The phases are separated and the organic stream is washed with brine (13.0 wt%, 1320 kg, 5.75 X) followed by extraction with a aqueous mixture of citric acid (according to residual MR84910 content) and sodium chloride (13.0 wt%, 794 kg, 3.45 X). The organic layer is separated and assayed by HPLC to ensure the level of residual MR84910 is not more than 0.5% a/a. In the event of a non-conforming IPC result the citric acid/sodium chloride wash is repeated. Upon obtaining a conforming IPC for residual MR84910 content, the organic phase is concentrated under vacuum. Azeotropic distillation is then performed with additional 2-MeTHF (593 kg, 2.58 X) until the water content is not more than 0.5% w/w as measured by Karl Fischer analysis. In the event of a failing IPC result, an additional 2-MeTHF azeotropic distillation cycle is performed. The content of MR84915 in solution is then quantified by HPLC assay analysis to determine the amount of p-toluenesulfonic acid (pTSA) to be charged in the subsequent salt formation operation. To the MR84915 free base solution is then added acetone (911 kg, 3.96 X) followed by the partial addition of a solution of pTSA•H2O (0.98 equiv.) in 2-MeTHF (198 kg, 0.86 X) to generate a seed bed. The resulting slurry is aged at 20-30°C and the remaining pTSA•H2O/2-MeTHF solution is added. The mixture is then heated to 50-60°C and subsequently cooled to -15 to -5°C. The slurry is held at this temperature for 17 hours, and the solids are collected by filtration and the wet cake is washed with precooled acetone (308 kg, 1.34 X). The solids are then dried until the level of residual acetone is not more than 4000 ppm and the water content is not more than 0.5%. 263.4 kg of product was collected with potency of 98.9 wt% and 98.1% a/a purity (70% yield). until the water content is not more than 0.3% w/w as measured by Karl Fischer analysis and the reaction volume is concentrated to 3.5 V. The concentrated MR84916 solution is then brought to 10-20°C and held. To a separate inerted reaction vessel is then charged acetonitrile (328 kg, 2.34 X) and MR84917-Na salt (50.4 kg, 0.36 X, 1.70 equiv.) at 10-20°C. The MR84917-Na salt solution is treated with a 50% w/w solution of T3P in ethyl acetate (251 kg, 1.79 X, 1.50 equiv.) while maintaining a temperature of 10-15°C and subsequently held at 14-18°C for not less than 2 hours. The MR84917 solution and the concentrated solution of MR84916 are combined while maintaining a batch temperature of 10-15°C. The reaction is held in this temperature range until the level of residual MR84916 is not more than 0.4% a/a relative to product MRTX849 by HPLC analysis. Upon achieving the end of reaction IPC criterion, the reaction mixture is basified with aqueous K2CO3 (11.9% w/w, 715 kg, 5.11 X) to give a mixture between pH 8-9. The organic phase is separated and washed with an aqueous solution of K3PO4 (20% w/w, 525 kg, 3.75 X) and the layers are separated. The organic solution is diluted with IPA (879 kg, 6.28 X) and treated with activated carbon. Solvent exchange to IPA is performed by cycles of concentration and addition of IPA under vacuum until the residual acetonitrile content is not more than 1.5% w/w. The batch is diluted with purified water (350 kg, 2.5 X). Following addition of MRTX849 seed, the batch is cooled, water added (350 kg, 2.5 X), and further cooled to 0-5°C.