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HETEROCYCLES, Vol. 73, 2007
other portions of NaHCO3 (2x10 mg, 2x119 µmol) and methyl formate (2x20 µL, 2x324 µmol) were
added. The reaction mixture was concentrated after 48 h (total) and purified by flash chromatography
over silica gel (EtOAc / MeOH / water 3:1:1), followed by passing through a column of Dowex H+
(50Wx8), yielding after concentration 14 mg (80%) of allyl 2-deoxy-2-formamido-β-D-glucopyranoside
as white solid: 1H NMR (250 MHz, D2O) δ (ppm) : 8.18 (s, 0.7 H, CHOtrans), 7.97 (s, 0.3 H, CHOcis), 5.90
(m, 1 H, Ha), 5.33 / 5.22 (2 m, 2 H, Hb and Hc), 4.60 (d, H-1βtrans, J1β,2 8.4 Hz), 4.56 (d, H-1βcis), 4.33 /
4.15 (2 m, 2 H, Hd and Hd’), 3.90 (dd, 1 H, H-6a, J6a,6b 12.2 Hz and J6a,5 1.8 Hz), 3.80 – 3.65 (m, 1.7 H,
H-6b and H-2trans), 3.60 - 3.40 (m, 3 H, H-3, H-4 and H-5), 3.21 (dd, 0.3 H, H-2cis, J2,3 8.5 Hz); 13C NMR
(62.5 MHz, D2O) δ (ppm) : (two sets of signals due to the presence of two trans / cis rotamers of the
formamide with slow equilibrium) 170 (CHOcis), 166 (CHOtrans), 134 (-OCH2-CH=CH2), 120
(-OCH2-CH=CH2), 101 (C-1β), 77 (C-5), 75 / 72 (C-3, C-4), 73 (-OCH2-CH=CH2), 62 (C-6), 60 (C-2cis),
56 (C-2trans); MS(ESI+) m/z: 517.2 [2M + Na]+; 270.1 [M + Na]+; HRMS(ESI+) calcd. for C10H17NO6Na
([M+Na]+): 270.0954; found m/z 270.0943.
Pyridine (1 mL) and acetic anhydride (0.5 mL) were added to 9 mg of the preceding N-formyl derivative
(37 µmol), and the reaction mixture was stirred at rt overnight, then concentrated and coevaporated
several times with toluene, diluted in CH2Cl2, washed with aqueous HCl (1 M), dried and concentrated,
yielding 12 mg of 9 (83%, white solid). 9: 1H NMR (250 MHz, CDCl3) δ (ppm) : 8.17 (d, 0.6 H, CHOtrans
,
J 1.7 Hz), 8.02 (d, 0.4 H, CHOcis, J 11.3 Hz), 6.00 (m, 1 H, NH), 5.80 (m, 1 H, Ha), 5.40 - 5.00 (m, 4 H,
Hb, Hc, H-3 and H-4), 4.74 (d, 0.6 H, H-1βtrans, J1β,2 8.3 Hz), 4.50 - 4.05 (m, 4.4 H, Hd, Hd’, H-6a,b and
H-1βcis), 3.95 (m, 0,6 H, H-2trans), 3.70 (m, 1 H, H-5), 3.46 (m, 0.4 H, H-2cis), 2.10 – 2.03 (6 s, 9 H,
CH3CO); MS(ESI+) m/z: 396.1 [M + Na]+.
Allyl 3,4,6-tri-O-acetyl-2-deoxy-2-isocyano-β-D-glucopyranoside (10)
A solutionof 9 (226 mg, 605 µmol) in anhydrous CH2Cl2 (15 mL) was treated with triethylamine (3.7 mL,
26.3 mmol) under an argon atmosphere, followed by dropwise addition of POCl3 (700 µL, 7.5 mmol) at
0°C. After 2 h at rt under argon, the reaction mixture was diluted with CH2Cl2, washed with saturated
aqueous NaHCO3, dried and concentrated. The residue was purified by flash chromatography over silica
1
gel (cyclohexane / EtOAc 2:1), yielding 163 mg of a white solid (10, 72%). 10: H NMR (250 MHz,
CDCl3) δ (ppm) : 5.95 (dddd, 1 H, Ha, JHa,Hc 17.1 Hz, JHa,Hb 10.0 Hz, JHa,Hd’ 6.6 Hz and JHa,Hd 5.1 Hz), 5.40
(dddd, 1 H, Hc, JHc,Hb 1.8 Hz, JHc,Hd’ 1.4 Hz and JHc,Hd 1.6 Hz), 5.30 (m, 2 H, Hb and H-3), 4.96 (m, 1 H,
H-4), 4.64 (d, 1 H, H-1β, J1β,2 8.0 Hz), 4.41 (m, 1 H, Hd, JHd,Hd’ 12.8 Hz and JHd,Hb 1.6 Hz), 4.28 (dd, 1 H,
H-6b, J6a,6b 12.3 Hz and J6b,5 4.6 Hz), 4.19 (dddd, 1 H, Hd’, JHd’,Hb 1.4 Hz), 4.13 (dd, 1 H, H-6a, J6a,5 2.4
Hz), 3.74 (ddd, 1 H, H-5, J5,4 10.1 Hz), 3.66 (dd, 1 H, H-2, J2,3 10.5 Hz), 2.12 / 2.09 / 2.04 (3 s, 9 H,