Potassium Hydroxide → Dinapsoline, (S)(-)

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A solution of racemic (±)-8,9-methylenedioxy-2,3,7,11b-tetrahydro-1H-napth[1,2,3-de]isoquinoline (3.0 gm, 11.3 mmol) in 100 mL of 95% ethyl alcohol at room temperature was mixed with a warm solution of (+)-dibenzoyl-D-tartaric acid in 40 mL of 95% ethyl alcohol. The solution was allowed to stand at room temperature for 4 hours and the grayish off-white crystals were collected by filtration and subsequently dried in a vacuum oven at 35° C. to give 1.3 gm (melting point: 175–176° C., 35.7%). The enantiomeric purity was determined by the same chiral HPLC conditions described above in Example 8: the salt was neutralized with 2M potassium hydroxide solution and the organic materials extracted with methylene chloride. The organic layers were combined and concentrated under reduced pressure to give a white solid which was redissolved in methanol prior to injection into HPLC Chiral column. The ratio of the second peak to the first was determined to be greater than 40:1. The identical resolution may also be. carried out using the unnatural D-tartaric acid. Melting points are uncorrected for the desired tartaric salts of the title compound.

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