(positive) m/z: 762.4432 (calcd for C41H64NO12, [M+H]+
3-O-(N-Acetyl-4,7,8,9-tetra-O-acetyl-1-methyl-β-
neuraminosyl)glycyrrhet-30-yl pivalate (5c)
Colorless powder; mp 151-153°C; [α]D +41.4 (c = 0.50,
1
762.4429); H-NMR and 13C-NMR see Tables S2-1 and S1-1,
24
respectively.
MeOH); UV λ max (MeOH) nm (log ε): 250 (4.29), 204 (3.95); IR
ν
(KBr) cm-1: 3440, 2960, 2360, 1740, 1650, 1560, 1470,
3.3.7. General procedure for the preparation of 5a from 5
max
1370, 1230, 1160, 1040; FAB-MS (positive) m/z: 1014.5
[M+H]+, 523.4, 474.2, 414.1; HR-FAB-MS (positive) m/z:
1014.5798 (calcd for C55H84NO16, [M+H]+ 1014.5790); 1H-NMR
and 13C-NMR see Tables S2-2 and S1-1, respectively.
Compound 5 (180.0 mg, 0.39 mmol) was dissolved in dry
pyridine (5 mL), and pivaloyl chloride (73 µl, 0.59 mmol) was
added under an Ar steam in the dark. After stirring at rt for 1 h,
CHCl3 was added and the solution was washed with water, then
the CHCl3 layer was dried over anhydrous sodium sulfate, and
the solution was evaporated. The residue was purified by column
chromatography on silica gel (n-hexane-acetone (10:1→5:1) to
give 5a (175.8 mg, 82%) as a colorless solid.Colorless powder;
3.3.9. General procedure for the preparation of 5d from 5b and
5e from 5c
Each solution of 5b (30.2 mg, 0.03 mmol) or 5c (26.0 mg, 0.03
mmol) and NaOMe (28% in MeOH) (5 mL) was stirred at rt for 5
h under Ar gas in the dark. Then H2O (10 mL) was added and
stirred for 19 h under Ar gas in the dark. The reaction mixture
was treated with 2M HCl for neutralization and the solution was
evaporated. The residue was purified by column chromatography
25
mp 222-223°C; [α]D +186.1 (c = 0.30, CHCl3); UV λ max
(MeOH) nm (log ε): 199 (3.47), 249 (4.18); IR ν max (KBr) cm-1:
3540, 2990, 1720, 1640, 1150; EI-MS m/z (rel. int. %): 540 (M+l,
100), 373 (80), 332 (64), 175 (30), 135 (28); HR-EI-MS m/z:
1
540.4174 (calcd for C35H56O4, 540.4179); H-NMR (DMSO-d6):
δ 0.69, 0.83, 0.91×2, 1.02, 1.04, 1.35 (each 3H, s), 0.69-2.14
(19H, m), 1.15 (9H, s), 2.32 (1H, s), 2.57 (1H, m), 3.01 (1H, m),
3.83 (1H, d, J = 11.0 Hz), 4.10 (1H, d, J = 11.0 Hz), 5.42 (1H, s);
13C-NMR (DMSO-d6): δ 15.9, 16.1, 17.0, 18.2, 23.1, 25.9×2,
26.8×2, 27.3, 28.0×2, 29.5, 31.7, 32.0, 34.1, 35.3, 36.5, 38.3,
38.4, 38.6, 39.5, 42.8, 44.8, 46.0, 53.9, 60.9, 66.4, 76.4, 127.1,
169.4, 177.0, 198.6.
ꢂMeOH) and the solvent was
on DIAION HP-20 (H2O
evaporated. The MeOH layer was purified by ODS-HPLC (80%
MeOH aq., flow 2.5 mL, detected 222 nm) to afford 5d, 3-O-(N-
acetyl-α-neuraminosyl)glycyrrhetol (9.3 mg, 41%) or 5e, 3-O-
(N-acetyl-β-neuraminosyl)glycyrrhetol (18.7 mg, 100%).
3-O-(N-Acetyl-α-neuraminosyl)glycyrrhetol (5d)
26
Colorless powder; mp 245-248°C; [α]D +17.1 (c = 0.47,
MeOH); UV λ max (MeOH) nm (log ε): 250 (3.98), 204 (3.79); IR
ν
(KBr) cm-1: 3450, 2920, 2350, 1730, 1650, 1560, 1440,
max
3.3.8. General procedure for the preparation of 5b and 5c from
5a
1110, 1040; FAB-MS (positive) m/z: 748.5 [M+H]+, 706.4,
439.4; HR-FAB-MS (positive) m/z: 748.4642 (calcd for
A solution of 5a (90.3 mg, 0.17 mmol) and 3 (173.6 mg, 0.33
mmol) in dry CH2Cl2 (5 mL) with molecular sieves of 4Å (1.0 g)
for dehydration was stirred at 0 °C under Ar gas. After stirring
the reaction mixture for 30 min, NIS (75.0 mg, 0.33 mmol) and
trifluoromethanesulfonic acid (29 µl, 0.33 mmol) were added and
stirred for 46 h at 0°C to rt under Ar gas in the dark. After
removal of molecular sieves by filtration, the reaction mixture
was evaporated. The solution was diluted with CHCl3 and washed
by aqueous Na2S2O3. The organic layer was separated and dried
over anhydrous sodium sulfate. After the CHCl3 was evaporated,
the residue was purified by column chromatography on silica gel
(n-hexane-acetone 10:1ꢂ5:1ꢂ3:1ꢂ2:1) to give 5b (α-form, 9.9
mg, 6%) and 5c (β-form, 61.5 mg, 36%).
Reaction-2: A solution of 5a (91.9 mg, 0.17 mmol) and 3 (177.0
mg, 0.34 mmol) in CH3CH2CN (5 mL) and dry CH2Cl2 (0.5 mL)
with molecular sieves of 4Å (1.0 g) for dehydration was stirred at
0°C under Ar gas. After stirring the reaction mixture for 30 min,
NIS (76.7 mg, 0.34 mmol) and trifluoromethanesulfonic acid (30
µl, 0.34 mmol) were added and stirred for 48 h at 0°C to rt under
Ar gas in the dark. After removal of molecular sieves by
filtration, the reaction mixture was evaporated. The solution was
diluted with CHCl3 and washed by aqueous Na2S2O3. The organic
layer was separated and dried over anhydrous sodium sulfate.
After the CHCl3 was evaporated, the residue was purified by
column chromatography on silica gel (n-hexane-acetone
C41H66NO11, [M+H]+ 748.4636); H-NMR and 13C-NMR see
Tables S2-2 and S1-1, respectively.
3-O-(N-Acetyl-β-neuraminosyl)glycyrrhetol (5e)
Colorless powder; mp (dec.) 258°C; [α]D +85.4 (c = 0.50,
1
27
MeOH); UV λ max (MeOH) nm (log ε): 250 (4.21), 205 (3.99); IR
ν
(KBr) cm-1: 3450, 2930, 2320, 1650, 1540, 1450, 1380,
max
1030; FAB-MS (positive) m/z: 748.4 [M+H]+, 706.4, 439.4; HR-
FAB-MS (positive) m/z: 748.4642 (calcd for C41H66NO11,
[M+H]+ 748.4636); H-NMR and 13C-NMR see Tables S2-2 and
1
S1-1, respectively.
3.3.10. General procedure for the preparation of 6a from 6.
Compound 6 (180.3 mg, 0.41 mmol) was dissolved in dry
pyridine (5 mL) and pivaloyl chloride (60 µl, 0.49 mmol) was
added under an Ar steam in the dark. After stirring at rt for 1 h,
CHCl3 was added and the solution was washed with water, then
the CHCl3 layer was dried over anhydrous sodium sulfate, and the
solution was evaporated. The residue was purified by column
ꢂ5:1) to
chromatography on silica gel (n-hexane-acetone 10:1
26
give 6a (205.4 mg, 96%). Colorless powder; mp 95-98°C; [α]D
+96.9 (c = 0.50, CHCl3); IR ν max (KBr) cm-1: 3420, 2940, 1780,
1720, 1450, 1380, 1280, 1160, 1030; EI-MS m/z (rel. int. %): 526
(M+, 13), 318 (100), 201 (23), 148 (25); HR-EI-MS m/z:
1
526.4388 (calcd for C35H58O3, 526.4386); H-NMR (DMSO-d6):
ꢂ5:1ꢂ4:1ꢂ3:1) to give
10:1
(β-form, 50.0 mg, 29%).
5b (α-form, 63.2 mg, 37%) and 5c
δ 0.67 (1H, br s, J = 11.2 Hz), 0.72, 0.76, 0.85, 0.86, 0.89, 0.93,
1.08 (each 3H, s), 0.65-1.97 (23H, m), 1.14 (9H, s), 3.15 (1H, dd,
J = 11.0, 4.9 Hz), 3.90 (2H, q, J = 11.2 Hz), 5.08 (1H, t, J = 3.5
Hz); 13C-NMR (DMSO-d6): δ 14.2, 15.6, 15.7, 16.9, 18.4, 23.6,
26.1, 27.2, 27.3, 28.1, 28.2×2, 29.7, 30.4, 32.4, 32.7, 34.5, 36.5,
37.0, 38.7, 38.8, 39.0, 39.8, 41.7, 42.2, 46.6, 47.7, 55.2, 67.7,
79.0, 122.3, 144.4, 178.5.
3-O-(N-Acetyl-4,7,8,9-tetra-O-acetyl-1-methyl-α-
neuraminosyl)glycyrrhet-30-yl pivalate (5b)
25
Colorless powder; mp 127-130°C; [α]D +55.5 (c = 0.50,
MeOH); UV λ max (MeOH) nm (log ε): 249 (4.29), 204 (3.98); IR
ν
(KBr) cm-1: 3420, 2950, 1740, 1560, 1460, 1470, 1260,
max
1090, 1040; FAB-MS (positive) m/z: 1014.7 [M+H]+, 541.5,
523.5, 414.2; HR-FAB-MS (positive) m/z: 1014.5785 (calcd for
3.3.11. General procedure for the preparation of 6b and 6c from
6a
C55H84NO16, [M+H]+ 1014.5790); H-NMR and 13C-NMR see
1
Tables S2-2 and S1-1, respectively.
Reaction-1: A solution of 6a (90.2 mg, 0.17 mmol) and 3 (178.2
mg, 0.34 mmol) in dry CH2Cl2 (5 mL) with molecular sieves of