The x-ray crystal and molecular structure of a tetracyclic diterpenoid - benzaldehyde reaction product and the long range protective influence of its benzene ring

ent-(1aR)-1-α-(1a-Hydroxy-1a-phenyl)-3β-hydroxy-11α-bromo-12-oxo-2-norbeyeran-3β-carboxylic acid 2,1a-lactone

“…The absolute configuration was determined, and it confirmed previous assignments for this family of compounds (Laing, Pegel & Piacenza, 1973;Laing, Pegel, Piaeenza, Waight & Phillips, 1974;Laing, Sommerville, Hanouskova, Pegel, Piacenza, Phillips & Waight, 1972;Laing & Sommerville, 1975;Sommerville & Laing, 1976a,b,c). (Sommerville & Laing, 1976a,b,c).…”

“…Rings C and D are distorted, e.g. C(14)-C(13)-C(16) 99 °, so that C(15) below ring C is now 3.45 A from C(20) compared with 3.17-3.26 A in related compounds (Laing, Pegel & Piacenza, 1973;Laing et al, 1974;Sommerville & Laing, 1976c). The dihedral…”