Mimetics of phosphotyrosine (pTyr) such as phosphonomethylphenylalanine (Pmp) have traditionally retained α-amino functionality. However, β-amino acids represent isomeric variants, which may exhibit properties that are distinct from the parent. Reported herein is the first β-amino pTyr mimetic (Pmpβ) bearing protection suitable for peptide synthesis. Preparation of Pmpβ was accomplished enantioselectively in 43% overall yield from ...