The mass spectra of the 4,4-dimethyloxazoline derivatives of some conjugated hydroxy ene-yne C17 and C18 fatty acids

The mass spectra of the 4,4-dimethyloxazoline derivatives from various fatty acids with a hydroxy group in conjugation with conjugated double-triple bonds (7-hydroxy-trans-10-heptadecene-8-ynoic acid; 7-hydroxy-trans-10, 16-heptadecadiene-8-ynoic acid; 8-hydroxy-rans-11-octadecene-9-ynoic acid; 8-hydroxy-trans-11, 17-octadecadiene-9-ynoic acid) have been examined and compared with their analogous nonhydroxy derivatives. The position of the hydroxy group was unequivocally proven by characteristic odd-numbered fragment peaks, explainable by α-cleavage at the hydroxy group at the oxazoline end of the molecule. The weak ions produced by α-cleavage at the other side of the hydroxy group indicated that the hydroxy group must be in conjugation with the ene-yne system. Fragments that allow one to distinguish between ene-yne or yne-ene systems were absent. In conjunction, the weak molecular ion and the more intense M-18 ion could confirm the molecular weight of each fatty acid. This work was presented in parts at the Second International Symposium of Natural Products and Their Applications in Concepción/Chile (30.11.-2.12.94). (Title of the symposium in Spanish is II Simposio internacional de productos naturales y sus applicaciones.)