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L-Ergothioneine (E) (0137) The solution of compound D (approximately 11 mmol) from step 2 was warmed to 85-90 C. and 5 g of KCNS in 10 mL water was added. This solution was stirred in a water bath at 85-90 C. for 1-2 hours. (0138) When reaction progress was complete by HPLC, this solution was cooled to approximately 30 C. Approximately 15 mL of concentrated HCl in 15 mL of water was added, and this acidic solution was evaporated (bath 30 C., vacuum). The residue was dissolved in 20 mL ethanol (200 proof) and was again evaporated. 30 mL ethanol (200 proof) was added. For a few minutes this mixture was stirred on bath at 30 C., and then cooled for 20 min on ice. The salts were filtered off and washed with 20 mL of ethanol (200 proof) and the filtrates were basified with a dilute solution of LiOH to pH 3.6-4 by pH meter. (0139) After total evaporation under vacuum in order to remove water, the residue was stirred on RVE overnight with 30 mL ethanol. Then the solid was filtered, washed with 2×5 mL ethanol and dried. Approximately 0.8 g of solid crystalline L-ergothioneine was obtained. Analysis by HPLC showed approximately 85% pure product. Optical rotation was approximately 80-90, and the color was light brown. From mother liquors, an additional 0.3 g was obtained, for a total 1.1 g (43%) of L-ergothioneine. (0140) The yield of L-ergothioneine (E) from hercynine (A) is approximately 40-50%.