Stereodivergent synthesis of the first bis(cyclobutane) γ-dipeptides and mixed γ-oligomers

Diastereomeric bis(cyclobutane) γ-dipeptides, a new class of γ-peptides, have been synthesized efficiently from both enantiomers of conveniently protected 3-amino-2,2-dimethyl-1-carboxylic acid. These amino acids have been prepared in very good overall yields through enantiodivergent synthetic routes starting from (−)-cis-pinononic acid. Mixed γ-oligomers have also been prepared from GABA and cyclobutane residues.