ASYMMETRIC-SYNTHESIS OF CYCLOALIPHATIC ALPHA-AMINO-ACIDS WITH A NORBORNANE SKELETON

The asymmetric synthesis of endo and exo 2-aminonorbornane-2-carboxylic acids is carried out via the Diels-Alder reaction between cyclopentadiene and (-)-menthyl N-acetyl-α,β-dehydroalaninate. It is shown that this dienophile is more reactive than the corresponding methyl ester, which opens the way for the use of chiral N-acetyl-α,β-dehydroalaninates as dienophiles in asymmetric Diels-Alder reactions. As high diastereofacial selectivity is obtained with what was previously considered a mediocre chiral auxiliary, the acetamido group must play an important role, which is discussed. © 1990.