COC(=O)[C@@H](NC1(c2ccccc2)c2ccccc2-c2ccccc21)[C@H](OC(=O)[C@H]1CCCN1S(=O)(=O)c1ccccc1)C(=O)OC
Hydrogen bond acceptor is the chemical compound which contains the lone electron pairs that participate in the hydrogen bond formation. How many hydrogen bond acceptors does the molecule contain?