Chiral resolution of furofuran lignans and their derivatives from the stems of Dendrobium 'Sonia'

Five new furofuran lignans and their derivatives, (−)-glaberide I 4-O-β-D-glucopyranoside (1a), (+)-glaberide I 4-O-β-D-glucopyranoside (1b), (+)-glaberide I 7'-ethoxy-4-O-β-D-glucopyranoside (2a), (−)-glaberide I 7'-ethoxy-4-O-β-D-glucopyranoside (2b), and (−)-isoeucommin A (3b), along with fifteen known analogs were isolated from the stems of Dendrobium 'Sonia'. These compounds were classified into ten pairs of enantiomers or diastereoisomers via chiral resolution, and their structures were determined based on extensive spectroscopic data. Their absolute configurations were determined by hydrolysis, comparison of experimental and calculated electronic circular dichroism (ECD) data, and single-crystal X-ray diffraction analysis. The isolates were evaluated for their ability to inhibit nitric oxide (NO) production in RAW264.7 cells. Among them, syringaresinol (5) exhibited prominent inhibition activity, with an IC₅₀ value of 28.4 ± 3.0 μmol·L⁻¹, and there was a slight difference between 5a, 5b and the racemic mixture 5.