A Macrocyclic Dimeric Diterpene with a C2 Symmetry Axis

An unprecedented macrocyclic dimeric diterpene containing a C2 symmetry axis was isolated from Acacia schaffneri. This compound, named schaffnerine, was characterized as (5S,7S,8R,9R,10S,17S,5?S,7?S,8?R,9?R,10?S,17?S)-7,8:7,17?:16,17:17,7?:7?,8?:16?,17?-hexaepoxy-7,8-seco-7?,8?-seco-dicassa-13,13?-diene (1) from its spectroscopic data. Comparison of its experimental vibrational circular dichroism spectrum with that calculated using density functional theory, at the B3LYP/DGDZVP level, assigned its preferred conformation and absolute configuration. The latter was confirmed by evaluation of the Flack and Hooft parameters obtained after single-crystal X-ray diffraction analysis.