27-Hydroxycholesterol, does it exist? On the nomenclature and stereochemistry of 26-hydroxylated sterols.

Significant ambiguity exists in the scientific community with regard to the nomenclature of 26-hydroxylated oxysterols. Oxysterols constitute an important class of compounds that have biological roles in the regulation of cholesterol synthesis and as endogenous selective estrogen receptor modulators (SERMs). The ambiguity is attributable to deviations from clearly stated IUPAC rules and is likely to increase as more biologically active oxysterols are identified. This review provides a uniform approach to the naming of 26-hydroxylated sterols for those of current interest and for those on the horizon such as oxysterols of lanosterol that retain the unsaturation at C-24 and C-25 such as (E)-26-hydroxylanosterol. Using this molecule as a starting point, this review hopes to establish a common language to keep all investigators on the same page.