COc1cc(NC(=O)C2CCN(C(=O)C3CC(=O)N(c4ccc(C)cc4)C3)CC2)cc(OC)c1OC
An acid's negative base-10 logarithmic dissociation constant (pka) follows directly from its underlying thermodynamics; pKa is directly proportional to its standard Gibbs free energy change. What is the pka value of this molecule?