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.