Stereochemical Definitions and Nomenclature: Changing Signs?

Abstract

Classification of chirality rests on the elements of asymmetry, a concept theoretically questionable, but useful. In chemistry, the Cahn, Ingold, Prelog (CIP) Convention is well-established, generally accepted, and applied. It introduced the R- and S- prefixes to be applied before the names of compounds involving a single asymmetry element, or the M- and P- prefixes for helical asymmetry. For molecules involving multiple elements of asymmetry, the prefixes were complementary with reference to the exact location and should be distinctively applied to each element. If the same system were applied to international nonproprietary (generic) drug names, awkward notations would result. To this end, the SIGNS nomenclature was proposed. In practice, neither of the stereochemical systems is applied, leading to a high degree of ignorance about the number and quality of the pharmacological entities implied by common drug names.