Collect. Czech. Chem. Commun. 1981, 46, 107-117

Preparation and absolute configuration at C(20) of 21-nor-5α-cholan-24→20-olide derivatives

Vladimír Pouzar and Miroslav Havel

Institute of Organic Chemistry and Biochemistry, Czechoslovak Academy of Sciences, 166 10 Prague 6


The lactones X and XI were obtained on reaction of the aldehyde III with lithium salt of methyl propionate followed by hydrogenation of the intermediary esters IV and V. Treatment of the epoxides XXI and XXII with dilithium salt of acetic acid yielded the lactones X and XI. These lactones were also obtained by reaction of the epoxides XXI and XXII with sodium diethyl malonate through intermediates XXIII and XXV. The preparation of α-methylene lactones XXVII and XXVIII is also described. The 20R configuration was established for the lactones X, XXIII and XXVII while the lactones XI, XXV and XXVIII were assigned the 20S configuration both on the basis of 1H-NMR spectra and chemical correlations.