Considering the predictable low radiochemical yield (RCY) for Cu-mediated aromatic 18 F-fluorination of benzoxazoles , we also evaluated benzothiazole 1f. This decision was based on the greater accessibility of benzothiazole BPin ester precursors for 18 F-fluorination via the same Cu-mediated approach. JH112, the 5-fluorobenzoxazole 1e and the 6-fluorobenzothiazole 1f were docked into the structure of the OX1R receptor bound with suvorexant (PDB: 6TO7; (24)). Our docking utilized core constraints referencing suvorexant with a tolerance of 2 Å, following our previously established protocol . The results indicated that the respective fluoro substitutions at the 5-position of the benzoxazole and the 6-position of the benzothiazole were well accommodated within the binding pocket (Figure ). Because docking was conducted with core constraints, the 6-fluoro-benzothiazole moiety of 1f (cf. Figure ) adopted a conformation similar to the 5-chlorobenzoxazole of suvorexant. However, the 6-fluoro-benzothiazole ring of 1f might be turned by 180 ° so that the fluoro substituent fills the same pocket as the chloro substituent of suvorexant. Since there are no interactions that favor one distinct conformation, we conducted the FEP calculation with the highest-scored binding pose represented in Figure . FEP calculations suggested only minor changes in relative binding free energy (ΔΔG) of -0.25 kcal/mol for 1e and -0.39 kcal/mol for 1f, compared to JH112.