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.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/38688/1/170180411_ftp.pd

Synthesis and optical properties of polyethylenimine containing L -proline and optically active thymine derivatives

Preparation and optical properties of linear polyethylenimine (PEI) containing L -(−)- N -[(−)-2-(thymin-1-yl) propionyl] prolyl group as grafting pendant, [P-(−)Pro-(−)T], and its related monomer and dimer model compounds are described. Hypochromic effects and circular dichroism of these compounds were compared with those of PEI containing (−)-2-(thymin-1-yl) propionyl group as grafting pendant, [P-(−)T], which has no L -proline ring as a spacing group. P-(−)Pro-(−)T showed no exciton coupling of B 2u Π-Π * transition although it showed large hypochromicity in neutral aqueous solution, implying that the stacking of the bases has no screw sense.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/38690/1/170180501_ftp.pd

Circular dichroism of polyethylenimine containing optically active thymine derivatives as grafted pendants

Optical properties of linear polyethylenimine containing optically active (+)- or (−)-2-(thymin-1-yl)propionyl group as grafted pendant were investigated by circular dichroism (CD) and compared with those of the related monomer and dimer model compounds. CD spectra of the polymer in neutral aqueous solution were different from those of related model compounds, which suggest that the polymer exists in some ordered conformation (at least locally) to allow exciton coupling of Π–Π * (B 2u ) transition in the base chromophores along the polymer chain. This ordered conformation tends to be randomized on heating. The effects of complementary base pairing on the CD spectra have also been studied by using a linear polyethylenimine containing (±)-2-(adenin-9-yl) propionyl grafts and its related monomer and dimer models.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/38689/1/170180412_ftp.pd