3-benzyl-4-oxo-4H-pyrido[1,2-a]pyrimidine-2-carbaldehyde → 3-benzyl-2-(1-hydroxy-2-methylprop-2-enyl)-4H-pyrido[1,2-a]pyrimidin-4-one

A mixture of 500 mg (1.9 mmol) of the product from Step 6 (16) in 15 ml THF was cooled to −78° C. To the resulting solution was added dropwise 7.6 ml (3.8 mmol) of isopropenylmagnesium bromide and stirred at −78° C. for 2 hours. The reaction was quenched with saturated NH4Cl and extracted with ethyl acetate (2×). The combined organic layers were dried over MgSO4 and the solvent was removed in vacuo yielding 613 mg (2.0 mmol, 106%) of 3-benzyl-2-(1-hydroxy-2-methylprop-2-enyl)-4H-pyrido [1,2-a]pyrimidin-4-one (17) as a pale yellow solid. This was purified by flash chromatography.