Process for the preparation of valacyclovir
The present invention relates to an improved process for the preparation of Valacyclovir or pharmaceutically acceptable salts thereof, which comprises reaction of amine-protected Valacyclovir or its salt with deprotecting agent in a continuous flow reactor.
1. A process for the preparation of Valacyclovir hydrochloride, which comprises:
a) providing a solution of Boc-protected Valacyclovir in a suitable solvent, selected from methanol and methylene chloride or mixture thereof, to obtain solution A;
b) providing aqueous solution of hydrochloric acid to obtain solution B;
c) feeding separately prepared solution A and solution B to a continuous flow reactor at a temperature of about 80-100 C;
d) continuously eluting the reaction mass from the reactor;
e) precipitating the solid from the reaction mass; and
f) drying the product to obtain Valacyclovir hydrochloride.
2. A process for the preparation of Valacyclovir hydrochloride, which comprises:
a) providing a solution of Boc-protected Valacyclovir in a suitable solvent, selected from an alcohol and chlorinated solvent or mixture thereof, to obtain solution A;
b) providing aqueous solution of hydrochloric acid and adding methanol to obtain solution B;
c) feeding separately prepared solution A and solution B to a continuous flow reactor at a temperature of about 80-100 C;
d) continuously eluting the reaction mass from the reactor;
e) precipitating the solid from the reaction mass; and
f) drying the product to obtain Valacyclovir hydrochloride.