Synthesis
4. Synthesis of L-fucoidan (6)
A mixture of L-fucoidan and L-fucoidan (1:1, 800 mg) was dissolved in water (50 mL) and the solution was cooled to 0°C. NaBH4 (500 mg) was slowly added at this temperature with continuous stirring. The reaction mixture was continued to be stirred at 0 °C for 1.5 hours. Subsequently, the reaction mixture was acidified by addition of Amberlite IR 120 (H+) resin. The aqueous phase was removed by evaporation under reduced pressure, and the residue was dissolved in methanol and the evaporation was repeated three times (note: filtration was required to remove the resin before the last evaporation). Eventually, the product was crystallized from methanol to give 700 mg (4.22 mmol, yield to be calculated) of white crystals.
Product characterization data:
1H NMR (CDCl3, 300 MHz): δ = 4.08-4.01 (m, 1H), 3.94-3.89 (m, 1H), 3.64-3.57 (m, 2H), 3.45-3.41 (m, 1H), 1.19 (d, 3H, J = 6.6 Hz).
13C NMR (CDCl3, 300 MHz): δ = 72.9, 70.5, 69.8, 66.1, 63.3, 18.7.
References
[1] Patent: WO2012/49257, 2012, A1. Location in patent: Page/Page column 17
[2] Patent: US2013/245250, 2013, A1. Location in patent: Paragraph 0062-0064
[3] Organic and Biomolecular Chemistry, 2017, vol. 15, # 45, p. 9727 - 9733
