Fumaric Acid → 2-(cyclohexylmethyl)-N-{2-[(2S)-1-methylpyrrolidin-2-yl]ethyl}-1,2,3,4-tetrahydroisoquinoline-7-sulfonamide difumarate monohydrate

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Reaction Steps

2-(Cyclohexylmethyl)-N-{2-[(2S)-1-methylpyrrolidin-2-yl]ethyl}-1,2,3,4-tetrahydroisoquinoline-7-sulfonamide (43.7 g, 104 mmol) was dissolved in 95% ethanol (200 mL) with warming on a steam bath. Fumaric acid (23.8 g, 203 mmol, 1.95 equivalents) was added, rinsing the flask with 95% ethanol (50 mL). The mixture was heated with swirling to near boiling on the steam bath until all of the fumaric acid dissolved. The solution was removed from the steam bath and allowed to stir at room temperature. When the temperature of the solution reached 48° C., it was seeded with previously isolated 2-(cyclohexyl methyl)-N-{2-[(2S)-1-methylpyrrolidin-2-yl]ethyl}-1,2,3,4-tetrahydroisoquinoline-7-sulfonamide difumarate monohydrate. The mixture was allowed to cool and by 27.7° C., it had largely set up. After standing over the weekend, the mixture was cooled in an ice bath. The solids were collected and washed with ice-cold 95% ethanol (175 mL). After air-drying overnight, the clumps were partially broken up to give a colorless solid: 58.4 g (84% yield).

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