Synthesis Of Firefly DL-Luciferin

Luciferin is one of the important compounds in the firefly bioluminesentsystem. A new method to synthesis luciferin was designed, and afterexperimentation the best conditions and operations in all of the steps wereconfirmed. The new way still use p-anisidine as starting material, which is quitecheap compound. And the route is unique because of the simple operations, thebest conditions and the high yield of the whole synthesis.In the acetic acid, p-anisidine and sodium thiocyanate were used as startingmaterials in the presence of bromine. After addition reaction and cyclization, theintermediate was synthesized in high yield, which is2-amino-6-methoxybenzothiazole.Firstly, 2-amino-6-methoxybenzothiazole, which was prepared previously,and NaNO2 were mixed with acid solution. After reaction, the diazonium solutionwas kept stirring and cooling in an ice bath. On the other hand, a cyano complexsolution was prepared from CuCN suspension and aqueous KCN. Finally in thesuspension of the cyano complex and NaHCO3, the cold diazonium solution wasadded slowly with vigorous strring. After substitution, as the intermediate2-cyano-6-methoxybenzothiazole was obtained in ideal yield.The methoxy intermediate and pyridinium chloride were heated into meltagewith stirring under a nitrogen atmosphere. In the same time, dealkylation washappened to give the intermediate 2-cyano-6-hydroxybenzothiazole in quite highyieldThe nitrile compound and cysteine hydrochloride monohydrate weredissolved in a composite solvent of MeOH and water. To the resulting solutionunder a nitrogen atmosphere K2CO3 was added, and the mixture was stirred indark. After the addition reaction in the molecules was complete, the racemicmixture of firefly luciferin was formed in high yield.In addition, three new methods of stereoselective reactions were alsodesigned to resolve the racemic mixture of firefly luciferin smoothly and directly.