Synthesis of Hydroxy Acids of Dinorcholane and 5β-Cholane

Enantiopure α-hydroxy acids (AHAs) are versatile building blocks in organic synthesis. They are used for obtaining pharmaceutically and biologically active substances, such as vitamins. α-Hydroxy acids are easily synthesized from cyanohydrins. Thus, molecules with cyanohydrin substructures are interesting intermediates for the synthesis of AHAs. Usually, cyanohydrins are prepared by the addition of a cyanide group to the carbonyl carbon of aldehydes or ketones resulting in enantiomeric mixtures of optically active cyanohydrins when aldehydes or asymmetric ketones are employed. However, if a chiral centre already exists next to the carbonyl carbon, two possible diastereomeric products are formed, and they are not of equal amounts. As part of our on-going studies on the synthesis and reactions of steroid monomers and dimers, we now report on the development of a convenient and general method for the synthesis of diasteriomerc (55:45) dinorcholane hydroxy acids and 5β-cholane hydroxy acid using readily available dinorcholanal and 5β-cholane3α,24-diol as the starting materials. Results and Discussion