Dong et al.
directly in the next step without further purification. TBANO2 (720
mg, 2.5 mmol) was added to a solution of the protected triflate
residue in dry acetonitrile (5 mL), and then allowed to react at 50
°C for 5 h. The resulting mixture was directly purified by flash
column chromatography (2:1 to 1:1 hexane-ethyl acetate), yielding
7 as a colorless syrup (117 mg, 85%). 1H NMR (CDCl3, 500
MHz): δ 4.75 (t, 1 H, J3,2 2.7 Hz, J3,4 2.7 Hz, H3), 4.31-4.42 (m,
3 H, H1, H6a, H6b), 4.09 (d, 1 H, J2,3 2.7 Hz, H2), 3.91 (dd, 1 H, J4,3
2.7 Hz, J4,OH 10.1 Hz H4), 3.65 (t, 1 H, J5, 6 6.3 Hz, H5), 3.60 (s, 3
H, OMe), 3.52 (d, 1 H, JOH,4 10.1 Hz, 4-OH), 2.78 (s, 1 H, 2-OH),
2.20 (s, 3H, OAc), 2.07 (s, 3H, OAc); 13C NMR (CDCl3 125
MHz): δ 171.0, 170.5, 100.6, 73.5, 70.9, 70.1, 67.3, 62.8, 57.1,
water, and brine. The organic phase was dried over Na2SO4 and
concentrated in vacuo at low temperature. The residue was used
directly in the next step without further purification. TBAOAc (180
mg, 0.6 mmol) was added to a solution of the protected triflate
residue in dry acetonitrile (5 mL), and then allowed to react at room
temperature for 0.5 h followed heating to 50 °C for 0.5 h. TBANO2
(430 mg, 1.5 mmol) was added to the mixture and heating was
continued at 50 °C for 24 h. The resulting mixture was directly
purified by flash column chromatography (2:1 hexane-ethyl
1
acetate), yielding 11 as a colorless syrup (73 mg, 45%). H NMR
(CDCl3, 400 MHz): δ 5.33 (d, 1 H, J4,3 3.5 Hz, J4,5 1.3 Hz, H4),
4.91 (t, 1 H, J3,4 3.4 Hz, J3,2 3.4 Hz, H3), 4.41 (s, 1 H, H1), 4.24
(dd, 1 H, J6a, 6b 11.2 Hz, J6a, 5 6.6 Hz, H6a), 4.18 (dd, 1 H, J6b, 6a
11.2 Hz, J6b, 5 6.6 Hz, H6b), 3.96 (b, 1 H, H2), 3.87 (dt, 1H, J5,4 1.3
Hz, J5,6 6.6 Hz, H5), 3.59 (s, 3 H, OMe), 2.47 (b, 1 H, 2-OH), 2.13
(s, 3H, OAc), 2.08 (s, 3H, OAc), 2.03 (s, 3H, OAc); 13C NMR
(CDCl3 125 MHz): δ 170.6, 170.3, 169.9, 101.9, 71.5, 69.6, 68.9,
66.7, 61.5, 57.4, 21.0, 20.9, 20.8; [R]20D ) -27 (c ) 0.6, CHCl3).
MS (M+Na):343.1005. Observed: 343.1000. Anal. Calcd for
C13H20O9: C, 48.75; H, 6.29. Found: C, 48.45; H, 6.20.
Methyl 2,3,6-Tri-O-acetyl-â-D-talopyranoside (12). Prepared
by the same route as methyl taloside 11, yielding 12 as a colorless
syrup (72 mg, 45%). 1H NMR (CDCl3, 400 MHz): δ 5.46 (d, 1 H,
J2,3 3.5 Hz, H2), 4.89 (t, 1 H, J3,2 3.5 Hz, J3,4 3.5 Hz, H3), 4.47 (d,
1 H, J1,2 1.0 Hz, H1), 4.40 (dd, 1 H, J6a, 6b 11.4 Hz, J6a, 5 6.8 Hz,
H6a), 4.32 (dd, 1 H, J6b, 6a 11.4 Hz, J6b, 5 5.9 Hz, H6b), 3.88 (b, 1 H,
H4), 3.69 (m, 1H, H5), 3.54 (s, 3 H, OMe), 2.61 (b, 1 H, 4-OH),
2.17 (s, 3H, OAc), 2.09 (s, 3H, OAc), 2.07 (s, 3H, OAc); 13C NMR
(CDCl3 125 MHz): δ 170.8, 170.1, 169.6, 100.2, 73.8, 69.5, 69.1,
66.8, 62.7, 57.4, 21.0, 21.0, 20.9; [R]20D ) -34 (c ) 0.6, CHCl3).
Anal. Calcd for C13H20O9· 1/2H2O: C, 47.42; H, 6.43. Found: C,
47.15; H, 6.13.
Methyl 3,4,6-Tri-O-acetyl-â-D-mannopyranoside (13). To a
solution of methyl â-D-galactoside 4 (140 mg, 0.5 mmol), in CH2-
Cl2 (5 mL) was added pyridine (0.53 mL) at -20 °C. Trifluo-
romethanesulfonic anhydride (420 mg, 1.5 mmol) in CH2Cl2 (2 mL)
was added dropwise, and the mixture was stirred while allowing
to warm from -20 °C to 10 °C over 2 h. The resulting mixture
was subsequently diluted with CH2Cl2 and washed with 1 M HCl,
aqueous NaHCO3, water, and brine. The organic phase was dried
over Na2SO4 and concentrated in vacuo at low temperature. The
residue was used directly in the next step without further purifica-
tion. TBAOAc (180 mg, 0.6 mmol) was added to a solution of the
protected triflate residue in dry toluene (5 mL), and then allowed
to react at room temperature for 0.5 h followed by heating to 50
°C for 0.5 h. TBANO2 (430 mg, 1.5 mmol) was added to the
mixture and kept at room temperature for 6 h. The resulting mixture
was directly purified by flash column chromatography (2:1 hexane-
ethyl acetate), yielding 13 as a colorless syrup (130 mg, 81%). 1H
NMR (CDCl3, 400 MHz): δ 5.37 (dd, 1 H, J4,3 9.8 Hz, J4,5 9.8 Hz
H4), 4.97 (dd, 1 H, J3,4 9.8 Hz, J3,2 3.0 Hz, H3), 4.49 (s, 1 H, H1),
4.30 (dd, 1 H, J6a, 6b 13.0 Hz, J6a, 5 4.9 Hz, H6a), 4.1-4.2 (m, 2 H,
H6b, H2), 3.62 (m, 1H, H5), 3.56 (s, 3 H, OMe), 2.33 (b, 1 H, 2-OH),
2.10 (s, 3H, OAc), 2.08 (s, 3H, OAc), 2.03 (s, 3H, OAc); 13C NMR
(CDCl3 125 MHz): δ 171.0, 170.6, 169.7, 100.6, 73.1, 72.4, 69.2,
66.1, 62.6, 57.3, 21.0, 20.9, 20.8; [R]20D ) -59 (c ) 0.3, CHCl3).
MS (M+Na): 343.1005. Observed: 343.1001. Anal. Calcd for
C13H20O9: C, 48.75; H, 6.29. Found: C, 48.60; H, 6.25.
Methyl 2,3,6-Tri-O-acetyl-â-D-mannopyranoside (14). To a
solution of methyl â-D-galactoside 4 (140 mg, 0.5 mmol), in CH2-
Cl2 (5 mL) was added pyridine (0.53 mL) at -20 °C. Trifluo-
romethanesulfonic anhydride (420 mg, 1.5 mmol) in CH2Cl2 (2 mL)
was added dropwise, and the mixture was stirred while allowing
to warm from -20 °C to 10 °C over 2 h. The resulting mixture
was subsequently diluted with CH2Cl2 and washed with 1 M HCl,
aqueous NaHCO3, water, and brine. The organic phase was dried
over Na2SO4 and concentrated in vacuo at low temperature. The
residue was used directly in the next step without further purifica-
tion. TBANO2 (170 mg, 0.6 mmol) was added to a solution of the
21.2, 21.0; [R]20 ) -16 (c ) 0.1, CHCl3). Anal. Calcd for
D
C11H18O8: C, 47.48; H, 6.52. Found: C, 47.37; H, 6.37.
Methyl 3,6-Di-O-acetyl-â-D-mannopyranoside (8). To a solu-
tion of methyl â-D-galactoside 4 (140 mg, 0.5 mmol), in CH2Cl2
(5 mL) was added pyridine (0.53 mL) at -20 °C. Trifluo-
romethanesulfonic anhydride (420 mg, 1.5 mmol) in CH2Cl2 (2 mL)
was added dropwise, and the mixture was stirred while allowing
to warm from -20 °C to 10 °C over 2 h. The resulting mixture
was subsequently diluted with CH2Cl2 and washed with 1 M HCl,
aqueous NaHCO3, water, and brine. The organic phase was dried
over Na2SO4 and concentrated in vacuo at low temperature. The
residue was used directly in the next step without further purifica-
tion. TBANO2 (720 g, 2.5 mmol.) was added to a solution of the
protected triflate residue in dry toluene (5.0 mL), and then allowed
to react at room temperature for 5 h. The resulting mixture was
directly purified by flash column chromatography (2:1 to 1:1
hexane-ethyl acetate), yielding 8 as a colorless syrup (105 mg,
1
76%). H NMR (CDCl3, 500 MHz): δ 4.81 (dd, 1 H, J3,2 3.0 Hz,
J3, 4 9.8 Hz, H3), 4.56 (dd, 1 H, J6a,6b 12.3 Hz, J6a,5 4.4 Hz, H6a),
4.47 (d, 1 H, J1, 2 0.6 Hz, H1), 4.30 (dd, 1 H, J6a, 6b 12.3 Hz, J6b, 5
2.2 Hz, H6b), 4.12 (d, 1 H, J2, 3 3.0 Hz, H2), 3.91 (t, 1H, J4,3 9.8 Hz,
J4,5 9.8 Hz, H4), 3.55 (s, 3 H, OMe), 3.45 (m, 1 H, H5), 2.17 (s,
3H, OAc), 2.12 (s, 3H, OAc); 13C NMR (CDCl3 125 MHz): δ
172.1, 171.3, 100.6, 75.5, 74.6, 69.3, 65.2, 63.3, 57.2, 21.3, 21.1;
[R]20 ) -118 (c ) 0.1, CHCl3). Anal. Calcd for C11H18O8: C,
D
47.48; H, 6.52. Found: C, 47.19; H, 6.36.
Methyl 3,6-Di-O-benzoyl-â-D-mannopyranoside (9). To a
solution of methyl â-D-galactoside 5 (201 mg, 0.5 mmol), in CH2-
Cl2 (5 mL) was added pyridine (0.53 mL) at -20 °C. Trifluo-
romethanesulfonic anhydride (420 mg, 1.5 mmol) in CH2Cl2 (1 mL)
was added dropwise, and the mixture was stirred while allowing
to warm from -20 °C to 10 °C over 2 h. The resulting mixture
was subsequently diluted with CH2Cl2 and washed with 1 M HCl,
aqueous NaHCO3, water, and brine. The organic phase was dried
over Na2SO4 and concentrated in vacuo at low temperature. The
residue was used directly in the next step without further purifica-
tion. TBANO2 (720 mg, 2.5 mmol) was added to a solution of the
protected triflate residue in dry acetonitrile (5 mL), and then allowed
to react at 50 °C for 5 h. The resulting mixture was directly purified
by flash column chromatography (2:1 hexane-ethyl acetate),
1
yielding 9 as a colorless syrup (140 mg, 70%). H NMR (CDCl3,
500 MHz): δ 7.4-8.2 (m, 10 H, 2 × OBz), 5.09 (dd, 1 H, J3, 2 2.8
Hz, J3,4 9.7 Hz, H4), 4.77 (dd, 1 H, J6a,6b 12.1 Hz, J6a,5 4.9 Hz, H6a),
4.64 (dd, 1 H, J6b,6a 12.1 Hz, J6b,5 2.4 Hz H6b), 4.58 (d, 1 H, J1, 2
0.63 Hz, H1), 4.26 (d, 1 H, J2,3 2.8 Hz, H2), 4.19 (t, 1 H, J4,3 9.7
Hz, J4,5 9.7 Hz, H4), 3.66 (m, 1 H, H5), 3.58 (s, 3 H, OMe); 13C
NMR (CDCl3 125 MHz): δ 167.3, 166.8, 133.7, 133.5, 130.2,
130.1, 128.7, 128.6, 100.8, 76.3, 74.8, 69.4, 65.7, 63.9, 57.2; [R]20
D
) -40 (c ) 0.7, CHCl3). Anal. Calcd for C21H22O8·1/2H2O: C,
61.31; H, 5.64. Found: C, 60.92; H, 5.55.
Methyl 3,4,6-Tri-O-acetyl-â-D-talopyranoside (11). To a solu-
tion of methyl â-D-glucoside 2 (140 mg, 0.5 mmol), in CH2Cl2 (5
mL) was added pyridine (0.53 mL) at -20 °C. Trifluoromethane-
sulfonic anhydride (420 mg, 1.5 mmol) in CH2Cl2 (2 mL) was added
dropwise, and the mixture was stirred while allowing to warm from
-20 °C to 10 °C over 2 h. The resulting mixture was subsequently
diluted with CH2Cl2 and washed with 1 M HCl, aqueous NaHCO3,
3700 J. Org. Chem., Vol. 72, No. 10, 2007