Preparation
Synthesis of 2,6-Diazaspiro[3.3]heptane-2-carboxylic acid tert-butyl ester hemioxylate: Take a 500mL single-necked bottle, add 6-toluenesulfonyl-2,6-diazaspiro[3.3]heptane-2-carboxylic acid tert-butyl ester (7g, 20mmol), dissolve in methanol (200mL), add magnesium chips (3.84 g) g, 0.16 mol, 8 equiv) and stirred at room temperature. The reaction solution gradually turned into a white viscous state with the dissolution of the magnesium scraps, and TLC showed that the reaction of the raw materials was completed. The solvent was removed by rotary evaporation, ether (150 mL) was added, stirred at room temperature for 1 h, filtered through celite, the filtrate was dried over anhydrous sodium sulfate, and an ethanol solution (3 mL) of anhydrous oxalic acid (0.89 g, 9.9 mmol, 0.5 equiv) was added dropwise, A white precipitate appeared immediately, which was filtered under reduced pressure to give 3.2 g of a colorless solid, 82%.
