The Application Of A Novel DNA-Based Catalyst To Friedel-Crafts Alkylation To Evaluate Its Performance

The catalysts of biomolecular, which comprise a transition metal complex and a chiral biomolecular scaffold, were invented by scientists on the basis of the structural characteristics of enzyme. DNA-based hybrid catalyst was first reported in 2005. Since then, significant success has been achieved in this field, and DNA-based hybrid catalysts have been widly applied to catalyze kinds of asymmetric reactions.We devised a new ligand-polyamide-dmbpy(Py4-dmbpy), which can be bound to DNA to develop a novel DNA hybrid catalyst(st-DNA/ Py4-dmbpy-Cu2+) through supramolecular interactions. As we all kown, polyamide can be specially anchored to DNA in the minor groove of AT rich sequences, which demonstrates that with DNA the complex of Poly4-dmbpy-Cu2+resides in the same micro environments. We utilized two kinds of catalysts of st-DNA/Py4-dmbpy-Cu2+ and st-DNA/dmbpy-Cu2+ to catalyse Friedel-Crafts alkylation of α,β-unsaturated 2-acyl imidazoles with indoles, in order to acquire differences between st-DNA/Py4-dmbpy-Cu2+ and st-DNA/dmbpy-Cu2+. Enantiomer excess Of products was abtained by HPLC. The observation that compared to the second generation catalysts, opposite enantiomers were found and enantiomer excess was lower when using the new DNA-based catalyst, suggested that there are different influences on the the results of reactions between the consistency of catalytic micro environment and the diversity of micro environment. We also synthesized a series of self-complimentary oligonucleotides to invest the effect of DNA sequence on Friedel-Crafts alkylation.Furthermore, the interaction between st-DNA and ligands was studied by CD spectroscopy. A CD-induced signal was observed between 300-400 nm when Py4-dmbpy was titrated into the solution of st-DNA, and the CD signal increased with further titration of Py4-dmbpy. This is a typical CD signal when a ployamide interacts with DNA in minor groove. In addition, this experiment also showed that the rigid structure of pyridine might hinder the interaction of the new ligand with DNA, resulting in the loose binding of Py4-dmbpy to DNA chain, or even making Py4-dmbpy outside the DNA chain. This subject provide researchers with a new method to design a new ligand with flexible structure, which can be bound to the minor groove of DNA.