Fimbriatols A–J, Highly Oxidized ent-Kaurane Diterpenoids from Traditional Chinese Plant Flickingeria fimbriata (B1.) Hawkes

Abstract

Fimbriatols A–J (1–10), ten new ent-kaurane diterpenoids possessing differently highly oxidized sites, were isolated from Flickingeria fimbriata (B1.) Hawkes. The structures of these new compounds were determined by HRESI-MS, NMR, CD spectra and X-ray diffraction analysis. Compound 1 displayed moderately inhibitory ratio (48.5%) compared with the positive compound NSC-87877 (81.6%) at the concentration of 0.022 μg/mL. Compounds 7–10 possess 3, 4-seco-ent-kaurane skeleton containing a disaccharide moiety with an unusual linkage at C-2′ to C-1′′ instead of the common linkage at C-6′ to C-1′′, and this is the first report in 600 more ent-kauranes found in nature, which might be originated from ent-kaurane diterpenoids through post-modified reactions of Baeyer-Villiger oxygenation and glycosylation.

Eight <i>ent</i>-Kaurane Diterpenoid Glycosides Named Diosmariosides A–H from the Leaves of <i>Diospyros maritima</i> and Their Cytotoxic Activity

“…Eight new compounds (1)(2)(3)(4)(5)(6)(7)(8) and two known ones (9 and 10) were isolated from the MeOH extract of leaves of D. maritima, using various kinds of chromatographic techniques. The structures of the new compounds were elucidated by intensive one-and two-dimensional NMR spectroscopic analyses and chemical conversion.…”

“…The structures of the known compounds were identified by the comparison of spectroscopic data with those reported in the literature. 6,7) Diosmarioside A (1), [α] D 26 −63.8, was isolated as colorless plates and its elemental composition was determined to be C 31 H 50 O 12 by the observation of a quasi-molecular ion peak [M+Na] + using high-resolution (HR) electrospray ionization (ESI) MS. The IR spectrum exhibited strong absorption bands at 3460 and 3341, and 1693 cm −1 ascribable to hydroxy groups and a carbonyl functional group, respectively.…”

“…In the 1 H-NMR spectrum, signals for three singlet methyls, methylene protons on an isolated primary alcohol [δ H 3.95 (1H, d, J=10. 8 Hz, H-17b) and 4.47 (1H, d, J=10. 8 Hz, H-17a)] and two anomeric protons (δ H 4.99 and 5.80) were observed.…”

“…8 Hz, H-17b) and 4.47 (1H, d, J=10. 8 Hz, H-17a)] and two anomeric protons (δ H 4.99 and 5.80) were observed. Thus, 1 was expected to be a glycosidic compound and sugar analysis of its hydrolysate using a chiral detector revealed the presence of D-apiose and D-glucose.…”

“…Thus, the ketone of sugeroside (9) must form a cyclic ketal with hydroxy groups at C-3″ and C-5″ of D-apiofuranoside of the unit A. The 13 C-NMR chemical shifts of C-3″ and C-5″ in the unit A were apparently shifted downfield [C-3″: δ C 80.5 (1) δ C 86.4 (8) and C-5″: δ C 65.7 (1) 73.9 (8)], when compared with those of 1, proving that these groups were involved in the cyclic ketal formation. The negative Cotton effect (∆ε: −0.73) at 289 nm in the CD spectrum confirmed that the unit A possessed an ent-series kaurene skeleton 11,12) and the stereochemistry of the ketal region was substantiated using the PS-nuclear Overhauser effect spectrum.…”