Acetic Acid → 7-Fluorotryptophan

Participants

Reaction Steps

A solution of 2-(7-Fluoro-1H-indol-3-ylmethyl)-2-formylamino-malonic acid diethyl ester in THF was treated with NaOH (300 mg in 10 mL water) at room temperature for 24 hr. The mixture was slowly acidified with acetic acid (5 mL) and then refluxed for 24 hr. The reaction mixture was concentrated under vacuum, and treated with dil. HCl (10 mL, 3M) and then again refluxed for ˜16 h. The reaction was allowed to cool to room temperature. The pH was adjusted to 6.0 with 2M KOH. The white solid that formed was filtered, washed with water, and dried under vacuum to give 7-fluoro-tryptophan (282 mg, 52%): mp 256-261° C., 1H NMR (500 MHz, DMSO-d6): 2.92-2.97 (dd, J=8.5 and 15 Hz, 1H), 3.25-3.29 (dd, J=4.0 and 15 Hz, 1H), 3.38-3.41 (dd, J=4.0 and 8.5 Hz, 1H), 6.87-6.96 (m, 2H), 7.25 (s, 1H), 7.37 (d, J=7.5 Hz, 1H), 11.36 (s, 1H).

Provenance & Evidence