Cytotoxic calanquinone A from Calanthe arisanensis and its first total synthesis

Calanquinone A (1) was isolated from an EtOAc-soluble extract of Calanthe arisanensis through bioassay-guided fractionation. Its structure was identified by spectroscopic methods. Compound 1 showed potent cytotoxicity (EC50 < 0.5 μg/mL) against lung (A549), prostate (PC-3 and DU145), colon (HCT-8), breast (MCF7), nasopharyngeal (KB), and vincristine-resistant nasopharyngeal (KB-VIN) cancer cell lines, and interestingly, showed an improved drug resistance profile compared to paclitaxel. The total synthesis of 1 was also achieved and is reported herein.