New Dammarane Triterpenes from the Aerial Parts of Ibicella lutea Grown in Argentina

Abstract

Two new dammarane triterpenes have been isolated from the aerial parts of Ibicella lutea, 3-acetyl-24-epi-polacandrin (1) and 1,3-diacetyl-24-epi-polacandrin (2), and were obtained along with the known compounds 20S,24S-epoxy-3beta,12beta,25-trihydroxydammarane (3) and apigenin. The structures of compounds 1 and 2 were deduced by spectroscopic studies and by chemical transformations leading to the preparation of derivatives 4-11. The structure and relative stereochemistry of 1 were verified by single-crystal X-ray analysis. The natural compounds and selected semisynthetic derivatives were evaluated against several tumor cells.

Dammaradienyl acetate

“…The skeleton of (I) is composed of a fused four-ring system, including three six-membered rings, A (C3-C7/C12), B (C7-C12) and C (C10-C16), and a five-membered ring, D (C15-C19). All the junctions are trans-fused, as indicated by their torsion angles (Table 1), which is similar to what is observed in 1-acetyl-24-epi-polacandrin (Simirgiotis et al, 2003). All three six-membered rings, A, B and C, adopt chair conformations, as shown by their puckering parameters (Cremer & Pople, 1975) [q 2 = 0.039 (5), q 3 = 0.553 (5), Q = 0.554 (5) Å , = 4.4 (5) and ' = 70 (8) for ring A; q 2 = 0.083 (5), q 3 = 0.564 (5), Q = 0.570 (5) Å , = 8.4 (5) and ' = 5(3) for ring B; q 2 = 0.071 (5), q 3 = 0.585 (5), Q = 0.589 (5) Å , = 6.9 (5) and ' = 311 (4) for ring C. The value for of 704.2 suggests that ring D is twisted about the C15-C16 bond [ = 2P (Altona et al 1968), P = 352.1 (4), (M) = 44.0 (3) for reference bond C15-C16, where P and (M) are the pseudorotation parameters (Rao et al, 1981)].…”

Semisynthesis and cytotoxicity evaluation of a series of ocotillol type saponins and aglycones from 20(S)-ginsenoside Rg2, Rh1, protopanaxatriol and their 20(R)-epimers

“…The 13 C NMR and 1 H NMR data are showed in Table 1. 4[M+Na] + . The NMR data of compound 6 and 7 were closely resemble except for the significant differences in signals appearing at the side chain, indicating the similar features in the molecular structure, and both of their data were agreed well with those of compound 1, suggesting that their structures belonged to the ocotillol type.…”

“…Nevertheless only pseudoginsenoside-RT 5 was found in the leaves of Panax ginseng C. A. Mey so far [1] . In addition, there are ocotillol type saponins in the Cucurbitaceae, Martyniaceae and Betulaceae species [2][3][4][5] . The results of the previous researches on pharmacological and biological activities indicated that ocotillol type saponin possessed myocardial protection effect, antibacterial activity, enhancing neuronal activity and anti-tumor promoting activity [6][7][8][9] .…”

Stereochemistry of 2,2,5‐trisubstituted tetrahydrofuran ring‐containing natural products based on 1H NMR spectroscopy: some observations

“…About 100 dammaranes, which contain a THF ring in the side chain, are found in the literature . These are often referred to as ocotillone‐type dammaranes.…”

“…Several natural products belonging to various classes like quassiols, squalene‐derived polyethers from red algae, malabaricane‐type triterpenoids, dammarane‐type triterpenoids, and miscellaneous contain 2,2,5‐trisubstituted tetrahydrofuran (THF) rings in their structures. In most cases, it is hydrogen on one side and a methyl group on the other, creating two stereocenters on the THF ring and necessitating the assignment of their configuration.…”