Nomenclature of steroids

Here is a short an detailed explanation on nomenclature of steroids for pharmacy students. It includes all the points necessary for the topic along with an example for better understanding

1. NOMENCLATURE OF STEROIDS By: Shruti Mistry Student of BPharm sem-5 SSSPC, Zundal

2. INTRODUCTION Steroids are a unique class of chemical compounds found widely in the animal and plant kingdom. They are biologically active organic compound with four rings arranged in a specific molecular configuration. They both occur naturally and man-made versions.

3. NOMENCLATURE OF STEROIDS Steroids are characterized by the presence of cyclopentanoperhydrophenanthrene nucleus in their structure OR it is also known as “Gonane” ring..
The core structure is composed of 17 C-atoms, bonded in 4 fused rings:
1. Three 6-membered cyclohexane rings,
i.e. Phenanthrene ring (A,B,C)
2. One 5-membered cyclopentane ring (D)

4. Almost all steroids are derivatives having 17 to 27 C-atoms in their structure. There are mostly 5 types of rings in steroids: Gonane : structure with 17 C-atoms Estrane : structure with 18 C-atoms Androstane : structure with 19 C-atoms Pregnane : structure with 21 C-atoms Cholestane : structure with 27 C-atoms

5. β configuration : Substituent attached to the ring system from above the plane are designated as β configuration. They are denoted by a solid line. α configuration: Substituent attached to the ring system from below the plane are designated as α configuration. They are denoted by a broken or dotted line. Unknown configuration: If the configuration of the substituent is not known its bond to the nucleus is represented by a wavy line.

6. In case of presence of double bond present in the 6-membered ring, it will be indicated by the symbol “∆” or the least number of presence of double bond, eg: 3-ene, 4-ene. Apart from the 17C ring, there is presence of methyl groups at position 10, 13 and alkyl side chain at position 17 . There is substitution of oxygen containing functional groups (mainly –OH and C=0) at position 3, 11, 17, 20, 21.

7. If there is contr a ction of ring of a steroid, this is indicated by the prefix NOR preceded by a capital letter indicating the ring affected. If there is enlargement of the ring of a steroid, this is indicated by the prefix HOMO preceded by a capital letter indicating the ring affected. A- NOR B-HOMO 5 β pregnane

8. IUPAC Nomenclature The naming begins with –OH group present on the steroidal moiety above or below the plane, eg: 17β- hydroxy. It is followed by the name of core ring, eg: Androstane If the ring consists of double bonds, the least number of C-atom having double bond is written after the name of core ring, eg: 3-ene At last, it is concluded by the ketone group present on the steroidal ring, eg: 3-one. Example: Testosterone IUPAC name: 17 β-hydroxyandrost-4-en-3-one

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