(+)- or (-)-
p-Menthane-3-carboxaldehyde is made in two easy steps from (+)- or (-)-menthone,respectively. This auxiliary allows for the synthesis of carbonyl compounds bearing a
-chiral quaternarycarbon. The flexibility, efficiency, and ease of use of the method are demonstrated in a series of examples,which include the total synthesis of (+)-cuparenone as well as a partial synthesis of (-)-cassiol.