Leojaponin (2), a labdane diterpene, was isolated from the EtOH extract of the herb of Leonurus japonicus together with a new halimane diterpene named isoleojaponin (1). Isoleojaponin has a new diterpene skeleton with a unique cross-conjugated α,β-unsaturated ketone system, Their structures were elucidated by physical and spectroscopic analysis, and the relative configuration of the chiral C-9 carbon was determined by a computational method, and analysis of its possible biogenesis pathways.
a b s t r a c tTwo new labdane-type diterpenoids, 5-ethoxy-3-(2-((R)-4-hydroxy-2,5,5,8a-tetramethyl-3-oxo-3,5,6,7,8,8a-hexahydronaphthalen-1-yl)ethyl)furan-2(5H)-one (1), and 5-hydroxy-4-(2-((1R,3S,7aS)-1-hydroxy-4,4,7a-trimethyl-3-propionyloctahydroisobenzofuran-1-yl)ethyl)furan-2(5H)-one (2), were isolated from the EtOH extract of the herb of Leonurus japonicus Houtt., Lamiaceae. Their chemical structures were determined by analysis of 1D, 2D NMR, HRESIMS, and by comparison with known analogs.
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