Structure elucidation of some naturally occurring carbonyl compounds upon coupled gas chromatography/mass spectrometry and micro-reactions

Mass spectrometry coupled with gas chromatography is the ideal tool for structure elucidation of minute amounts of target components contained in complex mixtures. Derivatization of these targets and GC/MS analyses of the reaction products may provide decisive information about the parent compound. Removal of oxygen-containing functional groups may be particularly advantageous. Even when the transformation of a target into an appropriate derivative needs several steps, and corresponding reactions furnish low yields, derivatization is useful. Females of the shrimp Crangon crangon contain (S)-3-hydroxydecanoic acid amide and 3-hydroxy-8-methyldecanoic acid amide. Ketones in the desert locust Schistocerca gregaria proved to be 3,7-dimethylheptacosan-2-one and 3,7,15-trimethylheptacosan-2-one. Double bond positions in unsaturated macrocyclic lactones, which occur in halictine bees, can be easily assigned upon GC/MS after the addition of dimethyldisulfide even when they occur as mixtures of isomers.