[{"from": "human", "value": "Provide a brief overview of this molecule. [C][=N][C][=C][Branch1][=N][N][Ring1][Branch1][C][C][C][Branch1][Ring1][C][O][C][O][N][=C][Branch1][=Branch1][N][C][Ring1][=C][=O][N]"}, {"from": "gpt", "value": "The molecule is a synthetic acyclic guanine derivative with antiviral activity used for the treatment of various herpes simplex virus (HSV) infections. Displaying low toxicity and good selectivity, penciclovir is a nucleoside analogue."}]