298 Letters in Organic Chemistry, 2011, Vol. 8, No. 5
Wang and Baker
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to give compound 6 as a white solid (273 mg, 63%). H
Allyl 2-acetamido-2-deoxy-3-O-levulinoyl-4,6-O-p-
methoxybenzylidene-ꢁ-D-glucopyranoside (4)
NMR (300 MHz, CDCl3): ꢁ 5.88 (m, 1H), 5.76 (d, J = 5.1
Hz, 1H), 5.28 (d, J = 15.9 Hz, 1H), 5.23 (d, J = 10.5 Hz,
1H), 4.92 (t, J = 9.0 Hz, 1H), 4.62 (d, J = 8.4 Hz, 1H), 4.36
(dd, J = 12.2 Hz, J = 5.1 Hz, 1H), 4.29 (dd, J = 12.3 Hz, J =
4.8 Hz, 1H), 4.12 (d, J = 12.2 Hz, 1H), 4.08 (t, J = 6.3 Hz,
1H), 3.95 (t, J = 9.0 Hz, 1H), 3.62 (m, 1H), 3.47 (m, 1H),
2.08 (s, 3H), 2.07 (s, 3H), 2.03 (s, 3H). 13C NMR (75 MHz,
CDCl3): ꢁ 172.27, 170.78, 170.38, 133.25, 118.55, 98.97,
72.86, 72.00, 71.31, 70.03, 62.33, 58.77, 23.58, 20.90, 20.79.
HRESIMS–DART: m/z [M + H]+ calcd for C15H24NO8:
346.1502; found: 346.1487.
To a suspension of 3 (8.0 g, 21 mmol) in dry CH2Cl2 (25
mL) were added levulinic acid (3.66 g, 31.7 mmol), EDCI
(5.28 g, 27.5 mmol), and a catalytic amount of DMAP. The
reaction was stirred at r.t. overnight, and then it was
quenched with water and extracted with CH2Cl2. The organic
phase was dried with anhyd MgSO4 and evaporated to
dryness. The residue was submitted to silica gel column
chromatography to give compound 4 as a white solid (7.5 g,
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74%). H NMR (300 MHz, CDCl3): ꢁ 7.37 (d, J = 8.4 Hz,
2H), 6.86 (d, J = 8.7 Hz, 2H), 6.03 (d, J = 9.0 Hz, 1H), 5.84
(m, 1H), 5.45 (s, 1H), 5.37 (t, J = 9.6 Hz, 1H), 5.25 (d, J =
17.4 Hz, 1H), 5.17 (d, J = 10.5 Hz, 1H), 4.68 (d, J = 8.7 Hz,
1H), 4.28 (t, J = 10.8 Hz, 1H), 4.26 (t, J = 9.6 Hz, 1H), 3.98
(dd, J = 12.6 Hz, J = 6.0 Hz, 1H), 3.91 (t, J = 10.2 Hz, 1H),
3.78 (s, 3H), 3.76 (t, J = 10.2 Hz, 1H), 3.66 (t, J = 9.3 Hz,
1H), 3.54 (m, 1H), 2.74 (m, 2H), 2.57 (m, 2H), 2.14 (s, 3H),
1.97 (s, 3H). 13C NMR (75 MHz, CDCl3): ꢁ 206.36, 172.75,
170.65, 160.03, 133.62, 129.48, 127.42, 117.33, 113.49,
101.23, 100.71, 78.73, 71.78, 70.16, 68.54, 66.06, 55.20,
55.01, 37.91, 29.64, 28.06, 23.26. HRESIMS–DART: m/z
[M + H]+ calcd for C24H32NO9: 478.2077; found: 478.2067.
Allyl 2,3,4,6-tetra-O-acetyl-ꢀ-D-mannopyranosyl-(1ꢂ3)-2-
acetamido-4,6-di-O-acetyl-2-deoxy-ꢁ-D-gluco-pyranoside
(8)
To a stirred suspension of acceptor 6 (244 mg, 0.707
mmol), 2,3,4,6-tetra-O-acetyl-ꢀ-D-manno-pyranosyl trichlo-
roacetimidate 7 (1.44 g, 2.93 mmol) and powdered 4 ꢄ
molecular sieves (400 mg, activated at 250 °C) in dry
CH2Cl2 (10 mL) was added TMSOTf (20 ꢅL) in CH2Cl2 (0.3
mL) solution at -30 oC. The reaction was stirred under N2 for
1 h and warmed to r.t.. After 7 h the reaction was quenched
with TEA, filtered through Celite, concentrated and purified
by silica gel column chromatography to give 8 (191 mg,
Allyl 2-acetamido-4,6-di-O-acetyl-2-deoxy-3-O-levulinoyl-
ꢁ-D-glucopyranoside (5)
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40%) as a white solid. H NMR (300 MHz, CDCl3): ꢁ 6.22
(d, J = 8.4 Hz, 1H), 5.85 (m, 1H), 5.73 (d, J = 6.9 Hz, 1H),
5.43 (d, J = 2.4 Hz, 1H), 5.25 (d, J = 17.4 Hz, 1H), 5.17 (d, J
= 7.2 Hz, 3H), 4.86 (t, J = 9.3 Hz, 1H), 4.53 (d, J = 2.4 Hz,
1H), 4.46 (t, J = 9.3 Hz, 1H), 4.30 (dd, J = 12.6 Hz, J = 5.1
Hz, 1H), 4.22 (t, J = 7.8 Hz, 1H), 4.19 (d, J = 7.8 Hz, 1H),
4.12-4.03 (m, 3H), 3.67-3.64 (m, 2H), 2.91 (dd, J = 15.6 Hz,
J = 7.8 Hz, 1H), 2.13 (s, 3H), 2.05 (s, 12H), 2.02 (s, 3H),
1.96 (s, 3H). 13C NMR (75 MHz, CDCl3): ꢁ 171.05, 170.77,
170.55, 170.12, 169.89, 169.58, 169.43, 133.74, 125.04,
117.80, 98.16, 96.91, 71.72, 71.62, 71.41, 70.41, 69.80,
69.62, 65.33, 62.46, 62.25, 58.26, 25.83, 23.62, 21.04, 20.93,
20.76, 20.66, 20.62. HRESIMS: m/z [M + Na]+ calcd for
C29H41NO17Na: 698.2267; found: 698.2311.
To a solution of 4 (621 mg, 1.30 mmol) in MeOH (25
mL) and CH2Cl2 (5 mL) were added two drops of HBF4. The
reaction was stirred at r.t. for 2 h. When TLC showed
complete consumption of the starting material and formation
of a new spot, the reaction was quenched with TEA and
evaporated to dryness. The resulting diol was re-dissolved in
dry pyridine (5 mL) and treated with Ac2O (5 mL) at r.t. for
10 h, after which time the reaction mixture was diluted with
CH2Cl2 and poured into ice water. The mixture was then
extracted with 3 ꢂ 10 mL of CH2Cl2, and the combined
organic phase was washed successively with dilute aq HCl
and satd aq NaHCO3. The organic phase was dried with
anhyd MgSO4 and evaporated to dryness. The residue was
submitted to silica gel column chromatography to give
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2,3,4,6-Tetra-O-acetyl-ꢀ-D-mannopyranosyl-(1ꢂ3)-2-
acetamido-4,6-di-O-acetyl-2-deoxy-ꢀ,ꢁ-D-glucopyranose
(9)
compound 5 as a white solid (495 mg, 89%). H NMR (300
MHz, CDCl3): ꢁ 5.87 (m, 1H), 5.74 (d, J = 8.7 Hz, 1H), 5.37
(t, J = 9.3 Hz, 1H), 5.28 (d, J = 15.9 Hz, 1H), 5.20 (d, J = 9.0
Hz, 1H), 5.07 (t, J = 9.9 Hz, 1H), 4.86 (d, J = 8.4 Hz, 1H),
4.34 (dd, J = 12.9 Hz, J = 5.1 Hz, 1H), 4.27 (dd, J = 12.0 Hz,
J = 4.5 Hz, 1H), 4.13 (dd, J = 12.3 Hz, J = 2.4 Hz, 1H), 4.09
(t, J = 6.3 Hz, 1H), 3.76-3.68 (m, 2H), 2.77-2.72 (m, 2H),
2.51-2.45 (m, 2H), 2.16 (s, 3H), 2.09 (s, 3H), 2.05 (s, 3H),
1.95 (s, 3H). 13C NMR (75 MHz, CDCl3): ꢁ 206.62, 172.31,
170.65, 169.67, 137.95, 133.54, 117.85, 99.42, 72.18, 71.72,
70.08, 68.30, 62.11, 55.35, 37.80, 29.61, 28.00, 23.35, 20.77,
To a solution of 8 (123 mg, 0.182 mmol) in dry MeOH (4
mL) and CH2Cl2 (4mL) was added a catalytic amount of
PdCl2 (10 mg). The reaction was stirred at r.t. for 7 h, after
which time it was filtered through Celite, concentrated and
purified by silica gel column chromatography to give
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compound 9 (82 mg, 71%) as a white solid. H NMR (300
MHz, CDCl3): ꢁ 6.03 (d, J = 8.4 Hz, 1H), 5.33 (d, J = 6.3
Hz, 1H), 5.28-5.20 (m, 2H), 5.13 (t, J = 9.6 Hz, 1H), 5.03
(dd, J = 11.1 Hz, J = 3.3 Hz, 1H), 4.94 (d, J = 1.8 Hz, 1H),
4.29-4.20 (m, 3H), 4.15-4.08 (m, 4H), 3.65 (m, 1H), 2.11 (s,
3H), 2.09 (s, 3H), 2.08 (s, 3H), 2.07 (s, 3H), 2.03 (s, 3H),
2.02 (s, 3H), 1.96 (s, 3H). 13C NMR (75 MHz, CDCl3): ꢁ
171.05, 170.99, 170.09, 170.01, 169.81, 169.71, 169.59,
98.90, 94.00, 71.96, 71.31, 70.40, 69.80, 69.53, 68.25, 66.25,
62.53, 62.39, 31.55, 25.22, 22.62, 20.90, 20.84, 20.78, 20.69,
20.59. HRESIMS: m/z [M + H]+ calcd for C26H38NO17:
636.2134; found: 636.2119.
20.70. HRESIMS–DART: m/z [M
C20H30NO10: 444.1864; found: 444.1893.
+
H]+ calcd for
Allyl 2-acetamido-4,6-di-O-acetyl-2-deoxy-ꢁ-D-
glucopyranoside (6)
To a solution of 5 (559 mg, 1.26 mmol) in 95% EtOH
(45 mL) and toluene (15 mL) was added hydrazine acetate
(110 mg, 1.22 mmol). The reaction was stirred at r.t. for
overnight, after which time it was concentrated, and the
residue was submitted to silica gel column chromatography