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.