulfonamides to give pyrrolidines. This reaction was also used to prepare polycyclic systems. Mass spectrometric analysis using classical electron ionisation spectra and accurate mass measurement played a vital role in confirming the proposed structures for the products. These materials were not amenable to newer mass spectrometric methods and this study shows the continuing importance of older techniques.     

Mass spectrometric studies of dithiophosphinato metal complexes

Electron impact induced fragmentation reactions of planar, tetrahedral, octahedral and oligomeric metal dithiophosphinates Me(II)L₂ (L=Et₂PS₂^?; Me(II)=Zn, Cd, Hg, Pb, Co, Mn, Ni, Pd, Pt), Me(III)L₃ (Me(III) = Sb, Bi, In, Rh, Ir) and (Me(I)I)_n (Me(I)/n=Tl/1, Au/2, Cu/4) have been studied. Fragmentation patterns, which are in accordance with metastable peak determinations by linked scans, are reported. In the case of the transition metals the spectra of the complexes show abundant [M]^+· predominantly metal containing ions and, the former being weak and the intensities of the latter being considerably reduced in the case of metal complexes with filled d shells. With planar or tetrahedral transition metal complexes no dependence of fragmentation on the coordination geometry can be observed. The dependence of fragmentation on d configuration, ionization energy of the metal and metal ligand π bonding is discussed. In the case of the oligomeric complexes strong metal-metal interaction is observed even under electron impact.     

Mass spectrometric studies of the pterocarpan skeleton

The mass spectrometric characteristics of the pterocarpan skeleton have been studied with the aid of metastable decomposition (CAD-MIKES), high resolution mass measurements and specific deuterium labeling. New structural rotations have been postulated for the [M - H](+) ions which can explain the fragmentation routes for the pterocarpan skeleton.     

Mass spectrometric studies of cisplatin-induced changes of hemoglobin

This study reports on structural changes of hemoglobin (Hb) that were induced by cisplatin binding. Two techniques, nanoelectrospray quadrupole time-of-flight mass spectrometry (nanoES-MS) and high-performance liquid chromatography with inductively coupled plasma mass spectrometry (HPLC/ICPMS), were developed to facilitate this study. Nanospray MS analyses of cisplatin and Hb reaction mixtures demonstrated that the ion at m/z 616.5, the heme group, increased with an increase of cisplatin concentration, indicating the loss of heme groups from the intact protein. This conclusion was also supported by the increase of cisplatin-alpha or -beta complex formation. The change of the Hb-bound Fe was further investigated by monitoring Fe signals using size-exclusion HPLC/ICPMS. After incubation with cisplatin at clinically relevant concentrations, under physiological conditions, the amount of Fe bound to Hb was reduced while formation of cisplatin-Hb complexes increased. Flow-injection ICPMS analysis of the Fe contents in the low molecular weight fraction (<3000 Da) of the reaction mixtures after size fractionation further demonstrated a corresponding increase of Fe with the increase of cisplatin concentrations. HPLC/ICPMS detected three Hb-cisplatin complexes, one of which eluted at the same retention time as Hb while the other two complexes eluted later than Hb. With clinically relevant concentrations of cisplatin (0.05-1.0 microM) and 10 microM of Hb, the concentrations of the Hb-cisplatin complexes were determined in the range 0.1-64 nM. These results, obtained from nanoES-MS, HPLC/ICPMS, and FIA-ICPMS, demonstrate that cisplatin binding to Hb resulted in the dissociation of the heme group from the intact protein.     

Mass spectrometric studies of 4-oxo-4,5,6,7-tetrahydrobenzofurans

The mass spectra of alkyl and aryl 4-oxo-4,5,6,7-tetrahydrobenzofurans have been determined and the fragmentation patterns are established unambiguously by deuterium labelling in the 5,5,7,7-d₄ position.     

Mass spectrometric characterization of substituted 2-thiazolin-4-one derivatives

Electron ionization mass spectrometry was used for the structural characterization of substituted 2-thiazolin-4-one derivatives in the gas phase. The compounds follow common fragmentation pathways, producing ions whose abundances are dependent on the chemical nature of the substituent at position 2. Collision-induced dissociation tandem mass spectrometric experiments, carried out on both molecular ions and fragment ions produced in the source, allowed the elucidation of gas-phase decompositions. The presence of tautomeric forms is suggested for some ionic species. Rapid identification of a primary or secondary amine moiety at position 2 of the thiazoline ring can be achieved by the detection of characteristic fragmentations occurring both in the ion source and under the collision-induced dissociation regime.