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.

The guaiol color reaction.

The common and biogenetically important sesquiterpene guaiol yields a deep purple color when treated with electrophilic bromine reagents. This interesting color reaction was observed over fifty years ago, but the chemistry of this process has not been investigated. Herein, we present the chemistry of the guaiol color reaction.