Coelenterazine 1 found in the jellyfish Aequorea victoria was the second imidazopyrazine- based chromophore to be isolated from luminescent marine organisms. 1 Its structure was determined in 19742 and it has been synthesised using an approach developed by Kishi3 in which the fully-substituted pyrazine ring is synthesised by a condensation reaction between an a-amino nitrile and an a-nitroso ketone. In the jellyfish, coelenterazine is bound ...