O=C1C[C@H](c2ccc(O)cc2)Oc2cc(O[C@@H]3O[C@H](CO)[C@@H](O)[C@H](O)[C@H]3O)cc(O[C@@H]3O[C@H](CO)[C@@H](O)[C@H](O)[C@H]3O)c21
A higher negative pKa value denotes a less powerful acid. What is this molecule's negative pKa value?