Modified Fusicoccane-Type Diterpenoids from <i>Alternaria brassicicola</i>

Seven new modified fusicoccane-type
diterpenoids (1–7), together with
two known congeners (8 and 9), were obtained
from Alternaria
brassicicola. Their structures were elucidated from a combination
of NMR and HRESIMS data and 13C NMR calculation as well
as DP4+ probability analyses, and the absolute configurations of 1–5 were determined by ECD calculation
and single-crystal X-ray diffraction (Cu Kα). Compounds 1–3 belong to a rare class of 16-nor-dicyclopenta­[a,d]­cyclooctane diterpenoids,
and compounds 2 and 4 represent the first
examples of fusicoccane-type diterpenoids featuring two previously
undescribed tetracyclic 5/6/6/5 ring systems, while compound 5 features a previously undescribed tetracyclic 5/8/5/3 ring
system. Compound 7 was moderately anti-inflammatory,
and compounds 2, 3, 5, and 7 were weakly cytotoxic.