COc1ccc(C(=O)COC(=O)CCN2C(=O)[C@@H]3[C@@H]4C[C@@H](C(Br)C4Br)[C@@H]3C2=O)cc1
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?