Sterol metabolism: XXXIII. On derivation of cholesterol 7-alkoxyl ethers

The facile acid-catalyzed conversion of cholest-5-ene-3 beta, 7 alpha-diol (but not of cholest-5-ene-3 beta, 7 beta-diol) in methanol or ethanol solution to the corresponding 7 alpha-methyl or 7 alpha-ethyl ethers and epimerization of the 7 alpha-alkyl ethers to the corresponding 7 beta-alkyl ethers were established. The epimeric cholest-5-ene-3 beta, 7-diols, their 7-methyl ethers, and their 7-ethyl ethers are readily interconverted in acidified solvents, the quasiequatorial 7 beta-epimer predominating in each case. Both 7 alpha- and 7 beta-alkyl ethers may be encountered as artifacts in analyses of sterol mixtures from mamalian tissues.