Reaction Steps
Methyl 3-O-benzyl-2,5-dideoxy-2,5-imino-α-D-lyxofuranoside (13α) (870 mg, 3.70 mmol) was stirred with a 3:2 mixture of ether and saturated aqueous sodium bicarbonate (60 ml). Benzyl chloroformate (1.57 ml, 11.1 mmol) was added to the mixture which was stirred at room temperature for 12 hours. The ether layer was separated and the aqueous phase further extracted with ether (4×25 ml). The combined extracts were dried, filtered and the solvent removed. Purification by flash chromatography (ether-hexane 1:10-1:3) afforded methyl 3-O-benzyl-N-benzyloxycarbonyl-2,5-dideoxy-2,5-imino-α-D-lyxofuranoside (1.04 g, 76%) as a white crystalline solid, m.p. 74°-75° C., Rf 0.2 (ether-hexane 1:3); [α]20D +12.0° (c, 0.98 in chloroform); νmax (chloroform) 2940, 1695 (C=O), 1420, 1260, 1230, 1090 and 750 cm-1 ; 1H NMR δ 3.38, 3.41 (3H, 2× s, CH3); 3.3-3.7 (2H, m, 5,5'-H); 4.05-4.90 (5H, m, H-3, H-2, H-4, CH2Ph); 5.12-5.20 (3H, m, H-1, CH2 -Z); 7.2-7.4 (10H, m, 2×H-Ph). 13C NMR δ 50.71 (t, C-5); 55.15, 55.33 (2×q, Me); 59.63, 60.17 (2×d, C-2); 66.95, 67.08 (2×t, CH2 -Z); 72.28 (t, CH2Ph); 75.09, 75.49, 77.93, 78.48 (4×d, C-3, C-4); 105.67, 105.90 (d, C-1); 127.83, 127.92, 128.15, 128.64 (4×d, HC-Ph); 136.68, 137.46 (2×s, C-Ph); 155.68, 155.81 (2×s, C=O). m/z: 91 (100%), 108 (25%), 158 (20%), 370 (M+H+, 10%). (Found C, 67.98; H, 6.39; N, 3.60. C21H23NO5 requires C, 68.28; H, 6.28; N, 3.79). Methyl 3-O-benzyl-2,5-dideoxy-2,5-imino-β-D-lyxofuranoside (13β) (829 mg, 3.53 mmol) was treated likewise giving methyl 3-O-benzyl-N-benzyloxycarbonyl-2,5-dideoxy-2,5-imino-β-D-lyxofuranoside (1.18 g, 90%) as a clear oil, Rf 0.35 (ether-hexane 1:3); [α]20D -75.2° (c, 0.83 in chloroform); νmax (film) 2930, 1705 (C=O), 1425, 1275, 1255, 1105 and 750 cm-1 ; 1H NMR δ 3.36, 3.42 (3H, 2×s, CH3); 3.50 (1H, 2×d 5-H); 3.67 (1H, 2×d, H-5'); 4.02-4.06 (1H, m, H-3); 4.29 (1H, bs, H-2); 4.49, 4.54 (1H, bs and dd, H-4); 4.52-4.65 (2H, m, CH2Ph); 5.0-5.2 (2H, 2×dd, CH2Ph); 5.21 (1H, s, H-1); 7.28-7.38 (10H, m, H-Ph). 13C NMR δ 50.02 (t, C-5); 55.70, 55.89 (2×q, Me); 60.17, 59.52 (2×d, C-2); 66.79 (t, CH2 -Z); 72.00, 72.10 (t, CH2Ph); 77.56, 78.08, 78.52, 79.18 (4×d, C-3, C-4); 104.71, 105.11 (2×d, C-1); 128.79, 127.96, 128.33, 128.61, 128.78 (5×d, HC-Ph); 137.09, 137.22 (2×s, C-Ph); 156.20, 156.45 (2×s, C=O). m/z: 91 (100%), 370 (M+H+, 60%), 202 (30%). (Found C, 68.08; H, 6.39; N, 3.40. C21H 23 NO5 requires C, 68.28; H, 6.28; N, 3.79).
