Crystal structure and absolute configuration of the diterpenoid, methyl 6α-bromo-12-methoxy-7-oxopodocarpate
The diterpenoid, of composition C19H23BrO4, crystallises in space group P212121 with cell parameters of a= 10·85, b= 11·16, and c= 15·05 Å. Three-dimensional X-ray structural analysis reveals the bromine atom in the α-configuration and verifies the stereochemistry at the other asymmetric centres. The conformation of ring B is nearly that of a classical boat with the oxygen atom of the associated carbonyl group twisted out of the plane of the molecule. The absolute configuration has been established. The final R value is 0·076.