S. Rat et al. / Tetrahedron 63 (2007) 12424–12428
12427
4.2. 2,3,4-Tri-O-acetyl-D-glucopyranosylurono-6,1-
lactone (2)
(2ꢂCO), 169.2 (CO), 167.7 (C6), 95.7 (C1), 70.5 (C2),
69.8 (C4), 69.6 (C3), 68.7 (OCH ), 68.2 (C5), 65.7
2
(
CO CH ), 31.1 (CH ), 30.2 (CH ), 20.4 (3ꢂCH CO),
2
2
2
2
3
To a mixture of GlcA (3 g, 15.45 mmol) and I (1.17 g,
2
4.46 mmol) in an open Pyrex flask was added acetic anhy-
dride (11.7 mL, 123.77 mmol). The mixture was irradiated
18.9 (2ꢂCH ), 13.6 (2ꢂCH CH ). HRMS [M+Na] calcd
20 32 10
2 3 2
for C H O Na: 455.1893. Found [M+Na]: 455.1889.
ꢀ
solved in CH Cl , then washed successively with saturated
(
300 W) at 115 C for 10 min. The crude product was dis-
4.3.3. Octyl (octyl 2,3,4-tri-O-acetyl-a,b-D-glucopyrano-
sid)uronate (4c). Mixture of a, b isomers: colorless syrup.
2
2
2
0
solution of Na S O , NaHCO , and NaCl. The organic
3
Yield: 317 mg (88%); a/b:90/10; [a]D +65.4 (c 1,
2
2
3
ꢁ
CH Cl ); IR: 2925, 2357, 1758, 1368, 1220, 1049 cm .
2 2
1
layers were dried on Na SO , concentrated and a flash chro-
2
4
1
matography (cyclohexane/ethyl acetate 7:3) gave the lactone
ꢀ
a isomer: H NMR (CDCl ) d 5.50 (t, 1H, J¼9.6 Hz, H-3),
3
1
4
2 (4.29 g, 92%) as white solid. Mp 127 C; NMR data were
in accordance with the literature.
5.15 (d, 1H, J¼9.6 Hz, H-4), 5.10 (d, J¼3.6 Hz, H-1), 4.85
(dd, 1H, J¼3.6, 9.6 Hz, H-2), 4.30 (d, 1H, J¼10.0 Hz,
H-5), 4.15–4.02 (m, 2H, CO CH ), 3.70 (m, 1H, OCH ),
1
4
2
2
2
4
1
.3. General procedure for the synthesis of compounds
b–5d
3.43 (m, 1H, OCH ), 2.03 (s, 3H, CH CO), 1.99 (s, 6H,
2 3
2ꢂCH CO), 1.58 (m, 4H, 2ꢂCH ), 1.25 (m, 20H,
3
2
1
3
1
0ꢂCH ), 0.86 (m, 6H, 2ꢂCH CH ). C NMR (CDCl )
2
3
2
3
To a mixture of GlcA (200 mg, 1.03 mmol) or 6,1-lactone 2
200 mg, 0.66 mmol) and alcohol (6 equiv) in an open Pyrex
d 169.9 (2ꢂCO), 169.3 (CO), 167.7 (C6), 95.7 (C1), 70.5
(
(C2), 69.7 (C4), 69.5 (C3), 69.0 (OCH ), 68.2 (C5), 66.0
2
flask was added the catalyst (0.3 equiv for PTSA, 1 equiv for
FeCl or 1 equiv for SnCl ). The flask was placed in the
(CO CH ), 31.7 (CH ), 29.1 (CH ), 28.2 (CH ), 25.8
2
2
2
2
2
(CH ), 25.6 (CH ), 22.5 (CH ), 20.5 (3ꢂCH CO), 14.0
3
4
2
2
2
3
microwave reactor and irradiated (reaction time, irradiation
power and assigned temperature are indicated in Tables 1, 3
and 4). Continuous stirring and heating of the semi-solid
reaction mixture provided homogeneity of materials. The
temperature was controlled all along the reaction and mea-
sured by an infrared detector. The crude was then chromato-
graphed on silica gel by gradient elution with mixtures of
cyclohexane and increasing amounts of ethyl acetate.
(2ꢂCH CH ). HRMS [M+Na] calcd for C H O Na:
3
2
28 48 10
567.3145. Found [M+Na]: 567.3148.
4.3.4. Dodecyl (dodecyl 2,3,4-tri-O-acetyl-a,b-D-gluco-
pyranosid)uronate (4d). Mixture of a, b isomers: white
solid. Yield: 369 mg (85%); a/b:95/5; [a]D +68.2 (c 1,
2
0
ꢁ
1
CH Cl ); IR: 2925, 2856, 1755, 1222, 1044 cm . a isomer:
2
2
1
H NMR (CDCl ) d 5.48 (t, 1H, J¼9.8 Hz, H-3), 5.15 (t, 1H,
3
J¼9.5 Hz, H-4), 5.10 (d, 1H, J¼3.4 Hz, H-1), 4.83 (dd, 1H,
J¼3.4, 10.0 Hz, H-2), 4.28 (d, 1H, J¼10.0 Hz, H-5),
4.06–3.93 (m, 2H, CO CH ), 3.61 (m, 1H, OCH ), 3.33
4.3.1. n-Butyl b-D-glucofuranosidurono-6,3-lactone (1b).
Colorless syrup. Yield: 194 mg (81%, a/b:20/80); a and
2
2
2
2
0
b isomers were isolated. b isomer: syrup, [a] ꢁ12.0 (c
(m, 1H, OCH ), 1.97 (s, 3H, CH CO), 1.94 (s, 6H,
2 3
D
ꢁ
1 1
0
.14, CH OH); IR: 3273, 2351, 2342, 1797 cm ; H NMR
3
2ꢂCH CO), 1.53 (m, 4H, 2ꢂCH ), 1.20 (m, 36H,
3
2
1
2 3 2 3
3
(
CD OD) 5.02 (s, 1H, H-1), 4.84 (dd, 1H, J¼6.5, 4.6 Hz,
18ꢂCH ), 0.81 (m, 6H, 2ꢂCH CH ). C NMR (CDCl )
3
H-4), 4.82 (m, 3H, H-3, 2ꢂOH), 4.51 (d, 1H, J¼6.5 Hz, H-
d 169.8 (2ꢂCO), 169.3 (CO), 167.7 (C6), 95.7 (C1), 71.1
5), 4.22 (s, 1H, H-2), 3.83 (m, 1H, OCH ), 3.33 (m, 1H,
OCH ), 1.50 (m, 2H, CH ), 1.33 (m, 2H, CH ), 0.92 (t, 3H,
(C2), 70.5 (C4), 69.6 (C3), 69.5 (OCH ), 68.2 (C5), 66.0
2
2
(CO CH ), 31.8 (CH ), 29.3 (CH ), 28.2 (CH ), 25.8
2
2
2
2
2
2
2
2
1
3
J¼7.2 Hz, CH ). C NMR (CD OD) d 175.8 (C6), 109.1
(CH ), 22.5 (CH ), 20.4 (3ꢂCH CO), 13.9 (2ꢂCH CH ).
3
3
2
2
3
3
2
(
(
C1), 83.4 (C3), 77.9 (C4), 77.2 (C2), 69.1 (C5), 69.6
OCH ), 31.0, 19.0 (2ꢂCH ), 12.9 (CH CH ). a isomer:
HRMS [M+Na] calcd for C H O Na: 679.4397. Found
36 64 10
[M+Na]: 679.4396.
2
2
3
2
ꢀ
20
D
1
white solid, mp 73–74 C; [a] +91.4 (c 1, CH OH); H
3
NMR (CD OD) 5.18 (d, 1H, J¼4.5 Hz, H-1), 4.75 (m, 4H,
4.3.5. Butyl 2,3,4-tri-O-acetyl-D-glucopyranuronate (5b).
Mixture of a, b isomers: colorless syrup. Yield: 202 mg
(81%); a/b:85/15; [a]D +71.3 (c 1, CH Cl ); IR: 3469,
3
H-3, H-4, 2OH), 4.57 (d, 1H, J¼4.8 Hz, H-5), 4.23 (d, 1H,
J¼4.5 Hz, H-2), 3.81 (m, 1H, OCH ), 3.56 (m, 1H, OCH ),
2
0
2
2
2
2
ꢁ
1
1
1
.61 (m, 2H, CH ), 1.41 (m, 2H, CH ), 0.92 (t, 3H,
2
2963, 1751, 1370, 1219, 1038 cm . a isomer: H NMR
2
3
1
J¼7.2 Hz, CH ). C NMR (CD OD) d 176.9 (C6), 104.4
(CDCl ) d 5.56 (t, 1H, J¼9.8 Hz, H-3), 5.55 (d, 1H,
3
3
3
(
(
[
[
C1), 86.6 (C3), 78.1 (C2), 76.9 (C4), 70.6 (C5), 69.8
OCH ), 32.6, 20.2 (2ꢂCH ), 14.2 (CH CH ). HRMS
J¼3.5 Hz, H-1), 5.18 (t, 1H, J¼9.8 Hz, H-4), 4.90 (dd, 1H,
J¼9.8, 3.5 Hz, H-2), 4.57 (d, 1H, J¼10.0 Hz, H-5), 4.24
(d, 1H, J¼3.5 Hz, OH), 4.17–4.09 (m, 2H, CO CH ), 2.07
2
2
3
2
M+Na] calcd for C H O Na: 255.0855. Found
0
2
32 10
2
2
M+Na]: 255.0845.
(s, 3H, CH CO), 2.02 (s, 6H, 2ꢂCH CO), 1.59 (m, 2H,
3
3
CH ), 1.36 (m, 2H, CH ), 0.91 (t, 3H, J¼7.3 Hz,
2 2
1
3
4.3.2. Butyl (butyl 2,3,4-tri-O-acetyl-a,b-D-glucopyrano-
sid)uronate (4b). Mixture of a, b isomers: colorless syrup.
CH CH ). C NMR (CDCl ) d 170.1 (2ꢂCO), 169.5
3
2
3
(CO), 168.2 (C6), 90.1 (C1), 71.1 (C2), 69.9 (C4), 69.7
(C3), 68.5 (C5), 66.5 (CO CH ), 30.7 (CH ), 21.1
2
0
Yield: 260 mg (91%) a/b:85/15; [a]
CH Cl ). IR: 1756, 1224, 1044 cm . a isomer: H NMR
+81.1 (c 1,
D
2
2
2
ꢁ
1
1
(3ꢂCH CO), 19.3 (CH ), 14.0 (CH CH ). HRMS [M+Na]
2
2
3
2
3
2
(
CDCl ) d 5.49 (t, 1H, J¼9.5 Hz, H-3), 5.14 (d, 1H,
calcd for C H O Na: 399.1257. Found [M+Na]:
20 32 10
3
J¼9.5 Hz, H-4), 5.10 (d, J¼3.7 Hz, H-1), 4.83 (dd, 1H,
J¼3.7, 9.5 Hz, H-2), 4.29 (d, 1H, J¼10.0 Hz, H-5), 4.17–
399.1267.
4
.09 (m, 2H, CO CH ), 3.72 (m, 1H, OCH ), 3.43 (m, 1H,
2
4.3.6. Octyl 2,3,4-tri-O-acetyl-D-glucopyranuronate (5c).
Mixture of a, b isomers: colorless syrup. Yield: 221 mg
2
2
OCH ), 2.03 (s, 3H, CH CO), 1.97 (s, 6H, 2ꢂCH CO),
2
3
3
2
0
1
.59 (m, 4H, 2ꢂCH ), 1.36 (m, 4H, 2ꢂCH ), 0.91 (t, 6H,
(79%); a/b:75/25; [a]D +60.5 (c 1, CH Cl ); IR: 3473,
2 2
2
2
1
3
ꢁ1
1
J¼7.3 Hz, 2ꢂCH CH ).
C NMR (CDCl ) d 169.9
3
2946, 1752, 1368, 1229, 1037 cm . a isomer: H NMR
3
2