What is the favoured conformation of the friedelane skeleton? A combined X-ray and molecular force-field study of friedelin, C₃₀H₅₀O

7β,8β-Epoxyfriedelane

“…These findings suggest that the introduction of a 14,15fl-epoxide function in an inactive tetracyclic triterpene might lead to a cytotoxic compound (Merrien, Meunier, Pascard & Polonsky, 1981). Very few X-ray structural studies have been carried out on epoxides of the friedelane series, though the structure of friedelin has been solved (Declercq, Puyvelde, Kimpe, Nagy, Verhegge & Vierman, 1991;Mo, Winther & Scrimgeour, 1989) and our molecular chirality matches this structure. The present molecule consists of five six-membered alicyclic fused rings in a friedelane structure with a fl-oriented epoxy O atom bridging the C7 and C8 atoms.…”

3β-Hydroxyfriedelan-17β-carboxylic acid

“…H2K. It is a new friedelan analogue (Dhaneshwar et al, 1987;Fun et al, 2007;Mo, 1977;Mo et al, 1989;Sun et al, 2004). We report here the structure of the title compound.…”

Combined experimental powder X-ray diffraction and DFT data to obtain the lowest energy molecular conformation of friedelin

“…It is envisaged that the implementation and optimization of methods commonly found in ordinary laboratories can contribute toward elucidating structural problems of PCTT family compounds, as well as other simple organic molecules, without the need for single-crystal experiments. Previously reported data for a single-crystal of friedelin 8 and NMR studies 9 were used to validate our results.…”

“…8 According to these calculations, the intermolecular forces related to crystal packing, solvation and solubility also determine the preferred conformer in crystalline state.…”