Journal of Lipid Research, Vol 26, 1333-1337, Copyright © 1985 by Lipid Research, Inc.
Uropygiols: confirmation of structure by proton magnetic resonance
PW Wertz, W Abraham, PM Stover and DT Downing
Lipids were extracted from excised uropygial glands of domestic chickens
and the wax diesters were isolated by preparative thin-layer chromatography
(TLC). The diesters were hydrolyzed and the liberated diols were resolved
by boric acid TLC into two fractions. These were investigated by proton
magnetic resonance at 360 MHz of the free diols and of their acetonide
derivatives. The results showed that the cis and trans acetonides, formed
from the erythro and threo isomers of the diols, respectively, could be
distinguished by the degree of magnetic nonequivalence of the two acetonide
methyl groups in each molecule. On the presumption that the cis isomer
should show the greater nonequivalence of the methyl groups, this
configuration was assigned to the acetonides of these diols which had the
lesser TLC mobility on boric acid/silica gel. This agrees with the
assignment of configuration made by earlier workers on the basis of the
relative TLC mobility of the diol isomers on boric acid/silica gel, but was
contrary to a previous assignment based on gas-liquid chromatographic (GLC)
retention times. We conclude that the erythro isomers of the diols are
characterized by lower mobility on boric acid TLC, as well as on silica gel
TLC, and form acetonides that have longer retention times on GLC, and
greater nonequivalence of the acetonide methyl groups in the NMR spectrum,
than do the acetonides of the threo isomers.