So we have DCC and Tbock that must be used in this method to basically prevent different types of competing reactions and competing products from actually forming. So in step number one, what we want to do is we want to prepare these amino acids. So by reacting our amino acids, so this molecule here with DCC, we're forming this attachment and that activates this carbon. And we'll see why that's important in just a moment. And by reacting that same amino acid with Tbock, we're essentially adding this entire component onto the nitrogen and that blocks and deactivates this nitrogen. What that means is this nitrogen no longer forms peptide bonds, but this carbon becomes much more likely to form peptide bonds and that will become important in just a moment.