Broadening antifungal spectrum and improving metabolic stablity based on a scaffold strategy: Design, synthesis, and evaluation of novel 4-phenyl-4,5-dihydrooxazole derivatives as potent fungistatic and fungicidal reagents.

5-phenylthiophene derivatives exhibited excellent antifungal activity against Candida albicans, Candida tropicalis and Cryptococcus neoformans. However, optimal compound 7 was inactive against Aspergillus fumigatus and unstable in human liver microsomes in vitro with a half-life of 18.6 min. To discover antifungal agents with a broad spectrum and improve the metabolic properties of the compounds, the scaffold hopping strategy was adopted and a series of 4-phenyl-4,5-dihydrooxazole derivatives were designed and synthesized. It was especially encouraging that compound 22a displayed significant antifungal activities against eight susceptible strains and seven FLC-resistant strains. Furthermore, the potent compound 22a could prevent the formation of fungalbiofilms and displayed satisfactory fungicidal activity. In addition, the metabolic stability of compound 22a was improved significantly, with the half-life of 70.5 min. Compound 22a was almost nontoxic to mammalian A549, MCF-7, HepG2, and 293T cells. Moreover, pharmacokinetic studies in SD rats showed that compound 22a exhibited pharmacokinetic properties with a bioavailability of 15.22% and a half-life of 4.44 h, indicating that compound 22a is worthy of further study.