Sodium Thiosulfate Pentahydrate → HCID 54498398, compound

Participants

Reaction Steps

N-Carboxy benzyl -D-phenylalaninol (100 g; 0.35M) is dissolved in dichloromethane (1.8 L) and a solution of sodium bromide (18 g; 0.175M) in water (250 mL) is added. The resulting two phase mixture is stirred and cooled to 0°-5° C. under a nitrogen atmosphere. 2,2,6,6-Tetramethyl-1-piperidinyloxy, free radical (TEMPO) (0.055 g; 3.5 mM) is added. A solution of buffered sodium hypochlorite, freshly prepared by dissolving sodium bicarbonate (10 g; 0.12M) and commercial sodium hypochlorite solution (12.5% w/w; 250 g; 0.42M) in water (250 g), is added over a period of one hour with fast agitation, maintaining the reaction temperature <5° C. A solution of sodium thiosulfate pentahydrate (21.8 g; 0.088M) in water (64 mL) is then immediately added and the reaction mixture efficiently stirred until excess oxidants have been quenched as demonstrated by starch/iodide test. Agitation is stopped and the mixture allowed to settle at 5°-10° C. After 15 minutes, the phases are separated. The organic phase is then washed with aqueous sodium bicarbonate solution (3% w/w; 500 mL) and aqueous sodium chloride solution (3% w/w; 500 mL). The organic phase is concentrated by vacuum distillation to a volume of approximately 300 mL maintaining the heating bath <20° C. Heptane (750 mL) is added and the vacuum distillation continued again maintaining the heating bath at <20° C. A white precipitate slowly forms as the dichloromethane is removed. The distillation is continued until the dichloromethane in heptane concentration is <5% w/w. The precipitate is filtered, washed with heptane (2× 200 mL) and dried under vacuum at 20° C. to constant weight to yield N-carboxybenzyl-D-phenylalaninal (90 g; 90% yield) as a white crystalline solid.

Provenance & Evidence