[discodermolide]

Do you really understand what is going on in the diagramm?
The reference you will have to get from a university library.

[nick123]

I think so or i have to try... But the question is this the synthesis for omega conopeptides or it is not???

[discodermolide]

It actually looks like a generic scheme for the synthesis of such molecules.

[Arkcon]

You could get it from a university library.  There appear to be several ways to make it.  First of all, this is a peptide, a short protein.  Living things make these all the time, from amino acids.  You could isolate the protein from a large mass of biomaterial -- harvesting a large number of these cone shells, and purifying away everything else.  You could bio-engineer this molecule, by cloning the gene into a simple life form, and harvesting/purifying from that.  One of your papers references this method.  Short peptides, like this one, are also made on a protein synthesizers, using active amino acids, with Fmoc or Boc derivatives.  And you have a reference to that process. 

In either case, a peptide isn't made by adding functional groups to a carbon chain, as we generally do in organic chemistry, but instead one amino acid subunit is built upon another, one at a time.

There is also something functionally similar, but not a peptide, and you have a reference to that as well. 

[discodermolide]

The reference I provided gives the experimental procedure for the disulfide bridge synthesis. You need to find out the difference in Aa sequence between the two condo toxins.

[nick123]

Thanks both of you...

I need an easy way which i can understand either my lecturers, in whom i m gonna make the presantation...

I am really very unhappy for the synthesis of this peptide... I search so many days and i didnt find something special...

I need a picture or a scheme...

I dont know the essential footsteps to make a peptide by myself.. I dont know many things for peptides either...

Thats why i ask for your help... Ιts not that i am boring or i want to spoil your time....

[Arkcon]

Look up how protein synthesizers work.  Try a biochemistry textbook.  They run in cycles, preparing a resin, activating the resin, adding the amino acid they that's needed next, couple it to the resin, and then, rinse the excess reagents away, so the next amino acid can be added to the growing chain.  We can't teach you everything these is to know on this topic one posting at a time.

[Arkcon]

I got the Smiles for this compound, non-cyclised. It's enormous, and it's not quite how I would draw the chirality, here it is, feel free to delete it if it is too large.

Here's an question for you, discodermolide:.  I doubt a sane person would prepare an peptide using organic synthesis instead of via biotechnology.  But suppose, for academic reasons, they just felt like it.  Could they?  Could you build a chain of an amine and a carbons and a carbonyl and an amide and a carbon and a carbonyl and a ..., with or without the appropriate side groups?

[nick123]

Hello again!!! I finally opened the chinese abstract ... here its the full version of the abstract http://www.doc88.com/p-187432926697.html  but is in chinese language!!

Is has a scheme for what i want... take a look



Now how can i explain that?? Could anybody tell me a general route for this synthesis??

[discodermolide]

I got the Smiles for this compound, non-cyclised. It's enormous, and it's not quite how I would draw the chirality, here it is, feel free to delete it if it is too large.

Here's an question for you, discodermolide:.  I doubt a sane person would prepare an peptide using organic synthesis instead of via biotechnology.  But suppose, for academic reasons, they just felt like it.  Could they?  Could you build a chain of an amine and a carbons and a carbonyl and an amide and a carbon and a carbonyl and a ..., with or without the appropriate side groups?

Some people do make peptides that way, usually on a resin and I believe that some very complex ones have been made. One company I know of had a decapeptide in production using resins. The problem with biotechnology is the extraction and purification process, but it is the way to go, no doubt.

[discodermolide]

Coming to your diagrams.
The one on the left is a general one explaining how the achieved an acyl transfer reaction from one amino acid to another. This has been used in the conotoxin synthesis.
The second is the actual synthesis scheme. They start off with a 15 amino-acid fragment protected with 11 protecting groups, then make the tiobenzyl ester.
The next step is removal of all the protection and the acyl transfer and finally cleavage from the resin and cyclisation.
Do you know what the letters stand for, i.e. the sequence CKGKGA……..?
I mean I can draw it for you if you want, but it will take me a while to get it correct.

[nick123]

Yes i think know  ...

So...
In the first step we have the first 15 amino acide sequence with the protecting groups, for example BOC for Lys, Trt for Cys and others... Fmoc is the protecting group for the N terminal of this sequence.

Then we protect the C terminal of the same sequence  with Bzl/DIPCDI and with TFA/Phenol/EDT we remove all the protected groups (except Fmoc group).

In the next step we conjugate the second sequence (10 amino acids) and with perpidine we remove the fmoc group..

And finaly with oxidation we have the disulfide bridges of the peptide...
Is that right?

 But i have some questions here...

1) TFA is the removing group for BOC and Trt i think. Whats the meaning of the Phenol/EDT/thioanisol?

2)The second sequense doesnt need protection groups to his amino acids? Or we conjugate it as is??? Ι try to say... why the first sequence must be protected and the second one no???

3)How do we unprotect the S-Bzl from the C terminal of the first sequence???

[discodermolide]

The second step is the formation of a benzyl ester of the fragment getting it ready for the acyl migration.
Then all the protecting groups are removed except for the Fmoc.
The next step is to carry out the S to N acyl transfer as per the other scheme with the two fragments.
Then piperidine removes the Fmoc and oxidation forms the disulphide bridges.
Questions:
1)The phenol/EDT/Thioanisol are there as radical trappers.
2)try and relate that on the right with that on the left. They carry out a S-N acyl transfer so you have a Sbenzyl ester on onside, along comes a second peptide with a cya on the end, you get an ester exchange and an acyl migration according to the left hand diagram.
3)Answered in 2 above.

[nick123]

I think that i now understand!!! It is like a classic nucleophilic substitution from S to C between those peptides and i like those kind of reactions!!!

But my question remains!!!

Why then do we have to protect the first sequence??? let me try to answer...

Because we need the conjugate ONLY on the C terminal of the first sequence otherwise without protection groups the nucleophilic substitution will happen from S to many carbons of the first sequence...

 Right???

[discodermolide]

Right!
here is my reaction scheme without all the protection. I hope it makes sense.