3-(2-(tert-Butyldimethylsilyloxy)ethyl)-2-fluorobenzaldehyde [Aromatic Intermediate 5] (5.0 g) was added to a solution of 2,2,2-trifluoro-1-(1-oxa-4,9-diazaspiro[5.5]undecan-4-yl)ethanone trifluoroacetate [Example 9, step a] (9.3 g) and acetic acid (1.0 mL) in N-methyl-2-pyrrolidinone (50 mL). The resulting mixture was stirred for 15 min, then cooled in an ice bath. Sodium triacetoxyborohydride (5.64 g) was then added and the mixture was stirred overnight. The reaction mixture was quenched by the addition of saturated sodium bicarbonate solution:brine (1:5) and extracted four times with ethyl acetate. The combined organic phases were dried (MgSO4), filtered and concentrated in vacuo to afford an oil. The oil was dissolved in THF (100 mL) and treated with TBAF (1M in THF, 18.0 mL). The resulting solution was stirred at room temperature for 50 minutes, then more TBAF (1M in THF, 18.0 mL) was added and the mixture was stirred for a further 100 minutes. The solution was then concentrated in vacuo to afford an oil. The oil was dissolved in methanol (100 mL), the solution was treated with ‘880’ aqueous ammonia (20 mL), stirred at room temperature for 50 minutes, then concentrated in vacuo to give an oil. The oil was dissolved in methanol and concentrated onto flash silica in vacuo. The resulting powder was purified by flash chromatography on silica eluted with ‘880’ aqueous ammonia:methanol:dichloromethane (1:10:89) to afford the subtitled compound as a yellow oil. Yield 5.8 g, 60% pure. Used crude.
