Unusual hemiacetal structure derived from Salvinorin A.

The salvinorin A analog dimethyl (2R,3aR,4R,6aR,7R,9S,9aS,9bS)-2-(3-fur-yl)-9,9a-dihydr-oxy-3a,6a-dimethyl-dodeca-hydro-benzo[de]chromene-4,7-dicarboxyl-ate, C(22)H(30)O(8), has a relatively simple spatial arrangement in which mol-ecules are linked into layers by two pairs of O-H⋯O hydrogen bonds. Each mol-ecule has as the central feature a dodeca-hydro-1H-phenalene ring system. Its three six-membered rings are in the chair conformation, with two axial methyl groups, one axial OH, and one equatorial OH, these OH groups being directly responsible for linking of the mol-ecules in the crystal structure.