Synthesis of 2-amino-apopinan-3-ol and applications of its derivatives in asymmetric reduction of ketones

Monoterpenes are optically active compounds which occurs in nature. This fact makes them interesting precursors for the synthesis of optically active ligands, which can be applied in various asymmetric reactions.

In this work, we present the synthesis of optically pure 2-amino-apopinan-3-ol from (–)-α-pinene. Next, the obtained amino alcohol was used as a precursor of oxazaborolidines, which were used as catalysts in the asymmetric reduction of aryl-alkyl ketones with borane. In the second part, we transformed 2-amino-apopinan-3-ol into PHOX ligand in a three-step reaction. The complex of ruthenium precursor with PHOX ligand was used as a catalyst in the asymmetric transfer hydrogenation of aryl-alkyl ketones. Alcohols with enantiomeric excesses of up to 97% were isolated using both ketone reduction methods.