Collisional activation spectra of quarternary ammonium cations produced by field desorption are reported. The principal fragmentation pathways of these ions are discussed. Furthermore, it is demonstrated that collisional activation in conjunction with field desorption is useful for the elucidation of the structure of complex organic cations.

Collisional activation spectra of quarternary ammonium cations produced by field desorption

Das Alstonia-Alkaloid Villalstonin liefert bei der Isomerisierung mit Trifluoressigsaure Villamin, welches thermisch in Pleiocarpamin(1) und Macrolin ubergeht. Auf Grund chemischer Reaktionen, spektroskopischer Analysen und Vergleiche wurde fur Macrolin die Struktur 13 abgeleitet. Daraus folgt fur Villamin die Formel 10 und schliesslich 2 fur Villalstonin.

The structure of the alstonia alkaloid villalstonin

Field desorption mass spectrometry quaternary ammonium salts

During the introduction of an organic compound into the mass spectrometer thermal reactions can take place before the ionisation process, thus changing the structure of the compound. On the basis of known experimental results the following reactions, which are independent of electron bombardment are discussed: decarboxylation, dehydration, loss of alcohols, decarbonylation, decomposition of carboxylic esters, retro aldol reaction and similar processes, retro DIELS-ALDER reaction, isomerisation, disproportionation, hydrogenolysis-dehydrogenolysis, transalkylation, dimerisation, and pyrolysis of quaternary nitrogen containing compounds. Finally, the results of novel model reactions concerning thermal transalkylation are discussed.

Thermische Reaktionen im Massenspektrometer Modellreaktionen zur Untersuchung thermischer Umalkylierungen. 11. Mitteilung über das massenspektrometrische Verhalten von Stickstoffverbindungen

Three spermidine alkaloids – oncinotine (1), neooncinotine (3), and isooncinotine (2) – have been isolated from the stem bark of Oncinotis nitida BENTH. (Scheme 1); 1 and 3 are so far an unseparable mixture. However, by treatment of this mixture with K-t-butoxide, neooncinotine is completely converted into isooncinotine, and oncinotine, the main alkaloid, is obtained in pure form.



The structural assigment of these alkaloids is based on chemical and spectral evidence. Thus oncinotine (1) has been degraded via24 (Scheme 4) and 32 to the putrescine derivative 35 and the piperidine derivative 34 (Scheme 5). Similarly neooncinotine (3) and isooncinotine (2), have given 34 along with the 1, 3-diaminopropane derivative 36 (Scheme 5). The major decomposition pathways of 24, 35 and 36 in the mass spectra are described in Schemes 8, 6 and 7 respectively. The absolute configuration of 1, 2 and 3 is derived by chiroptical correlations with (R)-(−)-N-methylconiine (38).

Über die Struktur der makrocyclischen Spermidin‐Alkaloide Oncinotin, Neooncinotin und Isooncinotin. 151. Mitteilung über Alkaloide

Es wurde das Verhalten quartarer Alkaloidsalze im Massenspektrometer untersucht. Dabei fanden sich drei prinzipiell verschiedene Verhaltensweisen: 

1
Angriff des Anions an der N(b)-Methylgruppe unter Bildung des tertiaren Amins (Demethylierungsbase)und des Methylhalogenids.

2
Thermischer HOFMANN-Abbau unter Bildung eines ungesattigten Amins (HOFMANN-Base) und des Halogenwasserstoffs.

3
Angriff des Anions an einem der drei anderen N(b)-Substituenten unter Bildung eines tertiaren Amins und Eintritt des Halogenatoms in dieses (Substitution).

M. Hesse

Papers

Das massenspektrometrische Verhalten quartärer Stickstoffverbindungen 1. Mitteilung