Mass spectrometric evidence for the anomalous chemical behavior of 11-dehydrothromboxane B2

When we subjected 11-dehydrothromboxane B2 (11-DTXB2), a metabolite of arachidonic acid, to standard chemical derivatization procedures we obtained a mixture of several products. Separation of the components was carried out by gas chromatography and their identification was accomplished through the study of their mass spectra, which are presented here. Anomalous behaviors include methylation of allylic and alcoholic hydroxyl groups by diazomethane, unusually slow derivatization of one of the hydroxyl groups with N,O-bis(trimethylsilyl)-trifluoroacetamide (BSTFA) and etherification of another with ethanol. The underlying causes of these abnormal behaviors are not obvious, but appear to be related, at least in part, to the opening/closure of a lactone ring in the molecule. These observations have some bearing on the development of valid procedures for GC-MS quantification of this important marker of thromboxane A2 synthesis in vivo, and of similar compounds.