Laboratorios Vita, S.a.

Pere Dalmases Barjoan

Salvador Puig Torres

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&#x2013;100&#xb0; 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&#xb0; C.&#x2013;160&#xb0; 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.

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Sant Feliu de Llobregat, Spain

Pere Dalmases Barjoan