Access to Enantiopure α‑Hydrazino Acids for <i>N</i>‑Amino Peptide Synthesis

Backbone <i>N</i>-methylation of α-peptides has been widely employed to enhance the bioavailability and bioactivity of parent sequences. Heteroatomic peptide amide substituents have received less attention due, in part, to the lack of practical synthetic strategies. Here, we report the synthesis of α-hydrazino acids derived from 19 out of the 20 canonical proteinogenic amino acids and demonstrate their use in the solid-phase synthesis of <i>N-</i>amino peptide derivatives