Efficient synthesis of 3-aminodigoxigenin and 3-aminodigitoxigenin probes.

Oxidation of digoxigenin and digitoxigenin to the 3-ketones followed by reductive amination produced a mixture of amine epimers. The inability to separate the epimeric mixtures of chemiluminescent digoxigenin probes derived by conjugation to the acridinium label prompted us to develop an HPLC method to separate the amines. Labeling of the pure amines resulted in good yields of the isomerically pure probes.