Syntheses of polyethylenimine containing asymmetric nucleic acid base derivatives as grafted pendants

Preparations of new model polymers of polynucleotides with linear polyethylenimine (PEI) backbones and optically active nucleic acid base derivatives as pending side chains are described. (±)-2-(Thymin-1-yl)propionic acid (II) and (±)-2-(adenin-9-yl)propionic acid (IV) were synthesized. These carboxylic acid derivatives were grafted onto PEI at the imino nitrogen by the p -nitrophenyl active ester method. The enantiomeric pairs of II were optically resolved with quinine to yield (−) and (+)-2-(thymin-1-yl)propionic acid (VII and VIII). VII and VIII were grafted onto PEI through amide bond by direct coupling with diethylphosphoryl cyanide to give optically active graft polymers. The related monomer and dimer model compounds were also prepared by the same method from diethylamine and dimethylethylene diamine, respectively.