AbstractIn continuation of our work on transannular cyclizations of trans‐3β‐sacetoxy‐5, 10‐seco‐cholest‐1 (10)‐en‐5‐one (1), the ringclosure of this compound and of its cis‐isomer (11) under UV.‐irradiation was examined: both yield the same mixture of oxetanes 2 and 3 exhibiting the natural steroid skeleton.