Journal of Lipid Research, Vol 18, 77-80, Copyright © 1977 by Lipid Research, Inc.
Analogs of natural lipids. III. Nonequivalence of methyl groups in methylated phospholipids
AA Gallo, AJ Hancock and HZ Sable
The dimethyl esters of a series of diastereoisomeric cyclopentanoid analogs
of phosphatidic acid (A.J. Hancock, M.H. Stokes, and H.Z. Sable. 1977. J.
Lipid Res. 18: 81-92.) have been studied by proton NMR spectroscopy at 60,
100, and 300 MHz. The signals of the P-O-CH3 protons near delta 3.80 show
the expected doubling due to the 31P-1H coupling. In addition, the spectra
of three of the isomers show additional multiplicity the line separation
(in Hz) being proportional to the frequency of the spectrometer. This
multiplicity is due to the nonequivalence of the two methoxyl groups on
phosphorus, predictable from their diastereotopic nature. The same
explanation is proposed for similar observations on other compounds made by
other authors. The practical utility of symmetry considerations in lipid
chemistry is discussed briefly.