This document provides an overview of steroids, including their core structure, nomenclature, stereochemistry, and classification. Steroids contain a 17 carbon core arranged in four fused rings. They are named based on this core structure and functional groups. Steroids can have 64 possible stereoisomers due to the asymmetric carbons in the core. They are classified into groups including sterols, sex hormones, cardiac glycosides, and bile acids based on the functional groups on the R group. Cholesterol is an important animal sterol that is a precursor to vitamins and hormones.

1. STEROIDS
PREAPRED BY : AZMIN MOGAL (M PHARM; SEM -1)
GUIDED BY : Mr. STEPHENAVVARU(Ph.d SCHOLER)
DEPARTMENT: PHARMACEUTICALCHEMISTRY

2. INTRODUCTION
 A steroid is an organic compound with
four rings arranged in a specific molecular
configuration.
 The steroid core structure is composed of
seventeen carbon atoms(17), bonded in
four "fused" rings.
 Three six-member cyclohexane rings
(rings A , B and C in the first illustration)
and one five-member cyclopentane ring
(the D ring). Steroids vary by the
functional groups attached to this four-
ring core and by the oxidation state of the
rings.
Cyclopentanoperhydrophenanthrene ring

3. NOMANCLATURE
Almost all steroids are named as derivatives of any one of the following basic steroidal ring.
1. 5 (α or β) gonane
(C =17)
2. 5 (α or β) estrane
(C=18)

4. 3. 5 (α or β) andrastane
(C=19)
4. 5 (α or β) pregnane
(C=21)

5. 5. 5 (α or β) cholestane
(C=27)
 Solid line indicate groups above the plane of the nucleus (β-configuration) and dotted line
denote groups below the plane (α- configuration).
 The configuration of the hydrogen (-H) at C-5 position is always indicate in the name.
 Compounds with 5-α cholestrane belongs to the ‘allo series’ while compounds derived
from the 5-β-cholestane belongs to the ‘normal series’.
 If the double bond is not between sequencely numbered carbon, in that case both carbons
are indicated in the name.

6.  The symbol Δ(delta) is used to indicate C=C bond in steroids.
 When a methyl group is missing from the side chain , these is indicated by the prefix ‘nor’
with the number of the carbon atom which are disappear.
Δ - Androstane
5

7. STEREOCHEMISTRY OF STEROIDS
■ There are six asymmetric carbon atoms 5,8,9,10,13,14 in the nucleus, therefore 64 optically
active forms are possible.
■ Cholestane , enfrostane and pregnane exist in two conformations:
1. chair form
2. boat form
5-α-cholestane

8. ■ Chair form is more stable then boat form due to less angle strength , therefore all
cyclohexane ring in steroid nucleus exist in the chair form.
■ The absolute stereochemistry of the molecule and any substituents is shown with solid
bond (β-configuration) and dotted bond (α-configuration).
■ The aliphatic side chain at C-17 position is always assumed to be β- configuration.
■ The term cis and trans are sometimes used to indicate the backbone stereochemistry
between the rings .
example; 5-α- steroid are A/BTRANS.
5-β- steroids are A/B CIS.
5-α-Steroid
A/B trans
5-β-Steroid
A/B cis

9. ■ If A/B fusion cis and trans both position possible or position is unknown ,it is indicated
by waving lines/bonds.
trans/cis

10. R

11. CLASSIFICATION OF STEROIDS
1. Sterols:- where R is an aliphatic side chain.They contain usually one or
more hydroxyl groups(-OH) attached in alicyclic linkage
2. Sex Hormones:- where R bears a ketonic (C=O) or hydroxyl group(-OH) and mostly
possess a two carbon side chain
3.Cardiac Glycoside :where R is a lactone ring.The gylcosides also contains sugars
linlked through oxygen in other parts of the molecule. Normally on hydrolysis it yields
this sugar together with cardiac aglycon.
4. Bile Acids :- where R is essentially a five-carbon side chain ending with a
carboxylic acid moiety
5.Sapogenins :- where R contains an oxacyclic (etheral) ring system.

12. cholesterol
sterol Sex hormone
Cardiac glycoside
Bile acids
Sapogenin

13. STEROL & ITS CHEMISTRY
■ Sterols is also known as steroid alcohols, are a subgroup of the steroids and an
important class of organic molecules.
■ They occur naturally in plants, animals, and fungi, with the most familiar type of
animal sterol being cholesterol. Cholesterol is vital to animal cell membrane
structure and function and a precursor to fat-soluble vitamins and steroid
hormones.
Sterol chemical structure

14. ■ Sterol is divided into three classes :
1. Zoosterol : sterol which is obtained from animal origin.
Example; Cholesterol
2. Phytosterol: derived from the plant source. Example; Sitosterol
3. Mycosterol : obtained from fungi such as yeast. Example; Ergosterol
- Sitosterol
Cholesterol
β