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.