O=C(N[C@@H](c1ccccc1)[C@@H](O)C(=O)OCc1ccc2c(c1)OCO2)c1ccccc1
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?