M. Ohashi

Alkaloids studies—LIII: The structures of nine new alkaloids from Aspidosperma dasycarpon A. DC.

Abstract The structures of twelve alkaloids (I–XII) isolated from Aspidosperma dasycarpon A. DC. are deduced. Nine of these indole alkaloids are new.

Mass spectrometry in structural and stereochemical problems—XXXIX : Tropane alkaloids☆☆☆

Abstract The mass spectra of a series of tropane alkaloids have been measured and the major fragments identified, largely through the use of deuterium or substituent labelling. The principal bond fissions follow the paths laid down earlier for simple amines, cyclic ketones and alcohols, thus affording characteristic fragmentation patterns, which may prove useful in the characterization of unknown members of this class.

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.

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 structures of five newAspidosperma alkaloids related to uleine

Aus der Rinde des brasilianischen BaumesAspidosperma dasycarpon A. DC. wurden fünf neue Alkaloide (II–VI) isoliert, die das selten vorkommende Uleinskelett besitzen. Die Strukturen wurden durch chemische Korrelation mit Ulein (I) sichergestellt.