5,10:8,9‐Disecosteroids (= Steroklastanes): A new type of modified steroids

Abstract

Abstract Thermolysis of steroidal 5α, 8α‐ peroxides of type 3a‐d generates as major products the corresponding diseco compounds containing a 14‐membered ring instead of the standard A‐B‐C‐ring skeleton. Depending on the reaction conditions, either the primary products of type 9 or the α, β‐unsaturated ketones of type 4 , formed by subsequent elimination of AcOH, are isolated. The latter, configurationally uniform compounds undergo epoxidation of the C(9)=C(10) bond followed by a Baeyer ‐ Villiger oxidation to give, as final products, the 15‐membered cyclic epoxyenol lactones of type 20 and 21 . The structures of the various products were determined by 1 H‐ and 13 C‐NMR spectroscopy. The conformations of the 14‐ and 15‐membered rings were established by X‐ray structure analyses of 7 and 21a . A reaction mechanism for the above transformations is discussed.