Liquid-phase synthesis of a cyclic hexameric peptide nucleic acid

A cyclic fully N-protected hexameric (aminoethylglycinamide) can be readily obtained by using a divergent approach in liquid phase and consists of coupling orthogonal fragments of suitable oligomers. This cyclic N-protected backbone is then converted into a peptide nucleic acid by a series of selective deprotection–coupling steps affording the desired structure in good overall yields. Such a procedure could provide a general approach for targeting any short cyclic peptide nucleic acids (containing every kind of nucleobase).