Bioluminescent coelenterazine derivatives with imidazopyrazinone C-6 extended substitutionElectronic supplementary information (ESI) available: Detailed synthetic procedures and spectral characterization of new compounds; additional information on chemiluminescence and bioluminescence properties as noted in the text; and summarized luminescence properties. See DOI: 10.1039/c4cc06886f

Three novel coelenterazine (CTZ) derivatives with extension at the C-6 position of the imidazopyrazinone structure show significant bioluminescence emission with known renilla luciferase variants, indicating a promising method to develop CTZ derivatives with superior optical properties compared to hitherto reported compounds. Coelenterazine derivatives with extended substituents show significant bioluminescence emission with known renilla luciferase variants, indicating a promising method to develop substrates with superior optical properties.