A study of the ester to ether reduction on some cholanate esters
A study of the ester to ether reduction by sodium boro-hydride-boron trifluoride etherate with four different cholinic acid esters was made to test this reduction reaction in the presence of other functional groups. To prepare the esters from 3d-hydroxy-5B-cholan-24-oic acid the 3d-hydroxyl moiety was first protected. This was accomplished by forming the nitrate ester with fuming nitric acid-acetic anhydride. The resulting 5B-cholan-24-oic acid 3d-nitrate was then converted into its acid chloride with oxalyl chloride or thionyl chloride, and from this acid chloride nitrate, the isopropyl, isobutyl, t-butyl, and t-amyl esters were obtained by dissolving it in a mixture of the corresponding alkyl alcohols and pyridine. The resulting esters XXa-d were then reduced catalytically to remove the nitrate moiety. The 3d-hydroxy esters XXIa-d thus obtained were then treated with the sodium borohydride-boron trifluoride etherate reagent. If was found that very little ether was formed and that the major product from each of the esters was 3d, 24-dihydroxy-5B-cholane. A study of the mass spectra of a few of the esters was also made.