Density Functional Theory Study of the Interaction between Guanine and Catechin

Abstract

The interacting patterns and mechanism of the catechin and guanine have been investigated with the density functional theory B3LYP method by 6-31G* basis set. Fourteen stable structures for the catechin-guanine complexes have been found which form two hydrogen bonds at least. The results indicate that the complexes are mainly stabilized by the hydrogen bonding interactions. At the same time, the number and strength of hydrogen bond play a co-determinant parts in the stability of the complexes which can form two or more hydrogen bonds. Theories of atoms in molecules (AIM) and natural bond orbital (NBO) have been adopted to investigate the hydrogen bonds involved in all systems. The interaction energies of all complexes have been corrected for basis set superposition error (BSSE), ranging from -38.86 to -14.56 kJ/mol. The results showed that the hydrogen bonding contributes to the interaction energies dominantly. The corresponding bonds stretching motions in all complexes are red-shifted relative to that of the monomer, which is in agreement with experimental results.

Reduction system “vitamin C/glycerol” promoted copper(II)‐catalyzed N‐arylation

“…Having established the optimal reaction conditions, we proceeded to evaluate the substrate scope of the reaction and obtained 14 products ( 1 H, 13 C, and 19 F NMR data and spectra for products were provided in Supporting Information), as shown in Scheme 2. It is noteworthy that the substrates with electron‐donating groups exhibited higher reactivity than those with electron‐withdrawing ones ( 3a , 3c , 3d , 3e and 3f vs. 3j and 3k ); this may be because that the substrate with electron‐donating group could easily coordinate with (Cu I L) to form active intermediate (ArCu I I XL) [ 24 ] (Scheme 4). Likely due to the steric hindrance, lower yields were observed ( 3a vs. 3b ).…”

“…[ 20,21 ] Glycerol is a benign solvent and features reducibility. [ 22,23 ] As part of our ongoing research on ligand‐promoted copper‐catalyzed CN coupling reactions, [ 24,25 ] we investigated the direct synthesis of various N ‐arylation products in glycerol solvents using CuO and ascorbic acid as the catalyst (Scheme 1). In addition, 2‐phenylindole, pyrrolo[1,2‐ a ]quinoxaline, 1,2,4‐triazole and 4‐amino‐7 H ‐pyrrolo[2,3‐ d ]pyrimidine derivative were obtained with the aid of CuO and reduction system “vitamin C/glycerol.”…”