A. Tatiboue¨t et al. / Carbohydrate Research 333 (2001) 327–334
333
diluted with DMF (4 mL) under Ar. Potas-
sium thioacetate (0.3 g, 3 mmol) was added to
the solution before heating to 100 °C for 90
min. After completion, the mixture was
poured in AcOEt then washed successively
with water (four times) and brine. After being
dried over MgSO4, decolorized with activated
carbon and filtrated over Celite® pad, the
mixture was evaporated to give 15 (0.435 g) of
good purity. Recrystallization in petroleum–
ether–Et2O gave pure 15 (0.35 g, 72%): mp
136–138 °C; [h]2D0 −141° (c 1.1, CHCl3); IR
(NaCl) w 1695 (thioester), 1738 cm−1 (esters);
ISMS(+): m/z 504.5 [M+NH4]+. Anal. Calcd
for C25H26O8S: C, 61.72; H, 5.39. Found: C,
61.45; H, 5.27.
92%). The crude compounds 18a, 18b (0.260
g) were separated on silica gel with CH2Cl2 as
eluent yielding 18a (0.058 g) as a syrup and
18b (0.2 g) which spontaneously crystallized:
1
18a: [h]2D0 +21° (c 1, CHCl3); H NMR (250
MHz, CDCl3): l 8.07–8.18 (m, 4 H, Harom),
7.60–7.63 (m, 4 H, Harom), 7.47–7.54 (m, 4 H,
H
arom), 5.84 (d, 1 H, H-3), 5.39 (dd, 1 H, J3,4
3.2 Hz, H-4), 4.85 (d, 1 H, H-1b), 4.42 (d, 1
H, J1a,1b 12.1 Hz, H-1a), 4.39 (ddd, 1 H, J4,5
3.2 Hz, H-5), 4.20 (dd, 1 H, J5,6b 11.9 Hz,
4
H-6b), 3.97 (ddd, 1 H, J6a,4 1.1, J6a,5 5.3, J6a,6b
11.3 Hz, H-6a), 2.32 (s, 3 H, SCOCH3), 1.96
(s, 3 H, CH3), 1.83 (s, 3 H, CH3); 13C NMR
(62.5 MHz, CDCl3): l 193.1 (SCO), 170.0,
168.4, 164.6, 164.2, 134.0, 133.9, 130.2, 129.9,
129.3, 128.9, 128.8, 128.7, 100.7 (C-2), 69.0
(C-4), 65.2 (C-3), 62.1 (C-1), 60.5 (C-6), 38.2
(C-5), 30.7 (SCOCH3), 21.8 (CH3), 20.7 (CH3);
ISMS(+): m/z 548 [M+NH4]+, 553 [M+
Na]+. Anal. Calcd for C26H28O8S: C, 58.86;
H, 4.94. Found: C, 59.03; H, 5.12. 18b: mp
5-Azido-3,4-di-O-benzoyl-5-deoxy-1,2-O-iso-
propylidene-i-
D
-fructopyranose
(16).—The
iodo derivative 11 (0.28 g, 0.52 mmol) was
dissolved in Me2SO (2 mL) and sodium azide
(0.345 g, 5.3 mmol) was added. The solution
was heated to 100 °C for 3 h, then poured into
AcOEt. The organic solution was washed with
water (three times), brine and dried over
MgSO4. After a short filtration over a silica
gel pad and evaporation to dryness, 16 (0.215
145–148 °C, [h]2D0 −108° (c 1, CHCl3); H
1
NMR (250 MHz, CDCl3): l 7.88–7.98 (m, 4
H, Harom), 7.46–7.55 (m, 4 H, Harom), 7.32–
7.42 (m, 4 H, Harom), 5.85 (dd, 1 H, J4,5 3.6
Hz, H-4), 5.79 (d, 1 H, J3,4 10.3 Hz, H-3), 4.80
(d, 1 H, H-1b), 4.57 (d, 1 H, J1a,1b 11.9 Hz,
H-1a), 4.53 (m, 1 H, H-5), 4.35 (dd, 1 H, J5,6b
2.3 Hz, H-6b), 4.02 (dd, 1 H, J6a,5 1.8, J6a,6b
12.8 Hz, H-6a), 2.29 (s, 3 H, SCOCH3), 2.25
(s, 3 H, CH3), 1.99 (s, 3 H, CH3); 13C NMR
(100 MHz, CDCl3): l 193.5 (SCO), 169.9,
168.1, 165.5, 165.3, 132.6, 132.4, 129.8, 129.7,
129.1, 129.0, 128.6, 128.5, 102.6 (C-2), 69.1
(C-4), 68.6 (C-3), 65.1 (C-6), 63.3 (C-1), 45.0
(C-5), 31.7 (SCOCH3), 21.7 (CH3), 20.6 (CH3);
ISMS(+): m/z 548 [M+NH4]+, 553 [M+
Na]+. Anal. Calcd for C26H28O8S: C, 58.86;
H, 4.94. Found: C, 59.15; H, 4.90.
g, 91%) was isolated: mp 84–86 °C; [h]D20
−
115° (c 1.15, CHCl3); IR (NaCl) w 2101 cm−1
(azide), 1729 cm−1 (ester); ISMS(+): m/z 471
[M+NH4]+. Anal. Calcd for C23H23N3O7: C,
60.92; H, 5.11. Found: C, 61.24; H, 5.23.
5-Azido-3,4-di-O-benzyl-5-deoxy-1,2-O-iso-
propylidene-i- -fructopyranose (17).—Same
D
conditions as those applied to 16 for 12 (0.134
g, 0.26 mmol) for 4 days at 90 °C. After usual
workup, 17 (0.094 g, 85%) was obtained: [h]D20
−87° (c 1, CHCl3); IR (NaCl) w 2107 (azide);
ISMS(+): m/z 443 [M+NH4]+, 448 [M+
Na]+. Anal. Calcd for C23H27N3O5: C, 64.93;
H, 6.40. Found: C, 65.03; H, 6.45.
5-S-Acetyl-3,4-di-O-benzoyl-1,2-di-O-acetyl-
5-Thio- -fructofuranose (2).—Compound
D
5-thio-
D
-fructopyranose (18a, 18b).—Under
18 (0.3 g, 0.567 mmol) was diluted in MeOH
and treated with sodium methoxide (0.6
mmol) at rt for 3 h. 2 (0.108 g, 97%) was
isolated after purification on silica gel (20:4:1
EtOAc–MeOH–water): [h]2D0 −7° (c 1.1,
MeOH), lit.3 −4° (c 0.72, MeOH). Anal.
Calcd for C6H12O5S: C, 36.73; H, 6.16.
Found: C, 37.01; H, 6.05.
Ar 15 (0.48 g, 1 mmol) was dissolved in Ac2O
(2.5 mL) and cooled (ice-salt bath) to −
10 °C. BF3·Et2O (0.1 mL) was added slowly.
After 90 min, the solution was diluted with
EtOAc, washed twice with ice cold water and
satd NaHCO3 then brine. The organic phase
was dried over MgSO4, evaporated under re-
duced pressure, and purified on silica gel (4:1
petroleum ether–EtOAc,) yielding 18 (0.485 g,
5-Azido-5-deoxy-1,2-O-isopropylidene-i-
D
-
fructopyranose (19).—Compound 16 (0.1 g,