Synthesis of a thymine-functionalized nucleoamino acid for the solid phase assembly of cationic nucleopeptides

In this work, we report the synthesis of a thymine-functionalized nucleoamino acid suitable for the solid phase synthesis of nucleopeptides. The monomer was obtained in solution starting from commercial compounds and after NMR (¹H and ¹³C) and ESIMS (positive ions) characterization it was used for the assembly of a cationic nucleopeptide obtained by sequentially introducing underivatized l-lysine units and nucleoamino acid monomers. After detachment from the resin, performed in acidic conditions, the oligomer was purified by HPLC and characterized by LC-ESIMS (positive ions) which confirmed the identity of the thymine-based nucleopeptide. The cationic nucleobase-containing peptide, well soluble in water, was studied by CD spectroscopy which allowed us to exclude any helical pre-organization of the nucleopeptide in the experimental conditions used. Furthermore, CD behavior of the oligomer at different temperatures was also studied as described in this work.