| Abstract: | The different influence of functional groups on fragmentation reactions is demonstrated by the example of 17β-hydroxy-5α-androstanes. In 17β-hydroxy-5α-androstane the tendency of steroids to be cleaved by rupture of the C-13/C-17 bond under production of a charged centre at C-13 is only enhanced by the hydroxyl group. This influence of the hydroxyl group only predominates as long as substituents are absent which need less energy for ionization than is necessary to ionize the C-13/C-17 bond. Even the presence of a double bond may change the fragmentation pattern completely. If, however, an additional alkyl group is located at C-17, ionization occurs with high probability by elimination of an electron from the OH group connected to C-17. Therefore, other main degradation reactions occur than in molecular ions, having the charge located at C-13. In such compounds even the dominant influence of a conjugated system on the fragmentation reactions is considerably reduced. By etherfication of the hydroxyl group this effect is still very much increased. In the course of this investigation some not yet known degradation reactions, rather typical for the presence of certain groups in the steroid skeleton, were found. These are discussed briefly. |
