... Journal of the American Chemical ... figure Scheme 2. Synthesis of Peptide Nucleic Acids Modified with Ester Groups at the N-Terminus a. a (a) 1. AcOCH 2 CO 2 H, HBTU, HOBT, DIEA, 2. NH 3 aq; (j) 1. 1-N-methyl-2-imidazolyl carboxylic acid, DIC, DMAP, 2. TFA, m-cresol. ...