Über Steroide und Sexualhormone. 225. Mitteilung. UV.‐Bestrahlung von 11‐Oxo‐Steroiden II Die Darstellung von Δ 4 ‐ und Delta; 5 ‐11β, 19‐Cyclo‐pregnen‐ sowie 5β‐11β, 19‐Cyclo‐ und 5, 19‐Cyclo‐pregnan‐Verbindungen

1 In analogy to the previously described photochemical isomerisation of 3,20‐diethylenedioxy‐11‐oxo‐5 α‐pregnane (I → II) the UV.‐irradiation of the Δ 5 ‐ and 5β‐11‐oxo‐steroids III and XXII gives rise to the 11 α‐hydroxy‐11, 19‐cyclo derivatives IV and XXIII, respectively. The observed yields of these tertiary cyclobutanol products decrease in the order II > IV > XXIII. The possible significance of these structure‐dependent rate differences is discussed.