Synthesis of alpha,alpha-Disubstituted Benzocyclobutane Amino Acids through [2+2] Annulation of Benzyne with Dehydroalanine

A mild and general method for the synthesis of alpha,alpha-disubstituted benzocyclobutane amino acids through a [2+2] annulation of benzyne with dehydroalanine is described. Yields up to 88% of the constrained quaternary amino acids can be obtained and its application in peptidomimetic synthesis is demonstrated.