Santal monohydrate, an isoflavone isolated from Wye-thia mollis.

THE TITLE COMPOUND [SYSTEMATIC NAME: 3-(3,4-di-hydroxy-phen-yl)-5-hy-droxy-7-meth-oxy-4H-chromen-4-one monohydrate], C16H12O6·H2O, is a monohydrate of a natural product santal isolated from Wye-thia mollis. In the santal mol-ecule, the dihedral angle between the benzo-quinone and di-hydroxy-phenyl fragments is 53.9 (1)° and an intra-molecular O-H⋯O hydrogen bond occurs.

Isotenulin.

Isotenulin, C17H22O5, is a sesquiterpene lactone isolated from sneezeweed Helenium amarum. It crystallizes with two independent mol-ecules in the asymmetric unit. In each mol-ecule, two five-membered rings (cyclo-pentenone and lactone) are trans-fused to the central seven-membered ring.

Tenulin 0.25-hydrate, a sesquiterpene lactone isolated from Helenium amarum.

The asymmetric unit of the title compound, C17H22O5·0.25H2O [systematic name: 2-hy-droxy-2,2a,6,9a-tetra-methyl-2a,4a,5,6,6a,9a,9b,9c-octa-hydro-2H-1,4-dioxadi-cyclo-pent[cd,f]azulene-3,9-dione 0.25-hydrate], a natural product isolated from Helenium amarum, contains two independent tenulin mol-ecules and half a water mol-ecule of crystallization situated on a twofold rotation axis.

The true identity of the triterpene component of Wyethia mollis, a lanosta-diene containing a tetrahydropyran E-ring.

The crystal structure of a triterpene component of Wyethia mollis has been obtained and compared with the previously reported structure of the compound. The compound in the crystal structure, lanosta-8,24-dien-3-one, 16,23-epoxy-(161beta, 23R), (1), is different from the previously reported compound, but has identical NMR and mass spectrometric data. The revised structure contains a tetrahydropyran E ring, a structural moiety rare in steroid triterpenes.