P. D’Arrigo et al. / Chemistry and Physics of Lipids 147 (2007) 113–118
117
Fig. 1. 1H NMR spectra (from 5.5 to 3.5 ppm) of compounds 4 and 13.
of derivatives (Ichihara et al., 2005). We have recently
discovered that mono- and regio-selective acylation of
GPC can be readily achieved with tin technology if per-
formed in 2-propanol, a solvent which will not compete
with the much more reactive tin ketal obtained from GPC
and alkyl-tin oxides. With this method high yields of
the range 5.5–3.5 ppm. Signals in this portion of spec-
trum are attributed to protons belonging to the glycerol
backbone and to the polar head of the compounds. Fig. 1
comparesthespectruminthatregionforthetwoisomeric
butanoyl-palmitoyl PCs 4 and 13. The signal attributed
+
to the –CH –N (CH3)3 in compound 4 (3.69 ppm), is
2
1
-acyl-2-lyso-glycero-3-phosphocholines or glycerol-3-
shifted upfield (3.61 ppm) when the palmitic chain is in
phosphates have been prepared in good yields (Fasoli
et al., 2006). We have extended this procedure to the
preparation of mixed chains-glycero-3-phosphocholines
alternating a short acyl residue (C-2 to C-9) to a long one
position sn-2 in compound 13. Moreover O-CH signals
2
in sn-1 position and O-CH ␣- to the phosphate on the
2
polar head are well resolved in spectrum b in compound
13 while they overlap partially when the palmitic chain
is in sn-1 position (compound 4, spectrum a).
Similar observation can be done for all the other iso-
meric mixed chains PCs prepared. The method seems to
be useful for the evaluation of the positional purity of
these compounds.
In conclusion we have described the preparation
of mixed chains PLs employing fewer synthetic steps
in comparison with known methods. This synthetic
approach also shows the versatility of GPC as starting
material for the preparation of an all set of glycerophos-
pholipids.
(
C-16).
In the first procedure (method A) GPC is transformed
into the cyclic tin ketal by treatment with DBTO in
-propanol at reflux. The mixture is then treated at
2
room temperature with triethylamine (TEA) and the acid
chloride. The formation of the lyso-PC was practically
complete in 15 min. Selective extraction allowed the
removal of the tin compounds and subsequent precip-
itation of the product. The lyso-PL was then dissolved
in dry dichloromethane and acylated with the acid anhy-
dride. Yields (see Table 1) from GPC were in the range
of 52–69%.
A direct method without the isolation of the lyso-PL
(
method B) consists in the formation of the tin ketal as
References
in method A and acylation with the acid chloride in the
presence of DMAP as a base. The solvent was removed
at room temperature and replaced with dichloromethane.
The second acylation followed the same procedure as in
method A. Yields from GPC were around 70%. Lower
yields are obtained with procedure A due to the isola-
tion of the intermediates. PLs with C-2 and C-3 chains
are obtained with a lower yield due to water solubility
Adlerkreutz, D., Wetije, E., 2004. An enzymatic method for the syn-
thesis of mixed chains acyl phosphocholines. JAOCS, 553–557.
Baer, E., Kates, M., 1948. l-␣-Glycerylphosphorylcholine. J. Am.
Chem. Soc. 70, 1394–1399.
Barenholz, Y., Cevc, G., 2000. In: Baskin, A., Norde, W. (Eds.),
Structure and Properties of Membranes in Physical Chemistry of
Biological Interfaces. Marcel Dekker, New York, pp. 171–242;
Barenholz, Y., Cevc, G., 2002. In: Baskin, A., Norde, W. (Eds.),
Structure and Properties of Membranes in Physical Chemistry of
Biological Interfaces. Marcel Dekker, New York, pp. 315–340.
Bayon, Y., Croset, M., Lagarde, M., Lecerf, J., Thies, F., Frank, T.,
Tayot, J.L., Chirouze, V., 1997. Docosahexaenoic acid-containing
(lyso)phosphatidylcholines for medicaments for treating cardio-
vascular disease and cerebral essential fatty acid deficiency. US
patent 5,654,290.
(Rosseto et al., 2006). TEA was the base of choice in
the acylation procedure described for the preparation of
compound 1. In all other cases acylation yields obtained
with DMAP were superior.
Although isomeric compounds showed slightly dif-
ferent retention times in HPLC analysis, inspection of
Bradshaw, J.P., Bushby, R.J., Giles, C.C.D., Saunders, M.R., 1999.
Orientation of the head group of phosphatidylinositol in a model
biomembrane as determined by neuron diffraction. Biochemistry
38, 8393–8401.
1
the H NMR proved a better tool for assessing the posi-
tional purity. In fact isomeric mixed-chains diacylated
1
PCs showed peculiar signals in the H NMR spectra in