Chiral synthesis of statine

Statine ($\text{8a}$) has been obtained in high enantiomeric purity as its N-Boc-ethyl ester ($\text{8b}$) in a chiral synthesis. The sequence involves the enantio- and erythro-selective aldol condensation of N-Boc-L-leucinal ($\text{5}$) with (S)-4-(1-methylethyl)-3-[(methylthio)acetyl]-2-oxazolidinone ($\text{1}$) via the boron enolate, followed by desulfurization and saponification in ethanol, according to the methodology of Evans.