(–)-2-(1,2,3,4,4a,5,6,7,8,8aα-Decahydro-4aβ,8α-dimethyl-7-oxo-2β-naphthyl)propionic acid: catemeric hydrogen bonding in a bicyclic sesquiterpenoid ζ-keto acid

Abstract

In the title compound, C(15)H(24)O(3), derived from a naturally occurring sesquiterpenoid, the asymmetric unit consists of two molecules differing by 167.4 (8) degrees in the rotational conformation of the carboxyl group. Each molecule aggregates separately with its own type as carboxyl-to-ketone hydrogen-bonding catemers [O...O = 2.715 (6) and 2.772 (6) A, and O-H...O = 169 and 168 degrees ]. This generates two crystallographically independent single-strand hydrogen-bonding helices passing through the cell in the b direction, with opposite end-to-end orientations. One intermolecular C-H...O=C close contact exists for the carboxyl group of one of the molecules. The structure is isostructural with that of a closely related unsaturated keto acid reported previously.

(+)-Santonide, a sesquiterpenoid enol lactone derived from Artemisia

“…(À)--Santonin is an antihelminthic sesquiterpenoid keto lactone, obtained from various Asia Minor species of Artemisia, that has recently aroused wide pharmaceutical interest. Among several structures we have published of keto acids synthesized from (À)--santonin (Brunskill et al, 1999(Brunskill et al, , 2001(Brunskill et al, , 2002Thompson & Lalancette, 2003) are those of a tricyclic diketo acid, (À)-parasantonic acid, and its enol lactone, (+)-parasantonide (Zinczuk et al, 2004). We report here the structure of (+)-santonide, (I), the C9-diastereomer of the latter compound.…”

(–)-Isosantonic acid: alteration of the hydrogen-bonding mode by configurational inversion at a single centre in a γ,∊-diketocarboxylic acid

“…Transformations of (À)--santonin, a sesquiterpenoid Artemisia isolate, offer a rich vein of chiral non-racemic keto acids (Brunskill et al, 1999(Brunskill et al, , 2001(Brunskill et al, , 2002Thompson & Lalancette, 2003). Several such compounds provide opportunities to examine hydrogen-bonding changes due to inversion at a single chiral centre.…”

Natural sesquiterpenoids

“…258 Another two compounds of this type 243 and 244 have been isolated from Atractylodes lancea. 259 X-Ray crystallographic studies 260 have revealed catemeric carboxyl-to-ketone hydrogen bonding in a bicyclic sesquiterpene keto acid 245. This compound is derived from a natural sesquiterpene isolated from species of the Artemisia genus.…”