Fungal metabolites. Part VIII. Sesquiterpenoids. Part VII. The structure of fomannosin: X-ray analysis of dihydrofomannosin p-bromobenzoylurethane

Abstract

X-Ray crystal-structure analysis of dihydrofomannosin p-bromobenzoylurethane has led to the elucidation of the structure of fomannosin, a biologically active sesquiterpenoid metabolite of the fungus Fomes annosus. The p-bromobenzoylurethane derivative crystallizes in the monoclinic system, space group P2₁, with two molecules of C₂₃H₂₄BrNO₆ in a unit cell of dimensions a= 11·57, b= 6·05, c= 15·78 Å, β= 95° 35′. The atomic co-ordinates were determined by Fourier and least-squares calculations, the final value of R being 11·2%. The molecule contains a puckered cyclobutane ring with dihedral angle 22°, and a cyclopentanone ring in an envelope conformation.