Asymmetric syntheses of APTO and AETD: the β-amino acid fragments within microsclerodermins C, D, and E.
Davies SG., Fletcher AM., Foster EM., Lee JA., Roberts PM., Thomson JE.
Efficient asymmetric syntheses of APTO and AETD, the highly functionalized β-amino acid fragments within microsclerodermins C, D, and E, are reported. The conjugate addition of lithium (R)-N-benzyl-N-(α-methylbenzyl)amide to tert-butyl (E,E)-7-(triisopropylsilyloxy)hepta-2,4-dienoate and in situ enolate oxidation with (-)-camphorsulfonyloxaziridine, diastereoselective dihydroxylation of a 2,3-syn-γ,δ-unsaturated-α-hydroxy-β-amino ester derivative under Donohoe conditions, and a Julia-Kocieński olefination were used as the key steps.