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 ), together with fifteen known analogues were isolated from the stems of Dendrobium 'Sonia'. The above compounds were divided into ten pairs of enantiomers or diastereoisomers by chiral resolution, and their structures were determined on the basis of extensive spectroscopic data, including 1D/2D NMR, IR, and HR-ESI-MS. Their absolute configurations were determined by hydrolysis, comparison of experimental and calculated ECD data, and single-crystal X-ray diffraction analysis. The isolates were tested for inhibition of nitric oxide production against RAW264.7 cells. Among them, syringaresinol ( 5 ) exhibited prominent inhibition activity with an IC₅₀ value of 28.4 ± 3.0 μM, and there was a slight difference between 5a , 5b and the racemic mixture 5 .