The name/synonym for ligand PNN (curated from ChEBI, PubChem, and PDB databases):

1BENZYLPENICILLIN
22,2-DIMETHYL-6BETA-(PHENYLACETAMIDO)PENAM-3ALPHA-CARBOXYLIC ACID
3(2S,5R,6R)-3,3-DIMETHYL-7-OXO-6-(PHENYLACETAMIDO)-4-THIA-1-AZABICYCLO[3.2.0]HEPTANE-2-CARBOXYLIC ACID
4PG
5BENZYLPENICILLINIC ACID
66-(2-PHENYLACETAMIDO)PENICILLANIC ACID
7FREE PENICILLIN II
8PENICILLIN G