NEW MATERIAL:The compound of formula I (R is -COOH or -CONHCH2COOH).

EXAMPLE: 3β,12β,14β-Trihydroxy-5β,17β-etianic acid-3-tridigitoxide.

USE: Useful as a hapten of hapten antigen for the preparation of antibody for the immunochemical determination of a digoxin (a cardiac glucoside). The metabolic product of digoxin can be discriminated from digoxin, and the level of digoxin in blood can be determined accurately.

PREPARATION: For example, the digoxin pentaacetate of formula II (Ac is acetyl) is oxidized with e.g. KMnO4 in an organic solvent such as acetone, and the resultant compound of formula III is hydrolyzed to obtain a compound of formula I wherein R is COOH, which can be converted to another compound of formula I wherein R is CONHCH2COOH by reacting with glycine.