The general procedure for the synthesis of (R)-2-N-Boc-1,2,3,4-tetrahydroisoquinoline-1-carboxylic acid from di-tert-butyl dicarbonate and (R)-1,2,3,4-tetrahydro-1-isoquinolinecarboxylic acid is as follows:
Example 8 Preparation of (1R)-2-[(tert-butyl)oxycarbonyl]-1,2,3,4-tetrahydroisoquinoline-1-carboxylic acid (Compound 4A):
1. (R)-1,2,3,4-tetrahydroisoquinoline-1-carboxylic acid (80 g, 0.45 mol) was dissolved in 845 mL of tetrahydrofuran (THF), mixed with sodium carbonate (191.5 g, 1.8 mol) dissolved in 845 mL of water, and the mixture was cooled to 0 °C.
2. Di-tert-butyl dicarbonate (108 g, 0.5 mol) dissolved in 280 mL of tetrahydrofuran was slowly added dropwise to the above solution at 0 °C.
3. After the dropwise addition was completed, the reaction system was stirred at 0 °C overnight.
4. After completion of the reaction, the reaction mixture was extracted with ethyl acetate (EA). The organic layers were combined, washed with saturated sodium chloride solution and dried over anhydrous sodium sulfate.
5. The solvent was removed by depressurized evaporation to give a dry residue.
6. The residue was purified by silica gel column chromatography using petroleum ether/ethyl acetate (1:1, v/v) as eluent to afford a white solid product, compound 4A (106 g, 85% yield).
