Enzymatic resolution of tropinone derivatives
The lipase-mediated kinetic resoln. of racemic scopoline and 6-hydroxytropinone is reported. Whereas (¬±)-scopoline is difficult to resolve due to steric hindrance of the hydroxy function, the resoln. of (¬±)-6-hydroxytropinone with vinyl acetate as acyl donor gave alc. (+)-6-hydroxytropinone and the corresponding acetate (-)-6-acetoxytropinone with high enantiomeric excess. In case of the optimal result of 99% ee for (+)-6-hydroxytropinone and 80% ee for (-)-6-acetoxytropinone, an E-value of 35 was calcd. The preparative lipase-catalyzed resoln. of (¬±)-6-hydroxytropinone resulted in almost enantiopure alc. (+)-6-hydroxytropinone with >99% ee after one recrystn.