Steroids, L. Ring D Cleavage of D‐Trisubstituted Steroids

In alkaline medium, 17β‐hydroxy‐15‐(hydroxymethylene)androst‐5‐en‐16‐one ( 2a ) is cleaved in two ways to give D‐ seco compounds. Dilute bases in protic solvents cause 1,3‐dicarbonyl splitting to the 15‐formyl‐15,16‐ seco ‐16‐oic acid 3 , while the use of sodium methanolate in benzene solution gives rise to 16,17‐splitting to afford the 15‐formyl‐16,17‐ seco ‐16,17‐dioic acid 5 . Both seco compounds readily undergo lactolone ring closure to give 4a and 6a , respectively. The malonaldehyde moiety of 5 is transformed in two directions: either loss of the formyl group to give 3β‐hydroxy‐16,17‐secoandrost‐5‐ene‐16,17‐dioic acid ( 7a ) or decarboxylation to 3β‐hydroxy‐16‐oxo‐16,17‐secoandrost‐5‐en‐17‐oic acid ( 9 ) is observed.