Chemi- and bioluminescence of coelenterazine analogues with a conjugated group at the C-8 position

The chemiliminescent compound coelenterazine is involved in various bioluminescence reactions as the substrates, causing the luminescence with an emission peak in the range of 450-475 nm. Anticipating the introduction of a bathochromicshift of the luminescence, several new coelenterazine analogues that have conjugated olefins or aromatic groups at the 8-position of imidazopyrazinone ring were synthesized. In the chemiluminescence reaction, the emission spectra of a majority of the compounds synthesized showed a bathochromic shift, giving an emission peak in the range of 520-580 nm. In the bioluminescence catalyzed by Oplophorus luciferase, the bisthienyl analogue of coelenterazine emitted a moderate intensity of luminescence (5% of coelenterazine) with an emission maximum at 528 nm, which was the longest wavelength of all the analogues tested. (C) 2001 Elsevier Science Ltd. All rights reserved.