反应详情

0.341 g (2.64 mmol) of N,N-diisopropylethylamine and 0.265 g (1.32 mmol) of 4-nitrophenyl chloroformate are added to a solution of 0.226 g (1.32 mmol) of ethyl 5-hydroxymethylisoxazole-3-carboxylate in 10 mL of dichloroethane. Stirring is continued at room temperature for hours and 0.280 g (1.32 mmol) of tert-butyl 6-amino-2-azaspiro[3.3]heptane-2-carboxylate, obtained in step 11.6., dissolved in 4 mL of dichloroethane, is then added. Stirring is continued at room temperature for 4 hours. Water is added to the reaction medium, the aqueous phase is separated out and extracted several times with dichloromethane, and the combined organic phases are washed with aqueous sodium hydroxide solution (1N) and then with saturated aqueous ammonium chloride solution. The resulting phase is dried over sodium sulfate and the filtrate is concentrated under reduced pressure. After evaporating off the solvent, the residue obtained is purified by chromatography on silica gel, eluting with a 98/2 mixture of dichloromethane and methanol.

1. waitis continued at room temperature for hours