Abstract: In order to determine the absolute configuration of the chiral center of viscumneoside Ⅳ, which was isolated from Viscum coloratum (Kom) Nakai, (R, S)-mevalonolactone was synthesized as shown in scheme 1. Then treatment with(S) (-)-1-phenylethylamine in THF gave two diasteromeric amides, which were transformed into the monoacetates and separated by HPLC. The first eluted peak (tR10.07 min.)had the (R)-configuration and the second one the (S)-configuration (tR 11.20 min).Viscumneoside Ⅳ was treated with borane and hydrolyzed to give mevalonolactone which was treated with (S)-(-)-1-phenylethylamine in THF as mentioned above. The monoacetates of the resulting amides were subjected to HPLC. By comparison with the reference peaks, the absolute configuration at the acyl moiety of viscumneoside Ⅳ was shown to have the (R)-configuration.