N. Ferlin et al. / Carbohydrate Research 343 (2008) 839–847
843
0
0
3.2. Octyl 2,3,4,6-tetra-O-acetyl-a,b-D-glucopyranoside
(2a,b)
1.08 (m, 10H, H-30 to H-70), 0.79 (t, 3H, J7 ;8 7.0 Hz,
H-80). 13C NMR (75.5 MHz, CDCl3): d 170.5, 170.2,
169.3, 169.1 (4C@O), 100.7 (C-1), 72.7 (C-3), 71.5
(C-5), 71.2 (C-2), 70.1 (C-10), 68.3 (C-4), 61.8 (C-6),
31.7, 29.2, 29.1 (2C), 25.7, 22.5 (C-20–C-70), 20.6, 20.5
(4CH3–CO), 13.9 (C-80).
A mixture of 1,2,3,4,6-penta-O-acetyl-D-glucopyranose
(1, 3.9 g, 10.0 mmol), 1-octanol (3.25 mL, 20.2 mmol),
and ZnCl2 (1.4 g, 10.0 mmol) in a 100-mL flask was stir-
red under argon in the microwave reactor. The follow-
ing conditions were used: T = 115 °C, P = 60 W, ramp
time = 3 min, holdtime = 3 min. After cooling, the
brown oil obtained was filtered through silica gel (eluant
EtOAc). After solvent evaporation, the mixture was
reacetylated using pyridine (4.1 mL) and Ac2O
(5.0 mL). After stirring overnight at rt, MeOH (10 mL)
was added, and the mixture was stirred for 10 min.
The solution was diluted with EtOAc (100 mL) and
washed with water (5 ꢂ 100 mL). The organic layer
was dried (Na2SO4), filtered, and concentrated to a
syrup. Flash chromatography on silica gel (1:4 to 2:3
EtOAc–cyclohexane) gave 2a (2.55 g, 55% yield) and
2b (0.81 g, 18% yield).
3.3. Octyl a-D-glucopyranoside (3a)
Compound 2a (2.5 g, 5.4 mmol) was dissolved in dry
MeOH (8 mL). A solution of 1 M NaOMe in MeOH
(2.7 mL) was added, and the mixture was stirred under
N2 at rt until total disappearance of starting materials
and intermediates (3 h). Amberlyst IR-120 (H+) was
added, and the mixture was stirred until the pH reached
5. The resin was filtered off, and the solution was eva-
porated to dryness leading to compound 3a (quantita-
20
tive yield), as a gum, Rf 0.53 (1:9 MeOH–EtOAc); ½aꢃD
23
+117 (c 1.0, MeOH); ½aꢃD (lit.17) +117.9 (c 1.0, MeOH);
IR (ATR in cmꢁ1): 3600–3000 (mOH), 2952, 2922, 2847
(mCH), 1655, 1637, 1459, 1410, 1379, 1352, 1145, 1112,
1
3.2.1. Octyl 2,3,4,6-tetra-O-acetyl-a-D-glucopyranoside
1086, 1050, 1024, 1002. H NMR (300 MHz, CD3OD):
d 4.78 (d, 1H, J1,2 3.7 Hz, H-1), 3.79 (dd, 1H, J5,6a
20
(2a). Oil, Rf 0.7 (1:1 EtOAc–cyclohexane); ½aꢃD +34
1
0
0
(c 0.27, CHCl3); H NMR (300 MHz, CDCl3): d 5.36
2.4 Hz, J6a,6b 11.8 Hz, H-6a), 3.72 (td, 1H, J1 a;1 b
0
0
(t, 1H, J2,3 10.2 Hz, J3,4 9.8 Hz, H-3), 4.94 (d, 1H, J1,2
3.7 Hz, H-1), 4.92 (t, 1H, J3,4 9.8 Hz, J4,5 10.2 Hz, H-
4), 4.72 (dd, 1H, J1,2 3.7 Hz, J2,3 10.2 Hz, H-2), 4.15
(dd, 1H, J5,6a 4.5 Hz, J6a,6b 12.2 Hz, H-6a), 3.96 (dd,
1H, J5,6b 2.2 Hz, J6a,6b 12.2 Hz, H-6b), 3.90 (ddd, 1H,
J4,5 10.2 Hz, J5,6a 4.5 Hz, J5,6b 2.2 Hz, H-5), 3.57 (td,
9.6 Hz, J1 a;2 6.9 Hz, H-10a), 3.66 (dd, 1H, J5,6b 5.4 Hz,
J6a,6b 11.8 Hz, H-6b), 3.65 (dd, 1H, J2,3 9.7 Hz, J3,4
9.3 Hz, H-3), 3.57 (ddd, 1H, J4,5 9.8 Hz, J5,6a 2.4 Hz,
0
0
0
0
J5,6b 5.4 Hz, H-5), 3.44 (td, 1H, J1 a;1 b 9.6 Hz, J1 b;2
6.4 Hz, H-10b), 3.40 (dd, 1H, J1,2 3.7 Hz, J2,3 9.7 Hz,
H-2), 3.31 (dd, 1H, J3,4 9.3 Hz, J4,5 9.8 Hz, H-4), 1.62
(m, 2H, H-20), 1.30 (m, 10H, H-30 to H-70), 0.89 (t,
1H, J1 a;1 b 9.7 Hz, J1 a;2 6.5 Hz, H-10a), 3.31 (td, 1H,
0
0
0
0
J1 a;1 b 9.7 Hz, J1 b;2 6.5 Hz, H-10b), 1.96, 1.93, 1.91,
3H, J7 ;8 6.8 Hz, H-80). 13C NMR (75.5 MHz, CD3OD):
d 100.0 (C-1), 75.0 (C-3), 73.50, 73.45 (C-2, C-5), 71.7
(C-4), 69.1 (C-10), 62.5 (C-6), 33.0, 30.6, 30.5, 30.3,
27.3, 23.7 (C-20 to C-70), 14.5 (C-80).
0
0
0
0
0
0
0
0
1.89 (4s, 3H each, 4CH3), 1.48 (quint, 2H, J1 ;2 6.5 Hz,
J2 ;3 6.5 Hz, H-20), 1.25–1.12 (m, 10H, H-30 to H-70),
0
0
0.76 (t, 3H, J7 ;8 6.8 Hz, H-80). 13C NMR (75.5 MHz,
CDCl3): d 170.2, 169.70, 169.68, 169.2 (4C@O), 95.3
(C-1), 70.6 (C-2), 69.9 (C-3), 68.3 (C-10, C-4), 66.8
(C-5), 61.6 (C-6), 31.5, 28.9, 25.7, 22.3 (C-20 to C-70),
20.3 (2CH3–CO), 20.24, 20.22 (2CH3–CO), 13.7 (C-80).
0
0
3.4. Octyl b-D-glucopyranoside (3b)
`
Compound 2b was deacetylated under Zemplen condi-
tions as for 3a to give compound 3b (quantitative yield),
20
3.2.2. Octyl 2,3,4,6-tetra-O-acetyl-b-D-glucopyranoside
(2b). White crystals (cyclohexane), mp 51.5–53 °C,
mp (lit.16) 53–54 °C, Rf 0.64 (1:1 EtOAc–cyclohexane);
as a gum: Rf 0.55 (1:9 MeOH–EtOAc); ½aꢃD ꢁ30 (c 1.0,
25
MeOH); ½aꢃD (lit.14) ꢁ30.3 (c 1.0, MeOH); IR (ATR in
cmꢁ1): 3600–2950 (mOH), 2923, 2854 (mCH), 1645, 1463,
1378, 1160, 1112, 1085, 1027, 919, 894. 1H NMR
(300 MHz, CD3OD): d 4.25 (d, 1H, J1,2 7.8 Hz, H-1),
25
25
½aꢃD ꢁ17 (c 1.02, CHCl3), ½aꢃ (lit.14) ꢁ21.7 (c 1.0,
D
MeOH); IR (ATR in cmꢁ1): 2922, 2874, 2854 (mCH),
1743 (mC@O), 1472, 1428, 1368, 1257, 1223, 1167, 1133,
1091, 1038. 1H NMR (300 MHz, CDCl3): d 5.13 (t,
1H, J2,3 9.6 Hz, J3,4 9.6 Hz, H-3), 5.00 (t, 1H, J3,4
9.6 Hz, J4,5 9.9 Hz, H-4), 4.90 (dd, 1H, J1,2 8.0 Hz, J2,3
9.6 Hz, H-2), 4.43 (d, 1H, J1,2 8.0 Hz, H-1), 4.20 (dd,
1H, J5,6a 4.7 Hz, J6a,6b 12.3 Hz, H-6a), 4.05 (dd, 1H,
3.90 (dt, 1H, J1 a;1 b 9.6 Hz, J1 a;2 6.8 Hz, H-10a), 3.86
(dd, 1H, J5,6a 1.7 Hz, J6a,6b 11.9 Hz, H-6a), 3.67 (dd,
1H, J5,6b 5.2 Hz, J6a,6b 11.9 Hz, H-6b), 3.53 (td, 1H,
0
0
0
0
J1 b;2 6.8 Hz, H-10b), 3.43–3.23 (m, 3H, H-3, H-4,
H-5), 3.18 (dd, 1H, J1,2 7.8 Hz, J2,3 8.9 Hz, H-2), 1.62
0
0
(quint, 2H, J1 a;2 6.8 Hz, J2 ;30 6.8 Hz, H-20), 1.45–1.23
0
0
0
(m, 10H, H-30 to H-70), 0.89 (t, 3H, J7 ;8 6.7 Hz, H-80).
13C NMR (75.5 MHz, CD3OD): d 104.3 (C-1), 78.0
(C-3), 77.8 (C-5), 75.0 (C-2), 71.5 (C-4), 70.9 (C-10),
62.7 (C-6), 33.0, 30.7, 30.5, 30.4, 27.1, 23.7 (C-20 to
C-70), 14.4 (C-80).
0
0
0
0
J5,6b 2.4 Hz, J6a,6b 12.3 Hz, H-6b), 3.79 (td, 1H, J1 a;1 b
9.6 Hz, J1 a;2 6.3 Hz, H-10a), 3.63 (ddd, 1H, J4,5
9.9 Hz, J5,6a 4.7 Hz, J5,6b 2.4 Hz, H-5), 3.40 (td, 1H,
0
0
J1 a;1 b 9.6 Hz, J1 b;2 6.7 Hz, H-10b), 2.00, 1.96, 1.94,
0
0
0
0
1.92 (4s, 3H each, 4 CH3), 1.48 (m, 2H, 2H-20), 1.28–