J. M. Wilson

Mass spectrometry in structural and Stereochemical problems—XXXIV : Aromatic methyl and ethyl ethers☆☆☆

Abstract The behavior under electron impact of a series of aromatic methoxy and ethoxy compounds has been observed. The more common fragmentation processes are interpreted and in some cases the differences among spectra of positional isomers can be explained.

Pyrroles and related compounds—X : Mass spectrometry in structural and stereochemical problems—XC Mass spectra of linear di=, tri- and tetrapyrrolic compounds☆☆☆

Abstract Mass spectra of 55 di-, tri- and tetra-pyrroles (Table 1) are recorded (Table 2); these include prodigiosin and five bile pigments. The factors affecting the various types of cleavages observed are discussed. Fragmentations of the side-chains usually follow similar patterns to those observed with mono-pyrroles, although, with pyrromethanes, cleavage of alkyl or carboxylic ester groups neighbouring the methylene bridge may be favoured by the formation of pyrromethene-like species or tricyclic pyrromethenes respectively. Cleavages between the nuclei are profoundly affected by the nature of the linkage involved e.g. pyrromethanes and pyrroketones undergo fairly ready inter-nuclear fragmentation, whereas the pyrromethenes (as might be expected) are much more stable, and cleavage of pyrrole-pyrrole bonds (as in prodigiosin) appears to be a very unfavourable process.

Determination of mass spectra of non-volatile substances

Ein einfaches Glas-Einlass-System wird beschrieben, das die direkte Einführung von organischen Substanzen in die Ionisationskammer eines Massenspek trometers gestattet. Es ist somit möglich Massenspektren von Substanzen zu bestimmen die man bisher nicht aufnehmen konnte. Beispiele werden angeführt.

Massenspektroskopie und ihre Anwendung auf strukturelle und stereochemische Probleme, 15. Mitt.1: Steroidsapogenine

Es wurden die Massenspektren einer Reihe von Steroidsapogeninen gemessen und Strukturen fur die wichtigsten Fragmentierungsionen vorgeschlagen. Steroidsapogenine geben ein charakteristisches Fragmentierungsmuster, das zur Identifizierung dieser Verbindungen herangezogen werden kann sowie Ruckschlusse auf bestimmte, Substituenten zulast.

Mass spectrometry in structural and stereochemical problems XXIII: Some observations on the mass spectral fragmentation of Δ1- and Δ4- 3-keto steroids

a , β-Unsaturated ketones possessing the grouping Download full-size image , such as Δ 1 - and Δ 4 -3-keto steroids exhibit a characteristic mass spectral peak in the high mass range at M-42, corresponding to the loss of the carbonyl function and the adjacent methylene grouping. This characteristic feature has been confirmed by deuterium labelling, during the course of which there was made the unexpected observation that deuterium exchange of Δ 1 -3-keto steroids leads to the introduction of three, rather than the expected two deuterium atoms. The third deuterium atom was shown to be located at C-2 and a plausible reaction path for this observation is outlined.

Mass spectrometry in structural and stereochemical problems—XIX : Akuammicine and related alkaloids☆

Abstract The mass spectral fragmentation patterns of akuammicine, dihydroakuammicine, tetra- hydroakuammicine and many of their relatives are summarized in the terms of the most characteristic mass spectral peaks. Plausible mechanism can be postulate in most instances for these ions and attention is called to the use of this information in the structure elucidation of alkaloids with a 2-methyleneindoline (I) chromophore.

Mass spectrometry in structural and Stereochemical problems—XXXVI : Alkaloids of periwinkles—27; the mass spectra of stereo-isomers of the sarpagine-akuammidine group

Abstract Mass spectra have been measured of members of the sarpagine-akuammidine group differing in stereochemistry at C-16. Attention is called to possible fallacies in expecting analogous fragmentation behavior of closely related compounds (N (a) —H vs. N (a) —Me) if the mechanism of a specific fragmentation is not known. Attention is drawn to the structural information which can be gained from thermal decomposition processes prior to electron impact. The mutual advantages of an all-glass and a direct inlet system are discussed.

Mass spectrometry in structural and stereochemical problems—XXXIII : Colchicine alkaloids

Abstract Mass spectra have been measured for a series of colchicine alkaloids and correlations between spectra and structure have been made. The results indicate that mass spectra will be of assistance in structure determination of such naturally occurring tropolones.

Mass spectrometry in structural and stereochemical problems—XXXVII. : Tropone and tropolone derivatives☆☆☆★

Abstract The general observation is made that on electron impact the molecular ions of tropone derivatives eliminate carbon monoxide as a neutral molecule and the resultant ions behave as benzene derivatives. Exceptions from this rule can be explained in terms of the presence of specific structural features.

The structure of theAspidosperma alkaloid compactinervine

Es wird über die Isolierung eines neuen Alkaloids — Compactinervin — aus der brasilianischen Apocynaceen-ArtAspidosperma compactinervium Kuhlm. berichtet. Durch massenspektroskopische und Kernresonanz-Messungen und chemische Umwandlungen konnte gezeigt werden, dass es sich beim Compactinervin um 19,20-Dihydroxy-19,20-dihydro-akuammicin handelt. Seine vollständige Stereochemie sowie die des verwandten Alkaloids Lochneridin konnte abgeleitet werden. Compactinervin stellt die erste Verbindung vom Akuammicin-Typ dar, die aus einerAspidosperma-Art isoliert worden ist.