Completely Stereocontrolled Aldol Reaction of Chiral β‑Amino Acids

A general
protocol to independently access stereoisomerically pure
β′-hydroxy-β-amino acid derivatives that is based
on dibutylboron triflate-mediated aldol reaction of suitably protected
β-amino acids bearing chiral oxazolidinone auxiliary is reported.
The method smoothly afforded syn-aldol (α,β′-syn) products in pure form and excellent isolated yield.
Both α,β-syn and α,β-anti isomers are readily accessible solely through the choice
of the oxazolidinone chirality. This method allows for the preparation
of stereoisomeric β′-hydroxy-β-amino acid derivatives
that were previously unreported.