In 1973, Shimomura and Johnson reported the chemical synthesis of coelenteramide to confirm the chemical structure of the light emitter in bioluminescence of aequorin [6]. They prepared coelenteramide at a micromole scale by the condensation reaction of coelenteramine with p-hydroxyphenylacetic
cyclin d1 and then purified by TLC in approximately 50% yield [6]. Later, a different synthetic method of coelenteramide and its analogues was reported; N,O-diacylation of coelenteramine by p-acetoxyphenylacetyl chloride followed by alkaline hydrolysis of ester moieties [25] and [26]. To prepare coelenteramide at a millimole scale in a
Human Genome Project more straightforward manner, we developed a new synthetic route. As shown in Fig. 1, coelenteramide was synthesized from coelenteramine methyl ether (3) [18] and [19] in two steps. Thus, coelenteramine methyl ether (3) was reacted with 4-methoxyphenylacetyl chloride to give coelenteramide dimethyl ether (4), which was treated with BBr3 to remove two ethereal methyl groups as described in Materials and methods. As the result, 570 mg of coelenteramide was obtained in 92% yield as a pale yellow solid, which was sufficiently pure for reconstitution of syn-BFP and syn-gFP without further purification.
