Design, synthesis, and biological evaluation of novel spiro[pyrrolidine-2,3′-quinolin]-2′-one derivatives as potential chitin synthase inhibitors and antifungal agents

A series of novel spiro-quinolinone derivatives were designed and synthesized and their structures were confirmed by spectroscopic methods. The enzymatic experiments showed that all the seventeen synthesized compounds had inhibition potency against chitin synthase, among them five compounds had excellent inhibition potency that equal to that of polyoxin B. The Kinetic parameters of enzymatic assays indicated that these compounds were non-competitive inhibitors of chitin synthase. The antimicrobial experiments displayed that the synthesized compounds had selectively and broad-spectrum antifungal activity in vitro Among them, two compounds had stronger antifungal activity against C. albicans than that of fluconazole meanwhile five others compounds showed antifungal activity against C. albicans being equal to that of fluconazole. Moreover, there are four or five compounds that possessed antifungal activities against C. neoformans, A. fumigatus and A. flavus as high as fluconazole had, respectively. The sorbitol protection assay and evaluation of antifungal activity against micafungin-resistant strain further verified that these compounds possessed antifungal activity through inhibiting the synthesis of chitin of cell wall. The evaluation of antifungal activity against others drug-resistant fungi variants showed these designed compounds had significant antifungal activity against these tested variants. The combination use experiments exhibited that the synthesized compounds had synergistic effects or additive effects with current used drugs in clinic. These results demonstrated that these synthesized compounds were chitin synthase inhibitors and had selective and broad-spectra antifungal activities.