Vero and HEp-2 cells were cultured in Dulbecco's modified Eagle's medium (Thermo Fisher Scientific) supplemented with 10% fetal bovine serum (FBS), 1% penicillin/streptomycin, and 1% GlutaMAX and were cultured at 37 °C with 5% CO 2 . Working stocks of rRSV-A-0594-EGFP, a recombinant respiratory syncytial virus (RSV) strain based on a contemporary subtype A strain, were generated, and titrated on HEp-2 cells as previously described. Presatovir (GS-5806) was purchased from MedChemExpress and has been previously shown to act as an RSV fusion inhibitor. In a round-bottom flask, geranylated acetyl phloroglucinol 13 (17.8 g, 51.4 mmol, 1.0 equiv.)