Synthesis of novel 20-oxo-pregnacalciferol analogs with binding affinity to the progesterone receptor

3-Desoxy-20-oxo-19-nor-pregnacaliferol (6a) and its 2-oxo analog 6c were prepared from 22-acetoxy-Grundmannʹs ketone 1 and the corresponding (cyclohexylidene)ethyl phosphine oxides 2a, b and their binding to the progesterone receptor examined.