1,3,4,9-Tetrahydro-β-carboline-2-carboxylic acid tert-butyl ester

Synthesis

The general procedure for the synthesis of tert-butyl 3,4-dihydro-1H-pyrido[3,4-b]indole-2(9H)-carboxylate (Intermediate B3) from 1,2,3,4-tetrahydro-9H-pyrido[3,4-B]indole (Intermediate A) and di-tert-butyl dicarbonate is as follows: 516 mg of Intermediate A was dissolved in dichloromethane (CH2Cl2), and di-tert-butyl dicarbonate was added. Butyl di-tert-butyl dicarbonate (Boc2O) was added and the reaction was stirred at room temperature for 9 hours. Upon completion of the reaction, the reaction mixture was diluted with 20 mL of dichloromethane, followed by extraction with purified water three times and washing with saturated saline once. The organic phase was collected, dried over anhydrous sodium sulfate and the solvent was removed by rotary evaporation. The resulting crude product was purified by silica gel column chromatography with the eluent of petroleum ether (PE)/ethyl acetate (EtOAc) = 4:1 (v/v), resulting in 665 mg of intermediate B3 in 81% yield.

References

[1] Journal of Medicinal Chemistry, 2002, vol. 45, # 11, p. 2197 - 2206
[2] Journal of Medicinal Chemistry, 2012, vol. 55, # 2, p. 639 - 651
[3] Patent: CN106883230, 2017, A. Location in patent: Paragraph 0037
[4] Angewandte Chemie - International Edition, 2017, vol. 56, # 47, p. 14968 - 14972
[5] Angew. Chem., 2017, vol. 129, # 47, p. 15164 - 15168,5