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Steroidal Nomenclature

Joe Canadian

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The Basics of Structural Diagrams

By: HenryV

It's so much easier to understand the nomenclature of steroids, if you first understand a little about the structural diagrams. This will help you to picture the steroid in your head, from the nomenclature. In order to achieve this, however, we'll need to learn a few new terms.

Lets start by introducing you to the steroid numbering and lettering conventions. In order that when the name of a steroid is written down, everyone agrees what that name refers to, certain conventions have to be adhered to. Each steroid is made up of four rings of carbon atoms, and each ring is given a letter. Each carbon atom in the steroid has a number, and everyone agrees which atom the numbers apply to, and which ring the letters apply to.



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The letters aren't used much, but most of the structural differences you will find between the prohormones and designer steroids are found in the A-ring. The numbers are much more important. Every time a steroid says a number in the nomenclature, it is to alert you that something is going on with the carbon atom at that position, identified in the key above.

Lets take a look at the structural diagram for testosterone:


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The nomenclature for testosterone can be written as 17b-Hydroxyandrost-4-en-3-one. Lets break that up into it's constituent parts.
17b-hydroxy
androst
4-en (or 4-ene)
3-one

Now look at testosterone again, with a few of the carbon atoms numbered as per the key:


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From this, we can deduce that
17b-hydroxy means that "OH" thing attached at the top right hand corner, at carbon 17
4-en (or 4-ene) means the line inside the A-ring that goes from carbon 4 to carbon 5
and 3-one means the "O" attachment in the bottom left hand corner, at carbon number 3.
androst is just a general description of the type of steroid we're looking at - an androgen.

So we've already worked out that "hydroxy" is represented by "OH" on the diagram. A hydroxyl group is sometimes written as "ol" in the nomenclature (so you may see "17b-ol", and it means the same thing). This is simply a functional group (an attachment) made up of a hydrogen atom and an oxygen atom (hence hydr-oxy).
If a compound has two hydroxyl groups, it is known as a "diol" (di meaning two, and ol is short for alcohol).

"4-ene" is indicated by that second line that joins carbons 4 and 5. This is a double bond. Ene is short for alkene. If something is described as a "1-ene" (like M1T, for example) the double bond connects carbons number 1 and 2. A "4-ene" (like testosterone) indicates a double-bond connection between carbons 4 and 5. A "5-ene" (like DHEA) is where carbons 5 and 6 are double-bonded. Simples.

"3-one" is that thing in the bottom left that looks like =O. It's simply an oxygen atom attached to the steroid A-ring at carbon position 3. The term "one" is not the number 1, it is actually short for "ketone", which is the proper term for a compound containing this carbonyl group.

Things to remember
"one" describes an oxygen atom, which is shown on diagrams as =O.
"ol" or "hydroxy" describes an oxygen atom and hydrogen atom attached to the steroid and drawn as "OH" (for Oxygen and Hydrogen).
"ene" means a double bond, joining whatever carbon is mentioned, and the next carbon along together. This is drawn as a double-line between the two carbon atoms =.
Any number written in the nomenclature is an indication of where on the steroid that thing is, for which you'll have to refer to the key above until you learn exactly where they are.
 

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Joe Canadian

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Methyl groups

I remember hearing the word "methyl" and "methylated" when I first started researching prohormones, and not really understanding what it meant. I understood that methylation was associated with stronger drugs, as well as liver damage, so I assumed that methylation must mean some kind of nasty chemical treatment that enhanced the power of the drug, but also made it somewhat poisonous. This is really doing something of a disservice to the methyl group, which is not (in and of itself) harmful at all.

A methyl group is actually a fairly simple naturally-occuring functional group, made up of one carbon atom and three hydrogen atoms (written as CH3). This group can be attached at a number of different positions on the sterane nucleus (the steroid's carbon rings).

Lets take another look at that image of testosterone:


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You see those two thick black vertical lines coming off the top of the steroid at positions 10 and 13? (refer to the key above if you're confused about those positions). Those are methyl groups. If you really wanted, you could describe testosterone as "10,13-dimethyl" because it has those methyl groups (don't believe me? check out the systematic name for testosterone on wikipedia, under the structural diagram).

The thing is, all steroids of this class (androstanes) have those methyl groups, so we just need to say "androsta" and everyone knows they are there. Lets take a look at a more detailed numbering diagram:



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The two numbers I'll draw your attention to are #18 and #19. These numbers indicate the two carbon atoms in the two methyl groups we previously discussed, attached at positions 13 and 10 respectively.

Now consider that estranes (estrogens) differ from androgens because of that #19 carbon - they don't have it. This is why they are described as "19-nor" (meaning carbon 19 is absent). This also explains why in the PH tren, "estra" (short for estrane) can be interchanged with "19-nor".

So methyls aren't bad?
That depends where you put them. When a prohormone or DS is described as "methylated", it usually means 17a-methylated. A methyl group at this position protects the previously mentioned 17b-hydroxy from being metabolised (oxidised) to a ketone, which would effectively deactivate the steroid. The 17b-hydroxy is the most important factor affecting androgen receptor binding - if it has one, it will probably bind, if it doesn't have one it wont. So protecting the 17b-hydroxy helps to prevent the steroid from being deactivated in the liver, which in turn makes it much more bioavailable by oral administration. This difficulty in deactivating the drug is also responsible for the stress caused to the liver (though non-methyls can also be liver toxic for the same reason - the liver finds it difficult to convert them to an excretable form).
 

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Joe Canadian

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Steroids in 3D

So far we've been looking at the compounds as flat, two-dimensional representations on paper (or the screen). The reality is that they aren't really flat, but we can't draw (easily) in 3D.

If we continue to use the example of testosterone, instead of the simplified structural diagrams we've used so far, a more accurate representation would look like this:


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Far too complicated to be practical. Nevertheless, we need to take into account that the steroid is not flat. Lets start by looking at the way in which the atoms join together.

Carbon can join together with up to four other atoms. Each of these will typically be as far away from the others as possible. This puts the carbon atom in the middle of a kind of pyramid shape, surrounded on all sides by other atoms it's joined to.


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Enough of testosterone, lets look at methyl testosterone. As previously discussed, a methyl group at 17a protects the hydroxyl group at 17b. But what do these letters a and b mean?


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Look closely at carbon 17, and how it's connected to carbons 13 and 16. If we assume that to be a flat plane, then the other two connections it has - to the methyl group (the dotted line) and the hydroxyl (the thick line with OH) - must be above and below the plane of the drawing. If that doesn't make a lot of sense, I'll illustrate it by labelling the carbon "pyramid".

4uubvb.jpg


Hopefully this illustrates that, relative to the carbons C16, 17, and 13, the hydroxyl (OH) is pointing "up". We call this the "beta" position, where something is coming up off the page towards the viewer, and the methyl (CH3) at the "alpha" position is going down, away from the viewer. "Alpha" position bonds are shown as a dotted line, like the one showing the methyl group on the diagram of methyl testosterone. Groups attached at the "beta" position are shown with a solid line, like the OH on the methyl test diagram.

Here's another diagram of testosterone, this one showing the 3-dimensional nature a little clearer.

http://i53.tinypic.com/oqwvpu.jpg
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The important thing to understand is that "beta" = "up" in relation to the steroid and is drawn with a solid line, and "alpha" is "down" and is drawn with a dotted line.

Structural images from Anabolenboek, Willem Koert
 

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Joe Canadian

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I know that some of the images are not displaying properly, I do not know why. I will ask a staff member to look into it.
 

P.S.

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Very interesting....Thanks for the post/thread. I decided to "stick" this thread as it's a good learning tool.
 

Mr. Burns

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very informative. you stated earlier 'when you first started researching pro-hormones', do you mean you learned about chemistry all on your own? if so, that's very impressive. I'm assuming this is organic chemistry right?
 

djm6464

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henry and pat arnold are close via phf and prototype
 

Bigbus

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Monsanto should get into the AAS game, they have been designing gmo crops for years, might as well get into designer steroids.
 

CrazyLoop

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Very interesting thread, normally hate chemistry but this wasnt too bad
 

objective33

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Extremely interesting read. Nice to see some more in depth information on the substances we are injecting into our bodies.
 

zoidberg22

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Thanks for the post! Takes me back to biochemistry class. Super interesting!

Sent from my HTC One M9 using Tapatalk
 
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Bstatic

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Can someone please reupload all the pictures?
 
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