Synthesis of (20R,25R)-Cholest-5-ene-3β,26-diol and the Occurence of Base-Catalyzed 1,5-Hydride Shift in a Steroidal 1,5-Ketol

Article abstract of DOI:10.1021/jo00213a031

Details are presented for the preparation of (20R,25R)-cholest-5-ene-3β,26-diol (2, "26-hydroxycholesterol").Kryptogenin diacetate (8) was converted to 2 in 39percent yield by successive removal of the C-16 and C-22 carbonyl functions (cycloethylene dithioketal formation followed by Raney nickel desulfurization). 22-Oxocholest-5-ene-3β,26-diol (17) was shown to be an intermediate in a previous preparation of 2, and it was shown to be a source of C-25 epimerization and byproducts in that procedure.The products seen in the Wolf-Kishner reduction of 17 are explained by base-catalyzed equalibration of 17 with 26-xocholest-5-ene-3β,22-diol (23).This equilibration by base-catalysed 1,5-hydride shift was demonstrated by deuterium labelling. 13C and 1H NMR correlations were developed for the above compounds.