Bulky 1,4-benzoxazine derivatives with antifungal activity.

For many years the development of new azole antifungals has been quite empirically based. More recently, the publication of the crystal structure of CYP51 of Mycobacterium tuberculosis (MT-CYP51) provided new opportunities to rationalize the knowledge about antifungal action of this class of compounds. Recent studies reported that a 'channel 2 opened' conformation of the enzyme could better explain the interaction with ketoconazole (KTZ)-like drugs. Conformational changes were made on our model of Candida albicans CYP51 (CA-CYP51) previously reported and docking experiments were performed. The results allowed new KTZ analogues to be designed, by predicting that the 1,4-benzoxazine moiety could replace the KTZ aryl-piperazinyl chain. The synthesis of derivatives 12 and 13 was planned. The in vitro antifungal activity was evaluated against different Candida species and low and high capsulated strains of Cryptococcus neoformans. Since the in vitro activity do not necessarily correlate with the in vivo antifungal activity the newly synthesized compounds were also tested in a murine model of systemic C. albicans infection. The therapeutic effect was evaluated in terms of animal survival and of fungal growth in the kidneys, the target organ in systemic candidiasis.