A solution of methyl 7-(2,3-di-p-tolyl-7,8-dihydropyrido[2,3-b]pyrazin-5(6H)-yl)-3-hydroxy heptanoate (step 3)(43 mg, 0.091 mmol) in EtOH (908 μL) was treated with sodium hydroxide (136 μL, 0.272 mmol) and stirred at room temperature for 1 hour. The resulting mixture was diluted with water (2 ml) and acidified to pH 2. The mixture was extracted with EtOAc and the combined organic extracts were washed with brine, dried by passing through a phase separator and concentrated under reduced pressure to give an oil. The oil was purified by flash column chromatography using the ISCO combiflash Rf, eluting with 0-50% EtOAc (containing 10% MeOH) in iso-hexane on a 4 g silca cartridge. The product fractions were combined and the solvent removed under reduced pressure to yield the titled compound as a colourless oil;
