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The structure and absolute configuration of Shuangkangsu: a novel natural cyclic peroxide from Lonicera japonica (Thunb.)

A novel cyclic peroxide, shuangkangsu (1), has been obtained from the water extract of the buds of Lonicera japonica (Thunb.). The structure was elucidated as 5,8-divinyl-1,4-dihydro-1,4-di-O-β-d-glucopyranosyl-2,3-dioxane (1) on the basis of the spectral data. Its absolute stereochemistry was determined to be (1S, 4S) by comparison of its CD curves with those of its optically pure analogs 2 and 3, which were synthesized from the phthalaldehyde. The absolute configurations of 2 and 3 were determined to be (1R, 4R) and (1S, 4S) by X-ray analysis and CD spectra, respectively. Compound 1 showed significant antiviral activities against influenza virus in chicken embryo and respiratory syncytial virus in cells.