Sesquiterpenoids. Part VI. The stereochemistry of desmotroposantonin: X-ray analysis of 2-bromo-(–)-β-desmotroposantonin

Abstract

From the results of a single-crystal X-ray analysis of 2-bromo-(–)-β-desmotroposantonin, we conclude that there is no change of configuration at C(11) during the formation of desmotroposantonin from santonin. Crystals of the bromo-derivative are orthorhombic, space group P2₁2₁2₁, with four molecules of C₁₅H₁₇BrO₃ in a unit cell of dimensions a= 15·77, b= 18·96, c= 4·90 Å. The atomic co-ordinates were determined by Fourier and least-squares calculations. The final value of the discrepancy R over 865 independent reflexions is 11·5%.