Design,Synthesis And Antibacterial Evaluation Of C-11, 4"-carbamate Clarithromycin Derivatives

Macrolide antibiotics have broad antibacterial spectrum, good bioavailability, few side effects and are very important for anti-infectious disease. However, the growth of drug-resistant problem appears rapidly due to the abuse of macrolide antibiotics, making the severely limited effectiveness of macrolide antibiotics. To solve this problem, a large number of modifications have been made by scientists. Now many macrolide derivatives with good antibacterial activity have been developed.The study indicates that the antibacterial mechanism of macrolide is that it can bind with the peptide channel of PTC of bacterial 50S ribosome. Macrolide can restrain the synthesis of protein, thus showing antibacterial activity. The major mechanism of bacteria resistance is the erm gene-mediated methylation of bacterial ribosome and the mef gene-mediated efflux pump.The macrolide derivative CP-544372 was obtained by modifying the 4"-O-hydroxy of macrolide. And telithromycin was obtained by modifying C-11,12 positions of macrolide. CP-544372 and telithromycin both showed excellent in vitro antibacterial activity. Based on the research results above, we selected clarithromycin as parent compound and synthesized 4"-O-carbamate-10,11-dehydration clarithromycin derivatives of A series. In addition, we also synthesized compounds of B series by introducing a series of carbamate side chain at 4" and 11 positions of clarithromycin.We changed the length and the terminal substituents of the side chain to examine the influence of combined modification on antibacterial activity.The synthesis routes, separation and purification ways were explored and optimized and had such features as operation simple, reaction conditions mild and yield high. A total of 30 target compounds were synthesized. The structures of compounds were determined by MS and 1H NMR spectrum. We tested in vitro antibacterial activities of compounds for 4 types of susceptible stains and 5 types of resistant stains by broth microdilution method, the results were following:All target compounds showed very good activity against sensitive Streptococcus pyogenes, with the MIC value of 0.25～0.002 μg/mL. In addition, compounds A1, B1 and B12 were best with MIC less than 0.002 μg/mL. Though all compounds showed good activity against sensitive S.aureus, with the MIC value of 1-4 μg/mL, they were still slightly weaker than references. For Pseudomonas aeruginosa, which belongs to Gram-negative bacteria, compounds A3, A9 and B1 were best with MIC value of 32 μg/mL, but other compounds showed poor activity. For ermB S. pneumoniae, many compounds showed excellent antibacterial activity. For example, the MIC of compounds A1, A3, A6 and B1, B3, B6, B11, B15 reached 0.5 μg/mL, showing more than 256-fold higher activity than references. For mefA S. pneumoniae, the best compound A15 displayed more than 64 times good antibacterial activity than clarithromycin. For ermB+mefA S. pneumoniae, compounds A4, A7, A8 and B7, B9 showed the best activity with the MIC values of 0.25 μg/mL, showing 64-fold higher activity than clarithromycin. All compounds were weak against erythromycin-resistant S. pyogenes, but the best compound B1 displayed more than 16 times good activity than references, with MIC value of 8μg/mL. It is disappointing that all target compounds showed poor activity agaist sensitive E. coli and methicillin-resistant S. aureus. Overall, almost all target compounds displayed better antibacterial activity than clarithromycin, the activities of A series were slightly better than that of B series.The structure activity relationship can be obtained as follows:all compounds show better activity against gram-positive bacteria than Gram-negative bacteria; The double bond between C-10 and C-11 positions can cause conformation change of compound, resulting in the change of binding site and the increase of antibacterial activity. The modification of the C-11 and 4"-O positions of CAM at the same time makes compounds bind several sites of bacterial ribosome, resulting in the increase of affinity, thus producing stronger antimicrobial activity. Besides, compounds, bearing the phenyl side chain of six atoms distance from 4"-O or 11-O position, exhibite better antibacterial activity than compounds that of eight atoms distance. What’s more, the electron-with drawing groups and the number of substitutions of aromatic ring are good for the improvement of antibacterial activity, while the positions of substitutions have little effect on antibacterial activity.