Compounds related to the steroid hormones. Part XVIII. Reaction of 16α,17α-epoxy-16β-methyl-5α-pregnan-20-ones with boron trifluoride

Abstract

Treatment of 3β-acetoxy-16α,17α-epoxy-16β-methyl-5α-pregn-9-en-20-one with boron trifluoride–ether complex in dioxan gave mainly 3β-acetoxy-17α-hydroxy-17β-methyl-16-methylene-D-homo-5α-androst-9-en-17a-one, whereas with benzene as solvent the product was a D-homo-fluorohydrin, probably 3β-acetoxy-16β-fluoro-17α-hydroxy-16α,17β-dimethyl-D-homo-5α-androst-9-en-17a-one. Longer reaction with boron trifluoride in benzene gave a mixture of the epimeric 3β-acetoxy-16-acetyl-16-methyl-5α-androst-9-en-17-ones, one of which was the sole product from the D-homo-fluorohydrin under the same conditions. Both epimeric 16-acetyl-16-methyl-17-ketones were cleaved by alkali to the same carboxylic acid, 16-acetyl-3β-hydroxy-16-methyl-16,17-seco-5α-androst-9-en-17-oic acid, which was also prepared from 3β,17α-dihydroxy-16β,17β-dimethyl-D-homo-5α-androst-9-en-17a-one.

Consideration of the mechanism of the reactions and of spectral properties has led to a tentative assignment of configuration for the 16-acetyl-16-methyl-17-ketones.