Acta Cryst. (2009). E65, o2564-o2565 [ doi:10.1107/S160053680903829X ]
Abstract: The title structure (systematic name: 9-hydroxymethyl-3,6-dimethyl-3-methylene-2,7-dioxo-3,3a,4,5,9a,9b-hexahydroazuleno[4,5-b]furan-4-yl acetate hemihydrate), C17H20O6·0.5H2O, from Lactuca floridana, has two independent sesquiterpene lactone molecules in the asymmetric unit. Both have their seven-membered rings in the chair conformation. In the crystal, the OH groups and the water molecule form classical O-HO hydrogen bonds with OO distances in the range 2.6750 (17)-2.8160 (18) Å.
Online 30 September 2009
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