γ‐Lactone‐cis‐annulation to Δ2‐ and Δ3‐ Cholestene.From Δ2‐ and Δ3‐ cholestene the γ‐lactones 11a, 11b, 12a, and 12b are synthesized through the dibromocarbene adducts 3 and 4, the bromohydrines 5 and 6, the oxapiropentanes 7 and 8, and the cyclobutanones 9a, 9b and 10a, 10b, respectively. The 13C‐NMR.‐spectra of 1–8 and 11 as well as the ORD.‐spectra of the cyclobutanones 9 and 10 are reported.
γ‐Lactone‐cis‐annulation to Δ2‐ and Δ3‐ Cholestene.From Δ2‐ and Δ3‐ cholestene the γ‐lactones 11a, 11b, 12a, and 12b are synthesized through the dibromocarbene adducts 3 and 4, the bromohydrines 5 and 6, the oxapiropentanes 7 and 8, and the cyclobutanones 9a, 9b and 10a, 10b, respectively. The 13C‐NMR.‐spectra of 1–8 and 11 as well as the ORD.‐spectra of the cyclobutanones 9 and 10 are reported.