At room temperature, 5.47 g (25.41 mmol) of methyl 8-amino-1,4-dioxaspiro[4.5]decane-8-carboxylate [T. Satoh et al., Tetrahedron 63 (2007), 4806-4813], 3.86 g (38.12 mmol) of triethylamine and 155 mg (1.27 mmol) of N,N-dimethylaminopyridine were dissolved in 45 ml of dichloromethane. A solution of 6.29 g (25.41 mmol) of (5-bromo-2-methylphenyl)acetyl chloride (Example 3A) in 45 ml of dichloromethane was then added dropwise to the mixture. The resulting reaction mixture was stirred at room temperature overnight. For work-up, the mixture was diluted with dichloromethane and the organic phase was washed with aqueous saturated sodium bicarbonate solution. After drying over sodium sulphate, the mixture was concentrated by evaporation and the residue was purified by chromatography on silica gel (mobile phase: hexane/ethyl acetate gradient/1% triethylamine) Evaporation and drying gave 3.64 g (34% of theory) of the title compound which was used without further characterization in the next step.
