Asymmetric syntheses of APTO and AETD: the β-amino acid fragments within microsclerodermins C, D, and E.

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.