PROCESS FOR PREPARING A PHARMACEUTICALLY ACTIVE COMPOUND (GRANISETRON)

摘要

The invention relates to a process for preparing granisetron, or a pharmaceutically acceptable salt thereof, which comprises: a) cyclisation of a compound of formula (I) in an inert solvent and at a temperature between 0-100°C, in the presence of a strong acid, in order to yield the compound of formula (II); b) methylation of the compound of formula (II), with an alkylating agent, in the presence of a base, in an inert solvent and at a temperature between 0°C-160°C, and with optional formation of a pharmaceutically acceptable salt.The process of the invention yields a granisetron of high purity, preventing impurities due to demethylation, by carrying out the methylation after rather than before cyclisation and with a higher yield.