Convenient synthesis of N-acetyl-5-methoxytryptamine(melatonin)

The title compound was prepared by a five-step reaction route with K-phthalimide, 1,3-dibromo-propane and 4-anisidine as the main reactants. After K-phthalimide reaction with 1,3-dibromo-propane at 155 approx. 160°C for 6h to give N-(3-bromopropyl) phthalimide(II) in 77% yield, II was condensed with Et acetacetate in the presence of NaOEt, leading to ethyl-5-phthalimido-pentanoate (III) in 72% yield. III was cyclocondensed with diazotized 4-anisidine to produce carboxyethyl-5-(2-phthalimidoethyl)-5-methoxy-indole(IV) in 74% yield, which after saponified with NaOH, hydrolyzed, decarboxylated in the solution of H2SO4 and purified with strip-extraction gave 5-methoxytryptamine (V) in 66% yield. V was acetylated to give the title compound (VI) in 82% yield.