Synthesis of 3-Deoxyclarithromycin through Biotransformation of Clarithromycin by Aspergillus niger and its Antibacterial Activity

Biotransformation of clarithromycin (1), by the plant pathogen Aspergillus niger ATCC 10549, produced one main metabolite identified as 3-deoxyclarithromycin (2). Testing the antibacterial activity against Staphylococcus aureus and Escherichia coli showed that compound 2 has a moderate activity against the tested bacteria. This result provides further evidence that the presence of oxygen at position 3 in clarithromycin enhances the antibacterial activity. The structure of compound 2 was elucidated by different NMR techniques. 2D-NMR (COSY, HMBC and HMQC) experiments allowed full assignments of the proton and carbon chemical shifts.