Completely stereocontrolled aldol reaction of chiral ß-amino acids.

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