ORDER
REPRINTS
UDP-Thiogal Sugar Nucleotide Donor Substrate
201
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This yielded 3.39 g of 4 (11.2 mmol, 98%). NMR data (CDCl3, TMS): H (300 MHz) d
5.81 (d, 1 H, H-1, J1,2 4.0), 5.08 (dd, 1 H, H-3, J2,3 5.6, J3,4 6.7), 4.82 (dd, 1 H, H-2,
J1,2 4.0, J2,3 5.6), 4.62 (ddd, 1 H, H-5), 4.08–4.12 (m, 2 H, H-6, H-6’), 3.53 (dd, 1 H,
H-4), 2.14 (s, 3 H, OAc), 1.59, 1.45, 1.39, 1.37 (each s, each 3 H, each Me). 13C (75
MHz) d 169.64, 111.48, 109.26, 105.01, 81.31, 78.49, 75.16, 71.76, 66.35, 26.76,
26.67, 25.25, 21.05, 20.62. HRMS for C14H22O7: 302.1368 observed, 302.1366 calcd.
1,2:5,6-Di-O-isopropylidene- -D-gulofuranose (5): The gulofuranose 3-O-ace-
tate 4 (3.25 g, 10.8 mmol) was dissolved in MeOH (20 mL), H2O (20 mL) and
triethylamine (4 mL). The mixture was stirred at room temperature for 3 h and
monitored by TLC using hexane:EtOAc (2:1, v/v) as the mobile phase. The solvent was
evaporated and the residue further dried by repeated coevaporation with toluene. This
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yielded 2.77 g of 5 (10.65 mmol, 99%). NMR data (CDCl3, TMS). H (300 MHz) d
5.82 (d, 1 H, H-1, J1,2 4.1), 4.67 (dd, 1 H, H-2, J1,2 4.1, J2,3 5.7), 4.48 (dd, 1 H, H-5),
4.22 (m, 2 H, H-6, H-6’), 3.88 (dd, 1 H, H-3, J2,3 5.7, J3,4 7.9), 3.72 (dd, 1 H, H-4, J4,5
7.4, J3,4 7.9), 2.67 (broad s, 1 H, 3-OH), 1.63, 1.46, 1.43, 1.38 (each s, each 3 H, each
Me). 13C (75 MHz) d 105.33, 84.35, 79.89, 75.59, 69.67, 66.38, 27.18, 27.13, 26.71,
25.21. HRMS for C12H20O6: 260.1252 observed, 260.1260 calcd.
1,2:5,6-Di-O-isopropylidene-3-S-acetyl-3-thio- -D-galactofuranose (6): Tri-
fluoromethanesulfonic acid anhydride (5 mL) was dissolved in dry CH2Cl2 (5 mL)
and dry pyridine (2 mL) previously cooled at –10°C. The alcohol 5 (1.0 g, 3.8 mmol)
was dissolved in dry CH2Cl2 (10 mL) and added dropwise to the triflic anhydride
solution at a constant –10°C. Additional CH2Cl2 was added to prevent the mixture
from freezing. TLC analysis using hexane:EtOAc (2:1, v/v) revealed the formation of a
new product at Rf 0.85. After 1 h, the reaction mixture was diluted with CH2Cl2 (40
mL) and washed with ice-cold 1 N HCl (2 ꢀ 20 mL), ice-cold 10 % NH4Cl (2 ꢀ 20
mL) and water (2 ꢀ 20 mL). The organic solution was dried over Mg2SO4, filtered and
concentrated to an orange oily residue which was immediately dissolved in 10 mL
EtOAc. K2CO3 (1.05 g), tetrabutylammonium hydrogen sulfate (2.58 g) were dissolved
in water (10 mL) and added to the gulose-3-O-triflate solution. KSAc (1.74 g) was
finally added and the biphasic mixture was stirred at room temperature for 4 h. TLC
analysis using hexane:EtOAc (4:1, v/v) revealed the formation of a new product at Rf
0.45 and the complete disappearance of the triflate. The organic layer was collected,
washed with water (2 ꢀ 10 mL) and purified using flash chromatography using
hexane:EtOAc (4:1, v/v) as the mobile phase. The fractions corresponding to the
product were collected and dried. This yielded 690 mg of 6 as a brown solid
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(2.2 mmol, 56%). NMR data (CDCl3, TMS): H (300 MHz) d 5.92 (d, 1 H, H-1, J1,2
3.7), 4.62 (dd, 1 H, H-2, J2,3 1.5, J1,2 3.7), 4.43 (dd, 1 H, H-5), 4.10 (dd, 1 H, H-6),
3.99 (dd, 1 H, H-4, J4,5 7.2, J3,4 4.7), 3.86 (dd, 1 H, H-6’), 3.70 (dd, 1 H, H-3, J3,4 4.7,
J2,3 1.5), 2.39 (s, 3 H, SAc), 1.62, 1.45, 1.38, 1.35 (each s, each 3 H, each Me). 13C (75
MHz) d 194.40, 114.25, 110.39, 106.20, 87.13, 85.54, 76.57, 66.23, 47.80, 31.97 (SAc),
27.75, 27.02, 25.76, 23.05. HRMS for C13H20O6S: 304.1147 observed, 304.1137 calcd.
1,2,4,6-Tetra-O-acetyl-3-S-acetyl-3-thio-( / )-D-galactopyranoside (7): To a
suspension of 6 (650 mg, 2.0 mmol) in water (10 mL), 550 mg of IR-20 (H+) was
added. Under a continuous gentle stream of nitrogen, the mixture was heated at 70°C