In order to investigate the bioluminescent process of dehydrocoelenterazine in a photoprotein, symplectin, various unnatural dehydrocoelenterazine analogues are required showing different wavelength in bioluminescence from the natural chromophore 470 nm. One possibility is to change the benzyl group at the 8-position of imidazopyrazinone ring into direct aromatic rings to enhance the conjugation. However, there is a synthetic limitation for this current purpose among the synthetic routes which have already been published. As a result, we developed a new synthetic route as discussed in this thesis. In the case of introducing aromatic rings at the 8-positio n, cross coupling reaction was used.
Compound (6) was prepared from 2-aminopyrazine (1) via iodination and bromination. It reacted with one equivalent of aryl boronic acid to afford the common intermediate (19) via the first Suzuki-Miyaura cross-coupling reaction. This intermediate (19) was applied to the second cross coupling reaction to afford aminopyrazine analogues having aromatic rings at the 3-position. These aminopyrazine analogues were further converted into dehydrocoelenterazine
analogues (15, 17, 31, 35).
In the chemiluminescence, the emission spectra of two analogues, in fact, showed red-shift (552 nm and 562 nm respectively).

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