反应详情

A suspension of 3.42 g of rac-1',2',3',4'-tetrahydro-2'-hydroxy-5',8'-dimethoxyspiro[1,3-dithiolane-2,4'-naphthalene]-2'-carboxylic acid [prepared as described in Example 4(iii)] and 4.0 g of brucine was heated under reflux until a clear solution was obtained. After seeding, the solution was left to cool slowly to room temperature. The crystalline precipitate (3.6 g) was collected after 2 days. The precipitate was dissolved in 1500 ml of boiling ethyl acetate, the solution was concentrated to 600 ml and left to cool slowly. The crystalline product [2.7 g [α]D20 =-46.6°, c=0.5% in dimethylformamide] was suspended in 150 ml of ethyl acetate and shaken with three 10 ml portions of 5-M hydrochloric acid and with two 100 ml portions of brine. After drying over magnesium sulphate, the solvent was evaporated to give a colourless oil which was crystallised from diethyl ether to yield 1.22 g of (R)-1',2',3',4'-tetrahydro-2'-hydroxy-5',8'-dimethoxyspiro[1,3-dithiolane-2,4'-naphthalene]-2'-carboxylic acid in the form of colourless crystals of melting point 147° -149° C.; [α]D20 =+13.8°, c=0.5% in dioxan.

1. temperaturewas heated
2. temperatureunder reflux until a clear solution
3. customwas obtained
4. waitthe solution was left
5. customThe crystalline precipitate (3.6 g) was collected after 2 days
6. dissolutionThe precipitate was dissolved in 1500 ml of boiling ethyl acetate
7. concentrationthe solution was concentrated to 600 ml
8. waitleft
9. temperatureto cool slowly
10. customThe crystalline product [2.7 g [α]D20 =-46.6°, c=0.5% in dimethylformamide]
11. dry with materialAfter drying over magnesium sulphate
12. customthe solvent was evaporated
13. customto give a colourless oil which
14. customwas crystallised from diethyl ether