Protecting Tactics of Histidine in Synthesis of Peptide Nucleic Acid Monomer

A chiral PNA monomer containing histidine residue has been designed and synthesized in 9 steps with an overall yield 13.3%.The protecting groups of α-amine,carboxyl,and imidazole are t-butyloxocarbonyl,benzyl,and benzyloxocarbonyl,respectively.The final protecting group of imidazole is 2,4-dinitrofluorobenzenyl(Dnp).