PNA Synthesis by Novel Amide Formation
Benzothiazole-2-sulfonyl (Bts) has been reported as an amine-protecting group of amino acid, and the stability of sulfonamide and the mild deprotection conditions are attractive properties for a protecting group. Due to the strong electron-withdrawing effect of the sulfonyl group, the acyl group of acylsulfonamideis easily attacked by nucleophiles after alkylation which was applied in the safety-catch strategy or the synthesis of a peptide thioester for native chemical ligation of the peptide. Using these characteristics of Bts, we designed self-activated cyclic PNA monomers. Herein we report a new type of cyclic PNA monomer and a new efficient method of PNA oligomer synthesis using Bts as an amine-protecting group.