CC(C)CC(NC(=O)OC(C)(C)C)c1cn([C@@H](CCC(=O)OC(C)(C)C)C(=O)N2CCN(C(=O)OC(C)(C)C)CC2)nn1
The electronegative atoms usually involved in hydrogen bonding are oxygen, nitrogen and fluorine. How many hydrogen bond acceptors does the molecule contain?