Chiral aminoalcohols with a menthane skeleton as catalysts for the enantioselective addition of diethylzinc to benzaldehyde

Novel chiral aminoalcohols were synthesized by highly diastereoselective addition of Me₃SiCN and LiCH₂CN to (−)-menthone followed by LiAlH₄ reduction. The addition of CH₂CH-MgBr and PhCHCH-MgBr to menthone and the following epoxidation, provided useful hydroxy epoxides, one of which could be aminolyzed to afford an aminodiol. In one case, the configuration of the newly formed epoxidic stereogenic center was determined by X-ray crystallography. When applied as catalysts in the enantioselective addition of Et₂Zn to benzaldehyde, the aminoalcohols induced enantiomeric excesses (e.e.s) of up to 77%.