Fungal metabolites. Part IV. The structure of ergoflavin: X-ray analysis of tetra-O-methylergoflavin di-p-iodobenzoate

Abstract

X-Ray crystal-structure analysis of tetra-O-methylergoflavin di-p-iodobenzoate has defined the constitution and absolute stereochemistry of ergoflavin, an ergot pigment, to be as shown in (II). The crystals are orthorhombic, space group P2₁2₁2₁, with four molecules of C₄₈H₄₀I₂O₁₆ in a unit cell of dimensions a= 13·23, b= 38·70, c= 9·37 Å. The crystal structure was elucidated by the heavy-atom method and the atomic co-ordinates were refined by Fourier and least-squares calculations. The final value of the discrepancy R over 3188 independent reflexions is 14·3%.