Human Biochemistry Volume 2 - Murray R. 1993

Biochemistry of Intra- and Intercellular Communication
Adrenocortical Hormones
Nomenclature and Chemistry of Steroids

All Steroid Hormones are based on the 17-carbon cyclopentanoperhydrophenanthrene ring system, which comprises four rings designated as A, B, C, and D (Fig. 48.1). Additional carbon atoms may be attached at positions 10 and 13 or, as a side chain, at C-17. Steroid hormones, their metabolites, and precursors vary in the number and type of substituents, the number and position of double bonds, and their stereochemical configuration. A precise nomenclature has been established to designate all these compounds. Asymmetric carbon atoms (highlighted with hatching in Fig. 48.1) determine the potential for stereoisomerism. The angular methyl groups (C-19 and C-18 at positions 10 and 13) are located above the plane of the ring system and serve as the reference point for determining the spatial orientation of stereoisomers. Thus, substituents at positions on the core Structure that project onto the same plane as these groups are designated as cis or "ß" and are represented in figures by solid lines. Substituents located behind the plane of the ring system are designated as trans or "a" and are represented by dashed lines. The positions of double bonds are indicated by the number of the preceding carbon atom (e.g., ∆³, ∆⁴). The names of steroid hormones depend on whether they contain a single angular methyl group (estrane, 18 carbon atoms), two angular methyl groups (androstane, 19 carbon atoms), or two angular groups plus a two-carbon side chain at C-17 (pregnane, 21 carbon atoms). Using this information, along with the glossary provided in Table 48.1, one can decipher the chemical names of the natural and synthetic Steroids listed in Table 48.2.

Class="center">Table 48.1. Steroid Nomenclature

Table 48.2. Trivial and Chemical Names of Selected Steroids