Synthesis
The general procedure for the synthesis of (3,5,6-trimethylpyrazin-2-yl)methanol from chuanxiongzine was as follows: chuanxiongzine (13.6 g, 100 mmol) was added to a 500 mL round-bottomed flask and dissolved in glacial acetic acid (15 mL). 30% hydrogen peroxide (8 mL, 75 mmol) was added slowly and the reaction was carried out at 70 °C for 4 hours. Subsequently, 30% hydrogen peroxide (8 mL, 75 mmol) was added again and the reaction continued for 4 h. The progress of the reaction was monitored by thin layer chromatography (TLC) until the feedstock was completely consumed. Upon completion of the reaction, the mixture was cooled to room temperature, poured into an ice bath, and the pH was adjusted to 10 with 10% sodium hydroxide solution. the reaction mixture was extracted with chloroform, the organic phase was dried with anhydrous sodium sulfate, filtered and concentrated to give the crude product of chuanxiongzine monooxide. Without further purification, acetic anhydride (14.3 mL, 150 mmol) was added to the crude product, heated to 125 °C and refluxed for 3 h. The reaction progress was monitored by TLC until complete conversion of the feedstock. Excess acetic anhydride was removed by distillation to give the chuanxiongzine acetyl compound. The reaction mixture was cooled to room temperature and then poured into an ice bath, pH was adjusted to 12 with 10% sodium hydroxide solution and stirred for 5 hours at room temperature. The reaction mixture was extracted with chloroform and the organic phase was dried with anhydrous sodium sulfate, filtered and concentrated. The crude product was purified by column chromatography using ethyl acetate/petroleum ether (1:1) as eluent to afford the target compound (3,5,6-trimethylpyrazin-2-yl)methanol (TMP-OH) as a white solid (9.88 g, 65% yield).
References
[1] Patent: WO2015/109935, 2015, A1. Location in patent: Page/Page column 17; 18
[2] Patent: US2016/326099, 2016, A1. Location in patent: Paragraph 0108
[3] Bioorganic and Medicinal Chemistry, 2007, vol. 15, # 10, p. 3315 - 3320
[4] Journal of Chemical Research, 2006, # 9, p. 577 - 579
[5] Bioorganic and Medicinal Chemistry Letters, 2003, vol. 13, # 13, p. 2123 - 2126
