Chemistry Query - Chirality of Cholestrol

Basil_Fawlty

Hi all,

Sorry, I know this board is predominantly for tech queries about pooters, but I'm looking at the structure of cholestrol and can only find one chiral centre, so does that mean that there are two potential enantiomers? I'm a student doing Biochemistry atm. :T Just hit a sticking point though

Here's the structure if anyone's knows about this stuff... (it's the one by "(d)" that's cholestrol)

Thanks hope you can help!!

zincoxide

I know nothing about this but google knows everything!!

[size=-1]www.biochemj.org/bj/imps_x/pdf/BJ20050649.pdf[/size]

Kentish

It's been a few years since I've studied biochem but I've done a quick search on medline and have found a paper by Jiang and Covey, 2002 in J. Org. Chem. which implies that there are indeed only two enantiomers of cholesterol, natural cholesterol (nat-cholesterol) and its enantiomer ent-cholesterol.

Quote from abstract: "For the first time, one of the two enantiomers of cholesterol (ent-cholesterol) has been synthesized by a synthetic route that..."

GreenNotM

kentish .. you just beat me to that ......

mikeyd

Just looked up my organic chemistry textbook and cholesterol has a total of 8 chirality centres which implies a possibility of 2^8 = 256 stereoisomers but most are too strained to exist and only one is found in nature. as detailed above

hardpressed

What's all this about, is it a secret code, have the Martians landed?
Sorry, I'm just thick.

Basil_Fawlty

Thanks for your help everyone! :T Really appreciate it!

Hardpressed, don't worry, aliens haven't landed. Unless one of them is teaching me, which I'm prepared to believe. I have just watched two X-Files... :rotfl:

mikeyd wrote:

Just looked up my organic chemistry textbook and cholesterol has a total of 8 chirality centres which implies a possibility of 2^8 = 256 stereoisomers but most are too strained to exist and only one is found in nature. as detailed above

Ah... I found out that there are indeed two enantiomers, ent and nat, but my friend came in and said that he'd found 8 chiral centres whereas I've only found one

Which chemistry book are you looking at?? We need to find the "theoretical number of enantiomers". I'm not the best chemist the world has ever seen but I do try!! I'm more into the medical effects of various substances...

adamuk_2

Bruice, Paula Yurkanis, 1941-. - Organic chemistry. - 3rd ed. - Upper Saddle River, N.J. : Prentice Hall, 2001. - 0130178586

In Chapter 4 problem 20 it asks the same question posed by yourself.
Although it doesnt give a diagram of chiral centres it does state that there are 8 chiral centres therefore a total of 256 theoretical stereoisomers but only one exists naturally.

mikeyd

Organic Chemistry by McMurry 5th Edition - P325 states:
"In general, a molecule with n chirality centres has a maximum of 2^n stereoisomers, or 2^(n-1) pairs of enatiomers"

It then uses cholesterol as an example and has marked the eight chirality centres on the picture of the molecule.

Basil_Fawlty

mikeyd wrote:

Organic Chemistry by McMurry 5th Edition - P325 states:
"In general, a molecule with n chirality centres has a maximum of 2^n stereoisomers, or 2^(n-1) pairs of enatiomers"

It then uses cholesterol as an example and has marked the eight chirality centres on the picture of the molecule.

Fantastic, Thanks so much!! :T Just popped over to the library, found the book and the diagram!

I'm not just going to copy the diagram though, I will understand why each one is chiral, because it's a simple concept and I need to understand it.

Cheers all of you! :beer: :T :cool:

spaceage :j