Mangelonoids A and B, Two Pairs of Macrocyclic Diterpenoid Enantiomers from Croton mangelong

(+)- and (−)-Mangelonoids A and B, two pairs of novel macrocyclic diterpenoid enantiomers featuring an unprecedented bicyclo[9.3.1]pentadecane core and a rare bridgehead double bond, were isolated from Croton mangelong. Their structures were unambiguously established using spectroscopic data, X-ray crystallography, and electronic circular dichroism analysis. A plausible biosynthesis pathway for these compounds was proposed. (−)-Mangelonoid A exhibited NF-κB inhibition with an IC50 value of 7.27 ± 1.30 μM.