Solid-Phase Synthesis of Amino- and Carboxyl-Functionalized Unnatural α-Amino Acid Amides

A new solid-phase synthesis efficiently incorporates three different substituents (from R(1)-X, R(2)-CO(2)H, and R(3)-NH(2)) into a glycine-based peptidomimetic scaffold. The synthetic sequence is general and is typically accomplished in >50% overall isolated yield. Alkylating agents with a range of reactivities and normal and branched primary amines give good results. Utility was demonstrated by the synthesis of a series of protected phosphotyrosine mimetics.