Positive desorption chemical ionization/tandem mass spectrometry of natural isomeric morphinans: Regioselectivity of protonation, positional and stereochemical effects upon decomposition

Ammonia chemical ionization tandem mass spectrometry in structure determination of alkaloids. I. Pyrrolidines, piperidines, decahydroquinolines, pyrrolizidines, indolizidines, quinolizidines and an azabicyclo[5.3.0]decane

CI-MS/MS of alkaloids with ammonia reagent gas and collision-induced dissociation provides unique structural information for certain mono- and bi-cyclic alkaloids. This technique was applied to solve the structures of 195C, a 4,6-disubstituted quinolizidine alkaloid found in frog skin and an ant, and 275A, a novel 3,5-disubstituted azabicyclo[5.3.0]decane found in frog skin.

An investigation of site-selective gas-phase reactions of amino alcohols with dimethyl ether ions

The reactions of dimethyl ether ions with neutral amino alcohols were examined in both a quadrupole ion trap mass spectrometer and a triple quadrupole mass spectrometer. These ion-molecule reactions produced two types of ions: the protonated species [M+l](+) and a more complex product at [M+13](+). The abundance of the [M+13](+) ions relative to that of the [M+1](+) ions decreases with increasing formal interfunctional distance. Multistage collision-activated dissociation techniques were used to characterize the [M+13](+) product ions, their reactivities, and the mechanisms for their formation and dissociation. In addition, molecular semiempirical calculation methods were used to probe the thermochemistry of these reactions. Reaction at the amino alcohol nitrogen site is favored, and the resulting [M+13](+) addition products may cyclize for additional stabilization. Comparisons were made among the behavior of related compounds, such as alcohols, diols, amines, and diamines. The alcohols reacted only to form the protonated species, but the diols, amines, and diamines all formed significant amounts of [M+13](+) ions or related dissociation products.