AN AZO COUPLING OF BERBERINE DERIVATIVES: AN EXPERIMENTAL AND QUANTUM-CHEMICAL STUDY

Abstract

The possibility of synthesizing 12-(aryldiazo)berberrubines was demonstrated experimentally and by quantum-chemical calculations based on the Density Functional Theory in the B3LYP/6-31G(d,p) basis set. In weakly alkaline media, berberrubine can be substituted at position 12 by azo coupling reactions with aryldiazonium salts. This process proceeds in steps: first, berberrubine transforms into the zwitterionic form of 9-oxoberberine, which then enters as a nucleophile into an azo coupling reaction with aryldiazonium salts to form a single product with the trans configuration of the fragments relative to the N=N double bond. The resulting 12-(aryldiazo)berberrubines may find use as antibiotic agents, as shown on the multidrug-resistant culture Acinetobacter lwoffii.