Synthesis and absolute configuration of (−)-chettaphanin II

Halimane diterpenoids: sources, structures, nomenclature and biological activities

“…A structural characteristic of this group of compounds (208)(209)(210)(211)(212)(213)(214)(215)(216)(217)(218)(219) is that all of them show oxygenated functions at C5, except diasin (219, from Croton diasii), 176 which we include in this group precisely for not having any unsaturation in the decalin system ( Fig. 15, Table S4 †).…”

Synthesis of an ent-Halimanolide from ent-Halimic Acid

“…The ent -halimic acid tetranorderivative 6 was obtained in excellent yield as described in the synthesis of chettaphanin I and II [4] [6]. Carbonyl protection of 6 with ethylene glycol in acid media gives the tetranorderivative 7 , that already contains the tetrasubstituted double bond in the required position.…”

“…Our new route for the synthesis of intermediate 19 gives a better global yield than one based on a Baeyer-Villiger reaction as a key step [4, 6], and can be done in a multigram scale.…”

“…Our group has transformed ent -halimic acid 1 , a diterpene of known structure and absolute configuration, into chettaphanin I and II, which confirmed their structure and absolute configuration [4,6]. In this paper, we report the synthesis of ent -halimanolide 2 , in order to confirm the structure of the natural compound and do SAR studies.…”

“…(Euphorbiaceae), known in Thailand as “Chettaphangki,” is the only member of the genus Cladogynos and the roots are used as a carminative in Thai folk medicine. Chettaphanin I [4,5] and II [6,7], are the main components from their roots of this plant and the first to be known. Recently, in addition to chettaphanin I and II, isolation from the root extract of a series of furan diterpenes 2 - 4 with ent -halimane skeletons has been described [8].…”