biostudies-literatureLi WFResearch Grants Council of the Hong Kong Special Administrative Region, ChinaNational Key R&amp;D Program of ChinaTip-top Talent Foundation of Department of EducationNational Natural Science Foundation of ChinaHong Kong Baptist University, Research Committee, and University Grants Committee of the Hong Kong Special Administrative Region, China3098https://www.ebi.ac.uk/biostudies/studies/S-EPMC9143206biostudies-literatureUnknown27(10)Three isopimarane diterpenes [fladins B (<b>1</b>), C (<b>2</b>), and D (<b>3</b>)] were isolated from the twigs and leaves of Chinese folk medicine, <i>Isodon flavidus</i>. The chemical structures were determined by the analysis of the comprehensive spectroscopic data, and the absolute configuration was confirmed by X-ray crystallographic analysis. The structures of <b>1</b>-<b>3</b> were formed from isopimaranes through the rearrangement of ring A by the bond break at C-3 and C-4 to form a new <i>δ</i>-lactone ring system between C-3 and C-9. This structure type represents the first discovery of a natural isopimarane diterpene with an unusual lactone moiety at C-9 and C-10. In the crystal of <b>1</b>, molecules are linked to each other by intermolecular O-H···O bonds, forming chains alonMolecules (Basel, Switzerland)3,4-<i>Seco</i>-Isopimarane Diterpenes from the Twigs and Leaves of <i>Isodon Flavidus</i>.PMC9143206KY (2021)034(UGC Research Matching Grant Scheme RMGS2019_1_1981760772131039172019YFC1712500Tsang NYZou JZhang HJPan LTLiu YHHe KLi WFLiang ZMLi JXZhao CLRong Lfalse3,4-<i>Seco</i>-Isopimarane Diterpenes from the Twigs and Leaves of <i>Isodon Flavidus</i>.Three isopimarane diterpenes [fladins B (<b>1</b>), C (<b>2</b>), and D (<b>3</b>)] were isolated from the twigs and leaves of Chinese folk medicine, <i>Isodon flavidus</i>. The chemical structures were determined by the analysis of the comprehensive spectroscopic data, and the absolute configuration was confirmed by X-ray crystallographic analysis. The structures of <b>1</b>-<b>3</b> were formed from isopimaranes through the rearrangement of ring A by the bond break at C-3 and C-4 to form a new <i>δ</i>-lactone ring system between C-3 and C-9. This structure type represents the first discovery of a natural isopimarane diterpene with an unusual lactone moiety at C-9 and C-10. In the crystal of <b>1</b>, molecules are linked to each other by intermolecular O-H···O bonds, forming chains alon2022-01-01T00:00:00Z2022 May2025-04-22T01:19:57.117Z2025-02-19T04:31:02.094ZS-EPMC91432063563057510.3390/molecules27103098