Synthesis of biologically active nickelocenyl–amino acid conjugates using 1,3-dipolar cycloaddition click reactions

Herein we present the study of synthesis of novel bio-organometallic conjugates using 1,3-dipolar cycloaddition click reactions. Amino acid azides such as 4-azido-D-homoalanine, 5-azido-D-ornithine and 6-azido-D-lysine were reacted with ethynyl nickelocene to synthesize nickelocenyl-homoalanine conjugate (1), nickelocenyl-ornithine conjugate (2), and nickelocenyl–lysine conjugate (3) using Cu(I) compounds as catalysts. This synthetic strategy resulted in high yields (68–76%) of nickelocene-amino acid conjugates. Structure characterization of these purified bio-organometallic conjugates was performed using FT-IR, ¹H, and ¹³C NMR spectroscopy. Antibacterial and antifungal activities of these products were tested against Staphylococcus aureus, Escherichia coli, Bacillus subtilis, Streptococcus pneumonia, Alternaria alternate, Aspergillus flavus, and Aspergillus niger using the disc diffusion method. Rifampicin (antibacterial) and fluconazole (antifungal) were used as standard drugs. Results of antimicrobial activities were found to be promising.