Asymmetric Syntheses of APTO and AETD: the β‑Amino Acid Fragments within Microsclerodermins C, D, and E

Abstract

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 (<i>R</i>)-<i>N</i>-benzyl-<i>N</i>-(α-methylbenzyl)­amide to <i>tert</i>-butyl (<i>E</i>,<i>E</i>)-7-(triisopropylsilyloxy)­hepta-2,4-dienoate and in situ enolate oxidation with (−)-camphorsulfonyloxaziridine, diastereoselective dihydroxylation of a 2,3-<i>syn</i>-γ,δ-unsaturated-α-hydroxy-β-amino ester derivative under Donohoe conditions, and a Julia–Kocieński olefination were used as the key steps