[Scylithe]

Hello. I'm sorry if this is the wrong forum. I opted to post in the Biological Chemistry section, but this question is more to do with synthesis and internal reactions, so I thought I'd put it here.

I'm having some trouble with a particular part of my course. Basically, we're usually given a couple of precursors, and we have to determine disconnections in a given polyketide. Some questions are quite straight forward, especially when it's easy to spot a stray methyl group or something. But the questions are a little harder when there are no obvious indications of where the primer group is located.

If you're confused about what I mean, check out the file I attached. The top reaction shows how Malonyl/Acetyl CoA derivative reacts with itself to form a polyketide, and the second shows what we're expected to be able to deduce from any given polyketide. The colours represent the carbons from the original reactants before they became a chain. The bottom examples are questions where I am unsure of how to determine such disconnections.

Basically, I am unsure of how to properly utilise the information given to me in those boxes.

Any help would be appreciated. I don't expect you to show me how to do all 3 (though that'd be awesome). I really just want to understand the logic in working backwards from any given polyketide. 1 would be enough. I understand the forward reaction, but going backwards really has me stumped.

Thank you.

[orgopete]

Two things here. When I was an undergrad, I had a course that looked at feeding labels to determine the carbon sources and where they ended up. This could be difficult to predict and the actual answer may have been quite different than expected. The point is that probably more than one way to make the connections may work. Given that, I suggest the first step is to write out several of the candidate routes. You may find that none of them are as simple as the connections shown in your example. You will have to try other pieces to contribute.

Secondly, in order for this forum to be useful, posting a link to a scheme that may be dead in the future is not useful. Please add schemes to forum using the "Additional Options" and attach the file.