Synthesis of $^3H$-Labeled dammarane triterpene glycosides of Korean ginseng

A procedure of $^3H$-radio labeling synthesis for the dammarane triterpene glycosides of Korean ginseng was established by using the ginsenoside $Rg_1$ as starting material. The protons in $C-{11}$ and $C_{13}$ of the aglycone moiety of the glycoside were exchanged with tritium by keto-enol tautomerization of 12-keto-ginsenoside $Rg_1$ which was prepared by partial acetylation, Sarett oxidation and saponification, producing nona-acetate, nonaside $Rg_1$. The acety1-ketone and 12-keto-derivative of ginsenotritated ketone was reduced by metallic sodium and isoproponol to produce the end product $^3H$-ginsenoside $Rg_1$ with 3% radio-chemical recovery in one experiment.