Synthesis intermediates useful for preparing zolmitriptan

In particular, this invention relates to the synthesis intermediates (IV), (V), (VI) and (VIII) useful for preparing zolmitriptanzohnitriptan or a pharmaceutically acceptable salt thereof, which includes a) Ppreparation of the diazonium salt of the aniline hydrochloride (II); followed by reduction and acidification to give hydrazine (III); b) In situ Reaction of the hydrazine hydrochloride (III) with α-keto-δ-valerolactone, to give the hydrazone (IV); c) Fischer indole synthesis of the hydrazone (IV), to give the pyranoindolone of formula (V); d) Ttransesterification of the pyranoindolone (V) to provide the compound (VI), in which R means a straight or branched C1-C4 alkyl; e) Conversion of the hydroxyl group of the compound (VI) into dimethylamino to give the indolecarboxylate (VII), in which R means a straight or branched C1-C4 alkyl; f) Ssaponification of the 2-carboalkoxy group of the compound (VII), to provide indolecarboxylic acid (VIII); g) Ddecarboxylation of the indolecarboxylic acid (VIII), to provide zolmitriptan and, eventually, to provide a pharmaceutically acceptable salt thereof.