Abstract
The lipase-mediated kinetic resolution of racemic scopoline [(±)-4] and 6-hydroxytropinone [(±)-7] is reported. Whereas (±)-4 is difficult to resolve due to steric hindrance of the hydroxy function, the resolution
of (±)-7 with vinyl acetate as acyl donor gave alcohol (+)-7 and the corresponding acetate (-)-9 with high enantiomeric excess. In case of the optimal result of 99% ee for (+)-7 and 80% ee for (-)-9, an E-value of 35 was calculated. The preparative lipase-catalyzed resolution of (±)-7 resulted in almost enantiopure alcohol (+)-7 with >99% ee after one recrystallization.
Key words
enantioselectivity - lipase - resolution - tropinone
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Screening Procedure for the Lipase-catalyzed Resolution. To a solution of the racemic substrate 4 or 7 (0.1 mmol) in the respective solvent was added vinyl acetate (13 µL, 0.30 mmol),
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Capillary GC: Bondex unβ (20 m × 2.5 mm), carrier gas H2 (0.4 bar), temperature program: 3 min at 100 °C, then 2.5 °C min-1 gradient to 150 °C, tR[(+)-8] = 15.09 min.
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