A Pair of Enantiomeric Dimers with an Unprecedented Skeleton from Stem Barks of Syringa Pinnatifolia

A pair of enantiomers with a rearranged dimeric phenylethanol skeleton, namely (±)-disyringol A (1a and 1b), were isolated from the stem barks of Syringa pinnatifolia. The structures were established using IR, UV, MS, and NMR data, and their absolute configurations were resolved by experimental and calculated ECD data analysis. Their biosynthetic pathway was speculated on the basis of a phenylethanoid precursor and was proved by a total synthesis. Compounds 1a and 1b showed the inhibition against NO production in LPS-induced RAW264.7 cells with their IC50 values of 27.28 and 24.64 μM, respectively, however no protective effect was observed against the hypoxia-induced injuries to H9c2 cells.