Synthesis
II. General procedure for the synthesis of 2,3,4-tri-O-acetyl-α-D-bromopyranose (formula XII): In a 1 L round-bottomed flask equipped with a protective tube was added tetra-O-acetyl-D-xylulose (formula XI; 25.0 g, 78.54 mmol) and dichloromethane (500 mL), and the mixture was cooled to 0°C in an ice bath. An acetic acid solution (56 mL) of 33% hydrogen bromide was slowly added to the cooled solution over a period of 1 h under constant stirring. After addition, the reaction mixture was continued stirring at room temperature for 1 hour. After the completion of the reaction was monitored by thin layer chromatography (TLC, unfolding reagent ratio of 4:6 ethyl acetate:hexane), the reaction mixture was washed sequentially with ice water (1 x 500mL), 1% sodium bicarbonate solution (1 x 500mL), 10% sodium bicarbonate solution (2 x 500mL) and saturated saline (1 x 500mL). The organic layer was separated, dried with anhydrous sodium sulfate, filtered and concentrated under reduced pressure to afford a white solid 2,3,4-tri-O-acetyl-α-D-bromopyranose (formula XII), which could be used in the next reaction without further purification. The yield and nuclear magnetic resonance (NMR) data of the compound of formula XII were as follows: yield: 24.0 g (90%); 1H NMR (300 MHz, CDCl3): δ=6.59 (d, 1H, J=3.9 Hz), 5.60 (t, 1H, J=9.9 Hz), 5.05-5.03 (m, 1H), 4.77 (dd, 1H, J= 3.9,9.6Hz), 4.07 (dd, 1H, J=6.3,11.4Hz), 3.88 (t, 1H, J=11.1Hz), 2.10 (s, 3H), 2.06 (s, 6H).
References
[1] Journal of Organic Chemistry, 2001, vol. 66, # 7, p. 2327 - 2342
[2] Organic Letters, 2007, vol. 9, # 20, p. 3897 - 3900
[3] Bulletin of the Korean Chemical Society, 2010, vol. 31, # 3, p. 653 - 663
[4] Patent: US2012/29179, 2012, A1. Location in patent: Page/Page column 7
[5] Tetrahedron, 2005, vol. 61, # 35, p. 8405 - 8409
