(±)-Rubioncolin D, a pair of enantiomeric naphthohydroquinone dimers from Rubia oncotricha

Abstract A pair of novel enantiomeric naphthohydroquinone dimers with an unprecedented spiro[4.5] carbon core, (±)-rubioncolin D ( 1 ), were isolated from Rubia oncotricha . The racemic mixture of 1 was separated by chiral column chromatography. Their structures and stereochemistry were elucidated by extensive spectroscopic analysis and electronic circular dichroism calculation. Both compounds (+)- 1 and (−)- 1 exhibit weak cytotoxicities against A549, SGC-7901 or HeLa cancer cell lines.