isoxazolyl

adjective

is·​ox·​az·​o·​lyl (ˌ)īs-ˌäk-ˈsaz-ə-ˌlil 

: relating to or being any of a group of semisynthetic penicillins (as oxacillin and cloxacillin) that are resistant to beta-lactamase, stable in acids, and active against gram-positive bacteria