This document discusses the nomenclature and systematic naming conventions for steroid compounds. It outlines the following key points in 3 sentences: Steroid names are designated using systematic IUPAC names rather than trivial names. The document describes the conventions for numbering steroid rings and indicating configuration, functionalization, ring alterations, unsaturation, and other structural features in systematic names. Special prefixes like nor, homo, seco are used to indicate modifications to the steroid core structure according to standardized IUPAC rules.

1. Nomenclature of
steroidsPrepared by
Dr. N.GOPINATHAN
ASSISTANT PROFESSOR
DEPARTMENT OF PHARMACEUTICAL CHEMISTRY
FACULTY OF PHARMACY
SRI RAMACHANDRA UNIVERSITY
CHENNAI-116
TAMILNADU

2. Nomenclature
• Designated by trivial names.
• Discard the names in favor of
systematic names which are
approved by the International
union of pure and applied
Chemistry

3. NUCLEUS AND NUMBERING

4. β
configuration
Substituent
attached to the
ring system
from above are
designated as β
preferably
thickened

5. α
configuration
Substituent
attached to the
ring system
from below
are designated
as α preferably
brokened or
dotted

6. Unknown
configuration
If the configuration
of the substituent
is not known its
bond to the
nucleus is
represented by a
wavy line and it is
indicated by

7. • One should specify
the stereo chemical
configuration of the
steroid

8. If some of the carbon atoms are missing in
steroid, the numbering of the remainder will
not change in order to illustrate the above rules
NORMAL ALTERED
Suppose angular methyl group is absent then also
the numbering wont change

9. If the side chain does not contain a
methylene group. This is indicated by the
prefix NOR preceded by the number of
carbon atom that has disappeared
Mentioned as 21 Nor

10. If the steroid does not contain
angular methyl group this is
again indicated by the prefix
NOR preceded by the number
in designating the methyl group

11. If contraction of ring of a steroid, this is again
indicated by the prefix NOR preceded by a small
capital letter indicating the ring affected
It is mentioned as A nor

12. If the enlargement of the ring of a
steroid this is indicated by the prefix
HOMO precede by a small capital
letter indicating the ring affected
CH3
B-HOMO 5 beta pregnane

13. If ring fission in a steroid with the addition
of a hydrogen atom to each new terminal
group, this is indicated by the numbers
showing the position of the bond broken,
followed by the prefix seco
O
OH
O
OH
2,3 Seco -5 β androstane 2,3 dioic acid

14. If steroid contain a three membered ring, this is
indicated by the prefix cyclo preceded by the
number of positions concerned
CH3
CH3
CH3

15. Due to introduction of the above
mentioned rules of nomenclature, some
names are employed in the earlier
literature have been rejected and replaced
by new names.
Coprostane is now called as 5β chloestane
Iso compounds are now called as cyclo
compounds

16. • Methyl groups are normally present at
C10 and C13.
• Alkyl side chain at C-17
• Sterols-
• OH at C-3

17. If one methyl group is attached
to C-25. It is assigned the
number 26.

18. If both are substituted that carrying the
substituent cites first in the alphabetical
order is assigned the lowest number

19. When the configuration is not
known for one or more centre it is
indicated by greek letter ε prefixed
by the appropriate locant [s]

20. If one of the bridge head
hydrogen atom is replaced it
may be desirable to restate the
stereochemistry
9 α fluro, 5 α pregnane
instead of
9fluro 5 α pregnane

21. 5 α pregnane

22. 5 α Cholane

23. 5 α Cholestane

24. • Unsaturation is indicated by
changing ane to ene if it
contains one double bond,
diene if it contains two double
bond and triene if it has three
double bond.

25. The symbol used to designate a C=C bond
• If C=C is between 4 and 5 referred as
4
• If C=C is between 5 and 10 designated
as 5
• If the double bond is not between
sequentially numbered carbon, both the
carbons are indicated in the name.

26. When an additional ring is formed by
means of direct line between any two
carbon atoms of steroid or attaches side
chain. The name of the steroid is prefixed
by cyclo. This is prefixed by number of
positions of lines given by the new bond.
Greek letter α, β, ε denotes the
configuration associates with new bond
3 α, 5 - cyclo

27. Naturally occuring steroids contain one or more
additional heterocyclic ring fused or attached to
ring D formed by the modification of the side
chain
O
O
Cardenolide-lactone-5
member
Bufanolide – pyranone-6
member

28. • Lengthening of side chain by insertion of
one or more CH2 group indicated by
prefix HOMO

29. Removal of terminal ring with addition of
hydrogen atom at junction where the
adjacent ring is indicated by the prefix DES
followed by italic capital letter designated
the ring
Des A

30. • Alternative application of nor and homo
to the same molecule the abeo system
is used
Abeo

31. The systematic names are based on the stem
name which in turn based on the hydrocarbon
system
Cholestane with 27 carbon
CH3
CH3
CH3
CH3
CH3
Pregnane with 21 carbon
CH3
CH3
CH3

32. CH3
CH3
CH3
Androstane-
carbon 19
Estrane –
carbon 18
Gonane –
carbon 17

33. Stereo chemistry

34. The stereo chemistry of the rings markedly
affects biological activity of a given class of
steroids
There are six asymmetric carbon atoms
5,8,9,10,13,14 in the nucleus.
Therefore 64 optically active forms are
possible

35. • It can exist in two conformations
namely chair form and boat
form.
• Chair conformation is more
stable than boat conformation
due to less angle strain.
• Hence all cyclohexane rings exist
in chair form

36. • Hydrogen or functional groups on the β
side of the molecule are denoted by
solid lines and the α side is denoted by
dotted lines