[N+:1]([C:4]1[CH:15]=[C:14]2[C:7]([NH:8][CH:9]=[C:10]2[CH2:11][CH2:12][NH2:13])=[CH:6][CH:5]=1)([O-:3])=[O:2].[CH:16](=O)[C:17]1[C:18](=[CH:20][CH:21]=[CH:22][CH:23]=1)[OH:19].[OH-].[K+].[BH4-].[Na+]>C(O)C>[N+:1]([C:4]1[CH:15]=[C:14]2[C:7](=[CH:6][CH:5]=1)[NH:8][CH:9]=[C:10]2[CH2:11][CH2:12][NH:13][CH2:16][C:17]1[CH:23]=[CH:22][CH:21]=[CH:20][C:18]=1[OH:19])([O-:3])=[O:2]5-Nitrotryptamine (6 mmol) and salicylaldehyde (7 mmol) are dissolved in ethanol (35 mL) buffered with potassium hydroxide (0.15 g) and treated with sodium borohydride (18 mmol) 8 h at 24° C. The ethanol is removed in vacuo and the residue partitioned between ether and water, the ether phase dried, evaporated and the oil chromatographed on silica gel with ethyl acetate-hexane to afford 2-{[2-(5-nitro-1H-indol-3-yl)-ethylamino]-methyl}-phenol. After hydrogenation over Pd/C as above, the residue is dissolved in pyridine (12 mL) and treated with methyl chloroformate (9 mmol). A brownish precipitate forms immediately upon addition of the chloroformate, which dissolves during 20 min. After a short time silica gel TLC (5% methanol-chloroform eluent) is performed to judge completion of the reaction. The mixture is evaporated to dryness and maintained at a vacuum of <0.1 mmHg at least 2 h. It is then dissolved in a small amount of methanol, and purified by reverse-phase HPLC with a gradient of water to methanol.
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