Preparation of optically pure 4-(hydroxymethyl)-2-pentadecyl-1,3-dioxolanes and their corresponding phosphodiester ether lipid derivatives

Article abstract of DOI:10.1016/S0009-3084(01)00185-2

Semi-preparative HPLC on a chiral stationary phase (Chiracel OD) was utilized in the course of this synthesis to separate the four possible diastereomers [cis-(2R,4S)-2a, trans-(2S,4S)-2b, cis-(2S,4R)-2a′, and trans-(2R,4R)-2b′] of a 2,4-disubstituted-1,3

Full text of DOI:10.1016/S0009-3084(01)00185-2

Chemistry and Physics of Lipids
113 (2001) 111–122
www.elsevier.com/locate/chemphyslip
Preparation of optically pure
4-(hydroxymethyl)-2-pentadecyl-1,3-dioxolanes and their
corresponding phosphodiester ether lipid derivatives
Sonyuan Lin a,1, Richard I. Duclos Jr. b, Alexandros Makriyannis a,c,
*
a School of Pharmacy, U-92, Uni6ersity of Connecticut, Storrs, CT 06269, USA
b Department of Physiology and Biophysics, Boston Uni6ersity School of Medicine, 715 Albany Street, Boston, MA 02118, USA
c Institute of Materials Science, U-136, Uni6ersity of Connecticut, Storrs, CT 06269, USA
Received 25 May 2001; received in revised form 21 August 2001; accepted 21 August 2001
Abstract
Semi-preparative HPLC on a chiral stationary phase (Chiracel OD) was utilized in the course of this synthesis to
separate the four possible diastereomers [cis-(2R,4S)-2a, trans-(2S,4S)-2b, cis-(2S,4R)-2a%, and trans-(2R,4R)-2b%] of
a 2,4-disubstituted-1,3-dioxolane into optically pure forms (100% de, 100% ee). The syntheses of phosphodiester head
group derivatives from each of these four conformationally constrained diastereomeric dioxolanes gave phospholipids
which are monocyclic ether lipid analogs. First, the series of four [[(2-pentadecyl-1,3-dioxolan-4-
yl)methyl]oxy]phosphocholines 5 were synthesized to give optically pure conformationally constrained analogues of
ET-16-OCH3. A head group variation was also demonstrated by the syntheses of the four diastereomeric [[(2-pentade-
cyl-1,3-dioxolan-4-yl)-methyl]oxy]phospho-b-(N-methylmorpholino)ethanols 6. © 2001 Published by Elsevier Science
Ireland Ltd.
Keywords: Ether lipid; Chiral chromatography; Benzyl glycerol; 1,3-Dioxolane; Phospholipid
1. Introduction
We have a continuing interest in the molecular
mechanism(s) of action of ether lipids (Duclos et
al., 1994; Duclos and Makriyannis, 1992; Koufaki
et al., 1996; Mavromoustakos et al., 1996). We
had previously synthesized a series of conforma-
tionally constrained monocyclic analogs of the
antineoplastic and immunomodulatory ether lipid
1-O-octadecyl-2-O-methylglycero-3-phosphocho-
line (ET-18-OCH3, Edelfosine) which were 1,4-
dioxane phospholipids (Duclos and Makriyannis,
Abbre6iations: bT, bath temperature; de, diastereomeric ex-
cess; ee, enantiomeric excess; EI, electron impact; ET-16-
OCH3,
rac-1-O-hexadecyl-2-O-methylglycero-3-phospho-
choline; ET-18-OCH3, rac-1-O-octadecyl-2-O-methylglycero-
3-phosphocholine; FAB, fast atom bombardment; pet,
petroleum hydrocarbons; tR, retention time.
* Corresponding author. Tel.: +1-860-486-2133; fax: +1-
860-486-3089.
E-mail
address:
makriyan@uconnvm.uconn.edu
(A.
Makriyannis).
1 Present address: Admetric Biochem, 200 Boston Avenue,
Medford, MA 02155, USA.
0009-3084/01/$ - see front matter © 2001 Published by Elsevier Science Ireland Ltd.
PII: S0009-3084(01)00185-2

112
S. Lin et al. / Chemistry and Physics of Lipids 113 (2001) 111–122
1992). This report details the syntheses of the
related 1,3-dioxolanes, which are a series of four
and Eibel, 1977; Weclas and Burczyk, 1981; Willy
et al., 1970), or important biological activities
(Bartrol´ı et al., 1991; Boekelheide et al., 1949;
Janes et al., 1999; Kim et al., 1992; Kucera et al.,
1990; Lin et al., 1999; Marasco et al., 1990; Marx
et al., 1989; Milbert and Wiley, 1978; Morris-
Natschke et al., 1990, 1993; Nagata et al., 1979;
Thurkauf et al., 1992; Wiley et al., 1970, 1982).
Some phosphorylated dioxolane derivatives were
also already reported (Bartrol´ı et al., 1991; Eibl
and Nicksch, 1978; Lacey and Loew, 1983; Marx
et al., 1989; Milbert and Wiley, 1978; Nagata et
al., 1979; Neher and Eibel, 1977; Wiley et al.,
1970, 1982). Antitumor ether phospholipids were
recently reviewed (Arthur and Bittman, 1998;
Houlihan et al., 1995; Principe and Braquet,
1995), and their primary mechanism of action has
been reported (Baburina and Jackowski, 1998;
Boggs et al., 1995). The ether lipids prepared from
this series of dioxolane diastereomers will be use-
ful to further evaluate what structural, stereo-
chemical, and conformational properties are
important for preferential accumulation within
neoplastic cell membranes, what biophysical dis-
turbances are caused in cell membranes by these
ether lipids, and what affects on cell–surface in-
teractions, signal transduction, and metabolism
by enzyme (cytidine triphosphate:phosphocholine
diastereomeric
2-alkyl-4-(hydroxymethyl)-1,3-
dioxolane derivatives.
Benzyl glycerol is one of the most useful of the
chiral 3-carbon synthons derived from natural
materials or available from asymmetric syntheses
in high optical purity, and both optical antipodes
were used as the starting materials for these chi-
rospecific syntheses. The enantiomers, 3-O-ben-
zyl-sn-glycerol 1 and 1-O-benzyl-sn-glycerol 1%,
are commercially available in 98–99% ee optical
purities. Also, the commercially available chiral
carboxylic acid derivatives commonly used
to establish optical purity, such as a-
(methoxy)phenylacetic acid (MPA) and a-
methoxy-a-(trifluoromethyl)phenylacetic
acid
(MTPA), are only 99% ee. Acid-catalyzed reac-
tion of 1- or 3-O-benzyl-sn-glycerol 1 with long
chain aldehydes (Takano et al., 1984), or prefer-
ably with their dimethylacetals, gives 1,3-diox-
olanes from the transacetalation reaction. Our
report will detail a novel chiral separation of these
synthetic derivatives to enrich these protected
starting materials to complete optical purities
(100% de, 100% ee) with semi-preparative HPLC
on a chiral stationary phase coupled with UV
detection for high sensitivity. This useful method-
ology provided gram quantities of all four possi-
ble 2,4-disubstituted-1,3-dioxolane derivatives in
optically pure forms. It was previously quite
difficult to even separate cis- from trans-diox-
olanes (Baumann, 1971; Craig et al., 1965; Inch
and Williams, 1970; Marasco et al., 1990; Piasecki
et al., 1996; Showler and Darley, 1967; Stefanovic
and Petrovic, 1967; Weclas et al., 1982; Wedmid
and Baumann, 1977), although there have been
some previous separations on chiral stationary
phases (Bernal et al., 2000; Foglia and Maeda,
1991) or enzymatically (Janes et al., 1999; Va¨ntti-
nen and Kanerva, 1996) to control the absolute
cytidylyltransferase,
phosphoinositide-specific
phospholipase C, calcium-dependent protein ki-
nase C, lysophosphocholine-acyltransferase, the
glucose transport protein, and others) inhibition
mechanisms result in selective neoplastic cytotoxi-
city and immunomodulation.
2. Experimental procedures
2.1. General
3-O-Benzyl-sn-glycerol (R)-1 and 1-O-benzyl-
sn-glycerol (S)-1% were purchased from Sigma.
p-TsOH was crystallized from C6H6. Reactions
were carried out under a N2 atmosphere with
magnetic stirring at ambient temperature in flame-
dried glassware and in anhydrous distilled sol-
vents. Reaction temperatures were reported as
bath temperatures (bT). Solutions containing
stereochemistries
dioxolanes.
of
2,4-disubstituted
1,3-
A variety of 1,3-dioxolane derivatives have al-
ready been reported to have important chemical
utilities (Li and Zhang, 2000), interesting biophys-
ical properties (Burczyk and Weclas, 1980; Jaeger
et al., 1990, 1994, 1996; Moss et al., 1990; Neher

S. Lin et al. / Chemistry and Physics of Lipids 113 (2001) 111–122
113
products were dried over anhydrous Na2SO4. Sol-
vents were removed by vacuum rotary evapora-
tion at a maximum temperature of approximately
40 °C. Silica gel 60 (230–400 mesh, E. Merck)
was used for column chromatography. The chiral
stationary phase for semi-preparative (250×20
diastereomers was further separated by HPLC
(Chiracel OD, 250×20 mm, 2.5:97.5 i-PrOH/n-
hexane, 2 ml/min, 0.12 g per injection). At a
retention time of 10 min 40 s eluted 4.8 g (12
mmol, 48% recovery) of cis-(2R,4S)-2a to give a
white solid: m.p. 32–33 °C; TLC (CHCl3) Rf
1
mm)
HPLC
was
Chiracel
OD
[(3,5-
0.56; H NMR (CDCl3) d 7.33 (br s, 5H), 4.88 (t,
dimethylphenyl)carbamoyl cellulose, 10 mm,
Daicel]. All products were demonstrated to be
homogeneous by analytical TLC on silica gel 60.
Iodine staining was used to visualize all chro-
matograms. Phosphorus-containing products were
also visualized on duplicate plates with phospho-
molybdic acid reagent (Sigma). All NMR spectra
(200, 270 or 500 MHz) utilized tetramethylsilane
(TMS) as an internal reference. Specific rotations
(90.1°) were determined from observed rotations
(90.001°) in a 1.00-dm cell. Electron impact (EI)
mass spectra and high-resolution mass spectra
were obtained with a Kratos MS-902 double-fo-
cusing magnetic sector mass spectrometer. Fast
atom bombardment (FAB) mass spectra and
high-resolution mass spectra were obtained with a
MAT 731 mass spectrometer fitted with an Ion
Tech gun for FAB.
1H, J=4.7 Hz, C2H), 4.58 (ABq, 2H), 4.24
(quintet, 1H), 3.90 (dd, 1H, J=8.0, 7.0 Hz), 3.77
(dd, 1H, J=8.0, 5.3 Hz), 3.56 (dd, 1H, J=9.7,
5.7 Hz), 3.44 (dd, 1H, J=9.7, 6.0 Hz), 1.60–1.65
(m, 2H), 1.25 (br s, 26H), 0.88 (t, 3H, J=6.0 Hz);
[a]2D5 +12.2° (c 1, CHCl3); EI mass spectrum m/z
404 (M+); EI HRMS calcd for C26H44O3 (M+)
m/z 404.3290, found m/z 404.3294. Anal. calcd
for C26H44O3: C, 77.18; H, 10.96. Found: C,
77.20; H, 11.14. Subsequently, 4.4 g (11 mmol,
44% recovery) of trans-(2S,4S)-2b eluted with a
retention time of 12 min 10 s to give a white solid:
1
m.p. 32–33 °C; TLC (CHCl3) Rf 0.56; H NMR
(CDCl3) d 7.34 (br s, 5H), 4.97 (t, 1H, J=4.7 Hz,
C2H), 4.57 (ABq, 2H), 4.28 (quintet, 1H), 4.11 (t,
1H, J=7.4 Hz), 3.64 (dd, 1H, J=7.7, 7.4 Hz),
3.58 (dd, 1H, J=10.1, 5.4 Hz), 3.48 (dd, 1H,
J=10.1, 4.9 Hz), 1.60–1.65 (m, 2H), 1.25 (br s,
26H), 0.88 (t, 3H, J=6.0 Hz); [a]2D5 +9.0° (c 1,
CHCl3); EI mass spectrum m/z 404 (M+); EI
HRMS calcd for C26H44O3 (M+) m/z 404.3290,
found m/z 404.3295. Anal. calcd for C26H44O3: C,
77.18; H, 10.96. Found: C, 77.29; H, 11.03.
2.2. cis-(2R,4S)-4-[(Benzyloxy)methyl]-2-
pentadecyl-1,3-dioxolane (cis-(2R,4S)-2a) and
trans-(2S,4S)-4-[(benzyloxy)methyl]-2-pentadecyl-
1,3-dioxolane (trans-(2S,4S)-2b)
To a stirred mixture of 10 g (55 mmol) of
3-O-benzyl-sn-glycerol (R)-1 and 31.4 g (110
mmol) of hexadecanal dimethylacetal (Piantadosi
et al., 1958) was added 240 mg of 5-sulfosalicylic
acid. The reaction mixture was heated at 140 °C
(bT) for 2 h, then at 170 °C (bT) for 15 min (4.5
ml of MeOH was distilled). The reaction mixture
was cooled to ambient temperature, then 100 ml
of 1 N NaOH was added with stirring. The reac-
tion mixture was diluted with 100 ml of H2O and
extracted with hexane (4×100 ml). The hexane
extracts were washed with H2O, saline, dried, and
the solvent removed. The residue was first purified
by column chromatography (40:60 CHCl3/pet) to
give 20 g (49 mmol, 89%) of a 55:45 mixture of
cis-(2R,4S)-2a to trans-(2S,4S)-2b as a white
solid. Then 10 g (25 mmol) of the mixture of
2.3. cis-(2S,4R)-4-[(Benzyloxy)methyl]-2-
pentadecyl-1,3-dioxolane (cis-(2S,4R)-2a%) and
trans-(2R,4R)-4-[(benzyloxy)methyl]-2-
pentadecyl-1,3-dioxolane (trans-(2R,4R)-2b%)
From 5.0 g (27 mmol) of 1-O-benzyl-sn-glyc-
erol (S)-1% and 15.7 g (55 mmol) of hexadecanal
dimethylacetal following the procedure described
for 2a and 2b was obtained 10.5 g (26 mmol, 96%)
of 55:45 2a%/2b% as a white solid. Then the two
diastereomers were separated by chiral HPLC as
previously detailed but with 0.15-g injections. At a
retention time of 11 min eluted a total of 4.3 g (11
mmol, 41%) of trans-(2R,4R)-2b% to give a white
1
solid: m.p. 32–33 °C; TLC (CHCl3) Rf 0.56; H
NMR (CDCl3) d 7.33 (br s, 5H), 4.97 (t, 1H,
J=4.7 Hz, C2H), 4.58 (ABq, 2H), 4.29 (quintet,

114
S. Lin et al. / Chemistry and Physics of Lipids 113 (2001) 111–122
1H), 4.12 (t, 1H, J=7.4 Hz), 3.64 (dd, 1H, J=
7.7, 7.4 Hz), 3.58 (dd, 1H, J=10.1, 5.4 Hz), 3.49
(dd, 1H, J=10.1, 4.9 Hz), 1.60–1.65 (m, 2H),
1.25 (br s, 26H), 0.88 (t, 3H, J=6.0 Hz); [a]D25
−9.0° (c 1, CHCl3); EI mass spectrum m/z 404
(M+); EI HRMS calcd for C26H44O3 (M+) m/z
404.3290, found m/z 404.3286. Anal. calcd for
C26H44O3: C, 77.18; H, 10.96. Found: C, 77.28; H,
11.02. Subsequently, 5.6 g (14 mmol, 52%) of
cis-(2S,4R)-2a% eluted with a retention time of 14
min to give a white solid: m.p. 32–33 °C; TLC
(dd, 1H, J=8.0, 5.3 Hz), 3.42 (ddd, 1H, J=12,
5.7, 4 Hz), 3.31 (ddd, 1H, J=12, 6, 5.7 Hz),
1.50–1.55 (m, 2H), 1.25–1.35 (m, 2H), 1.23 (br s,
24H), 0.85 (t, 3H, J=6.9 Hz); [a]2D5 −1.9° (c 1,
CHCl3); EI mass spectrum m/z 314 (M+); EI
HRMS calcd for C19H38O3 (M+) m/z 314.2821,
found m/z 314.2824. Anal. calcd for C19H38O3: C,
72.56; H, 12.18. Found: C, 72.54; H, 12.25.
2.5. trans-(2S,4S)-4-(Hydroxymethyl)-2-
pentadecyl-1,3-dioxolane (trans-(2S,4S)-3b)
1
(CHCl3) Rf 0.56; H NMR (CDCl3) d 7.33 (br s,
5H), 4.89 (t, 1H, J=4.7 Hz, C2H), 4.58 (ABq,
2H), 4.24 (quintet, 1H), 3.90 (dd, 1H, J=8.0, 7.0
Hz), 3.78 (dd, 1H, J=8.0, 5.3 Hz), 3.56 (dd, 1H,
J=9.7, 5.7 Hz), 3.44 (dd, 1H, J=9.7, 6.0 Hz),
1.60–1.65 (m, 2H), 1.25 (br s, 26H), 0.88 (t, 3H,
J=6.0 Hz); [a]2D5 −12.2° (c 1, CHCl3); EI mass
spectrum m/z 404 (M+); EI HRMS calcd for
C26H44O3 (M+) m/z 404.3290, found m/z
404.3294. Anal. calcd for C26H44O3: C, 77.18; H,
10.96. Found: C, 77.29; H, 11.04.
Hydrogenolysis of trans-(2S,4S)-2b (3.5 g, 8.6
mmol) following the procedure described above
gave 2.6 g (8.3 mmol, 96%) of trans-(2S,4S)-3b as
a white solid: m.p. 49–50 °C; TLC (5:95 MeOH/
1
CHCl3) Rf 0.31; H NMR (CDCl3) d 4.99 (t, 1H,
J=4.8 Hz), 4.19 (m, 1H), 4.09 (dd, 1H, J=8.1,
6.7 Hz), 3.69 (dd, 1H, J=11.8, 3.7 Hz), 3.65 (dd,
1H, J=8.1, 7.3 Hz), 3.61 (dd, 1H, J=11.8, 5.6
Hz), 1.95 (br s, 1H, OH), 1.59–1.67 (m, 2H),
1.30–1.45 (m, 2H), 1.25 (br s, 24H), 0.87 (t, 3H,
J=6.9 Hz); 13C NMR (CDCl3) d 104.85, 76.08,
66.51, 62.70, 34.10, 31.90, 29.33–29.67, 23.96,
2.4. cis-(2R,4S)-4-(Hydroxymethyl)-2-pentadecyl-
1,3-dioxolane (cis-(2R,4S)-3a)
1
22.66, 14.08; H NMR (DMSO-d6) d 4.86 (t, 1H,
J=4.8 Hz), 4.78 (t, 1H, J=5.5 Hz), 3.95–4.05
(m, 2H), 3.52 (m, 1H), 3.35–3.50 (m, 2H), 1.45–
1.55 (m, 2H), 1.25–1.35 (m, 2H), 1.23 (br s, 24H),
0.85 (t, 3H, J=6.7 Hz); [a]2D5 −0.5° (c 1, CHCl3);
EI mass spectrum m/z 314 (M+); EI HRMS calcd
for C19H38O3 (M+) m/z 314.2821, found m/z
314.2817. Anal. calcd for C19H38O3: C, 72.56; H,
12.18. Found: C, 72.60; H, 12.27.
Hydrogenolysis of 4.0 g (9.9 mmol) of cis-
(2R,4S)-2a was performed with 400 mg of palla-
dium hydroxide (20% on carbon) in 50 ml of
EtOH under 40 psi of H2 with mechanical shaking
on a Parr apparatus overnight. The catalyst was
removed by suction filtration through celite, and
the residue was washed with CH2Cl2. The com-
bined filtrates were evaporated and the residue
chromatographed (50:50 CHCl3/pet) to give 3.0 g
(9.5 mmol, 96%) of cis-(2R,4S)-3a as a white
solid: m.p. 49–50 °C; TLC (5:95 MeOH/CHCl3)
2.6. cis-(2S,4R)-4-(Hydroxymethyl)-2-
pentadecyl-1,3-dioxolane (cis-(2S,4R)-3a%)
1
Rf 0.31; H NMR (CDCl3) d 4.89 (t, 1H, J=4.8
Hydrogenolysis of cis-(2S,4R)-2a% (4.0 g, 9.9
mmol) following the procedure described above
gave 3.0 g (9.5 mmol, 96%) of cis-(2S,4R)-3a% as a
white solid: m.p. 49–50 °C; TLC (5:95 MeOH/
Hz), 4.17 (m, 1H), 3.88 (dd, 1H, J=8.0, 7.3 Hz),
3.81 (dd, 1H, J=8.0, 5.3 Hz), 3.72 (ddd, 1H,
J=11.6, 5.9, 3.8 Hz), 3.57 (ddd, 1H, J=11.6, 5.9,
5.8 Hz), 1.95 (t, 1H, J=5.7 Hz, OH), 1.65–1.70
(m, 2H), 1.30–1.45 (m, 2H), 1.25 (br s, 24H), 0.87
(t, 3H, J=6.9 Hz); 13C NMR (CDCl3) d 105.16,
76.22, 66.33, 63.41, 33.84, 31.90, 29.33–29.67,
1
CHCl3) Rf 0.31; H NMR (CDCl3) d 4.91 (t, 1H,
J=4.8 Hz), 4.18 (m, 1H), 3.91 (dd, 1H, J=8.1,
7.3 Hz), 3.82 (dd, 1H, J=8.1, 5.3 Hz), 3.73 (dd,
1H, J=11.7, 3.6 Hz), 3.57 (dd, 1H, J=11.7, 5.3
Hz), 1.96 (br s, 1H, OH), 1.65–1.70 (m, 2H),
1.30–1.45 (m, 2H), 1.24 (br s, 24H), 0.87 (t, 3H,
J=6.9 Hz); [a]2D5 +1.9° (c 1, CHCl3); EI mass
1
23.98, 22.66, 14.08; H NMR (DMSO-d6) d 4.78
(t, 1H, J=4.8 Hz), 4.76 (t, 1H, J=5.7 Hz, OH),
3.97 (m, 1H), 3.78 (dd, 1H, J=8.0, 6.9 Hz), 3.65

S. Lin et al. / Chemistry and Physics of Lipids 113 (2001) 111–122
115
spectrum m/z 314 (M+); EI HRMS calcd for
C19H38O3 (M+) m/z 314.2821, found m/z
314.2824. Anal. calcd for C19H38O3: C, 72.56; H,
12.18. Found: C, 72.64; H, 12.25.
NMR (1:2 CD3OD/CDCl3) d 4.87 (t, 1H, J=4.7
Hz), 4.15–4.45 (m, 3H), 3.80–4.10 (m, 4H), 3.56
(t, 2H, J=6 Hz), 1.50–1.75 (m, 2H), 1.25 (br s,
26H), 0.89 (t, 3H, J=6 Hz); [a]2D5 +0.5° (c 1,
20:80 MeOH/CHCl3); FAB mass spectrum m/z
501, 503 (MH+); FAB HRMS calcd for
C21H43O679BrP (MH+) m/z 501.1981, found m/z
501.1993. Anal. calcd for C21H42O6BrP–H2O: C,
48.56; H, 8.54. Found: C, 48.58; H, 8.31.
2.7. trans-(2R,4R)-4-(Hydroxymethyl)-2-
pentadecyl-1,3-dioxolane (trans-(2R,4R)-3b%)
Hydrogenolysis of trans-(2R,4R)-2b% (3.1 g, 7.7
mmol) following the procedure described above
gave 2.4 g (7.6 mmol, 99%) of trans-(2R,4R)-3b%
as a white solid: m.p. 49–50 °C; TLC (5:95
2.9. trans-(2S,4R)-[[(2-Pentadecyl-1,3-dioxolan-4-
yl)methyl]oxy]phospho-i-bromoethanol (trans-
(2S,4R)-4b)
1
MeOH/CHCl3) Rf 0.31; H NMR (CDCl3) d 4.99
(t, 1H, J=4.8 Hz), 4.20 (m, 1H), 4.10 (dd, 1H,
J=8.1, 6.8 Hz), 3.70 (dd, 1H, J=11.8, 3.3 Hz),
3.65 (dd, 1H, J=8.1, 7.3 Hz), 3.62 (dd, 1H,
J=11.8, 5.7 Hz), 2.02 (br s, 1H, OH), 1.61–1.65
(m, 2H), 1.30–1.45 (m, 2H), 1.24 (br s, 24H), 0.87
(t, 3H, J=6.9 Hz); [a]2D5 +0.5° (c 1, CHCl3); EI
mass spectrum m/z 314 (M+); EI HRMS calcd
for C19H38O3 (M+) m/z 314.2821, found m/z
314.2825. Anal. calcd for C19H38O3: C, 72.56; H,
12.18. Found: C, 72.59; H, 12.24.
The phosphorylation of trans-(2S,4S)-3b (1.5 g,
4.8 mmol) with b-bromoethyldichlorophosphate
(2.4 g, 9.9 mmol) as described above gave 2.0 g
(4.0 mmol, 83%) of trans-(2S,4R)-4b as a white
solid: TLC (25:75 MeOH/CHCl3) Rf 0.10; 1H
NMR (1:2 CD3OD/CDCl3) d 4.99 (t, 1H, J=4.6
Hz), 3.85–4.40 (m, 5H), 3.60–3.80 (m, 2H), 3.58
(t, 2H, J=6 Hz), 1.50–1.70 (m, 2H), 1.25 (br s,
26H), 0.88 (t, 3H, J=6 Hz); [a]2D5 +2.1° (c 1,
20:80 MeOH/CHCl3); FAB mass spectrum m/z
501, 503 (MH+); FAB HRMS calcd for
C21H43O679BrP (MH+) m/z 501.1981, found m/z
501.1974. Anal. calcd for C21H42O6BrP–H2O: C,
48.56; H, 8.54. Found: C, 48.76; H, 8.49.
2.8. cis-(2R,4R)-[[(2-Pentadecyl-1,3-dioxolan-4-
yl)methyl]oxy]phospho-i-bromoethanol (cis-
(2R,4R)-4a)
To a stirred solution of 2.0 g (8.3 mmol) of
b-bromoethyldichlorophosphate
(Eibl
and
Nicksch, 1978; Hansen et al., 1982; Hirt and
Berchtold, 1958) in 50 ml of Et2O was added 5 ml
(57 mmol) of pyridine followed by 1.3 g (4.1
mmol) of cis-(2R,4S)-3a in 50 ml of Et2O over 30
min. The reaction mixture was refluxed for 5 h,
cooled to 0 °C (bT), and then 1 ml of H2O was
added. The reaction was stirred for an additional
30 min, then allowed to warm to ambient temper-
ature and stirred overnight. The reaction mixture
was concentrated to 10 ml with a stream of N2
and the residue partitioned between 100 ml of
10:90 MeOH/CHCl3 and 100 ml of H2O. The
aqueous phase was extracted with additional (3×
100 ml) 10:90 MeOH/CHCl3 and the organic ex-
tracts were all combined and evaporated.
Chromatography (10:90 MeOH/CHCl3) gave 1.7
g (3.4 mmol, 83%) of cis-(2R,4R)-4a as a white
solid: TLC (25:75 MeOH/CHCl3) Rf 0.10; 1H
2.10. cis-(2S,4S)-[[(2-Pentadecyl-1,3-dioxolan-4-
yl)methyl]oxy]phospho-i-bromoethanol (cis-
(2S,4S)-4a%)
The phosphorylation of cis-(2S,4R)-3a% (1.1 g,
3.5 mmol) with b-bromoethyldichlorophosphate
(1.7 g, 7.0 mmol) as described above gave 1.4 g
(2.8 mmol, 80%) of cis-(2S,4S)-4a% as a white
solid: TLC (25:75 MeOH/CHCl3) Rf 0.10; 1H
NMR (1:2 CD3OD/CDCl3) d 4.88 (t, 1H, J=4.7
Hz), 4.15–4.45 (m, 3H), 3.80–4.10 (m, 4H), 3.57
(t, 2H, J=6 Hz), 1.50–1.75 (m, 2H), 1.25 (br s,
26H), 0.88 (t, 3H, J=6 Hz); [a]2D5 −0.5° (c 1,
20:80 MeOH/CHCl3); FAB mass spectrum m/z
501, 503 (MH+); FAB HRMS calcd for
C21H43O679BrP (MH+) m/z 501.1981, found m/z
501.1997. Anal. calcd for C21H42O6BrP–H2O: C,
48.56; H, 8.54. Found: C, 48.52; H, 8.41.

116
S. Lin et al. / Chemistry and Physics of Lipids 113 (2001) 111–122
2.11. trans-(2R,4S)-[[(2-Pentadecyl-1,3-dioxolan-
4-yl)methyl]oxy]phospho-i-bromoethanol (trans-
(2R,4S)-4b%)
(dd, 1H, J=8, 7 Hz), 3.80–4.10 (m, 2H), 3.70
(dd, 1H, J=8, 7 Hz), 3.55–3.65 (m, 2H), 3.23 (s,
9H), 1.50–1.75 (m, 2H), 1.27 (br s, 26H), 0.89 (t,
3H, J=6 Hz); [a]2D5 +0.8° (c 1, 20:80 MeOH/
CHCl3); FAB mass spectrum m/z 480 (MH+);
FAB HRMS calcd for C24H51NO6P (MH+) m/z
480.3454, found m/z 480.3461. Anal. calcd for
C24H50NO6P–H2O: C, 57.92; H, 10.53; N, 2.81.
Found: C, 58.04; H, 10.36; N, 2.71.
The phosphorylation of trans-(2R,4R)-3b% (1.1
g, 3.5 mmol) with b-bromoethyldichlorophos-
phate (1.6 g, 6.6 mmol) as described above gave
1.2 g (2.4 mmol, 69%) of trans-(2R,4S)-4b% as a
white solid: TLC (25:75 MeOH/CHCl3) Rf 0.10;
1H NMR (1:2 CD3OD/CDCl3) d 4.99 (t, 1H,
J=4.6 Hz), 3.85–4.40 (m, 5H), 3.60–3.80 (m,
2H), 3.57 (t, 2H, J=6 Hz), 1.50–1.70 (m, 2H),
1.25 (br s, 26H), 0.88 (t, 3H, J=6 Hz); [a]D25
−2.1° (c 1, 20:80 MeOH/CHCl3); FAB mass
spectrum m/z 501, 503 (MH+); FAB HRMS
calcd for C21H43O679BrP (MH+) m/z 501.1981,
2.14. cis-(2S,4S)-[[(2-Pentadecyl-1,3-dioxolan-
4-yl)methyl]oxy]phosphocholine (cis-(2S,4S)-5a%)
The quaternization of trimethylamine with cis-
(2S,4S)-4a% (600 mg, 1.2 mmol) as above gave 395
mg (0.79 mmol, 66%) of cis-(2S,4S)-5a% as a white
solid: TLC (60:30:4 CHCl3/MeOH/H2O) Rf 0.20;
1H NMR (1:2 CD3OD/CDCl3) d 4.88 (t, 1H,
J=4 Hz), 4.20–4.35 (m, 3H), 3.80–4.00 (m, 4H),
3.60–3.75 (m, 2H), 3.23 (s, 9H), 1.50–1.75 (m,
2H), 1.27 (br s, 26H), 0.89 (t, 3H, J=6 Hz); [a]D25
−3.6° (c 1, 20:80 MeOH/CHCl3); FAB mass
spectrum m/z 480 (MH+); FAB HRMS calcd for
C24H51NO6P (MH+) m/z 480.3454, found m/z
480.3459. Anal. calcd for C24H50NO6P–H2O: C,
57.92; H, 10.53; N, 2.81. Found: C, 57.98; H,
10.38; N, 2.89.
found
m/z
501.1976.
Anal.
calcd
for
C21H42O6BrP–H2O: C, 48.56; H, 8.54. Found: C,
48.71; H, 8.45.
2.12. cis-(2R,4R)-[[(2-Pentadecyl-1,3-dioxolan-
4-yl)methyl]oxy]phosphocholine (cis-(2R,4R)-5a)
The quaternization of trimethylamine with cis-
(2R,4R)-4a (600 mg, 1.2 mmol) according to a
reported method (Duclos et al., 1994; Duclos and
Makriyannis, 1992) gave 434 mg (0.87 mmol,
72%) of cis-(2R,4R)-5a as a white solid: TLC
(60:30:4 CHCl3/MeOH/H2O) Rf 0.20; 1H NMR
(1:2 CD3OD/CDCl3) d 4.87 (t, 1H, J=4 Hz),
4.20–4.35 (m, 3H), 3.80–4.00 (m, 4H), 3.60–3.80
(m, 2H), 3.24 (s, 9H), 1.50–1.75 (m, 2H), 1.27 (br
s, 26H), 0.89 (t, 3H, J=6 Hz); [a]2D5 +3.6° (c 1,
20:80 MeOH/CHCl3); FAB mass spectrum m/z
480 (MH+); FAB HRMS calcd for C24H51NO6P
(MH+) m/z 480.3454, found m/z 480.3449. Anal.
calcd for C24H50NO6P–H2O: C, 57.92; H, 10.53;
N, 2.81. Found: C, 58.08; H, 10.39; N, 2.86.
2.15. trans-(2R,4S)-[[(2-Pentadecyl-1,3-dioxolan-
4-yl)methyl]oxy]phosphocholine (trans-(2R,4S)-
5b%)
The quaternization of trimethylamine with
trans-(2R,4S)-4b% (680 mg, 1.4 mmol) as above
gave 535 mg (1.1 mmol, 79%) of trans-(2R,4S)-5b%
as a white solid: TLC (60:30:4 CHCl3/MeOH/
1
H2O) Rf 0.20; H NMR (1:2 CD3OD/CDCl3) d
4.99 (t, 1H, J=4 Hz), 4.20–4.35 (m, 3H), 4.15
(dd, 1H, J=8, 7 Hz), 3.80–4.10 (m, 2H), 3.72
(dd, 1H, J=8, 7 Hz), 3.55–3.65 (m, 2H), 3.23 (s,
9H), 1.50–1.75 (m, 2H), 1.27 (br s, 26H), 0.89 (t,
3H, J=6 Hz); [a]2D5 −0.8° (c 1, 20:80 MeOH/
CHCl3); FAB mass spectrum m/z 480 (MH+);
FAB HRMS calcd for C24H51NO6P (MH+) m/z
480.3454, found m/z 480.3466. Anal. calcd for
C24H50NO6P–H2O: C, 57.92; H, 10.53; N, 2.81.
Found: C, 57.80; H, 10.60; N, 2.69.
2.13. trans-(2S,4R)-[[(2-Pentadecyl-1,3-dioxolan-
4-yl)methyl]oxy]phosphocholine (trans-(2S,4R)-5b)
The quaternization of trimethylamine with
trans-(2S,4R)-4b (560 mg, 1.1 mmol) as above
gave 322 mg (0.65 mmol, 59%) of trans-(2S,4R)-
5b as a white solid: TLC (60:30:4 CHCl3/MeOH/
1
H2O) Rf 0.20; H NMR (1:2 CD3OD/CDCl3) d
4.99 (t, 1H, J=4 Hz), 4.20–4.35 (m, 3H), 4.14

S. Lin et al. / Chemistry and Physics of Lipids 113 (2001) 111–122
117
2.16. cis-(2R,4R)-[[(2-Pentadecyl-1,3-dioxolan-
4-yl)methyl]oxy]phospho-i-(N-methylmorpholino)-
ethanol (cis-(2R,4R)-6a)
(m, 2H), 1.26 (br s, 26H), 0.88 (t, 3H, J=6 Hz);
[a]2D5 −1.7° (c 1, CHCl3); FAB mass spectrum
m/z 522 (MH+); FAB HRMS calcd for
C26H53NO7P (MH+) m/z 522.3559, found m/z
522.3568. Anal. calcd for C26H52NO7P–H2O: C,
57.86; H, 10.09; N, 2.60. Found: C, 57.93; H,
9.98; N, 2.70.
The quaternization of N-methylmorpholine
with cis-(2R,4R)-4a (600 mg, 1.2 mmol) according
to a reported method (Duclos et al., 1994) gave
130 mg (0.25 mmol, 21%) of cis-(2R,4R)-6a as a
white solid: TLC (60:30:4 CHCl3/MeOH/H2O) Rf
0.14; 1H NMR (1:2 CD3OD/CDCl3) d 4.87 (t, 1H,
J=4 Hz), 4.20–4.35 (m, 3H), 3.45–4.10 (m,
14H), 3.31 (s, 3H), 1.50–1.75 (m, 2H), 1.27 (br s,
26H), 0.88 (t, 3H, J=6 Hz); [a]2D5 +1.7° (c 1,
CHCl3); FAB mass spectrum m/z 522 (MH+);
FAB HRMS calcd for C26H53NO7P (MH+) m/z
522.3559, found m/z 522.3571. Anal. calcd for
C26H52NO7P–H2O: C, 57.86; H, 10.09; N, 2.60.
Found: C, 57.94; H, 10.21; N, 2.72.
2.19. trans-(2R,4S)-[[(2-Pentadecyl-1,3-dioxolan-
4-yl)methyl]oxy]phospho-i-(N-methylmorpholino)-
ethanol (trans-(2R,4S)-6b%)
The quaternization of N-methylmorpholine
with trans-(2R,4S)-4b% (430 mg, 0.86 mmol) as
above gave 48 mg (0.092 mmol, 11%) of trans-
(2R,4S)-6b% as a white solid: TLC (60:30:4 CHCl3/
1
MeOH/H2O) Rf 0.14; H NMR (CDCl3) d 4.94 (t,
1H, J=4 Hz), 3.30–4.60 (m, 17H), 3.34 (s, 3H),
1.50–1.75 (m, 2H), 1.26 (br s, 26H), 0.88 (t, 3H,
J=6 Hz); [a]2D5 +1.4° (c 1, CHCl3); FAB mass
spectrum m/z 522 (MH+); FAB HRMS calcd for
C26H53NO7P (MH+) m/z 522.3559, found m/z
522.3550. Anal. calcd for C26H52NO7P–H2O: C,
57.86; H, 10.09; N, 2.60. Found: C, 57.64; H,
10.11; N, 2.49.
2.17. trans-(2S,4R)-[[(2-Pentadecyl-1,3-dioxolan-
4-yl)methyl]oxy]phospho-i-(N-methylmorpholino)-
ethanol (trans-(2S,4R)-6b)
The quaternization of N-methylmorpholine
with trans-(2S,4R)-4b (800 mg, 1.6 mmol) as
above gave 305 mg (0.58 mmol, 36%) of trans-
(2S,4R)-6b as a white solid: TLC (60:30:4 CHCl3/
MeOH/H2O)
Rf
0.14;
1H
NMR
(1:2
3. Results and discussion
CD3OD/CDCl3) d 4.98 (t, 1H, J=4 Hz), 4.20–
4.35 (m, 3H), 4.13 (dd, 1H, J=8, 7 Hz), 3.45–
4.10 (m, 13H), 3.32 (s, 3H), 1.50–1.75 (m, 2H),
1.26 (br s, 26H), 0.88 (t, 3H, J=6 Hz); [a]D25
−1.4° (c 1, CHCl3); FAB mass spectrum m/z 522
(MH+); FAB HRMS calcd for C26H53NO7P
(MH+) m/z 522.3559, found m/z 522.3554. Anal.
calcd for C26H52NO7P–H2O: C, 57.86; H, 10.09;
N, 2.60. Found: C, 57.99; H, 10.16; N, 2.34.
The syntheses of both head group series of the
four possible conformationally constrained
diastereomeric dioxolane phospholipid analogs in
optically pure forms are shown in Scheme 1. The
acid-catalyzed
hexadecanal
dimethylacetal
transacetalations with the 3- and 1-O-benzyl-sn-
glycerols, (R)-1 and (S)-1%, were found to be
superior to the acetalations of these diols with
hexadecanal, which for example, only gave a 60%
yield of a mixture of the diastereomeric diox-
olanes cis-(2R,4S)-2a and trans-(2S,4S)-2b from
3-O-benzyl-sn-glycerol (R)-1 with loss of the wa-
ter byproduct at a high reaction temperature. For
the transacetalations, the hexadecanal dimethylac-
etal (Piantadosi et al., 1958) was first prepared by
the oxidation of hexadecanol with pyridinium
chlorochromate in anhydrous dichloromethane to
form hexadecanal, which was then converted to
its dimethyl acetal with catalytic p-toluenesulfonic
2.18. cis-(2S,4S)-[[(2-Pentadecyl-1,3-dioxolan-
4-yl)methyl]oxy]phospho-i-(N-methylmorpholino)-
ethanol (cis-(2S,4S)-6a%)
The quaternization of N-methylmorpholine
with cis-(2S,4S)-4a% (600 mg, 1.2 mmol) as above
gave 89 mg (0.17 mmol, 14%) of cis-(2S,4S)-6a% as
a white solid: TLC (60:30:4 CHCl3/MeOH/H2O)
1
Rf 0.14; H NMR (CDCl3) d 4.82 (t, 1H, J=4
Hz), 3.40–4.50 (m, 17H), 3.32 (s, 3H), 1.50–1.75

118
S. Lin et al. / Chemistry and Physics of Lipids 113 (2001) 111–122
acid in methanol. The transacetalation of hexade-
canal dimethylacetal with 3-O-benzyl-sn-glycerol
(R)-1 and catalytic 5-sulfosalicylic acid gave an
improved 90% yield of the (4S)-4-[(benzy-
120 mg onto the chiral column (Chiracel OD)
readily produced gram quantities of optically pure
cis-(2R,4S)-4-[(benzyloxy)methyl]-2-pentadecyl-
1,3-dioxolane cis-(2R,4S)-2a (tR 10 min 40 s) and
trans-(2S,4S)-4-[(benzyloxy)methyl]-2-pentadecyl-
1,3-dioxolane trans-(2S,4S)-2b (tR 12 min 10 s).
No epimerizations occurred during these separa-
tions and the subsequent product isolations.
The syntheses of the other two possible
diastereomers cis-(2S,4R)-2a% and trans-(2R,4R)-
2b% were performed by the same procedure except
starting with 1-O-benzyl-sn-glycerol (S)-1%. Inter-
estingly, on the chiral stationary phase the trans-
dioxolane eluted before the cis-dioxolane, the
opposite of the previous separation where the
cis-diastereomer eluted first. Not only did trans-
(2R,4R)-4-[(benzyloxy)methyl]-2-pentadecyl-1,3-
dioxolane trans-(2R,4R)-2b% (tR 11 min) elute
ahead of cis-(2S,4R)-4-[(benzyloxy)methyl]-2-pen-
tadecyl-1,3-dioxolane cis-(2S,4R)-2a% (tR 14 min),
but higher loadings of 150 mg per injection were
possible due to the longer retention times and
better separation. These four diastereomers 2a,
2b, 2a%, 2b% were utilized in our ether lipid synthe-
loxy)methyl]-2-pentadecyl-1,3-dioxolanes
[cis-
(2R,4S)-2a and trans-(2S,4S)-2b] at a lower
reaction temperature with removal of the
methanol byproduct. The reaction with an achiral
reagent created a second chiral center to give a
55:45 mixture of cis- to trans-dioxolanes. The
transacetalation product was a mixture of the two
major products cis-(2R,4S)-2a and trans-(2S,4S)-
2b, and trace amounts (generally well under 1%)
of two diastereomers cis-(2S,4R)-2a% and trans-
(2R,4R)-2b%.
The
separation
of
these
diastereomers was not feasible with silica gel chro-
matography. However, the isolations of both the
cis-(2R,4S)-2a and trans-(2S,4S)-2b diastereomers
were accomplished by semi-preparative HPLC on
a chiral stationary phase, which was also useful
for removing any traces of the other two diox-
olane diastereomers resulting from the presence of
any (S)-enantiomer (S)-1% in the starting (R)-3-O-
benzyl-sn-glycerol (R)-1. Multiple injections of
Scheme 1.

S. Lin et al. / Chemistry and Physics of Lipids 113 (2001) 111–122
119
ses, alternatively, acetal deprotection could give
optically pure forms of the 3- and 1-O-benzyl-sn-
glycerols (R)-1 and (S)-1%.
quaternizations of trimethylamine gave cis-
(2R,4R)-[[(2-pentadecyl-1,3-dioxolan-4-yl)methyl]-
oxy]phosphocholine
cis-(2R,4R)-5a,
trans-
The benzyl protecting group of each dioxolane
2 diastereomer was removed by hydrogenolysis
with palladium hydroxide in ethanol to give the
corresponding alcohols 3 in high yield. Both cis-3
and trans-3 have been previously reported as
racemic mixtures (Baumann, 1971; Wedmid and
Baumann, 1977). 2,4-Disubstituted-1,3-dioxolanes
are readily assigned as cis or trans. The C2 acetal
proton for the trans-diastereomers are always
(2S,4R)-[[(2-pentadecyl-1,3-dioxolan-4-yl)methyl]-
oxy]phosphocholine trans-(2S,4R)-5b, cis-(2S,4S)-
[[(2 - pentadecyl - 1,3 - dioxolan - 4 - yl)methyl]oxy]
phosphocholine cis-(2S,4S)-5a%, and trans-
(2R,4S)-[[(2-pentadecyl-1,3-dioxolan-4-yl)methyl]-
oxy]phosphocholine trans-(2R,4S)-5b% in overall
yields of 23, 18, 25, and 21%, respectively. The
phosphocholines cis-(2R,4R)-5a and trans-
(2S,4R)-5b are the cyclized structures derived
from the enol ether lysoplasmalogen phospho-
choline (Pietruszko and Gray, 1962). This series
of four monocyclic conformationally constrained
phosphocholine ether lipids which are 1,3-diox-
olane derivatives are also closely structurally re-
lated to both lysophosphocholine and the ether
1
downfield in the H NMR spectra (Baggett et al.,
1966; Baumann, 1971; Carman and Kibby, 1976;
Duclos and Makriyannis, 1992; Inch and
Williams, 1970; Wedmid and Baumann, 1977).
This was demonstrated unambiguously by the
intramolecular cyclizations of some cis-dioxolanes
(Baggett et al., 1966; Duclos and Makriyannis,
1992; Inch and Williams, 1970). The assignments
of the dioxolane ring protons, especially the
diastereotopic C5-H2 protons, have been dis-
cussed (Carman and Kibby, 1976; Inch and
Williams, 1970). Our NOESY analysis of cis-3 in
CDCl3 demonstrated nOe contact of the C2-H
acetal with both the C4-H and with the downfield
C5-H, which was also more strongly coupled to
the syn C4-H proton. The upfield C5-H proton is
syn to the exocyclic hydroxymethyl group, and
nOe contact with that methylene was observed.
The NOESY analysis of trans-3 in CDCl3 only
showed nOe contact of the C2-H acetal with the
upfield C5-H.
Two series of zwitterionic phosphodiester
derivatives were prepared which had choline and
N-methylmorpholinium head groups, respectively.
Each of the four optically pure diastereomeric
alcohols cis-(2R,4S)-3a, trans-(2S,4S)-3b, cis-
(2S,4R)-3a%, and trans-(2R,4R)-3b% was first phos-
phorylated by the mild procedure previously
detailed (Duclos et al., 1994; Duclos and
Makriyannis, 1992). The condensations of the
alcohols 3 with b-bromoethyldichlorophosphate
(Eibl and Nicksch, 1978; Hansen et al., 1982; Hirt
and Berchtold, 1958) in the presence of pyridine
gave their corresponding b-bromoethylphosphodi-
esters 4, which were each used to quaternize both
trimethylamine and N-methylmorpholine. The
lipid
1-O-hexadecyl-2-O-methylglycero-3-phos-
phocholine (ET-16-OCH3).
The quaternizations of N-methylmorpholine
with the b-bromoethylphosphodiesters 4 tended to
give lower yields (Duclos et al., 1994; Ohno et al.,
1985) and some variations have been reported
(Koufaki et al., 1996; Takatani et al., 1989). Over-
all yields of the series of N-methylmorpholinium
head group analogs cis-(2R,4R)-[[(2-pentadecyl-
1,3-dioxolan-4-yl)
methyl]oxy]phospho-b-(N-
methylmorpholino)ethanol cis-(2R,4R)-6a, trans-
(2S,4R)-[[(2-pentadecyl-1,3-dioxolan-4-yl) methyl]
oxy]phospho - b - (N - methylmorpholino)ethanol
trans-(2S,4R)-6b, cis-(2S,4S)-[[(2-pentadecyl-1,3-
dioxolan-4-yl) methyl]oxy]phospho-b-(N-methyl-
morpholino)ethanol cis-(2S,4S)-6a%, and trans-
(2R,4S)-[[(2-pentadecyl-1,3-dioxolan-4-yl) methyl]
oxy]phospho - b - (N - methylmorpholino)ethanol
trans-(2R,4S)-6b% were 7, 10, 5, and 3%, respec-
tively.
It is still difficult to tell in advance when chiral
chromatography will be effective for any specific
separation, though there are a growing number of
reports (Okamoto and Yashima, 1998; Yashima
et al., 1998). Semi-preparative HPLC on a chiral
stationary phase was utilized in the course of this
synthesis to purify optically active commercially
available synthons following derivitizations to
complete optical purities (100% de, 100% ee).
Larger scale separations or simulated moving bed

120
S. Lin et al. / Chemistry and Physics of Lipids 113 (2001) 111–122
derivatives by supercritical fluid chromatography on an
separations (Ludemann-Hombourger et al., 2000;
Miller et al., 1999; Terfloth, 1999) with Chiracel
OD might also be possible. Optically pure forms
of the four possible diastereomeric 1,3-dioxolane
intermediates were converted to ether lipids, and
two head group variations were initially prepared.
Both series of four head group analogs, which
are sterically conformationally constrained
diastereomeric 1,3-dioxolane ether lipids, are cur-
rently the subjects of biophysical studies as well as
biochemical screenings.
amylose-based column. J. Chromatogr.
137.
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Boekelheide, V., Liberman, L., Figueras, J., Krespan, C.,
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lated compounds. J. Am. Chem. Soc. 71, 3303–3307.
Boggs, K.P., Rock, C.O., Jackowski, S., 1995. Lysophos-
phatidylcholine and 1-O-octadecyl-2-O-methyl-rac-glyc-
ero-3-phosphocholine inhibit the CDP-choline pathway of
phosphatidylcholine synthesis at the CTP:phosphocholine
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Burczyk, B., Weclas, L., 1980. Chemical structure and surface
activity. Part II: Synthesis and surface properties of 2-al-
kyl-4-hydroxy-methyl-1,3-dioxolanes at the oil–water in-
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Carman, R.M., Kibby, J.J., 1976. Chiral benzylidene deriva-
tives of glycerol. Aust. J. Chem. 29, 1761–1767.
Craig, J.C., Hamon, D.P.G., Brewer, H.W., Ha¨rle, H., 1965.
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Acknowledgements
We gratefully acknowledge support by a grant
from the National Institute on Drug Abuse (DA-
3801 to A. Makriyannis). The EI MS and EI
HRMS data were measured by M.R. Thompson
at the University of Connecticut Department of
Chemistry. The FAB MS and FAB HRMS data
were measured by C.E. Costello and C.-H. Zeng
at the Massachusetts Institute of Technology
Mass Spectrometry Facility which was supported
by NIH Grant No. RR00317 (to K. Biemann).
Special thanks to S.-L. Wu, O. H. Abdel-Mageed,
R.A. Zoeller, and G.G. Shipley.
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