3ß-Acet-oxy-19-hy-droxy-Δ(5)-pregnen-20-one.

In the title compound, C(23)H(34)O(4), the C/D and D/E rings are trans fused and the A/B ring possesses an anti fusion. The two cyclo-hexane rings adopt a chair conformation while the cyclo-hexene ring exhibits a half-chair conformation. The cyclo-pentane ring displays an envelope conformation with the C atom bearing the methyl group as the flap. In the crystal, the mol-ecules are linked by O-H⋯O hydrogen bonds, forming chains along the b axis.

Synthesis of B-ring-modified steroids through BF3-promoted rearrangement/substitution of 6ß-hydroxy-5,19-cyclosteroids.

The BF3·Et2O-promoted reaction of 3ß-acetoxy-5,19-cyclo-pregnan-6ß-ol-20-one with different nucleophiles was investigated. B-homo steroids (3ß-acetoxy-B-homo-6a-ß-alkoxy-pregna-5(10)-en-20-ones) were obtained with primary and secondary alcohols, while the reaction with common carboxylic acids selectively afforded the corresponding 3ß-acetoxy-6ß-(acyloxymethyl)-pregna-5(10)-en-20-ones. The transformations are supposed to proceed via the rearrangement of a cyclopropyl-methyl cation (bicyclobutonium) intermediate, which is regioselectively opened in dependence on the nucleophile employed. The method represents an efficient, diversity-oriented entry to new B-ring-modified steroids, which are of potential pharmaceutical relevance.