Whentris(1,1,1,2,2,3,3‐heptafluoro‐7,7‐dimethyl‐4,6‐octaneodionato)europium (III)—Eu(fod)3—forms a complex with a sufficiently basic functional group in a donor molecule, the change in the magnetic environment of protons near the coordination site causes their nuclear magnetic resonance (NMR) signals to shift to different positions. Consequently Eu(fod)3 and other compounds that similarly affect NMR signals have been designated chemical shift reagents (csr). Because of their ability to shift proton signals, csr substantially increase the amount of structural information that can be obtained from NMR spectroscopy, frequently converting complicated splitting patterns into first‐order spectra. Some generally useful experimental and interpretive csr techniques are described here using methyl petroselinate and methyl oleate as examples. Csr studies of methyl petroselinate reveal that the position of the double bond is at C‐6, and that there is no chain substitution or branching before C‐9. Csr studies of methyl oleate reveal that the position of the double bond is at or beyond C‐9, and that there is no chain substitution or branching before C‐6. Some suggestions are presented for expanding the amount of structural information that can be obtained by csr studies of unsaturated lipid derivatives.

Chemical shift reagents (csr) markedly expand the nuclear magnetic resonance spectra of lipid derivatives thus providing considerably more structural information than it has hitherto been possible to obtain. Preferred csr are rare earth complexes of europium (III) and praseodymium (III) with certain anionic ligands. The use of csr with methyl oleate is described here.

Chemical shift reagents (CSR) can substantially increase the amount of structural information obtainable from NMR studies of saturated and unsaturated lipid derivatives. It is theoretically possible to obtain even more information from CSR studies of unsaturated lipid derivatives by introducing additional CSR‐active functional groups into those molecules through derivatization of their double bonds. However additional CSR coordination sites complicate spectral interpretation, because they increase the number of signals that overlap. Therefore two model compounds were investigated to test the feasibility of attempting other CSR analyses of polyfunctional molecules of unknown structure. This paper describes successful CSR studies of methyl ricinoleate and methyl 12‐hydroxystearate. A series of complementary interpretive techniques was used to assign proton signals in spectra obtained during incremental Eu(fod)3 addition studies with these compounds. Individual proton signals can be observed and assigned for all the protons in methyl ricinoleate, except those on carbons 5, 6 and 7. Information obtained for methyl 12‐hydroxystearate is less specific. Signals are observed for all protons in methyl 12‐hydroxystearate, although in some cases several proton signals overlap.

Improved, high yield procedures for the preparation of unsaturated γ‐lactones (I‐IV) from saturated γ‐lactones (V) are described. Compounds V are first converted to the sodium salts of the corresponding γ‐hydroxy acids (VI) (100%) which are oxidized within fifteen minutes to the γ‐keto acids (VII) (75–85%) by bromine at pH 6‐7.5. Acid‐catalyzed reaction of VII with acetic anhydride at room temperature for fifteen minutes yields γ‐acetoxy‐γ‐lactones (VIII) (70–90%). Pyrolysis of VIII at 200–330° yields I‐IV (70–95%), the composition of which depends on whether strongly acidic contaminants have been completely removed from VIII prior to pyrolysis. In selected cases studied, fractional distillation permits the isolation of pure unsaturated lactones. Nmr has been extensively used to determine purity at each step and the composition of mixtures of I‐IV.

Chemical shift reagents were used to expand the amount of structural information obtainable from NMR studies of derivatives of methyl oleate and elaidate: methyl cis-9,10-epoxystearate, methyl trans-9,10-epoxystearate, methyl erythro-9,10-dihydroxystearate, and methyl threo-9,10-dihydroxystearate.Chemical shift reagent studies of methyl trans-9 ,10epoxystearate and methyl threo-9,10-dihydroxystearate afforded the most information. Chemical shift reagent studies of methyl cis-9,10-epoxystearate and methyl erythro-9,10-dihydroxystearate were decidedly inferior. The series of complementary interpretive techniques previously developed during chemical shift reagent studies of monofunctional fatty esters and model polyfunctional fatty esters were found to be applicable in the current study. However, to avoid ambiguity in several proton assignments, supplementary spin decoupling experiments were necessary.