COc1ccc(-c2coc3ccc(O[C@@H]4O[C@@H](COC(C)=O)[C@@H](OC(C)=O)[C@@H](OC(C)=O)[C@H]4OC(C)=O)cc3c2=O)cc1
PSA is a commonly used medicinal chemistry metric for the optimization of a drug's ability to permeate cells. Please predict psa of this molecule.