Pure erythro-m-chloro-3-hydroxytyrosine having the (2R, 3R)) configuration, a residue of Vancomycin and Aridicin A, has been prepared in 4 steps using an aldol addition involving a directly generated titanium enolate derived from a chiral iminoglycinate.(+)- Hydroxypinanone was used as a recoverable chiral auxiliary. The (2S, 3S)-erythro isomer will be, of course, available from (−)-hydroxypinanone.
