Asymmetric synthesis of (–)-(1R,2S)-cispentacin and related cis- and trans-2-amino cyclopentane- and cyclohexane-1-carboxylic acids

The antifungal antibiotic (–)-(1R,2S)-2-aminocyclopentane-1-carboxylic acid (cispentacin)8 and its cyclohexane homologue 14 have been prepared utilizing the highly stereoselective conjugate addition of homochiral lithium N-benzyl-N-α-methylbenzylamide 5. The corresponding trans-β-amino acids 10 and 16 were also prepared via the selective epimerization of the cis-β-amino ester conjugate addition products.