Water → 9-Benzenesulfonyl-1,3,4,9-tetrahydro-beta-carboline-2-carboxylic acid benzyl ester

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Reaction Steps

Powdered sodium hydroxide (1.73 g, 43.3 mmol) and tetra-n-butylammonium hydrogen sulfate (111 mg) were added to a solution of the product from stage 1 (6.61 g, 21.6 mmol) in anhydrous methylene chloride (100 ml) and the mixture was stirred at room temperature for 1 h. Benzenesulfonyl chloride (4.21 g, 3.07 ml, 23.8 mmol) was added to the suspension, while cooling with ice. The mixture was stirred at room temperature for 16 h and water and methylene chloride (50 ml of each) were then added. The organic phase was separated off and washed with sodium chloride solution (40 ml). The organic phase was dried with sodium sulfate and concentrated i. vac. The residue was purified by flash chromatography with cyclohexane/ethyl acetate (4:2).

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