Preparations of ginsenoside Rg(1) immunogen and I-125-labeled antigen

This work began with the side chain of ginsenoside Rg(1) which was acetylized with Ac2O-Pyr and oxidized by OsO4 and NaIO4 to give ginsenoside Rg(1) aldehyde(2), which was further converted into an unsaturated ester(3) by Wittig-Horner reaction. The unsaturated ester(3) was treated with N2H4 and HNO2 to yield Rg(1) azide(4) which was directly conjugated with BSA to give immunogen: ginsenoside Rg(1)-BSA conjugate(5). This azide(4) was conjugated with tyramine to give ginsenoside Rg(1)-tyramine conjugate which was labelled with free (NaI)-I-125 by CH-T to yield I-125-labeled antigen: gensenoside Rg(1)-I-125-tyramine(6). The labelling rate was 40%-50% and specific activity was 3.0-4.0 MBq/mu g.