<unk>  is a pivaloyloxymethyl ester of ampicillin. It is a prodrug, which is thought to enhance the oral bioavailability of ampicillin because of its greater lipophilicity compared to that of ampicillin.
Pivampicillin
Plicamycin
Hetacillin
Clindamycin hydrochloride 
Vancomycin 
Temocillin
Amoxicillin
Trovafloxacin mesylate