Acetic Acid → 6-(2,3-dimethyl-5-sulfo-3H-indol-3-yl)hexanoic acid

Participants

Reaction Conditions

Reaction Steps

6-(2,3-Dimethyl-5-sulfo-3H-indol-3-yl)hexanoic acid was synthesised as described in Example 5. To a stirred solution of 6-(1-ethyl-2,3-dimethyl-5-sulfo-3H-indol-3-yl)hexanoic acid (1.8 g, 5.3 mmol) in ethanol (200 ml) at ambient temperature was added hydrobromic acid (10 ml 48% aqueous solution). After 1 Hr the reaction solvent was removed in vacuo. The hydrobromide salt was re-dissolved in acetonitrile (150 ml) and acetic acid (1.54 ml) and acrolein diethyl acetal (6.6 g, 51 mmol). The reaction mixture was heated to 70° C. for 30 minutes. The solution was cooled and the solvent removed in vacuum. The product was rapidly purified by preparative HPLC on reverse phase C18 column using gradient elution of water containing 10% acetonitrile to acetonitrile (containing 0.1% TFA) as solvent over 30 minutes. All fractions were monitored by MALDI-TOF mass spectrometry (M/Z=498). Fractions containing product mass were pooled. Evaporation of the solvent gave a sticky mass (162 mg 11%). It was immediately used for the next reaction.

Provenance & Evidence