So next in step three, we deprotect the nitrogen by removing our Tbock and we mix this molecule with a dilute acid. So for example, we have triflora acetic acid. So CF three, COOH if we mix this with this molecule, we essentially remove our TBA group. And so what that does is now in step four, if we mix this molecule here with this molecule here, this carbon will be activated to form a peptide bond by the DCC molecule. And because this nitrogen will be missing that Tbag group, it will be very likely to form that peptide bond. And this nitrogen, because we still have the Tbock attached here, it will not be reactive at all.