Synthesis of plasmalogen via 2,3-Bis-O-(4′-methoxybenzyl)-sn-glycerol

Article abstract of DOI:10.1021/ja982837o

The synthesis of the O-vinyl ether phospholipid plasmalogen 1 from 2,3-bis-O-[p-methoxybenzyl (PMB)]-sn-glycerol (13) is described. Treatment of 13 with potassium hydride, trichloroethylene, and n-butyllithium gave a 1-O-alkynyl glycerol derivative, which

Full text of DOI:10.1021/ja982837o

662
J. Am. Chem. Soc. 1999, 121, 662-668
Synthesis of Plasmalogen via
2,3-Bis-O-(4′-methoxybenzyl)-sn-glycerol
Donghui Qin, Hoe-Sup Byun, and Robert Bittman*
Contribution from the Department of Chemistry and Biochemistry, Graduate School and UniVersity Center
& Queens College of the City UniVersity of New York, Flushing, New York 11367-1597
ReceiVed August 10, 1998
Abstract: The synthesis of the O-vinyl ether phospholipid plasmalogen 1 from 2,3-bis-O-[p-methoxybenzyl
(PMB)]-sn-glycerol (13) is described. Treatment of 13 with potassium hydride, trichloroethylene, and
n-butyllithium gave a 1-O-alkynyl glycerol derivative, which was alkylated with 1-iodohexadecane to afford
the long-chain O-alkynyl ether 14. The latter was quantitatively converted to cis-enol ether 15 (Z/E ratio between
35:1 and 100:1) with Lindlar catalyst in hexane/EtOAc 1:1 containing quinoline. The PMB groups of 15 were
removed by Birch reduction (Na, NH3), giving 1-O-[1′-(Z)-octadecenyl]-sn-glycerol (2) in 95% yield.
Regioselective silylation of 2 followed by palmitoylation provided 1-O-[1′-(Z)-octadecenyl]-2-O-palmitoyl-
3-(tert-butyldiphenylsilyl)-sn-glycerol (17). Desilylation with Bu4NF/imidazole at -23 °C followed by
phosphocholine insertion (using 2-chloro-2-oxo-1,3,2-dioxaphospholane with 2 equiv of pyridine in benzene
at 4 °C and then trimethylamine in benzene/MeCN 1:3 at 70 °C) completes the synthesis of plasmalogen (1).
Introduction
and Alzheimer’s disease,7 and may be associated with membrane
destabilization7 and impaired secretion of amyloid precursor
protein.8 On the other hand, since the enol ether linkage is
susceptible to oxidation, plasmalogens have a different pathway
of oxidative degradation compared with other phospholipids.
Thus, they may protect endothelial cells and plasma lipoproteins
by scavenging peroxyl radicals and other reactive oxygen
species,9 thereby inhibiting initiation of atherosclerosis. Plas-
malogen has also been proposed to have an important function
in the processes of membrane fusion (such as exocytosis and
endocytosis)4 and high-density lipoprotein (HDL) mediated
efflux of cholesterol from cells.10
Plasmalogens (1) are phospholipids that contain a cis-O-vinyl
ether group at the sn-1 position of the glycerol backbone, an
O-acyl group at the sn-2 position, and a phosphocholine or
phosphoethanolamine group at the sn-3 position. They are
widely distributed in mammalian cell membranes1 and are the
predominant phospholipids in membranes of the heart2 and
brain.3 Although their specific physiological roles in cellular
functions have not yet been fully established, it is well known
that several properties of plasmalogens differ from those of other
phospholipids. Plasmalogen phosphoethanolamines that contain
an arachidonoyl group at the sn-2 position are prone (a) to form
an inverted hexagonal phase, which promotes fusion of mem-
brane bilayers,4 and (b) to undergo rapid production of arachi-
donic acid and other lipid second messengers (eicosanoids,
platelet-activating factor, and lysophosphatidic acid) upon
activation of a plasmalogen-selective phospholipase A2, espe-
cially under pathological conditions.5 In several disease states,
Previous efforts11 to achieve a chemical synthesis of plas-
malogens focused on preparation of 1-O-[1′-(Z)-alkenylglycerol]
(3) Snipes, J.; Suter, U. In Cholesterol: Its Functions and Metabolism
in Biology and Medicine; Subcellular Biochemistry; Bittman, R., Ed.;
Plenum: New York, 1997; Vol. 28, pp 173-204.
(4) (a) Glaser, P. E.; Gross, R. W. Biochemistry 1994, 33, 5805-5812.
(b) Lohner, K. Chem. Phys. Lipids 1996, 81, 67-184.
(5) (a) Farooqui, A. A.; Yang, H.-C.; Horrocks, L. A. Brain Res. ReV.
1995, 21, 152-161. (b) Portilla, D.; Creer, M. H. Kidney Int. 1995, 47,
1087-1094. (c) Farooqui, A. A.; Rapoport, S. I.; Horrocks, L. A.
Neurochem. Res. 1997, 22, 523-527. (d) McHowat, J.; Liu, S.; Creer, M.
H. Am. J. Physiol. 1998, 274, C1727-C1737.
(6) Schedin, S.; Sindelar, P. J.; Pentchev, P.; Brunk, U.; Dallner, G. J.
Biol. Chem. 1997, 272, 6245-6251.
(7) (a) Farooqui, A. A.; Horrocks, L. A. Biochem. Soc. Trans. 1998, 26,
243-246. (b) Ginsberg, L.; Xuereb, J. H.; Gershfeld, N. L. J. Neurochem.
1998, 70, 2533-2538.
(8) Perichon, R.; Moser, A. B.; Wallace, W. C.; Cunningham, S. C.;
Roth, G. S.; Moser, H. W. Biochem. Biophys. Res. Commun. 1998, 248,
57-61.
(9) (a) Paltauf, F. Chem. Phys. Lipids 1994, 74, 101-139. (b) Bra¨utigam,
C.; Engelmann, B.; Reiss, D.; Reinhardt, U.; Thiery, J.; Richter, W. O.;
Brosche, T. Atherosclerosis 1996, 119, 77-88. (c) Hofer, G.; Lichtenberg,
D.; Kostner, G. M.; Hermetter, A. Clin. Biochem. 1996, 29, 445-450. (d)
Jira, W.; Spiteller, G. Chem. Phys. Lipids 1996, 79, 95-100.
(10) Mandel, H.; Sharf, R.; Berant, M.; Wanders, R. J. A.; Vreken, P.;
Aviram, M. Biochem. Biophys. Res. Commun. 1998, 250, 369-373.
(11) For a review of the early literature, see: (a) Rosenthal, A. F. Methods
Enzymol. 1975, 35, 429-529. (b) Paltauf, F. In Ether Lipids: Biochemical
and Biomedical Aspects; Mangold, H. K., Paltauf, F., Eds.; Academic: New
York, 1983; pp 49-84.
the normal level of plasmalogen phosphoethanolamines is
decreased, e.g., in the brain in Niemann-Pick-type C disease6
(1) (a) Klenk, E.; Debuch, H. In Progress in the Chemistry of Fats and
Other Lipids; Holman, R. T., Lundberg, W. O., Malkin, T., Eds.;
Pergamon: New York, 1963; pp 1-29. (b) Horrocks, L. A.; Sharma, M.
In Phospholipids; Hawthorne, J. N., Ansell, G. B., Eds.; Elsevier: Am-
sterdam, 1982; Vol. 4, pp 50-93.
(2) (a) Gross, R. W. Biochemistry 1984, 23, 158-165. (b) Gross, R. W.
Biochemistry 1985, 24, 1662-1668.
10.1021/ja982837o CCC: $18.00 © 1999 American Chemical Society
Published on Web 01/20/1999

Synthesis of Plasmalogen
J. Am. Chem. Soc., Vol. 121, No. 4, 1999 663
Scheme 1. Outline of the Synthetic Plan
Scheme 2. Synthesis of 2-O-PMB-3-O-PMP-sn-Glycerol (5)
from 3-O-PMP-sn-Glycerol (3)
Scheme 3. Synthesis of Enol Ether 7 by Partial
Hydrogenation of Acetylenic Ether 6
2. The principal challenges in the preparation of 2 arise from
its lability, since it is unstable to Lewis acids and oxidative
reagents, and from the difficulty in generating the (Z)-O-alkenyl
functionality stereoselectively. Thus many protecting groups
commonly used in lipid chemistry to carry out acylation and
phosphorylation cannot be manipulated without disturbing the
cis-enol ether linkage. Obviously, basic conditions are required
to accomplish the synthetic steps remaining after installation
of the vinyl ether moiety; however, strongly basic conditions
cannot be employed when the phosphocholine polar headgroup
is present during the preparation of 1, since phosphocholine is
a good leaving group.
Synthesis of a cis-vinyl ether linkage has presented consider-
able difficulty. Base-mediated dehydrohalogenation of various
halo ethers gave mixtures of (E) and (Z) derivatives of 2 together
with 2′-alkenyl byproducts.12 Alkylidenation of an ester has been
reported to provide Z-alkenyl ethers13 but was not successful
when long-chain 1,1-dibromides were used.14 Enolization of an
ester, followed by Birch reduction of the R-alkoxy enol phos-
phate or triethylaluminum/tetrakis(triphenylphosphine)palladium-
mediated hydrogenolysis,15a gave alkenyl diol 2 in 37% overall
yield;14,15b the latter was subsequently converted into 1.15b
We present herein an efficient total synthesis of plasmalogen
(1) that utilizes commercially available 1,2-isopropylidene-sn-
glycerol as the starting material and proceeds via diol 2, with
excellent stereoselectivity, in 6 steps and 60% overall yield. A
key precursor to 2 is 2,3-bis-O-PMB-sn-glycerol (13), which
to our knowledge has not been used previously as a synthon in
lipid chemistry. After introduction of the cis-O-vinyl ether
linkage at the sn-1 position, the PMB groups were removed to
give diol 2, which was converted to plasmalogen (1).
Scheme 4. Deprotection of the PMB Group of 7 by Birch
Reduction and Decomposition of Enol O-PMP 9 by CAN
the cis-vinyl ether moiety, and then selectively remove the PMB
and PMP protecting groups stepwise with 2,3-dichloro-5,6-
dicyanobenzoquinone (DDQ) and ceric ammonium nitrate
(CAN), respectively. As discussed below (Schemes 2-4), the
configuration of the enol ether could not be maintained when
CAN was used to remove the PMP group. The synthesis was
completed, therefore, using cis-O-alkenyl diol 2, which was
generated from the bis-O-PMB-protected glycerol 13 (Schemes
5 and 6).
The protection strategy leading to glycerol 5 started with
highly enantioenriched 3-O-PMP-sn-glycerol 316 and was ac-
complished by the sequence of reactions shown in Scheme 2:
(1) selective protection of the primary alcohol with a trityl group,
(2) introduction of the PMB group at the sn-2 position, and (3)
detritylation. Tritylation of glycerol 3 with trityl chloride and
pyridine in methylene chloride in the presence of a catalytic
amount of 4-(N,N-dimethylamino)pyridine (DMAP) gave 1-O-
trityl ether 4 in quantitative yield. Treatment of 4 with NaH,
p-methoxybenzyl chloride (PMBCl), and n-Bu4NI in THF
followed by detritylation furnished protected glycerol 5 in 89%
yield. An alternative route to 5 involved blocking of the primary
hydroxy group of 3 as a tert-butyldiphenylsilyl ether. This route
was abandoned, however, when substantial silyl group migration
Results and Discussion
Synthetic Plan. Our approach to 1, outlined in Scheme 1,
entails cis O-alkenation of a 2,3-di-O-protected sn-glycerol
followed by deprotection and selective introduction of the
requisite 2-O-acyl and 3-O-phosphocholine moieties. Our initial
route to 1 (Scheme 2) was to generate 2-O-[(p-methoxybenzyl
(PMB)]-3-O-[(p-methoxyphenyl (PMP)]-sn-glycerol (5), install
(12) For dehydrohalogenation of 1′- or 2′-halo-1-alkoxy glyceryl ethers
and dehalogenation of 1′,2′-dichloroalkoxy glyceryl ethers (principally
glycerol 1,2-cyclic carbonates), see: (a) Chebyshev, A. V.; Serebrennikova,
G. A.; Evstigneeva, R. P. Zh. Org. Khim. 1977, 13, 703-709; Chem. Abstr.
1977, 87, 38790s. (b) Chebyshev, A. V.; Serebrennikova, G. A.; Evstigne-
eva, R. P. Bioorg. Khim. 1977, 3, 1362-1369; Chem. Abstr. 1977, 88,
37184f. (c) Titov, V. I.; Serebrennikov, G. A.; Preobrazhenskii, N. A. Zh.
Org. Khim. 1970, 6, 1154-1159; Chem. Abstr. 1970, 73, 65983z. (d)
Pfaendler, H. R.; Mu¨ller, F. X. Synthesis 1992, 350-352.
(13) (a) Takai, K.; Kakiuchi, T.; Kataoka, Y.; Utimoto, K. J. Org. Chem.
1994, 59, 2668-2670. (b) Okazoe, T.; Takai, K.; Oshima, K.; Utimoto, K.
J. Org. Chem. 1987, 52, 4412-4414.
(14) Rui, Y.; Thompson, D. H. J. Org. Chem. 1994, 59, 5758-5762.
(15) (a) Charbonnier, F.; Moyano, A.; Greene, A. E. J. Org. Chem. 1987,
52, 2303-2306. (b) Rui, Y.; Thompson, D. H. Chem. Eur. J. 1996, 2, 1505-
1508.
(16) Byun, H.-S.; Kumar, E. R.; Bittman, R. J. Org. Chem. 1994, 59,
2630-2633.

664 J. Am. Chem. Soc., Vol. 121, No. 4, 1999
Qin et al.
Table 1. Effects of Solvent and Quinoline on the Partial
Hydrogenation of Alkynyl Ether 6 with Lindlar Catalysta
Scheme 5. Synthesis of 1-O-[1′-(Z)-Octadecenyl]-sn-
Glycerol (2) via 2,3-Bis-O-PMB-glycerol 13a
quinoline
(µL)
reaction
time (h)
Z/E ratio
of 7
yield
of 7 (%)
solvent
MeOH
EtOAc/hexane 1:1
EtOAc/hexane 1:1
EtOAc/hexane 1:1
0
3
6
10:1
25:1
35:1
86:1
95
95
94
94
0
20
50
24
a Reaction conditions: solvent volume, 10 mL; O-alkynyl ether 6,
100 mg (0.18 mmol); Lindlar catalyst, 20 mg.
hexane/EtOAc 1:1 (Z/E ratio, 25:1). On addition of quinoline,21
not only did the hydrogenation reaction proceed more slowly
but also the stereoselectivity was improved, since the Z/E ratio
increased to 86:1 in hexanes/EtOAc 1:1.
a Reagents: (a) i. KH, PMBCl, Bu4NI, THF, rt, 2 h; ii. p-TsOH,
MeOH, rt (98% overall); (b) TrCl, py, DMAP, CH2Cl2, rt (100%); (c)
i. NaH, PMBCl, Bu4NI, THF, rt; ii. p-TsOH, MeOH (97% overall);
(d) i. KH, CHCldCCl2, THF, -42 °C to room temperature; ii. n-BuLi,
C16H33I, HMPA, -78 to -42 °C to room temperature (67%); (e) H2/
Lindlar catalyst, quinoline, hexane/EtOAc 1:1, 2 h (100%); (f) Na/
NH3, THF, -78 °C to room temperature (95%).
Deprotection of PMB and PMP Groups from Alkenyl
Ether 7. Oxidative deprotection of the PMB group from alkenyl
ether 7 was attempted with DDQ.22 However, not only was the
PMB group oxidized but some of the enol ether was also
destroyed, even when the reaction was carried out at -78 °C
in wet methylene chloride. On the other hand, Birch reduction
successfully removed the PMB group from 7, particularly when
sodium metal was employed (Scheme 4). The reaction could
be finished within 10 min to give alcohol 8 without cleavage
of the enol ether and without affecting the PMP group. However,
when a longer reaction time was applied, the PMP group was
also reduced to give 4-methoxycyclohexa-1,4-dienyl derivative
8a. Careful timing of the reaction avoids the over-reduction.
When lithium was used as the metal in the Birch reduction, it
was almost impossible to control the reaction time in order to
avoid reduction of the PMP group. Furthermore, isomerization
of the enol was observed; the Z/E ratio was reduced from 30:1
to 4:1.
Scheme 6. Synthesis of Plasmalogen (1) from Diol 2a
Alcohol 8 was converted into ester 9 in 86% yield by reaction
with palmitic acid in the presence of DCC and catalytic DMAP23
in methylene chloride. On the basis of the precedent that acyl
group migration from a secondary to a primary position was
not observed during deprotection of the PMP group by CAN,24
reaction of ester 9 with CAN in MeCN/H2O 4:1 at 0 °C was
tried. However, enol ether 9 was totally destroyed in the course
of PMP deprotection, and the desired alcohol 10 was not formed.
Therefore, the key intermediate 2 was assembled by the
sequence of steps outlined in Scheme 5.
Synthesis of 1-O-(Z)-Octadecenyl-sn-glycerol 2. Since the
PMP group could not be removed without cleaving the enol
ether, a PMB group was used to protect the hydroxyl group at
the sn-3 position as well. Diol 2 was prepared with excellent
stereoselectivity in 6 steps and 60% overall yield starting from
1,2-isopropylidene-sn-glycerol (Scheme 5). A key precursor for
2 is 2,3-bis-O-PMB-sn-glycerol 13, which to our knowledge
has not been used previously as a synthon in lipid chemistry.
Treatment of 1,2-O-isopropylidene-sn-glycerol with KH and
PMBCl in THF followed by deacetonation with p-toluene-
sulfonic acid (p-TsOH) in MeOH gave 3-O-PMB-sn-glycerol
(11) in 98% yield. O-Alkenyl ether bis-O-PMB-glycerol 15 was
a Reagents: (a) TBDPSCl (1.2 equiv), Im (2 equiv), DMF, 0 °C to
room temperature (90%); (b) (C15H31CO)2O, DMAP, CHCl3, rt (98%);
(c) Im (3.5 equiv), TBAF (3 equiv), THF, -23 °C, 1 h; (d) 2-chloro-
2-oxo-1,3,2-dioxaphospholane, py (2 equiv), benzene, 4 °C; (e) NMe3,
MeCN/C6H6 (3:1), 70 °C, 24 h (74% in 3 steps).
was detected during the base-mediated PMB protection of the
2-hydroxy group (using NaH and PMBCl in benzene).
Synthesis of Enol Ether 7 by Partial Hydrogenation of
Alkynyl Ether 6. An early report that a 1-O-alkynyl linkage
could be introduced by reaction of an alkoxide ion with a
1-bromoalkyne17 was found to be in error: an allenic ether was
formed instead.18 The method of Greene et al. for preparation
of short-chain acetylenic ethers19 was successful. Thus suc-
cessive treatment of glycerol 5 with KH, trichloroethylene,
n-BuLi, and C16H33I provided 1-O-alkynyl ether 6 in 86% yield
(Scheme 3).
Partial reduction of alkynyl ether 6 with Red-Al and NaAlH4
failed; in fact, no hydrogenation was observed. Although partial
hydrogenation of O-alkynyl ethers using Lindlar catalyst was
reported to be unsuccessful,20 we found that alkyne 6 was
quantitatively converted to cis-enol ether 7 with Lindlar catalyst
(Scheme 3). As shown in Table 1, the Z/E ratio was enhanced
when the solvent was changed from MeOH (Z/E ratio, 10:1) to
(21) (a) Lindlar, H. HelV. Chim. Acta 1952, 35, 446-450. (b) McEwen,
A. B.; Guttieri, M. J.; Maier, W. F.; Laine, R. M.; Shvo, Y. J. Org. Chem.
1983, 48, 4436-4438.
(22) (a) Oikawa, Y.; Yoshioka, T.; Yonemitsu, O. Tetrahedron Lett. 1982,
23, 885-888. (b) Buckle, D. R. 2,3-Dichloro-5,6-dicyano-1,4-benzoquinone.
In Encyclopedia of Reagents for Organic Synthesis; Paquette, L. A., Ed.;
Wiley: Chichester, 1995; Vol. 3, pp 1699-1704.
(23) For reviews of acylation of lipid hydroxy groups, see: (a)
Radhakrishnan, R.; Robson, R. J.; Takagaki, Y.; Khorana, H. G. Methods
Enzymol. 1981, 72, 408-435. (b) Bittman, R. In Phospholipids Handbook;
Cevc, G., Ed.; Marcel Dekker: New York, 1993; pp 141-232.
(24) Vilche`ze, C.; Bittman, R. J. Lipid Res. 1994, 35, 734-738.
(17) Berezovskaya, M. V.; Sarycheva, I. K.; Preobrazhenskii, N. A. Zh.
Obshch. Khim. 1964, 34, 543-545; Chem. Abstr. 1964, 60, 11886f.
(18) Chacko, G. K.; Schilling, K.; Perkins, E. G. J. Org. Chem. 1967,
32, 3698-3700.
(19) Moyano, A.; Charbonnier, F.; Greene, A. E. J. Org. Chem. 1987,
52, 2919-2922.
(20) Mangold, H. K. Angew. Chem., Intl. Ed. Engl. 1979, 18, 493-503.

Synthesis of Plasmalogen
J. Am. Chem. Soc., Vol. 121, No. 4, 1999 665
Figure 2. Isomerization of 16 by a trace of acid in chloroform.
1-O-(1′-(Z)-octadecenyl)-2-O-palmitoyl-sn-glycerol (18). With-
out addition of imidazole, substantial migration of the palmitoyl
group from the sn-2 to the sn-3 position took place on
desilylation. Prompt reaction of alcohol 18 with 2-chloro-2-
oxo-1,3,2-dioxaphospholane28 at 4 °C in benzene in the presence
of pyridine afforded phospholane 19 and avoided acyl migration,
as judged by the 1H NMR signal of the sn-2 proton, δ 5.1 (m),
and by the absence of a signal at δ 4.5 (m), which corresponds
to the sn-2 proton in the migration product. Opening of the
phospholane ring of 19 with anhydrous trimethylamine in
benzene/MeCN 1:3 at 70 °C gave plasmalogen (1) in 74%
overall yield from enol ether 16.29
Figure 1. The E/Z ratio was determined by integration of the 1H NMR
spectrum of 15 on an expanded scale.
prepared by the same steps used in the synthesis of enol ether
7. Reaction of alcohol 13 with KH, trichloroethylene, n-BuLi,
and C16H33I provided O-alkynyl ether 14 in 67% yield. Enol
ether 15 was obtained in quantitative yield and with high
stereoselectivity by partial hydrogenation with Lindlar catalyst.
As with the reduction of 6 to 7, the Z/E ratio was affected by
the solvent used (Z/E ratio: in MeOH, 9:1; in hexane/EtOAc
1:1, 20:1). Addition of quinoline in hexane/EtOAc 1:1 raised
the Z/E ratio to 66:1 (Figure 1).25 The individual stereotopic
O-vinylic protons in the cis and trans isomers of 15 show base-
line separation. The higher field doublet (δ 5.9, J ) 6.2 Hz) is
assigned to the cis O-vinylic proton, and the lower field doublet
(δ 6.2, J ) 12.6 Hz) corresponds to the trans O-vinylic proton.
When oxidative cleavage of the PMB groups of alkenyl
glycerol 15 (using DDQ or CAN) again produced mixtures, we
applied Birch reduction to unmask the sn-2 and sn-3 hydroxy
groups. Again, with lithium, isomerization of the enol double
bond was observed (reduction in Z/E ratio from ∼100:1 to 50:
1). However, when sodium was used, there was no isomeriza-
tion, even under extended reaction time (20 h), and 1-O-[1′-
(Z)-octadecenyl)]-sn-glycerol (2) was obtained in 95% yield.
Synthesis of Plasmalogen (1). In the final stage of the
synthesis of 1, an acyl chain (palmitoyl) and a phosphocholine
headgroup were introduced at the sn-2 and sn-3 positions,
respectively.26 As outlined in Scheme 6, protection of the
primary hydroxy group of 2 as a tert-butyldiphenylsilyl ether
gave silyl ether 16 in 90% yield. Isomerization of 16 to a ∼1:1
mixture of 16a/16b during contact with unneutralized CDCl3
Conclusions
A 1-O-alkynyl moiety was introduced at the sn-1 position of
2,3-protected glycerol derivatives. Partial hydrogenation of
O-alkynyl ether 14 with Lindlar catalyst in EtOAc/hexane 1:1
in the presence of quinoline provided cis O-alkenyl ether 15
almost exclusively. The PMB group of protected glycerol 7 was
removed selectively by Birch reduction without affecting the
PMP group. During dissolving metal reduction the configuration
of the enol ether in glycerol derivatives 7 and 15 was not
affected when sodium in ammonia was used, whereas with
lithium in ammonia the Z/E ratio of the enol was decreased.
Ring opening of phospholane 19 by NMe3 in MeCN/benzene
3:1 gave 1 in moderate yield. This synthesis makes it possible
to prepare chiral plasmalogen derivatives with different chain
lengths and degrees of unsaturation.
Experimental Section
General Procedures. All reactions were carried out under dry argon
atmosphere. Flash chromatography was carried out with Merck silica
gel 60 (230-400 ASTM mesh). TLC was carried out using Merck
60F254 (0.25-mm thick) sheets. THF was distilled from Na and
benzophenone before use. Benzene, CH2Cl2, and DMF were distilled
from CaH2. MeCN and CHCl3 were distilled from P2O5. Pyridine was
dried over NaOH pellets. 2-Chloro-2-oxo-1,3,2-dioxaphospholane was
purchased from Fluka. NMR spectra were recorded on a Bruker
spectrometer at 400 MHz for 1H and 100 MHz for 13C. Low- and high-
resolution FAB mass spectra were recorded at the Michigan State
University Mass Spectrometry Facility.
1-O-(Triphenylmethyl)-3-O-(4′-methoxyphenyl)-sn-glycerol (4).
To a solution of 3.00 g (15.1 mmol) of PMP-sn-glycerol (3), 2.0 mL
(24.7 mmol) of pyridine, and 0.18 g (1.50 mmol) of DMAP in 50 mL
of CH2Cl2 was added 5.49 g (19.7 mmol) of Ph3CCl at room
temperature. After the mixture was stirred overnight, it was diluted
1
for several hours at room temperature was noted by H NMR
(Figure 2). Isomerization was avoided by pretreating CDCl3 with
potassium carbonate. Esterification of 16 with palmitic anhydride
and DMAP in alcohol-free CHCl3 at room temperature23 gave
ester 17 quantitatively.27 Desilylation of 17 with Bu4NF (TBAF)
in the presence of the mild base imidazole (Im) at -23 °C gave
(25) The Z/E ratio is highly sensitive to the concentrations of substrate
and catalyst. This ratio was obtained by using 1.0 g (1.72 mmol) of 14,
100 mg of Lindlar catalyst, and 50 µL of quinoline in 30 mL of hexane/
EtOAc 1:1; reaction time, 2 h. It should be noted that Z/E ratios higher
than 66:1 were obtained when shorter reaction times were used. Under these
conditions, however, unreacted alkyne was sometimes present, and when
the reaction mixture was subjected to another cycle of Lindlar reduction,
the Z/E ratio of 15 was reduced.
(26) Direct introduction of a phosphocholine group at the sn-3 position
of diol 2 could not be achieved without obtaining a substantial amount of
byproduct from reaction at the sn-2 hydroxy group. However, for selective
phosphitylation of other glycerol diol derivatives, see: (a) Erukulla, R. K.;
Byun, H.-S.; Bittman, R. Tetrahedron Lett. 1994, 35, 5783-5784. (b) Byun,
H.-S.; Erukulla, R. K.; Bittman, R. J. Org. Chem. 1994, 59, 6495-6498.
(27) The yield of palmitoylation using palmitoyl chloride and pyridine
was lower (85%), probably because the pyridinium chloride formed during
the reaction caused some decomposition of enol ether 16.
(28) For reviews about the use of this cyclic phosphochloridate for
phosphorylation of glycerol derivatives, see: (a) Reference 23b. (b) Bittman,
R. In Lipid Synthesis and Manufacture; Gunstone, F. D., Ed.; Sheffield
Academic Press: Sheffield, U. K.; CRC Press: Boca Raton, FL, 1998; pp
185-207.
(29) When MeCN was the sole solvent, the yield was 53%.15b

666 J. Am. Chem. Soc., Vol. 121, No. 4, 1999
Qin et al.
with EtOAc and washed with aqueous 10% NaHSO4 solution, water,
and brine. The organic layer was dried over Na2SO4 and concentrated.
The product was purified by column chromatography, eluting with
(0.654 mmol) of sodium at -78 °C. The solution was stirred until a
blue color persisted. A solution of 62 mg (0.11 mmol) of 7 in 4 mL of
dry Et2O was added. After the mixture was stirred for 15 min, the
reaction was quenched by addition of wet MeOH. The solution was
poured into a separatory funnel and washed with H2O (3 × 20 mL)
without shaking. The ether layer was dried over Na2SO4. Evaporation
of the solvent gave a white solid that was purified by preparative TLC
hexanes/EtOAc 5:1 to give 6.61 g (100%) of 1-O-trityl glycerol 4 as
1
a sticky liquid: [R]25 -2.96° (c 5.45, CHCl3); H NMR (CDCl3) δ
D
7.42-7.44 (m, 6H), 7.18-7.31 (m, 9H), 6.82 (s, 4H), 4.09-4.15 (m,
1H), 3.95-4.05 (m, 2H), 3.77 (s, 3H), 3.32-3.34 (m, 2H), 2.45 (d, J
) 5.12 Hz, 1H); 13C NMR δ 154.02, 152.65, 143.71, 128.63, 127.88,
127.12, 115.52, 114.60, 86.79, 69.73, 69.55, 64.23, 55.72.
to give 50 mg (95%) of 8 as a white solid: mp 41.5-42.0 °C; [R]25
D
1
-3.2° (c 1.00, CHCl3); H NMR (CDCl3) δ 6.76-6.87 (m, 4H), 5.98
and 5.96 (dt, J ) 6.12 Hz, J ) 1.34 Hz, 1H), 4.40 (m, 1H), 4.41 and
4.39 (dt, J ) 6.36 Hz, J ) 7.24 Hz, 1H), 4.16-4.19 (m, 1H), 4.39-
4.04 (m, 2H), 3.86-3.96 (m, 2H), 3.77 (s, 3H), 2.49 (d, J ) 13.08 Hz,
2-O-(4′-Methoxybenzyl)-3-O-(4′-methoxyphenyl)-sn-glycerol (5).
To a suspension of 0.55 g (19.5 mmol, 80% in white oil, washed twice
with dry hexane) of NaH in 100 mL of THF was added 5.42 g (12.3
mmol) of O-trityl glycerol 4 at 0 °C. After the evolution of hydrogen
had stopped, 2.2 mL (16.2 mmol) of PMBCl and 0.37 g (1.0 mmol) of
n-Bu4NI were added, and the reaction mixture was stirred for 24 h at
room temperature. After the excess amount of NaH was destroyed by
addition of 1 mL of MeOH, the reaction mixture was poured into 100
mL of water, acidified with 3 N HCl, and stirred for 1 h. The product
was extracted with EtOAc. The organic layer was dried over Na2SO4
and concentrated to give a residue that was purified by column
chromatography, eluting with hexanes/EtOAc 4:1 to give 3.52 g (89%)
of PMB-glycerol 5 as a yellow oil: [R]25D +22.2° (c 4.67, CHCl3); 1H
NMR (CDCl3) δ 7.29 (d, J ) 8.52 Hz, 2H), 6.89 (d, J ) 8.52 Hz, 2H),
6.83 (s, 4H), 4.66 (ABq, J ) 11.36 Hz, ∆ν ) 39.62 Hz, 2H), 4.05-
3.99 (m, 2H), 3.63-3.88 (m, 3H), 3.81 (s, 3H), 3.77 (s, 3H), 1.98 (br
s, 1H); 13C NMR δ 159.41, 154.02, 152.72, 130.12, 129.59, 115.46,
114.64, 113.94, 72.14, 68.25, 62.54, 55.74, 55.30.
1-O-(1′-Octadecynyl)-2-O-(4′-methoxybenzyl)-3-O-(4′-meth-
oxyphenyl)-sn-glycerol (6). To a suspension of 2.10 g (17.6 mmol,
35 wt % dispersion in mineral oil, washed with dry hexane twice) of
KH in 50 mL of THF was added 2.80 g (8.8 mmol) of 5 at 0 °C. After
the evolution of hydrogen stopped, the reaction mixture was cooled to
-40 °C, treated with 790 µL (8.8 mmol) of trichloroethylene, and
allowed to warm to room temperature. After 1 h the brown reaction
mixture was treated dropwise with 7.1 mL (17.8 mmol, 2.5 M in
hexane) of n-butyllithium at -78 °C. After 0.5 h the mixture was
warmed to -40 °C, and 4.05 g (11.5 mmol) of 1-iodohexadecane and
50 mL of HMPA were added. After the mixture was stirred for 24 h at
room temperature, the reaction was quenched by addition of 1 mL of
MeOH. The mixture was poured into saturated aqueous NH4Cl solution.
The product was extracted with Et2O and purified by column chroma-
tography, eluting with hexanes/EtOAc 50:1 containing 2.5% of Et3N
1H), 2.00-2.06 (m, 2H), 1.25 (s, 28H), 0.88 (t, J ) 6.52 Hz, 3H); 13
C
NMR δ 154.18, 152.63, 144.68, 115.58, 114.70, 108.24, 72.61, 69.38,
69.22, 55.73, 31.96, 29.74, 29.71, 29.58, 29.40, 29.35, 24.84, 23.98,
22.73, 14.17.
1-O-[1′-(Z)-Octadecenyl)]-2-O-palmitoyl-3-O-(4′-methoxyphenyl)-
sn-glycerol (9). A mixture of 42 mg (0.0938 mmol) of 8, 58 mg (0.28
mmol) of DCC, 48 mg (0.19 mmol) of palmitic acid, and 5.7 mg (0.047
mmol) of DMAP in 4 mL of dry CH2Cl2 was stirred for 3 h at room
temperature. The mixture was filtered through a pad of Celite. After
the filtrate was concentrated, the residue was purified by preparative
TLC (developed with hexane/EtOAc 20:1) to give 55 mg (86%) of 9
as a white solid: mp 54.0-54.6 °C; [R]25 +4.48° (c 1.05, CHCl3);
D
1H NMR (CDCl3) δ 6.80-6.86 (m, 4H), 5.92 and 5.94 (dt, J ) 6.12
Hz, J ) 1.58 Hz, 1H), 5.27-5.34 (m, 1H), 4.35-4.40 (m, 1H), 4.11
(ABq, J ) 4.82 Hz, ∆ν ) 9.22 Hz, 1H), 4.07 (ABq, J ) 5.21 Hz, ∆ν
) 8.89 Hz, 1H), 3.93-4.00 (m, 2H), 3.76 (s, 3H), 2.34 (t, J ) 7.50
Hz, 2H), 2.04-2.09 (m, 2H), 1.59-1.66 (m, 2H), 1.25 (s, 52H), 0.88
(t, J ) 6.52 Hz, 6H); 13C NMR δ 173.23, 154.17, 152.64, 144.72,
115.69, 114.62, 108.12, 70.74, 70.00, 66.88, 55.68, 34.36, 31.95, 29.74,
29.69, 29.65, 29.59, 29.50, 29.39, 29.35, 29.31, 29.11, 24.95, 23.92,
22.71, 14.14.
3-O-(4′-Methoxybenzyl)-sn-glycerol (11). To a solution of (S)-
isopropylideneglycerol (10.0 g, 75.66 mmol) in 300 mL of THF was
added KH (3.64 g, 90.8 mmol) in portions over a 10-min period. The
solution was stirred until the evolution of H2 gas stopped. After 13.0
g (9.24 mmol) of PMBCl and 1.0 g (2.7 mmol) of n-Bu4NI were added,
the solution was stirred for 4 h. Methanol was added to destroy excess
KH, and the solution was washed with saturated aqueous NH4Cl
solution and water. Evaporation of the solvent gave a residue that was
redissolved in MeOH. The solution was treated with p-TsOH for 2 h
at room temperature. After the solution was neutralized with NH4OH,
the solvent was evaporated and the residue was purified by flash
chromatography (elution with hexane/EtOAc 2:1) to give 15.7 g (98%)
of PMB diol 11 as a white solid: mp 42.5-43.5 °C [lit.30 mp 43.5-
by volume, to give 4.29 g (86%) of O-alkynyl ether 6 as a colorless
1
oil: [R]25 +3.88° (c 5.03, CHCl3); H NMR (CDCl3) δ 7.30 (d, J )
D
8.48 Hz, 2H), 6.88 (d, J ) 8.48 Hz, 2H), 6.81 (s, 4H), 4.67 (ABq, J )
11.40 Hz, ∆ν ) 17.80 Hz, 2H), 4.19 (ABq, J ) 4.22 Hz, ∆ν ) 9.70
Hz, 2H), 4.02-4.07 (m, 1H), 3.98-4.00 (m, 2H), 3.80 (s, 3H), 3.76
(s, 3H), 2.08 (t, J ) 6.9 Hz, 2H), 1.39-1.46 (m, 2H), 1.25 (s, 26H),
0.88 (t, J ) 6.70 Hz, 3H); 13C NMR δ 159.36, 154.06, 152.61, 129.95,
129.62, 115.51, 114.60, 113.82, 89.53, 77.55, 72.37, 67.66, 55.70, 55.27,
37.48, 31.94, 29.71, 29.63, 29.50, 29.38, 29.24, 28.90, 22.70, 17.14,
14.14.
1-O-[1′-(Z)-(Octadecenyl)]-2-O-(4′-methoxybenzyl)-3-O-(4′-meth-
oxyphenyl)-sn-glycerol (7). To a solution of 300 mg (0.53 mmol) of
6 in 9 mL of hexane/EtOAc 1:1 were added 60 mg of Lindlar catalyst
and 50 µL (0.45 mmol) of quinoline. The resulting suspension was
degassed by H2, and then a H2 balloon was applied. The reaction mixture
was stirred for 24 h. The solution was concentrated to give a light
yellow residue that was purified by flash chromatography (elution with
hexane/EtOAc 20:1 containing 2.5% of Et3N by volume) to provide
284 mg (94%) of 7 as a colorless oil: [R]25D +5.79° (c 2.50, CHCl3);
1H NMR (CDCl3) δ 7.29 (d, J ) 8.56 Hz, 2H), 6.87 (d, J ) 8.68 Hz,
2H), 6.82 (s, 4H), 5.96 (d, J ) 6.20 Hz, 1H), 4.66 (ABq, J ) 11.62
Hz, ∆ν ) 5.85 Hz, 2H), 4.34-4.39 (m, 1H), 3.85-4.06 (m, 5H), 3.80
(s, 3H), 3.76 (s, 1H), 2.07 (m, 2H), 1.25 (s, 28H), 0.88 (t, J ) 6.78
Hz, 3H); 13C NMR δ 159.28, 153.96, 152.82, 145.02, 130.33, 129.48,
115.50, 114.79, 113.78, 107.43, 75.87, 72.29, 71.97, 68.28, 55.69, 55.25,
31.94, 29.72, 29.68, 29.53, 29.50, 29.38, 29.09, 24.01, 22.70, 14.14;
FAB HRMS (M+) calcd for C36H56O5 568.4128, found 568.4133.
1-O-(1′-(Z)-Octadecenyl)-3-O-(4′-methoxyphenyl)-sn-glycerol (8).
To a solution of NH3 (10 mL) and dry Et2O (3 mL) was added 15 mg
45.5 °C; lit.31 mp 40-41 °C]; [R]25 -2.21° (c 1.00, CHCl3) [lit.30
D
1
[R]D -1.54° (c 3.7, CHCl3)]; H NMR (CDCl3) δ 7.25 (d, J ) 8.57
Hz, 2H), 6.89 (d, J ) 8.58 Hz, 2H), 4.48 (s, 2H), 3.84-3.90 (m, 1H),
3.81 (s, 3H), 3.70 (ABq, J ) 5.59 Hz, ∆ν ) 10.74 Hz, 1H), 3.62 (ABq,
J ) 5.64 Hz, ∆ν ) 9.78 Hz, 1H), 3.56 (ABq, J ) 3.96 Hz, ∆ν ) 8.77
Hz, 1H), 3.51 (ABq, J ) 6.28 Hz, ∆ν ) 7.30 Hz, 1H), 2.70 (br s, 1H),
2.17 (br s, 1H); 13C NMR (CDCl3) δ 159.39, 129.72, 129.48, 113.90,
73.26, 71.52, 70.56, 64.11, 55.29; EI HRMS calcd for C11H16O4 (M+)
m/z 212.1049, found 212.1052.
1-O-(Triphenylmethyl)-3-O-(4′-methoxybenzyl)-sn-glycerol (12).
To a solution of 3.00 g (15.1 mmol) of 3-O-PMB-sn-glycerol (11) and
2.0 mL (24.7 mmol) of pyridine in 50 mL of CH2Cl2 were added 5.49
g (19.7 mmol) of Ph3CCl and 367 mg (2.0 mmol) of DMAP at room
temperature. The mixture was stirred overnight at room temperature,
diluted with EtOAc, and washed with 10% aqueous NaHSO4 solution,
water, and brine. The organic layer was dried over Na2SO4 and
concentrated. The product was purified by flash chromatography
(elution with hexanes/EtOAc 5:1) to give 6.60 g (100%) of 1-O-trityl-
2-O-PMB-glycerol (12) as a colorless liquid: [R]25 -0.65° (c 2.50,
D
CHCl3); [R]25D -0.68° (c 4.40, CHCl3/MeOH 1:1); 1H NMR (CDCl3)
(30) DeMedeiros, E. F.; Herbert, J. M.; Taylor, R. J. K. J. Chem. Soc.,
Perkin Trans. 1 1991, 2725-2730.
(31) He´bert, N.; Beck, A.; Lennox, R. B.; Just, G. J. Org. Chem. 1992,
57, 1777-1783.

Synthesis of Plasmalogen
J. Am. Chem. Soc., Vol. 121, No. 4, 1999 667
δ 7.43 (s, 3H), 7.41 (s, 3H), 7.25-7.29 (m, 6H), 7.18-7.23 (m, 5H),
6.84 (d, J ) 8.45 Hz, 2H), 4.44 (s, 2H), 3.93-4.00 (m, 1H), 3.76 (s,
3H), 3.56 (ABq, J ) 4.21 Hz, ∆ν ) 8.57 Hz, 1H), 3.51 (ABq, J )
6.20 Hz, ∆ν ) 7.27 Hz, 1H), 3.22 (ABq, J ) 5.95 Hz, ∆ν ) 7.24 Hz,
1H), 3.18 (ABq, J ) 5.29 Hz, ∆ν ) 7.79 Hz, 1H), 2.50 (s, 1H); 13C
NMR (CDCl3) δ 159.19, 143.82, 130.03, 129.32, 128.64, 128.30,
127.80, 127.02, 113.74, 86.59, 72.97, 71.22, 69.87, 64.56, 55.21; FAB
HRMS calcd for C30H29O4 (M - H)+ m/z 453.2066, found 453.2050.
2,3-Bis-O-(4′-methoxybenzyl)-sn-glycerol (13). To a solution of
12.0 g (26.43 mmol) of 1-O-trityl-3-O-PMB-glycerol (12) in 300 mL
of THF was added 761 mg (31.7 mmol) of NaH. After the evolution
of hydrogen ceased, PMBCl (4.97 g, 31.7 mmol) and n-Bu4NI (975
mg, 2.64 mmol) were added. The solution was stirred at room
temperature for 2 h, and MeOH was added to destroy the excess
hydride. The solution was diluted with 200 mL of Et2O and washed
with saturated aqueous NH4Cl solution and water. Evaporation of the
solvents under vacuum gave a residue that was dissolved in 50 mL of
MeOH. The resulting solution was treated overnight with p-TsOH (200
mg, 1.04 mmol) at room temperature. The solution was neutralized
with concentrated aqueous NH4OH solution, and the solvent was
evaporated to give a residue that was purified by flash chromatography
(elution with hexane/EtOAc 9:1) to give 8.5 g (97%) of 2,3-bis-O-
PMB-glycerol (13) as a colorless oil: [R]25D +17.31° (c 1.80, CHCl3);
1H NMR (CDCl3) δ 7.24-7.27 (m, 4H), 6.86-6.87 (m, 4H), 4.58 (ABq,
J ) 11.38 Hz, ∆ν ) 38.89 Hz, 2H), 4.47 (ABq, J ) 11.78 Hz, ∆ν )
6.78 Hz, 2H), 3.81 (s, 3H), 3.80 (s, 3H), 3.52-3.76 (m, 5H), 2.01 (br
s, 1H); 13C NMR (CDCl3) δ 159.31, 159.26, 130.34, 130.03, 129.46,
129.32, 113.87, 113.82, 77.60, 73.18, 71.80, 69.90, 62.95, 55.28; FAB
HRMS calcd for C19H23O5 (M - H)+ m/z 331.1545, found 331.1550.
1-O-(1′-Octadecynyl)-2,3-bis-O-(4′-methoxybenzyl)-sn-glycerol (14).
A solution of 2,3-bis-O-PMB-glycerol (13) (1.10 g, 3.33 mmol) in 20
mL of THF was treated with KH (268 mg, 6.69 mmol) for 1 h. The
reaction mixture was cooled to -42 °C, and trichloroethylene (302
µL, 3.34 mmol) was added. The solution was warmed slowly to room
temperature and stirred for 2 h. The resulting dark brown solution was
cooled to -78 °C and treated with 3.0 mL (7.0 mmol) of n-BuLi (a
2.5 M solution in hexane). The reaction mixture was stirred for 1 h,
warmed to -42 °C, and stirred for 1 h. Hexadecyl iodide (1.29 g, 3.65
mmol) and HMPA (5 mL) were added, and the solution was warmed
to room temperature and stirred for 4 h. After MeOH was added to
destroy excess KH, the mixture was diluted with 100 mL of Et2O,
washed with water (3 × 50 mL), and dried over Na2SO4. Evaporation
of the solvents under vacuum gave a brown residue that was purified
by flash chromatography (elution with hexane/EtOAc 15:1 in the
1-O-(1′-(Z)-Octadecenyl)-sn-glycerol (2). Twenty milliliters of
liquid NH3 was collected in a three-neck round-bottom flask by using
a Dewar trap at -78 °C. Sodium (100 mg, 4.35 mmol) was added,
and the solution was stirred for 1 h until it had a stable blue color. A
solution of alkenyl ether 15 (1.0 g, 1.72 mmol) in 20 mL of THF was
added dropwise over a 3-min period. The reaction mixture was stirred
for 2 h and warmed slowly to room temperature. After MeOH was
added to destroy the excess Na, the solution was diluted with 100 mL
of Et2O, and water was added slowly to remove NH3 by separation.
The organic layer was dried over Na2SO4, and the solvents were
removed under vacuum. The residue was purified by flash chroma-
tography (elution with hexane/EtOAc 3:1 with 1% Et3N by volume)
to give 560 mg (95%) of diol 2 as a white solid after lyophilization
1
from benzene: mp 56.0-57.0 °C; [R]25 -1.65° (c 4.10, CHCl3); H
D
NMR (CDCl3) δ ∼6.2 (trace of E isomer, with an integral of 1/62 of
that of the Z O-vinyl proton), 5.94 (dt, J ) 6.28 Hz, J ) 0.97 Hz, 1H),
4.34 (m, 1H), 3.90-3.95 (m, 1H), 3.78-3.81 (m, 2H), 3.75 (ABq, J
) 3.68 Hz, ∆ν ) 10.84 Hz, 1H), 3.65 (ABq, J ) 5.56 Hz, ∆ν )
10.07 Hz, 1H), 2.51 (br s, 2H), 2.03-2.08 (m, 2H), 1.26 (s, 28H),
0.88 (t, J ) 6.51 Hz, 3H); 13C NMR (CDCl3) δ 144.47, 108.30, 73.13,
70.63, 63.58, 31.91, 29.69, 29.65, 29.51, 29.35, 29.29, 23.94, 22.67,
14.10; EI HRMS calcd for C21H42O3 (M+) m/z 342.3134, found
342.3138.
1-O-(1′-(Z)-Octadecenyl)-3-O-(tert-butyldiphenylsilyl)-sn-glyc-
erol (16). A solution of imidazole (60 mg, 0.88 mmol) and tert-
butyldiphenylsilyl chloride (144 mg, 0.53 mmol) in 3 mL of dry DMF
was stirred at room temperature for 30 min until a white precipitate
formed. The suspension was cooled to 0 °C, and 150 mg (0.44 mmol)
of 1-O-alkenyl-sn-glycerol 2 was added. The reaction mixture was
allowed to warm to room temperature with stirring for 1 h and then
diluted with 150 mL of Et2O, washed with water, and dried (Na2SO4).
Purification by column chromatography (elution with hexane/EtOAc
9:1) gave 230 mg (90%) of silyl ether 16 as a colorless oil: [R]25
D
+1.88° (c 0.64, CHCl3); 1H NMR (CDCl3) δ 7.65-7.67 (m, 4H), 7.37-
7.46 (m, 6H), 5.94 (d, J ) 6.20 Hz, 1H), 4.33-4.38 (m, 1H), 3.87-
3.94 (m, 1H), 3.83 (ABq, J ) 5.17 Hz, ∆ν ) 9.09 Hz, 1H), 3.78 (ABq,
J ) 5.86 Hz, ∆ν ) 8.67 Hz, 1H), 3.73 (d, 1H), 3.72 (s, 1H), 2.40 (d,
J ) 5.52 Hz, 1H), 1.98-2.03 (m, 2H), 1.25 (s, 28H), 1.06 (s, 9H),
0.88 (t, J ) 6.60 Hz, 3H); 13C NMR (CDCl3/CD3OD) δ 145.75, 136.18,
133.94, 130.36, 128.32, 107.78, 73.25, 71.40, 65.11, 32.56, 30.43, 30.30,
30.16, 29.98, 29.92, 27.16, 27.12, 24.50, 23.27, 19.27, 14.33; FAB
HRMS calcd for C37H59O3Si (M - H)+ m/z 579.4233, found 579.4245.
1-O-(1′-(Z)-Octadecenyl)-2-O-palmitoyl-3-O-(tert-butyldiphenyl-
silyl)-sn-glycerol (17). A solution of alcohol 16 (400 mg, 0.68 mmol),
palmitic anhydride (374 mg, 0.755 mmol), and DMAP (100 mg, 0.823
mmol) in 4 mL of alcohol-free CHCl3 was stirred for 16 h at room
temperature. The solvent was evaporated under vacuum, giving a
residue that was purified by column chromatography (elution with
presence of 1% Et3N by volume) to give 1.30 g (67%) of alkyne 14 as
1
a light yellow oil: [R]25 +4.80° (c 0.50, CHCl3); H NMR (CDCl3)
D
δ 7.22-7.28 (m, 4H), 6.84-6.89 (m, 4H), 4.60 (ABq, J ) 11.45 Hz,
∆ν ) 15.74 Hz, 2H), 4.45 (s, 2H), 4.10 (ABq, J ) 4.41 Hz, ∆ν )
9.85 Hz, 1H), 4.05 (ABq, J ) 6.04 Hz, 8.80 Hz, 1H), 3.84-3.90 (m,
1H), 3.80 (s, 3H), 3.79 (s, 3H), 3.52 (s, 1H), 3.51 (s, 1H), 2.09 (t, J )
7.04 Hz, 2H), 1.40-1.47 (m, 2H), 1.25 (s, 26H), 0.88 (t, J ) 6.48 Hz,
3H); 13C NMR (CDCl3) δ 159.25, 130.24, 130.05, 129.48, 129.29,
113.77, 113.75, 89.65, 78.03, 75.25, 73.10, 72.16, 68.90, 55.23, 37.26,
31.94, 29.72, 29.64, 29.38, 29.25, 28.92, 22.71, 17.19, 14.14; FAB
HRMS calcd for C37H55O5 (M - H)+ m/z 579.4050, found 579.4052.
1-O-(1′-(Z)-Octadecenyl)-2,3-bis-O-(4′-methoxybenzyl)-sn-glyc-
erol (15). A mixture of alkyne 14 (1.00 g, 1.72 mmol), Lindlar catalyst
(100 mg), and quinoline (50 µL, 0.42 mmol) in 30 mL of hexane/
EtOAc 1:1 was stirred under H2 at 1 atm for 2 h. The solid was filtered
through a silica gel pad, which was washed with hexane/EtOAc 1:1.
The filtrate was concentrated to give 1.00 g (100%) of O-alkenyl ether
hexane/EtOAc 9:1) to give 540 mg (98%) of product 17 as a colorless
1
oil: [R]25 +4.26° (c 5.00, CHCl3); H NMR (CDCl3) δ 7.65-7.67
D
(m, 4H), 7.35-7.43 (m, 6H), 5.91 (d, J ) 6.20 Hz, 1H), 5.09-5.14
(m, 1H), 4.32-4.37 (m, 1H), 3.95 (ABq, J ) 4.87 Hz, ∆ν ) 10.10
Hz, 1H), 3.90 (ABq, J ) 5.56 Hz, ∆ν ) 9.67 Hz, 1H), 3.80 (d, J )
4.91 Hz, 2H), 2.22-2.34 (m, 2H), 1.98-2.03 (m, 1H), 1.60 (quintet,
J ) 7.14 Hz, 2H), 1.25 (s, 52H), 1.05 (s, 9H), 0.88 (t, J ) 6.73 Hz,
6H); 13C NMR (CDCl3) δ 173.07, 144.90, 135.58, 135.53, 133.21,
133.16, 129.75, 127.73, 127.71, 107.71, 72.58, 69.96, 62.21, 34.41,
31.96, 29.79, 29.75, 29.70, 29.67, 29.61, 29.50, 29.40, 29.37, 29.34,
29.18, 26.75, 25.01, 24.95, 23.93, 22.72, 19.26, 14.14; FAB HRMS
calcd for C53H89O4Si (M - H)+ m/z 817.6530, found 817.6533.
1-O-(1′-(Z)-Octadecenyl)-2-O-palmitoyl-sn-glycero-3-phosphocho-
line (1). A solution of silyl ether 17 (200 mg, 0.244 mmol) and
imidazole (60 mg, 0.854 mmol) in 3 mL of THF was treated with 0.73
mL (0.73 mmol) of tetra-n-butylammonium fluoride (a 1.0 M solution
in THF) at -23 °C for 1 h. The reaction mixture was passed through
a silica gel pad, which was cooled to -78 °C and washed with cold
hexane/Et2O 1:1. The solvents were evaporated under vacuum, and the
residue was lyophilized with benzene. To a solution of the resulting
white solid (compound 18) in 4 mL of benzene were added 2-chloro-
2-oxo-1,3,2-dioxaphospholane (52 mg, 0.366 mmol) and pyridine (59
µL, 0.732 mmol). The reaction mixture was stirred overnight at 4 °C.
15 as a light yellow oil: [R]25 +6.70° (c 1.00, CHCl3); 1H NMR
D
(CDCl3) δ 7.22-7.28 (m, 4H), 6.83-6.87 (m, 4H), 5.92 (d, J ) 6.16
Hz, 1H), 4.60 (s, 2H), 4.45 (s, 2H), 4.31-4.36 (m, 1H), 3.86 (ABq, J
) 4.42 Hz, ∆ν ) 9.63 Hz, 1H), 3.78 (s, 3H), 3.77 (s, 3H), 3.73-3.82
(m, 2H), 3.49-3.56 (m, 2H), 2.03-2.08 (m, 2H), 1.25 (s, 28H), 0.88
(t, J ) 6.44 Hz, 3H); 13C NMR (CDCl3) δ 159.11, 159.09, 145.10,
130.52, 130.17, 129.32, 129.16, 113.65, 113.62, 106.97, 76.58, 72.97,
72.24, 71.96, 69.35, 55.11, 31.87, 29.79, 29.66, 29.61, 29.53, 29.31,
23.93, 23.64, 14.07; FAB HRMS calcd for C37H57O5 (M - H)+ m/z
581.4206, found 581.4208.

668 J. Am. Chem. Soc., Vol. 121, No. 4, 1999
Qin et al.
The solution was then frozen at -20 °C, and benzene was evaporated
under vacuum. The resulting white solid (compound 19) was transferred
to a pressure tube with 2 mL of benzene and diluted with 6 mL of
MeCN. The solution was cooled to -10 °C, and ∼4 mL (∼44 mmol)
of NMe3 was collected. The reaction mixture was stirred in the sealed
pressure tube at 70 °C for 24 h, then cooled to 0 °C, and applied to a
chromatography column (elution with a gradient of CHCl3/MeOH/H2O,
100:0:0, 80:20:0, 65:25:4) to give, after two filtrations through a Cameo
cartridge (Fisher Scientific) to remove suspended silica, 135 mg (74%)
of plasmalogen 1 as a white solid after lyophilization from benzene:
[R]25 -2.33° (c 0.90, CHCl3); [R]25 +1.50° (c 1.00, CHCl3/MeOH
0.88 (t, J ) 6.43 Hz, 6H); 13C NMR (CDCl3) δ 173.29, 144.82, 107.67,
71.69 (d, JCP ) 5.84 Hz), 70.50, 66.36 (d, JCP ) 3.82 Hz), 63.37 (d,
JCP ) 3.82 Hz), 59.36, 54.43, 34.41, 31.92, 29.80, 29.74, 29.73, 29.67,
29.56, 29.42, 29.38, 29.37, 29.19, 24.97, 23.96, 22.68, 14.11; FAB
HRMS calcd for C42H85O7PN (M + H)+ m/z 746.6064, found 746.6082.
Acknowledgment. This work was supported by NIH Grant
HL-16660. We thank Professor William F. Berkowitz for helpful
discussions. We gratefully acknowledge NSF Grant CHE-
9408535 for the purchase of the 400-MHz NMR spectrometer
and the mass spectrometry facility at Michigan State University
for HRMS data.
D
1
D
1:1); H NMR (CDCl3) δ 5.90 (d, J ) 6.13 Hz, 1H), 5.10-5.18 (m,
1H), 4.28-4.35 (m, 3H), 3.76-3.98 (m, 6H), 3.36 (s, 9H), 2.30 (t, J
) 7.27 Hz, 2H), 1.96-2.02 (m, 2H), 1.55-1.60 (m, 2H), 1.25 (s, 52H),
JA982837O