Chirality of isomers of aldosterone formed in dilute alkali

Abstract

In the presence of dilute alkali at room temperature aldosterone undergoes rearrangement to form 11 beta,18:18,21-diepoxy-20,21-dihydroxy-4-pregnen-3-one (V). X-Ray crystallographic analysis demonstrates that isomers of both 18R, 20S, 21S and 18R, 20S, 21R configuration are formed rather than the 18R, 20R, 21R isomer postulated on the basis of examination of 1H-NMR spectra. The spectra appears to be consistent with the major component of the mixture. The 20S configuration observed is in agreement with the chirality assigned to the degradation product obtained when the same alkaline solution of aldosterone is subjected to reflux. The crystals of (V) are monoclinic P2(1), Z = 4 with a = 20.891(2), b = 6.3848(5), c = 16.067(2)A, beta = 122.09 degrees(1) with two molecules in the asymmetric unit. Molecule A has the 20S,21S configuration and the molecules in the second site are a mixture of the 20S, 21S and 20S, 21R configuration in the ratio of 3:2.

Steroid reactions and partial synthesis

“…The isomerization of aldosterone in dilute alkali has been examined. 68 Diiodosilane has provedG9 to be a useful reagent for the direct reduction of acetals in the presence of unprotected carbonyl groups allowing the partial reduction of steroidal ketones (e.g. 67 + 68).…”