Patent ID: 7378531

Claim:
A process for preparing valsartan that is substantially free of an impurity that is an isoleucine analogue of valsartan having the formula: from an initial sample of L-valine or an L-valine ester, wherein the process comprises: a) analyzing the level of L-isoleucine or corresponding L-isoleucine ester present in at least one initial sample of L-valine or an L-valine ester at least at a single stage during the synthetic process to control the amount of said isoleucine analogue of valsartan; being present in the prepared valsartan b) selecting an initial sample of L-valine or an L-valine ester that has not more than about 0.1% as area percentage GC of the isoleucine analogue of said L-valine or L-valine ester; and c) reacting said initial sample of L-valine or L-valine ester with a biphenyl compound to synthesize said valsartan, that is substantially free of said isoleucine analogue of valsartan.