Crystal and molecular structure of 2α-bromo-α-tetrahydrosantonin

Abstract

X-Ray analysis of 2α-bromo-α-tetrahydrosantonin, in addition to confirming the stereochemistry of α-tetrahydrosantonin as envisaged by earlier workers, shows that the trans-fused rings A and B adopt the chair conformation and the trans-fused γ-lactone ring adopts an envelope conformation with C(7) being the out-of-plane atom. The crystals are monoclinic, space group P2₁, with a= 8.099(5), b= 7.248(6), c= 13.317(4)Å, β= 102.74°, Z= 2. The structure was solved by the heavy atom method and refined by full matrix least squares calculations to an R value of 0.086 using 1 008 independent photographically recorded reflections.