ENT-16α,17-dihydroxykauran-19-oic acid isolated from Oratea semiserrata and the stereochemistry defiances of the chiral carbons C-4 and C-16.

Phytochemical investigation of the leaves and branches of a specimen of Ouratea semiserrata led to the isolation and characterization of ent-16 alpha,17-dihydroxgkauran-19-oic acid, along with other natural products. This diterpenoid and its derivatives were used to unambiguous H-1 and C-13 chemical shifts assignments and to indicate some mistake data described in the literature as consequence mainly of the stereochemicals of the chiral carbons C-4 and C-16. The HRMS spectra were also analysed.