Synthesis and mass spectrometry of benzoxazoline, dimethyloxazoline and 4-phenyloxazoline derivatives of polyunsaturated fatty acids.

Cyclic nitrogen moieties have proved to be of great value for the mass spectrometric location of double bonds in polyunsaturated fatty acids. However, their synthesis has traditionally required long reaction times and/or high temperatures. Recently, we introduced a one-pot, high-yield, mild and efficient method for the synthesis of various fatty acid amide derivatives. We have now extended this procedure to include the synthesis of benzoxazoline, dimethyloxazoline and 4-phenyloxazoline analogs of a series of fatty acids containing 18 to 22 carbon atoms and 0 to 6 double bonds. A comparison of the mass spectral properties of the three derivatives of these saturated and unsaturated fatty acids is described.

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