L-t-Leucine-Catalyzed Direct Asymmetric Aldol Reaction of Cyclic Ketones

L‐t‐Leucine‐catalyzed direct asymmetric aldol reactions are described. In the aldol reaction of p‐nitrobenzaldehyde with a cyclic ketone at room temperature, L‐t‐leucine exhibits catalytic activity resulting in moderate to high diastereo‐ and enantioselectivity. Use of cycloheptanone or cyclooctanone as a substrate resulted in production of the syn selective product. L‐t‐Leucine‐catalyzed direct asymmetric aldol reactions are described. Use of cyclopentanone or cyclohexanone as substrates resulted in production of the anti selectivecompound. On the other hand, in the case of cycloheptanone or cyclooctanone, the L‐t‐leucine‐catalyzed reaction afforded the product with high syn selectivity.