Problems associated with this synthetic process have been (a) the use of highly toxic tri-n-butyltinazide in the conversion of compound 5 to compound 6(8, 9) at the penultimate stage of valsartan synthesis, (b) contamination of final product with traces of toxic tin metal, (c) racemisation of valsartan up to 15% during hydrolysis under basic conditions,(10) and (d) low purity and low yield of valsartan. To achieve acceptable purity, chiral purity and acceptable limit of tin as per ICH ...