Remote group derivatives: limitations on the effectiveness of pyrrolidide derivatives of oxygen-containing fatty acids.

The pyrrolidides of a number of fatty acids containing oxygen functions (ether linkage, epoxide ring and hydroxyl group) have been prepared and their mass spectra recorded. Detailed analyses of these, supported by accurate mass measurement, indicate that the presence of the oxygen atom has a profound effect on the normal, sequential, mode of pyrrolidide fragmentation. Cleavage adjacent to the oxygen is enhanced, this being most marked in the spectra of those compounds containing an ether linkage. However, further fragmentation of the carbon chain distal to the pyrrolidide group is minimal and prevents any structural information being obtained. These findings indicate that the usefulness of the pyrrolidide derivative for structural elucidation purposes is severely limited in some cases when an oxygen atom is present in the chain. However, for both the epoxy- and hydroxy-fatty acids, complementary derivatization methods are available.