[fragmented3]

In class, we learned about claisen condensation of dicarbonyl compounds. My professor asked a question about claisen condensation applied to polyketide synthases, specifically, that of Erythronolide B. I have no clue how to answer this question, but I have gotten somewhere with my research..

The question was: How does the Claisen Condensation reaction proceed without a strong base in a cell, and why does nature select thioesters instead of esters for the transformation

My answer is: Thioesters are more reactive than esters because of the double bond between sulfur and carbon. Since sulfur is a row 3 compound, the sizing between the carbon and sulfur is very different than that of carbon and oxygen, therefore, it is not as stabilized as a double bonded oxygen to carbon, making the alpha proton more acidic. As for why the claisen condensation proceeds without a strong base in a cell, I'm not sure how to answer that

Any help would be appreciated, thank you!

[hollytara]

You may have answered your own question - if the hydrogens are more acidic, do you need as strong of a base? 

And there are some reasonable strong bases in a cell - like the guanidine of arginine

[fragmented3]

Ohh I see, so, if I'm getting this right, the thiosulfates inside the cell drives and catalyzes the claisen condensation. Is my reasoning correct? (this is for extra credit points hehe)