Oxidative fluorination of several protected tryptophans 8b-g with Selectfluor™ proceeded smoothly in aqueous media to give a diastereomeric mixture of the corresponding 3-fluorooxindoles 9b-g. Attempted deprotection of the 3-fluorooxindoles 9b-g under various conditions did not afford 3-(3-fluorooxindol-3-yl)-L-alanine (6). Reaction of the suitably protected tryptophan derivative 16 with Selectfluor™ produced the fluorinated product 17. Simultaneous cleavage of all protective groups of 17 under acidic conditions successfully gave the target compound 6 in excellent yield.
Amino acids U 0400Synthetic Studies of 3-(3-Fluorooxindol-3-yl)-L-alanine. -The synthesis of alanine derivative (III) as potential building block for drug development proceeds smoothly via oxidative fluorination of the suitably protected tryptophan derivative (I) and subsequent simultaneous deprotection under acidic conditions. -(FUJIWARA*, T.; YIN, B.; JIN, M.; KIRK, K. L.; TAKEUCHI, Y.; J. Fluorine Chem. 129 (2008) 9, 829-835; Grad. Sch. Med. Pharm. Sci., Univ. Toyama, Toyama 930, Japan; Eng.) -H. Hoennerscheid 04-185
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