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Bis-spirolabdane Diterpenoids from Leonotis nepetaefolia

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journal contribution
posted on 27.04.2012 by Jun Li, Frank R. Fronczek, Daneel Ferreira, Charles L. Burandt, Vincent Setola, Bryan L. Roth, Jordan K. Zjawiony
Ten new bis-spirolabdane diterpenoids, leonepetaefolins A–E (1, 3, 5, 7, 9) and 15-epi-leonepetaefolins A–E (2, 4, 6, 8, 10), together with eight known labdane diterpenoids (1118) as well as two known flavonoids, apigenin and cirsiliol, were isolated from the leaves of Leonotis nepetaefolia. The structures of the new compounds were determined on the basis of 1D- and 2D-NMR experiments including 1H, 13C, DEPT, 1H–1H COSY, HSQC, HMBC, and NOESY. The absolute configuration of an epimeric mixture of 1 and 2 was determined by X-ray crystallographic analysis. The compounds isolated were evaluated for their binding propensity in several CNS G-protein-coupled receptor assays in vitro.