Journal of Lipid Research, Vol 37, 1224-1233, Copyright © 1996 by Lipid Research, Inc.
Benzoolysis of diacylglycerophosphocholines: dephosphorylation and sequential formation of isomeric reaction products
WJ Gelsema, OF van den Brink and H van den Bosch
Department of Analytical Chemistry, Utrecht University, The Netherlands.
Benzoolysis experiments are reported in which diacylglycerophosphocholine
is heated at 100 degrees C with benzoic anhydride for variable periods of
time. It is shown that more than 90% of the phospholipid is
dephosphorylated after 5 h of heating. Lipid extracts of the reaction
mixture contained 1,2- and 1,3- diacylglycerobenzoate and 1,2- and
1,3-diacylglycerol in nearly constant isomer ratios of about 3:1 and 1:2,
respectively, independent of the heating and extraction time. The total
amount of isomeric diacylglycerobenzoates increased more slowly with
increasing heating time that corresponded with the dephosphorylation rate,
complete benzoylation being attained only after a 15 h heating period. The
total amount of isomeric diacylglycerols went through a maximum after about
4 h and vanished after 15 h of heating. Addition of 4-
dimethylaminopyridine subsequent to the heating period resulted in rapid
and complete benzoylation of dephosphorylated phospholipid. However, the
ratio of 1,2- to 1,3-diacylglycerobenzoate then found in the lipid extract
depended on heating time, changing from less than 1:1 to about 3:1 upon an
increase of heating time from 1 to 15 h. The results are interpreted in
terms of two consecutive reactions. In a relatively fast first step, a
dephosphorylated intermediate is formed, which in the molten benzoic
anhydride, is slowly benzoylated. The intermediate yields diacylglycerols
upon extraction in the absence of 4- dimethylaminopyridine and
diacylglycerobenzoates upon extraction in the presence of
4-dimethylaminopyridine.
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