The Significance of Oligomer C‐Terminus Design in Solid‐Phase Synthesis of Peptide Nucleic Acid Tetramers With the Incorporation of γ‐S‐Monomer Units Based on L‐Glu

Peptide nucleic acids (PNAs) containing γ‐ S ‐modified monomers show promise for antisense applications but face synthetic challenges due to their charged backbone. This study aimed to optimize the Boc solid‐phase synthesis protocol for L‐Glu‐based γ‐S‐PNA oligomers. We systematically evaluated four tetramer designs incorporating glycine or β‐alanine C‐terminal linkers, monitoring resin loading (0.1–0.2 mmol/g), chain elongation (via a novel N = M × Q mass‐corrected metric), and cleavage stability. While monomer sequence order in the C‐terminal region showed no significant impact, spacer presence proved critical: β‐alanine linkers enabled target oligomer isolation (≤ 10% yields), whereas linker‐free tetramers degraded during acidic cleavage. These findings establish a foundation for synthesizing γ‐S‐PNAs while highlighting the need for further linker optimization to improve yields.