1. 17.9 g (0.1 mol) of halide-free glucosamine base and 125 mL of pure water were added to the reaction vessel and the mixture was stirred until the base was completely dissolved.
2. 11.5 g of polyethylene glycol homopolymer with a molecular weight of 4,000 was added and stirring was continued until a clarified solution was formed.
3. the solution was cooled to 5-10°C, and 4.9 g of concentrated sulfuric acid was slowly added while maintaining stirring and controlling the temperature in the range of 5-10°C. 4. after the sulfuric acid was added, the temperature was confirmed to be within the range of 5-10°C.
4. After the addition of sulfuric acid, the pH of the reaction mixture was confirmed to be 3.5 and stirring was continued for 30 minutes.
5. The product was isolated by freeze-drying at a pressure of about 200 mTorr and a temperature of -45 °C to give stable glucosamine sulfate. 6. The product was snow-white in color, and the temperature was controlled in the range of 5-10 °C.
6. The product was snow white in color with a yield of 33 g (96% yield). The specific optical rotation of glucosamine sulfate was measured to be +62.99°. 7.
7. The product was stored in a capped vial at room temperature. The product remained snow white when observed after one year.
