Synthesis
Step 2: Synthesis of 1-methyl-1H-indole-6-carboxylic acid (167). Methyl 1-methyl-1H-indole-6-carboxylate (166, 1.24 mmol) was reacted with sodium hydroxide (0.59 g, 14.88 mmol) in a solvent mixture of methanol/THF/water (2:2:1, 7.5 mL) with stirring for 36 h at room temperature. A precipitate was generated during the reaction and the precipitate was collected by filtration followed by lyophilization overnight to afford the target product 1-methyl-6-indolecarboxylic acid (167, 0.54 g, 99% yield). Mass spectral data: calculated (Calc) 175.06, observed (Obs) 176.1.
References
[1] Patent: WO2005/30704, 2005, A1. Location in patent: Page/Page column 199-200
[2] Patent: WO2008/65508, 2008, A1. Location in patent: Page/Page column 32
[3] Heterocycles, 2006, vol. 67, # 2, p. 643 - 653
