Cytotoxic turrianes from Kermadecia elliptica: Hemisynthesis and biological activities of kermadecin A derivatives

- Phenol alkylation is very detrimental for kermadecin A cytotoxicity.
- Oxidation of the pyran double bond restores the activity of methylated kermadecin A.
- Reduction of the double bond of kermadecin A maintains its activity.