STEROIDS

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STEROIDS:

STEROIDS Prepared by Jisha Shamsudeen Mpharm Part 1

Contents:

Contents Introduction Properties Nomenclature of Steroids Stereochemistry of Steroids Conclusion References

Introduction:

Introduction Steroids are the members of a large class of organic compounds occuring widely in plants and animals Steroids are characterised by the presence of 1,2 cyclopenteno phenanthrene nucleus in their structure

1,2 cyclo pentenophenanthrene nucleus:

1,2 cyclo pentenophenanthrene nucleus

Source of Steroids:

Source of Steroids Vitamin D Bile acids Adrenal Cortical and Sex hormones Cardioactive lactones Sapogenins Certain alkaloids and antibiotics

Definition of Steroid:

Definition of Steroid Steroid may be defined as a compound which yields Diel’s hydrocarbon when distilled with Selenium .

Definition of Steroid:

Definition of Steroid If Steroids are distilled with Selenium at 420 degree celsius , chrysene is produced and a small amount of picene . Chrysene Picene

Properties of Steroids:

Properties of Steroids They have relatively flat and rigid molecular framework They have high crystalline properties Enormous number of derivatives have been prepared

Steroid based drugs in use today:

Steroid based drugs in use today Male Sex Hormone Female Sex Hormone Anti-inflammatory Agent

Nomenclature of Steroids:

Nomenclature of Steroids General Structure of Steroid is as follows

Orientation of Projection Formula:

Orientation of Projection Formula When the rings of a steroid are oriented o nto the plane of a paper, the formula is nor mally oriented as shown below: Substituents attached to ring system from above the plane are designated as β ( thick lines) Substituents attached to ring system from below the plane are designated as α ( dotted lines) If the configuration of the substituent is not known, the bond to the nucleus is depicted by a wavy line .

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Some examples of steroids are as follows 5( α or β ) oestrane 5( α or β ) gonane

Rules for naming of steroids:

Rules for naming of steroids If the sidechain does not contain a methylene group, it is indicated by prefix “ nor” preceeded by the number of carbon atoms that has disappeared

NOMENCLATURE OF STEROIDS:

NOMENCLATURE OF STEROIDS If the steroid does not contain angular methyl group, it is indicated by prefix “ nor”preceeded by the number designating the methyl group

Nomenclature of steroids:

Nomenclature of steroids If there occurs a contraction of the ring of a steroid, this is indicated by prefix ‘nor preceeded by a small capital letter indicating the ring affected.

Nomenclature of steroids:

Nomenclature of steroids Enlargement of a ring of steroid, indicated by prefix ‘ homo’ preceeded by a small capital letter indicating the ring affected

Stereochemistry of steroids:

Stereochemistry of steroids 8 dissimilar chiral centres Dissimilar centres are 3, 5,8,9,10,13& 14 No of possible isomers are 256 If chiral centre in carbon 20 is taken into consideration , there would be 512 isomers.

Stereochemistry of Steroids:

Stereochemistry of Steroids Stereochemistry of steroid is defined in terms of the following: Ring fusion of the steroids Configuration of substituent groups

Stereochemistry of steroids:

Stereochemistry of steroids Ring A-B Cis fusion Ring C-D Trans fusion

Evidence……:

Evidence…… Oxidative degradation method gives a great deal for the stereochemistry of the nucleus Windaus synthesized four isomeric acids namely… Lithobilianic acid Allolithobilianic acid Isolithobilianic acid Alloisolithobilianic acid

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Lithobilianic and allolithobilianic acid on heating provided pyrolithobilianic acid

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Clemmenson reduction of both pyrolithobilianic acid and pyroallolithobilianic acid gave deoxypyroacid . Pyrolithobilianic acid possess cis configuration. This is supported by the fact that two carbonyl groups are present in cis position, cyclisation will take place. In case of allolithobilianic acid, it does not give deoxypyroacid , inversion at C5 has occured

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Lithobilianic acid and isolithobilianic acid can be prepared from natural bile acids, lithocholic acid and so all have same cis A/B configuration These acids are prepared from 5 b cholestane, this compound also have cis A/B fusion.

Ring fusion OF B AND C:

Ring fusion OF B AND C X ray analysis Steroid nucleus is long and thin Rings b and C fused in trans manner

Ring fusion of c and d:

Ring fusion of c and d Wieland et al show that rings C/D HAVE TRANS FUSION in sterols and bile acids. Degradation of deoxycholic acid did not give an anhydride readily It was obtained readily after heating in vaccuo and after hydrolysis formed the next product. Thus the anhydride and the intermediate must have cis configuration so the ringd C and D must have trans configuration Trans C/D fusion occur in most steroids including bileacids except cardiac glycosides and toad poison, where fusion is cis ..

Reference:

Reference Organic Chemistry volume 2 : Stereochemistry and the Chemistry of Natural Products Fifth Edition: IL Finar Organic Chemistry of Natural Products by Gurdeep . R Chatwal , Vol 2

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