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A solution of 1,5-imino-1,2,5-trideoxy-D-arabino-hexitol (24) (407 mg, 1.10 mmol) in a 1:3 mixture of water and 1,4-dioxan containing barium carbonate (653 mg, 3.31 mmol), was cooled to 0° C. and treated with bromine (70 μl, 221 mg, 1.37 mmol), then stirred at room temperature for 24 hours. Sodium thiosulphate solution (1M, aqueous) was added until the bromine was removed then the solution acidified with hydrochloric acid (2M, aq, 30 ml) and centrifuged. The supernatent was removed and extracted with ethyl acetate (4×20 ml). The combined organic phase was dried, filtered and evaporated. Purification by flash chromatography gave 3-O-benzyl-N-benzyloxycarbonyl-2,6-imino-2,5,6-trideoxy-D-lyxo-hexono-1,4-lactone (342 mg, 84%) as a clear oil, [α]20D -13.7° (c, 1.42 in chloroform); νmax (film) 3030, 2880, 1790 (lactone CO), 1700 (Z CO), 1425, 1260, 1170, 1060, and 700 cm-1 ; 1H NMR δ 1.80-1.93 (1H, m, H-5); 2.28-2.35 (1H, m, H-5'); 3.15-3.20 (1H, m, H-6); 3.93-4.07 (1H, m, H-6'); 4.15, 4.28 (1H, 2×dd, H-3); 4.39-4.61 (2H, m, H-2, H-4); 4.74-4.83 (2H, m, CH2Ph; 5.04-5.20 (3H, m, H-1, CH2 -Z), 7.17-7.35 (10H, m, 2×H-Ph). 13C NMR δ 26.25 (t, C-5); 35.27, 35.49 (2×t, C-6); 65.92, 66.17 (2×d, C-4); 67.38 (t, CH2 -Z); 71.45 (t, CH2Ph); 75.86 (d, C-3); 127.87, 127.98, 128.08, 128.57 (4×d, HC-Ph); 136.78, 137.73 (2×s, C-Ph); 155.15 (s, C=O-Z); 170.34 (s, C-1). m/z (CI NH3): 91 (100%), 324 (M-CO2 +H+, 60%), 385 (M+NH4+, 25%). (Found C, 68.56; H, 5.96; N, 3.51. C21H21NO5 requires C, 68.68; H, 5.76; N, 3.81).

1. customwas removed
2. customThe supernatent was removed
3. extractionextracted with ethyl acetate (4×20 ml)
4. customThe combined organic phase was dried
5. filtrationfiltered
6. customevaporated
7. customPurification by flash chromatography