Neolignans with a Rare 2‑Oxaspiro[4.5]deca-6,9-dien-8-one Motif from the Stem Bark of Cinnamomum subavenium

Two pairs of racemic spirodienone
neolignans with a rare 2-oxaspiro[4.5]­deca-6,9-dien-8-one
motif, named (±)-subaveniumins A (1) and B (2), were isolated from the bark of Cinnamomum
subavenium. The chiral separation of the (+)-1, (−)-1, (+)-2, and (−)-2 enantiomers was accomplished via high-performance liquid
chromatography on a chiral column. Their structures were elucidated
using single-crystal X-ray diffraction and spectroscopic analyses
(UV, IR, HRESIMS, and 1D and 2D NMR). The absolute configurations
of the enantiomers were determined by comparing the experimental and
calculated electronic circular dichroic spectra. The (+)-1, (−)-1, (+)-2, and (−)-2 enantiomers exhibited moderate inhibitory effects against
NO production in RAW264.7 mouse macrophages induced by lipopolysaccharide,
with IC50 values of 17.9, 5.6, 15.1, and 4.3 μM,
respectively.