Structure and absolute configuration of methyl (3R)-malonyl-(13S)-hydroxycheilanth-17-en-19-oate, a sesterterpene derivative from the roots of Aletris farinosa.

We report the isolation and structure elucidation of a new cheilanthane sesterterpene from the roots of Aletris farinosa that possesses an unusual malonate half-ester functional group. The structure of 1 was determined via mass spectrometry and 1D and 2D NMR spectroscopy, while its absolute configuration was determined via X-ray crystallographic analysis performed on its methyl ester derivative 2.