Diterpenes from Coleus forskohlii (WILLD.) BRIQ. (Labiatae).
Three new minor labdane diterpene glycosides, forskoditerpenoside C, D, and E (1-3), and a novel labdane diterpene forskoditerpene A (4) were isolated from the ethanol extract of the whole plant of Coleus forskohlii. Their structures and relative stereochemistry were elucidated on the basis of extensive spectroscopic analyses including 1D-, 2D-NMR, and HR-ESI-MS experiments. Compounds 1-3 showed an unusual 8,13-epoxy-labd-14-en-11-one glycoside pattern. They showed relaxative effects on isolated guinea pig tracheal spirals in vitro. Compound 4 with a cyclopropyl, confirmed by a single-crystal X-ray diffraction determination, is the first known labdane derivative with a spiro element.
Syntheses of 12-oxygenated forskolins
The preparation of selectively oxygenated forskolin derivatives has been achieved with reagent, solvent, and steric environment as key factors in selectivity of the oxidation.
Studies on the terpenoids and related alicyclic compounds—XXII: Stereochemical study on the angular hydroxylation of polycyclic ketones using benzeneseleninic anhydride
Abstract Introduction of an OH group to the tertiary carbon of simple ketones (1, 2 and 6), furanoeremophilane-type ketones (12–19), and tricyclic ketones (20–22) by the use of benzeneseleninic anhydride is described. 10β-Hydroxy compounds were obtained in the case of 12–14 and 20–22. 10α-Hydroxy compounds were obtained in the case of 15 and 16. In the hydroxylation reaction of polycyclic ketones using benzeneseleninic anhydride, the results suggest that the thermodynamically more stable product was usually produced as the major product.