Reaction Steps
A solution of methyl 3-O-benzyl-2,6-imino-2,5,6-trideoxy-β-D-lyxo-hexofuranoside (23β) (762 mg, 2.06 mmol) in a 1:1 mixture of trifluoroacetic acid and water (20 ml) was stirred at room temperature for 20 minutes. The solvents were removed in vacuo and the crude material purified by flash chromatography (ethyl acetate-hexane 1:2) to give 3-O-benzyl-N-benzyloxycarbonyl-2,6-imino-2,5,6-trideoxy-D-lyxo-hexose (640 mg, 87%) as a clear oil, [α]20D -17.2° (c, 0.73 in chloroform); νmax (film) 3400 (OH), 2920, 1690 (C=O), 1410, 1345 and 1060 cm-1 ; 1H NMR δ 1.50-1.71 (1H, m, H-5); 1.80 (1H, bs, OH); 2.02-2.20 (1H, m, H-5'); 3.08-3.27 (1H, m, H-6); 3.94-4.20 (2H, m, 6-H, H-3); 4.25-4.85 (4H, m, H-2, H-4, CH2 -Ph); 5.05-5.18 (2H, m, CH2 -Z); 5.50, 5.53 (0.75H, 2×s, H-1-hemiacetal); 7.20-7.40 (10H, m, 2×H-Ph); 9.68 (0.25H, s, H-1-aldehyde). 13C NMR δ 24.17 (t, C-5); 38.10 (t, C-6); 57.26, 57.77 (2×d, C-2); 67.30, 67.48, 67.58 (3×t, CH2 -Z); 71.38, 71.84, 72.12 (3×t, CH2Ph); 74.00, 74.63, 74.76 (3×d, C-3, C-4); 98.72, 98.88, 198.17 (3×d, C-1); 127.35, 127.58, 127.85, 128.01, 128.23, 128.63 (6×d, HC-Ph); 136.51, 136.62, 136.73, 137.46, 155.60 (s, C=O-Z); 137.74, 137.88 (6×s, C-Ph). m/z: 91 (100%), 262 (20%), 370 (M+H+, 15%). (Found C, 68.68; H, 6.40; N, 3.71. C21H23NO5 requires C, 68.28; H, 6.28; N, 3.79).
