CC(=O)O.COc1cc(C)cc2c(-c3c(O)cc(O)c4c3C[C@H](C)N[C@@H]4C)cc(-c3cc(-c4c(O)cc(O)c5c4C[C@H](C)N[C@@H]5C)c4cc(C)cc(OC)c4c3O)c(O)c12
A higher negative pKa value denotes a less powerful acid. What is this molecule's negative pKa value?