O=S1(=O)C[C@@H](N2CCC(Cc3ccccc3)CC2)[C@H](COCc2ccccc2)N1
The negative base-10 logarithmic of dissociation constant (pka) for an acid is a direct consequence of the underlying thermodynamics of the dissociation reaction; the pKa value is directly proportional to the standard Gibbs free energy change for the reaction. What is the pka value of this molecule?