L. Gandolfi-Donadı´o et al. / Carbohydrate Research 341 (2006) 2487–2497
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timidate (5) as 10:1 b:a anomeric mixture (1.94 g, 93%)
that showed Rf 0.59 (b anomer); 0.50 (a anomer)
(3:1:0.03 hexane–EtOAc–TEA); 1H NMR (CDCl3,
500 MHz): d (for the b anomer, only diagnostic signals
are listed for the a anomer) 8.50 (NH, 0.91H), 8.44
(NH, 0.09H a anomer), 7.41–7.34 (m, 20H), 6.44 (d,
0.09H, J 4.2 Hz, H-1a), 6.38 (d, 0.91H, J 0.8 Hz, H-1),
4.73, 4.40 (2d, 1.82H, J 11.7 Hz), 4.68, 4.57 (2d,
1.82H, J 11.8 Hz), 4.53, 4.32 (2d, 1.82H, J 11.8 Hz),
4.51–4.45 (m, 1.82H), 4.42 (dd, 0.91H, J 6.1, 4.2 Hz),
4.21 (dd, 0.91H, J 0.8, 2.3 Hz), 4.12 (dd, 0.91H, J 2.3,
6.1 Hz), 4.83 (ddd, 0.91H, J 4.2, 5.5, 5.8 Hz), 3.72–3.65
(m, 1.82H); 13C NMR (CDCl3, 125.8 MHz): d (for the
b anomer, only the anomeric carbon is listed for the a
anomer) 160.9 (C@NH), 138.4–127.5, 104.2 (C-1), 98.2
(C-1 a anomer), 91.2, 86.7, 84.3, 82.8, 76.5; 73.4, 73.2,
71.9, 70.5. The anomeric resonances are in agreement
with literature values.31
H-10), 4.92, 4.66 (2d, 2H, J 11.6 Hz, CH2Ph), 4.83,
4.59 (2d, 2H, J 12.1 Hz, CH2Ph), 4.69 (d, 1H, J
2.3 Hz, OH), 4.54, 4.51 (2d, 2H, J 12.1 Hz, CH2Ph),
4.48, 4.13 (2d, 2H, J 11.2 Hz, CH2Ph), 4.45 (t, 1H, J
8.2 Hz, H-30), 4.24 (d, 1H, J 8.4 Hz, H-2), 4.12 (dd, J
4.1, 7.8 Hz, H-20), 3.98 (d, 1H, J 8.2, H-40), 3.91 (dd,
1H, J 5.7, 8.5 Hz, H-4), 3.91–3.86 (m, 1H, H-5), 3.78
(dt, 1H, J 8.5, 2.3 Hz, H-3), 3.78–3.74 (m, 2H, H-6a,
H-6b), 3.66–3.63 (m, 3H, H-50, H-6a0, H-6b0), 1.38,
1.36 (2s, 6H, (CH3)2C). 13C NMR (CDCl3, 125.8
MHz): d 171.4 (C-1), 137.9–127.6 (aromatic), 109.9
((CH3)2C), 100.0 (C-10), 83.0 (C-20), 79.9 (C-40), 79.2
(C-2), 79.1 (C-4), 77.7 (C-30), 76.0 (C-50), 75.6 (C-5);
74.6, 73.6 (CH2Ph), 72.5 (C-3); 72.2, 72.0 (CH2Ph),
70.3 (C-60), 64.8 (C-6), 26.3, 25.7 ((CH3)2C). Anal. Calcd
for C43H48O11: C, 69.71; H, 6.53. Found: C, 69.87; H,
6.50.
3.3.2. Mixture of 2,3,5,6-tetra-O-benzyl-b-D-galactofur-
anosyl-(1!3)-5,6-O-isopropylidene-D-galactono-1,4-lac-
tone (10) and 2,3,5,6-tetra-O-benzyl-a-D-galactofuran-
osyl-(1!3)-5,6-O-isopropylidene-D-galactono-1,4-lactone
(11). The third fraction from the column (Rf 0.31, 4:1
toluene–EtOAc) was identified as a mixture of 2,3,5,
6-tetra-O-benzyl-b-D-galactofuranosyl-(1!3)-5,6-O-iso-
propylidene-D-galactono-1,4-lactone (10) and 2,3,5,
6-tetra-O-benzyl-a-D-galactofuranosyl-(1!3)-5,6-O-iso-
3.3. 2,3,5,6-Tetra-O-benzyl-a-D-galactofuranosyl-(1!2)-
5,6-O-isopropylidene-D-galactono-1,4-lactone (6)
3.3.1. 2,3,5,6-Tetra-O-benzyl-N-trichloroacetyl-b-D-gala-
ctofuranosylamine (14). A vigorously stirred suspen-
sion of dried trichloroacetimidate 5 (1.90 g, 2.78 mmol),
5,6-O-isopropylidene-D-galactono-1,4-lactone36 (3, 0.86
˚
g, 3.89 mmol) and dried 4 A powdered molecular sieves
(0.9 g) in anhyd CH2Cl2 (50 mL) was cooled to ꢀ27 ꢁC.
After 10 min, TMSOTf (0.131 mL, 0.74 mmol) was
slowly added. After 1 h, TLC monitoring showed con-
sumption of imidate 5, the mixture was rapidly filtered
and quenched by the addition of satd aq NaHCO3
(25 mL). After dilution with CH2Cl2 (220 mL) and addi-
tional satd aq NaHCO3, the organic phase was sepa-
rated and washed with water, dried (MgSO4), and
concentrated. The oily residue was purified by column
chromatography (9:1 toluene–EtOAc and then 4:1 tolu-
ene–EtOAc). The fastest migrating component (Rf 0.76,
4:1 toluene–EtOAc) was identified as 2,3,5,6-tetra-
O-benzyl-N-trichloroacetyl-b-D-galactofuranosylamine
(14, 0.24 g, 13%): [a]D +5.6 (c 1, CHCl3); 1H NMR
(CDCl3, 500 MHz): d 8.02 (d, 1H, J 8.8 Hz, NH),
7.35–7.22 (m, 20H), 5.88 (dd, 1H, J 5.7, 8.8 Hz, H-1),
4.70, 4.61 (2d, 2H, J 11.4 Hz), 4.55, 4.50 (2d, 2H, J
12.0 Hz), 4.46, 4.44 (2d, 2H, J 11.7 Hz), 4.46, 4.30 (2d,
2H, J 11.9 Hz), 4.24 (t, 1H, J 5.7 Hz), 4.15–4.10 (m,
2H), 3.71 (dd, 1H, J 6.1, 9.2 Hz), 3.63 (dd, 1H, J 5.4,
9.2 Hz), 3.63 (m, 1H). 13C NMR (CDCl3, 125.8 MHz):
d 161.3 (NHCOCl3), 137.9–127.6, 83.8, 82.1, 81.4,
81.3, 76.7, 73.9, 73.6, 72.9, 72.0, 70.4. HRMS (MALDI)
Calcd for C36H36Cl3NO6 [M+Na]+ 706.1506. Found:
[M+Na]+ 706.1499. The second fraction from the col-
umn (Rf 0.48, 4:1 toluene–EtOAc) afforded crystalline
6 (1.05 g, 51%): mp 101–102 ꢁC (9:1 hexane–EtOAc);
propylidene-D-galactono-1,4-lactone
(11)
(330 mg,
1
16%): H NMR (CDCl3, 500 MHz, anomeric region):
d 5.28 (d, J 1.3 Hz, 0.3H, b anomer, H-10), 4.92 (d, J
4.4 Hz, 0.7H, a anomer, H-10); 13C NMR (CDCl3,
125.8 MHz): d 171.5 (C-1 of a and b anomer), 138.2–
127.5, 110.4, 110.2, 106.0 (C-10b), 99.9 (C-10a), 88.3,
83.4, 82.7, 81.8, 81.7, 80.0, 79.8, 79.4, 78.2, 76.1, 76.0,
74.8, 74.3, 73.6, 73.4, 73.3, 73.2, 73.1, 72.8, 72.7, 72.6,
72.2, 70.0, 69.6, 65.1, 65.0, 25.9, 25.8, 25.7, 25.6.
3.3.3.
2,3,5,6-Tetra-O-benzyl-b-D-galactofuranosyl-
(1!2)-5,6-O-isopropylidene-D-galactono-1,4-lactone (8).
The lowest migrating component from the column (Rf
0.12, 4:1 toluene–EtOAc) was identified as 2,3,5,6-tetra-
O-benzyl-b-D-galactofuranosyl-(1!2)-5,6-O-isopropyl-
idene-D-galactono-1,4-lactone (8) (165 mg, 8%). Com-
pound 8 was crystallized from 6:1 hexane–EtOAc, mp
105–107 ꢁC; [a]D ꢀ66.1 (c 1, CHCl3); 1H NMR (CDCl3,
500 MHz): d 7.38–7.20 (m, 20H, aromatic), 5.31 (d, 1H,
J 1.3 Hz, H-10), 4.64, 4.54 (2d, 2H, J 12.0 Hz, CH2Ph),
4.62, 4.47 (2d, 2H, J 11.8 Hz, CH2Ph), 4.58 (ddd, 1H,
J 3.5, 8.4, 9.5 Hz, H-3), 4.52, 4.49 (2d, 2H, J 12.0 Hz,
CH2Ph), 4.46 (d, 1H, J 9.5 Hz, H-2), 4.45, 4.32 (2d,
2H, J 11.6 Hz, CH2Ph), 4.39 (dd, 1H, J 3.2, 7.6 Hz,
H-30), 4.27 (dt, 1H, J 3.8, 6.9 Hz, H-5), 4.14 (dd, J 1.3,
3.2 Hz, H-20), 4.07 (dd, 1H, J 3.6, 7.6 Hz, H-40), 4.04
(dd, 1H, J 6.9, 8.6 Hz, H-6a), 3.99 (dd, 1H, J 3.8,
8.4 Hz, H-4), 3.95 (dd, 1H, J 6.9, 8.6 Hz, H-6b), 3.76–
3.71 (m, 2H, H-50, H-6a0), 3.73 (dd, 1H, J 5.5,
1
[a]D +17.4 (c 1, CHCl3); H NMR (CDCl3, 500 MHz):
d 7.47–7.18 (m, 20H, aromatic), 5.12 (d, 1H, J 4.1 Hz,