Cinchonidine → (S)-indole-3-succinic acid cinchonidine

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반응 단계

A mixture of 1.26 g (4.29 mmole) of cinchonidine and 1.00 g (4.29 mmole) of racemic indole-3-succinic acid in 10 mL of 96% ethanol was heated on a steam bath with magnetic stirring until all of the solid dissolved. The solution was cooled slowly to room temperature, and the white precipitate formed was collected and washed with ether. After 11 recrystallizations from 96% ethanol and one solution of 96% ethanol:methanol, 80:20 by volume, and drying, colorless fine needles of (S)-indole-3-succinic acid-cinchonidine salt was obtained. 0.296 g, yield: 13.1%, ee: 99.3%. Mp: 196-198° C. (with gas evolution). Elemental analysis: Calculated for C31H33N3O55: C=70.57%, H=6.30%, N=7.96% Found: C=70.00%; H=6.42%; N=7.84%. IR: 3500-2900, 1592, 1460 cm-1. By fractional removal of (S)-indole-3-succinic acid salt, followed by rotary evaporation of the solvent and recrystallization (supra vide), the (R)-indole-3-succinic acid-cinchonidine salt was obtained.

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