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.