C[C@@H]1[C@H]2C3=CC[C@@H]4[C@@]5(C)C[C@@H](O)[C@H](O)[C@@](C)(CO)[C@@H]5CC[C@@]4(C)[C@]3(C)CC[C@@]2(C=O)CC[C@H]1C
A higher negative pKa value denotes a less powerful acid. What is this molecule's negative pKa value?