815 768 741 711 678 86 444 9 the xrd pattern dsc tga as summarized in fig1 fig2 and fig3 respectively dicyclohexylamine dca salt of perindopril 12 g obtained in example 1 was taken in water 60 ml and acidified till ph 4 4 5 at temperature 0 5 u00b0 c using conc hcl the reaction mixture was stirred for about 15 minutes it was then filtered and the filtrate was extracted with dichloromethane 72 ml u00d7 2 the dichloromethane layer was washed with water 24 ml u00d7 2 concentration of the organic layer under reduced pressure afforded highly pure perindopril 7 g this perindopril was taken in 2 2 dimethoxy propane 70 ml and treated with tert butyl amine 1 5 g to get the salt as a white solid the reaction mixture was subjected to a gentle reflux till a solution resulted the solution was then cooled to 25 30 u00b0 c filtered and dried under reduced pressure the perindopril thus obtained is having purity of more than 99 9 by hplc dry weight of perindopril tertiary butyl amine 6 5 g dicyclohexyl amine salt of perindopril 10 g obtained in example 1 was slurried in 2 2 dimethoxy propane 100 ml to the slurry was added tertiary butyl amine 5 8 ml at 25 30 c to afford the tertiary butyl amine salt of perindopril as a white solid the product was collected by filtration under suction it was dried under reduced pressure.