COC(=O)C(Cc1c[nH]c2ccccc12)NC(=O)C(Cc1c[nH]c2ccccc12)NC(=O)C(Cc1c[nH]c2ccccc12)NC(=O)OC(C)(C)C
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?