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G.-W. Xing et al. / Bioorg. Med. Chem. 13 (2005) 2907–2916
constant(s) in hertz (Hz) were measured from one-
dimensional spectra. 13C Attached Proton Test (C-
Apt) spectra were obtained with the NMR-400, -500,
or -600 spectrometer (100, 125, or 150 Hz) and were cal-
ibrated with either CDCl3 (d 77.23 ppm) or Py-d5 (d
123.87 ppm).
4.4. O-(2-O-Benzyl-4,6-O-benzylidene-3-O-levulinoyl-D-
galactopyranosyl)trichloroacetimidate, 8
To a solution of 7 (188.5 mg, 0.46 mmol) dissolved in
4 mL of DCM was added CCl3CN (0.46 mL,
4.62 mmol) and DBU (31 lL, 0.21 mmol). After 2 h at
room temperature, the dark solution was concentrated
and then purified by flash chromatography hexanes–
EtOAc (2:1) and 1% triethylamine to yield 8 (211 mg,
77%).
4.2. p-Methylphenyl 2-O-benzyl-4,6-O-benzylidene-3-O-
levulinoyl-1-thio-D-galactopyranoside, 6
Compound 5 (3 g, 6.45 mmol) was dissolved in DCM.
LevOH (0.9 mL, 1.35 equiv), EDC (1.6 g, 1.3 equiv),
and DMAP (197 mg, 0.25 equiv) were added. The reac-
tion was allowed to proceed overnight while covered in
foil. The reaction was then diluted with DCM, washed
with water, saturated sodium bicarbonate solution,
brine, and dried over sodium sulfate. After removal of
the solvent the mixture was purified by column chroma-
tography (hexanes–EtOAc–DCM 3:1:1) to give 2.83 g of
6 in 78% yield.
1H NMR (CDCl3, 500 MHz): d 7.59–7.34 (m, 10H), 5.61
(s, 1H), 5.45 (dd, 1H, J = 3.2, 10.7 Hz), 4.80–4.72 (m,
2H), 4.60 (d, 2H, J = 3.3 Hz), 4.38–4.33 (m, 2H), 4.13–
4.10 (dd, 1H, J = 1.8, 12.5 Hz), 4.05 (s, 1H), 2.79–2.72
(m, 2H), 2.65 (m, 2H), 2.16 (s, 3H); 13C NMR (CDCl3,
125 MHz): d 206.43, 177.73, 172.35, 172.27, 138.41,
137.78, 137.63, 137.57, 128.89, 128.85, 128.38, 128.21,
128.03, 127.86, 127.75, 127.67, 127.51, 126.15, 126.12,
100.61, 97.50, 91.98, 77.57, 74.68, 74.10, 73.56, 73.38,
73.28, 70.55, 69.17, 68.93, 66.24, 62.18, 37.82, 37.79,
29.67, 29.38, 28.11, 28.04.
1H NMR (CDCl3, 500 MHz): d 7.61–7.03 (m, 14H), 5.48
(s, 1H), 4.98 (dd, 1H, J = 3.7, 9.6 Hz), 4.77 (d, 1H,
J = 11.0 Hz), 4.63 (d, 1H, J = 9.5 Hz), 4.51 (d, 1H,
J = 11.0 Hz,), 4.36–4.32 (m, 2H), 3.99–3.97 (m, 1H),
3.90–3.86 (m, 1H), 3.51 (s, 1H), 2.56–2.50 (m, 2H),
2.46–2.40 (m, 2H), 2.31 (s, 3H), 2.09, (s, 3H); 13C
NMR (CDCl3, 125 MHz): d 206.05, 172.09, 138.18,
137.76, 137.64, 133.11, 129.61, 128.98, 128.57, 128.22,
128.01, 127.68, 127.57, 126.45, 100.83, 86.53, 75.41,
75.05, 73.77, 73.71, 69.09, 37.70, 29.60, 27.99; HRMS
(MALDI-FTMS) calcd for C32H34O7SNa [M+Na]+
585.1923. Found: 585.1900.
4.5. 2-Azido-3,4-di-O-benzyl-1-O-(2-O-benzyl-4,6-O-benz-
ylidene-3-O-levulinoyl-a-D-galactopyranosyl)-D-ribo-
octadeca-6-ene-1-ol, 10
A solution of trichloroacetimidate 8 (150 mg, 0.25
mmol, 1.5 equiv) and sphingosine derivative 9 (86 mg,
0.16 mmol) in 2.5 mL of anhydrous THF was added
over freshly dried powdered AW-300 molecular sieves
and cooled to ꢀ20 ꢁC. TMSOTf (23 lL, 0.8 equiv) was
slowly added to the solution, and the mixture was
warmed up to 0 ꢁC in 2.5 h. The reaction was quenched
by addition of Et3N (0.1 mL), and the mixture was
diluted with EtOAc and filtered through Celite. The
organic layer was washed with saturated aqueous
NaHCO3 and brine, dried (Na2SO4), and concentrated.
The residue was purified by column chromatography on
silica gel (hexanes–EtOAc 6:1) to furnish 10 (57 mg, 46%
based on consumed acceptor 9) as a syrup, and recover 9
(18 mg).
4.3. 2-O-Benzyl-4,6-O-benzylidene-3-O-levulinoyl-D-
galactopyranoside, 7
Compound 6 (600 mg, 1.07 mmol) was dissolved in
50 mL of acetone. The reaction mixture was cooled to
0 ꢁC, and NBS (228 mg, 1.28 mmol, 1.2 equiv) was
added. The reaction mixture turned orange immediately.
After 10 min the reaction was quenched by addition of
solid NH4Cl. The mixture was diluted with water and
ethyl acetate, and the aqueous layer was extracted with
ethyl acetate (3 ·). The combined organic layer was ex-
tracted with brine, dried over sodium sulfate, and evap-
orated. The residue was subjected to column
chromatography (hexanes–EtOAc–DCM 1:1:1) to give
442 mg (91%) of 7.
1H NMR (CDCl3, 400 MHz): d 7.49–7.23 (m, 20H),
5.56–5.45 (m, 3H), 5.32 (dd, 1H, J = 3.5, 10.5 Hz),
4.98 (d, 1H, J = 3.1 Hz), 4.70–4.51 (m, 6H), 4.38 (m,
1H), 4.13–3.82 (m, 5H), 3.71–3.62 (m, 4H), 2.75–2.40
(m, 6H), 2.08 (s, 3H), 2.06–1.97 (m, 2H), 1.25 (br s,
18H), 0.88 (t, 3H, J = 7.0 Hz); 13C NMR (CDCl3,
125 MHz): d 206.30, 172.25, 138.21, 137.93, 137.67,
132.60, 128.89, 128.37, 128.35, 128.33, 129.29, 128.08,
127.27, 128.08, 127.78, 127.73, 127.69, 127.63, 127.60,
127.17, 124.69, 100.65, 98.61, 79.41, 78.95, 74.06,
73.65, 73.41, 73.10, 71.94, 70.79, 69.02, 68.21, 62.41,
61.97, 37.93, 31.89, 29.71–29.32, 28.19, 27.58, 22.66,
14.10; ESI-MS (positive-ion mode): m/z 982.4 [M+Na]+.
1H NMR (CDCl3, 500 MHz): d 7.50–7.25 (m, 10H), 5.48
(d, 1H, J = 4.8 Hz), 5.38 (s, 1H), 5.32 (dd, 1H, J = 3.7,
10.3 Hz), 4.94–4.90 (m, 1H), 4.73–4.62 (m, 3H), 4.36
(d, 1H, J = 3.3 Hz), 4.05 (dd, 1H, J = 3.3, 10.3 Hz),
4.00–3.98 (m, 2H), 3.93, (s, 1H), 3.52–3.51 (m, 1H),
2.71–2.53 (m, 4H), 2.08 (s, 3H); 13C NMR (CDCl3,
125 MHz): d 206.43, 177.73, 172.35, 172.24, 138.41,
137.78, 137.63, 137.57, 128.89, 128.85, 128.38, 128.21,
128.03, 127.75, 127.67, 127.51, 126.15, 126.12, 100.61,
97.50, 91.98, 77.57, 74.68, 74.10, 73.82, 73.56, 73.38,
73.28, 70.55, 69.17, 68.93, 66.24, 62.18, 37.82, 37.79,
29.67, 28.38, 28.11, 28.04; HRMS (MALDI-FTMS)
calcd for C25H29O8 [M+H]+ 457.1862. Found: 457.1856.
4.6. Di-O-benzyl-1-O-(2-O-benzyl-4,6-O-benzylidene-a-
D-galactopyranosyl)-2-hexacosylamino-D-ribo-octadeca-
6-ene-1-ol, 14
The azide 10 (57 mg, 0.059 mmol) was dissolved in
2.0 mL of anhydrous THF and cooled to 0 ꢁC. PMe3