New clerodane diterpenoids from Solidago altissima and stereochemical elucidation via 13C NMR chemical shift analysis

Five new clerodane diterpenoids along with ten known compounds were isolated from the underground parts of Solidago altissima L. Compounds 1-4 were rare ent-neo-clerodanes with the cis A/B ring and a trans-configuration between the methyl groups at C-8 and C-9. Compound 5 was identified as trans-neo- clerodane. Revised stereochemical configurations for two known compounds were proposed. Additionally, the stereochemical configurations of the four stereogenic carbons in the 6/6 fused A/B rings of the clerodane diterpenoids were elucidated via C-13 NMR spectral analysis. This analysis validated the proposed structural revisions and suggested the reassignments of other clerodane diterpenoids. (c) 2022 Elsevier Ltd. All rights reserved.