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From the carbon-13 spectra of over 40 fatty acids and their derivatives, a set of substituent shift parameters have been derived which uniquely define saturated, unsaturated, polyunsaturated, or cyclopropane fatty acids.Together with model compounds and selectively enriched compounds, lanthanide shift reagents were used to confirm carbon-13 shift assignments. Carbon-13 substituent shifts are interpreted in terms of steric and linear electric field effects and a rationale is given for linear electric field effects. Qualitative agreement between calculated electric field shifts for saturated carbons and the observed shifts has been obtained. Since both steric and linear electric field effects show both angle and distance dependence, they should be considered powerful tools for conformational as well as structural analysis.Carbon-13 chemical shifts are reported for over 40 fatty acids, their methyl esters, triglycerides, and related compounds. Interest in these molecules derives from several sources, among which are their roles as an energy store for animal life and as a major class of tissue components. In their free acid form they are intermediates in fat transport;2 in combined form they represent a very high proportion of fat deposits,2 lipoprotein,2•3 and biological membrane material.4In this study we have been able to derive a set of substituent shift parameters which describes the shifts of all the carbons in fatty acid chains such that the complete structures of unknown fatty acids may now be determined solely from their 13C spectra. Application of these substituent shifts will prove useful in the analysis of fatty acid components in biological tissues.The present study has delineated the significant roles of steric and electric field effects in producing the observed shift differences between alkane and fatty acid spectra. The shifts of the unsaturated carbons, in particular, are strongly dependent on electric field effects and hence on conformation and solvent properties.8 The linear electric field effects can be estimated in a simple way, giving good qualitative agreement with our observed values. We have also, in specific instances, been able to ascribe individual shifts induced by substituent changes to a conformational mechanism. Such information will help to further the application of 13C shift measurements to conformational analysis6 as well as the structural and analytical problems considered here.

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was also isolated which had the following spectroscopic properties: ir spectrum (CH2CI2) showed absorptions characteristic of sulfinates, 1128 (s) and 952 (s), and of sulfinamides, 1085 (s), 1057 (s), 1016 (m), 868 (m); nmr (CDC13) 1,39 (d, 3, J = 7.0 Hz), 2.38 (s, 3), 2.41 (s, 3), 3.70 (quintet, 1,7 = 7.0 Hz), 5.24 (d, 1,7 = 7.0 Hz), 7.2-7.61 (m, 13). This material was presumably /-ephedrine 0-(p-toluenesulfinyl)-p-toluenesulfinamide. Methylmagnesium Bromide. A solution of methylmagnesium bromide (based on 40 mg (1.64 mmol) of magnesium) and 190 mg of (1.64 mmol) TMEDA in 15 ml THE was added dropwise with stirring to a soluton of 250 mg (0.82 mmol) of (i?)-/-ephedrine ptoluenesulfinate [(7?)-7a] in 20 ml of THE at -25°. The reaction was allowed to continue for 1.5 hr. The usual work-up followed by thick-layer chromatography using 20% methylene chloride and acetonitrile solvent mixture as the eluent afforded 63 mg (51 %) of pure methyl p-tolyl sulfoxide: mp 75-76°(lit.3•36 mp 74-75.5°); M25546 +182.5°(c 2.13, acetone) (lit.36 [a]2S546 +180.5°(c 1.61, acetone)). No /-ephedrine p-toluenesulfinamide (3a) could be detected or isolated.A similar result was obtained when this reaction was carried out in the absence of TMEDA.Acknowledgment. The authors thank the Petroleum Research Fund, administered by the American Chemical Society, the Research Corporation for a Frederick Gardner Cottrell Grant, the Merck Fund for an award, and the Research Foundation of SUNY for partial support of this work. We thank Professor J. J. Tufariello for helpful discussions.

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