Pyrrolizidine alkaloids of the endemic Mexican genus Pittocaulon and assignment of stereoisomeric 1,2-saturated necine bases

Pittocaulon species contain mixed profiles of macrocyclic 1,2-unsaturated pyrrolizidine alkaloids and angeloylesters of different 1,2-saturated necine bases. A GC-MS method for an unequivocal assignment of the stereoisomeric 1,2-saturated necine bases and their discrimination by NMR is presented.