COC(=O)C1=C(C(=O)OC)SC2(S1)C(C(=O)OC)=C(C(=O)OC)Sc1c2ssc1=O
Molecules with a polar surface area of greater than 140 angstroms squared (Å2) tend to be poor at permeating cell membranes. What's the psa of this molecule?