Stereodependent Fusion and Fission of Vesicles
J. Am. Chem. Soc., Vol. 119, No. 19, 1997 4343
under reflux for 48 h. The reaction mixture was filtered, and the filtrate
was concentrated in vacuo. The residue was dissolved in ethyl acetate
and washed with aqueous 10% NaS2O3 and brine. After drying over
MgSO4 and evaporation of the solvent, a diastereomeric mixture of 3c
was obtained to which trifluoroacetic acid/methanol/water (4:1:8, v/v/
v) was added. The reaction mixture was stirred for 48 h at room
temperature and then poured into ethyl acetate. The organic layer was
washed with an aqueous 5% solution of Na2CO3 and brine, dried over
MgSO4, and concentrated. After crystallization from chloroform, 4c
was obtained in a yield of 94%. Mp 129-131 °C. Anal.
(C4H8O2I2): C, H, Calcd: 14.05, 2.36. Found: 14.43, 2.43. IR (KBr,
cm-1): ν 3250 (OH), 2910, 2850 (C-H). 1H-NMR (CDCl3/CD3OD,
ppm): δ 3.25 (m, 2H, CH), 3.50 (m, 4H, CH2). MS (EI+, m/z): 342
(M+), 215 (M - I).
Experimental Section
General Methods. 1H-NMR spectra were recorded on a Bruker
AM-400 spectrometer using tetramethylsilane as the internal standard.
Proton-decoupled 81 MHz 31P and 50 MHz 13C NMR spectra were
obtained using a Bruker WM-200 spectrometer. Chemical shifts are
reported relative to trimethyl phosphate and CDCl3, respectively. IR
spectra were recorded with a Perkin Elmer 298 spectrometer. Mass
spectra were recorded on a VG 7070 E spectrometer. Optical rotations
were measured on a Perkin Elmer 241 polarimeter. Melting points
were determined using a Reichert Thermopan microscope and are
uncorrected. In chromatographic procedures silica gel 60H (Merck art.
no. 7736) or silica gel 60 silanated (Merck art. no. 7719) were used as
the stationary phase. For ion exchange Dowex 50 W × 2 in Na+-
form (Fluka AG, art. no. 44465) was used. Thin layer chromatograms
(2R,3R)-1,4-Iodobutane-2,3-diyl Dioctadecanoate, 5a. Stearoyl
chloride (3.5 g, 11.5 mmol) in dry ether was added at 0 °C to a solution
of 4a (0.85 g, 2.5 mmol) in dry diethyl ether (34 mL) and dry pyridine
(4.3 mL). After standing for 24 h at room temperature, the reaction
mixture was poured into ice water and extracted with diethyl ether.
The organic layer was washed with aqueous 2 N H2SO4 and with a
saturated solution of Na2S2O3, dried over MgSO4 and concentrated.
The product 5a crystallized from acetonitrile and was isolated as a white
solid in 97% yield. Mp 54-56 °C.25 [R]D20) +5.3° (CH2Cl2, c 1.0).
IR (KBr, cm-1): ν 2950, 2910, 2850 (C-H), 1740 (CdO). 1H-NMR
(CDCl3, ppm): δ 0.88 (t, 6H, CH3, J ) 6.7 Hz), 1.25 (m, 56H,
CH2(CH2)14CH3), 1.56 (m, 4H, C(O)CH2CH2), 2,31 (t, 4H, C(O)CH2,
J ) 7.5 Hz), 3.22 (d, 4H, CH2I, J ) 5.8 Hz), 4.66 (m, 2H, CH). 13C-
NMR {H}(CDCl3, ppm): δ 9.3 CH2I, 13.9-34.11 (C-stearoyl), 72.0
(CH), 172.7 (CdO). MS (FB+, m/z): 875 (M + 1), 747 (M - I).
were run on glass supported silica gel 60 plates (0.25 mm-layer, F254
,
Merck art. no. 5715). The molybdate23 and Knight and Young24 sprays
were used as location reagents. Solvents were dried and distilled, when
appropriate, using the following methods: diethyl ether, benzene, and
dichloromethane were distilled from calcium hydride; toluene was
distilled from sodium, pyridine was distilled from sodium hydroxide,
and THF was distilled from lithium aluminium hydride. All other
solvents used were of analytical grade.
1,4-Ditosyl Erythritol. Erythritol (4 g, 33 mmol) was dissolved in
pyridine (80 mL) and cooled to -20 °C. A solution of tosyl chloride
(12.5 g, 30 mmol) in dry dichloromethane (40 mL) was added dropwise
over a period of 8 h. The reaction mixture was stirred for another 16
h while warming to room temperature. After concentration in vacuo
dichloromethane was added to the mixture, and the organic layer was
washed with aqueous 1 M sulfuric acid, water, and brine. After drying
over MgSO4 and evaporation of the solvent, the mixture was subjected
to column chromatography (silica gel, ethyl acetate/hexane 1:1, v/v).
After crystallization from chloroform, 1,4-ditosyl erythritol was obtained
in 55% yield (mp 88 °C). IR (KBr, cm-1): ν 3500 (O-H), 3020 (C-H
arom), 2980, 2920, 2850 (C-H alkyl), 1600 (SdO). 1H-NMR (CDCl3,
ppm): δ 1.60 (br.s, 2H, OH), 2.45 (s, 6H, CH3C6H5) 4.05 (m, 4H,
CH2), 4.65 (m, 2H, CH), 7.25 (d, 4H, H3 and H5 arom, J ) 5 Hz),
7.80 (d, 4H, H2 and H6 arom, J ) 5 Hz).
1,4-Ditosyl-2,3-O-isopropylidene Erythritol, 2c. To a suspension
of 1,4-ditosyl erythritol (1.0 g, 2.39 mmol) in 2,2-dimethoxypropane
(10 mL) was then added p-toluenesulfonic acid (45 mg, 2.4 mmol),
and the mixture was stirred for 16 h at room temperature. A saturated
aqueous solution of NaHCO3 was added, and the mixture was extracted
with ethyl acetate. The organic layer was washed with water and brine,
dried over MgSO4, and concentrated in vacuo. Crystallization from
ethyl acetate gave pure 2c in 94% yield (Mp 127-129 °C) Anal.
(C21H26S2O8) C, H, S Calcd: 52.60, 5.57, 13.63. Found: 52.60, 5.37,
13.50. IR (KBr, cm-1): ν 3020 (C-H arom), 2980, 2920, 2850 (C-H
alkyl), 1600 (SdO). 1H-NMR (CDCl3, ppm): δ 1.30 (s, 3H, CH3),
1.32 (s, 3H, CH3), 2.45 (s, 6H, CH3Tos) 4.05 (m, 4H, CH2), 4.30 (m,
2H, CH), 7.25 (d 4H, H3 and H5 arom, J ) 5 Hz,), 7.80 (d, 4H, H2
and H6 arom, J ) 5 Hz). MS (EI, m/z): 470 (M+), 285 (M -
CH2OTos).
(2S,3S)-1,4-Diiodobutane-2,3-diyl Dioctadecanoate, 5b. Com-
pound 5b was synthesized starting from 4b using the same procedure
as described for compound 5a. A white solid was obtained in 96%
20
yield. Mp 54-56 °C.25 [R]D ) -6.8° (CH2Cl2, c 1.0).
(2S,3R)-1,4-Diiodobutane-2,3-diyl Dioctadecanoate, 5c. Com-
pound 5c was synthesized starting from 4c using the same procedure
as described for compound 5a. A white solid was obtained in 90%
yield. Mp 79-81 °C.25 Anal. (C40H76O4I2): C, H, Calcd: 54.92, 8.76.
Found: 55.47, 8.79. IR (KBr, cm-1): ν 2950, 2910, 2840 (C-H),
1740 (CdO). 1H-NMR (CDCl3, ppm): δ 0.88 (t, 6H, CH3, J ) 6.7
Hz), 1.25 (m, 56H CH2(CH2)14CH3), 1.66 (m, 4H, C(O)CH2CH2), 2,37
(t, 4H, C(O)CH2, J ) 7.5 Hz), 3.30 (dd, AA′XX′YY′, 2H, CH2I), 3.30
(dd, AA′XX′YY′, 2H, CH2I), 4.86 (m, AA′XX′YY′, 2H, CH). MS (FB+,
m/z): 897 (M + Na+), 747 (M - I).
(2R,3R)-Di(octadecanoyloxy)butane-1,4-diyl Bis(dibenzylphos-
phate), 6a. To a solution of 5a (2.7 g, 3.0 mmol) in dry toluene (40
mL) was added silver dibenzyl phosphate16 (6.6 mmol) while stirring
under argon. The mixture was heated under reflux for 4 h with
exclusion of light. The suspension was filtered over Hyflo, and the
filtrate was concentrated under reduced pressure. After flash chroma-
tography (silicagel, hexane/ethyl acetate ) 7/3, v/v) the product 6a
was obtained as a colorless oil and crystallized from its acetonitrile
solution (yield 85%). Mp 44-45 °C; [R]D20 ) -1.69° (CH2Cl2, c 1.0).
IR (KBr, cm-1): ν 3090, 3060, 3030 (C-H aryl), 2920, 2840 (C-H),
1745 (CdO), 1285 (PdO), 1010 (P-O-C). 1H-NMR (CDCl3, ppm):
δ 0.88 (t, 6H, CH3, J ) 6.7 Hz), 1.25 (m, 56H CH2(CH2)14CH3), 1.56
(m, 4H, C(O)CH2CH2), 2.31 (t, 4H, C(O)CH2 J ) 7.5 Hz), 4.12 (m,
4H, CHCH2O), 5.07 (dd, 8H, CH2Bz, JP-H ) 8.4 Hz, JH-H ) 1.0 Hz)
5.28 (m, 2H, CH), 7.37 (s, 20H, C6H5). 31P-NMR {H}(CDCl3, ppm):
δ -3.06. 13C-NMR {H}(acetone D6, ppm): δ 14.9-35.1 (C-stearoyl),
66.6 (CH2O, JP-C ) 5.5 Hz), 70.5 (CH2Bz), 71.2 (CH), 128.2, 129.8,
129.9, 137.6, 138.1 (C6H5), 173.6 (CdO). MS (FB+, m/z): 897 (M -
HOP(O)(OBz)2).
(2R,3R)-1,4-Diiodobutane-2,3-diol, 4a. Compound 3a12 (2.75 g,
7.2 mmol) was added to a mixture of trifluoroacetic acid/methanol/
water (4:1:8, v/v/v). The reaction mixture was stirred for 5 min at
room temperature and then poured into ethyl acetate. The organic layer
was washed with a 5% solution of sodium carbonate and brine, dried
over MgSO4, and concentrated. Product 4a was purified by sublimation
(T ) 110 °C, P ) 3 mmHg) and obtained in a yield of 97%. Mp
20
104-105 °C; [R]D ) -7.4° (methanol, c 1.0). IR (KBr, cm-1): ν
3230 (OH), 2950, 2910, 2920 (C-H). 1H-NMR (CDCl3, ppm): δ 2.56
(s, 2H, OH), 3.33 (m, 4H, CH2I), 3.93 (m, 2H, CH). MS(CI+, m/z):
343 (M + 1), 215 (M - I).
(2S,3S)-Di(octadecanoyloxy)butane-1,4-diyl Bis(dibenzylphos-
phate), 6b. Compound 6b was synthesized starting from 5b using the
same procedure as described for compound 6a. Mp 44-45 °C.
Identical spectroscopic data were obtained as described for 6a, except
(2S,3S)-1,4-Diiodobutane-2,3-diol, 4b. Compound 4b was syn-
thesized starting from 3b12 by using the same procedure as described
for compound 4a. A white solid was obtained in 96% yield. Mp 105
20
20
°C; [R]D ) +7.6° (methanol, c 1.0).
for the optical rotation: [R]D ) +1.58° (CH2Cl2, c 1.0).
(2R,3S)-1,4-Diiodobutane-2,3-diol, 4c. A solution of 2c (870 mg,
(25) This melting point range suggests the presence of impurities. They
could not be removed despite several attempts to obtain analytically pure
material. It was then decided to purify the compound at a later stage in the
synthetic sequence.
2.5 mmol) and NaI (1.49 g, 9.3 mmol) in butanone (200 mL) was heated
(23) Dittmer, J. C. Lester, R. L. J. Lipid Res. 1964, 5, 126.
(24) Knight, R. H.; Young, L. Biochem. J. 1981, 70, 111.