Steroid nitrogen compounds. I. Synthesis, structure, and properties of methyl 3α,7α-diacetoxy-11α-chloro-12α-nitro-5β-cholanoate

The reaction between methyl 3α,7α-diacetoxy-5β-chol-11-enoate (I) and nitrosyl chloride is shown to give methyl 3α,7α-diacetoxy-11α-chloro-12α-nitro-5β-cholanoate (III) in moderate yield. In the presence of nitrogen dioxide the nitro-chloride III is formed rapidly, probably by a free radical mechanism. On treatment of III with zinc dust in acetic acid, chloro and nitro groups are expelled to regenerate the 11-ene in good yield. In contrast with 5α-chloro-6β-nitro steroids the cis nitro-chloride shows remarkable resistance towards dehydrochlorination, and treatment with refluxing γ-collidine affords only the starting nitro-chloride unchanged. The action of sodium carbonate on III yields 3α-hydroxy-7α-acetoxy-11α-chloro-12α-nitro-5β-cholanoic acid (IV), the chloro nitro moiety being unattacked. The methyl ester V and the acetate VI of IV, and the 3-one VII derived from V are described. The stereochemistry of the nitro-chloride, III, was confirmed by a detailed X-ray crystallographic structure analysis, the results of this analysis being described in detail.