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SZNAIDMAN, ALMOND, AND PESYAN
and the aqueous layer washed with methylene chloride (26125 mL). The
combined organic layers were successively washed with: water (26250 mL),
sat. NaHCO3 (261250 mL) and water (26250 mL), dried, filtered, and
evaporated to a colorless syrup ( ꢂ 20 g). The syrup was purified by flash
column chromatography (300 g silica gel, hexane:EtOAc 4:1) to afford 4
(12.0 g, 60 mmol, 60%) as a colorless syrup; 1H-NMR (CDCL3) d: 6.48 (1H,
d, J ¼ 6.0, H-1), 5.44 (1H, m, H-3), 5.19 (1H, dt, J ¼ 4.0, J ¼ 4.0, J ¼ 9, H-4),
4.83 (1H, dd, J ¼ 5.0, J ¼ 6.0, H-4), 4.00 (2H, m, H-5 and H-50), 2.08 (3H, s,
CH3COO), 2.07 (3H, s, CH3COO).
3,4-di-O-Acetyl-2-deoxy-2-£uro-L-arabinopyranose (5). To a well
stirred solution of glycal 4 (12.0 g, 60 mmol) in nitromethane:water (4:2,
120 mL) was added SelectfluorTM (26 g, 73 mmol). The solution was stirred
overnight at room temperature. The solution was then heated at reflux for
1 h to complete the reaction. After cooling to room temperature, the nitro-
methane was removed in vacuo. Water (150 mL) was added and extracted
with EtOAc (36150 mL). The combined organic fractions were successively
washed with: 1N HCl (26200 mL), and water (26200 mL), dried, filtered,
and evaporated to afford crude 5 (9.9 g, 42 mmol, 70%) as a syrup; 13C-
NMR (CDCl3) d: 170.35 (CH3COO), 170.27 (CH3COO), 95.01 (C-1a, d,
JC-1,F ¼ 24.5), 90.81 (C-1b, d, JC-1,F ¼ 21.5), 89.10 (C-2a, d, JC-2,F ¼ 184.3),
85.85 (C-2b, d, JC-2,F ¼ 188.0), 70.61 (C-3a, d, JC-3,F ¼ 19.5), 69.57 (C-4b, d,
JC-4,F ¼ 7.7), 68.66 (C-4a, d, JC-4,F ¼ 8.3), 67.53 (C-3b, d, JC-3,F ¼ 17.8), 63.90
(C-5a), 60.26 (C-5b), 20.73 (CH3COO), 20.67 (CH3COO), 20.62 (CH3COO),
20.56 (CH3COO). 19F-NMR (CDCl3) d -205.61 (dd, J ¼ 11.0 and J ¼ 51.8,
F-2a-anomer), -207.02 (dd, J ¼ 9.0 and J ¼ 49.0, F-2b-anomer).
Anal.Calcd. For C9H13O6F: C, 45.77; H, 5.55. Found: C, 45.64; H, 5.51.
2-Deoxy-2-£uoro-L-arabinopyranose (6). Asolution of
5 (5.7 g,
24.1 mmol) in dry methanol (220 mL) was treated with 0.1 N NaOMe in
methanol (114 mL, 11.4 mmol) and stirred for 1 h at room temperature. The
solution was then neutralized with DOWEX 50W X8-100, filtered and eva-
porated to afford crude 6 (3.7 g, 24 mmol, 100%) as a yellow syrup; 13C-
NMR (D2O) d: 94.19 (C-1a, d, JC-1,F ¼ 23.0), 92.24(C-2a, d, JC-2,F ¼ 179.6),
90.10 (C-1b, d, JC-1,F ¼ 20.3), 88.60 (C-2b, d, JC-2,F ¼ 182.3), 70.77 (C-3a, d,
JC-3,F ¼ 18.2), 69.03 (C-4b, d, JC-4,F ¼ 8.0), 68.90 (C-4a, d, JC-4,F ¼ 10.2),
66.85 (C-3b, d, JC-3,F ¼ 18.2), 66.32 (C-5a), 62.21 (C-5b). 19F-NMR
(CD3OD) d -204.11 (dd, J ¼ 12.6 and J ¼ 51.7, F-2a-anomer), -206.45 (d,
J ¼ 47.3, F-2b-anomer).
1-O-Methyl-2-deoxy-2-£uoro-L-arabinofuranoside (7). Asolution of 6
(790 mg, 5.2 mmol) and H2SO4 (60.1 mL, 1.1 mmol) in dry methanol
(12.2 mL) was heated at reflux for 6 hs. The reaction was cooled to room
temperature, neutralized with DOWEX SBR, filtered and evaporated to