Acetic Anhydride → N-formyl-3,4-dimethoxy-L-phenylalanine ethyl ester

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Reaction Steps

To a mixture of 3,4-dimethoxy-L-phenylalanine ethyl ester-hydrochloride 1 (Luxen, A., Perlmutter M., Bida, G. T., Van Moffaert, G., Cook, J. S., Satyamurthy, N., Phelps, M. E. and Barrio, J. R. (1990) Remote, semiautomated production of 6- 18F!fluoro-L-dopa for human studies with PET. Appl. Radiat. Isot. 41, 275) (5.3 g, 18.3 mmol) and sodium formate (1.44 g, 21.2 mmol) in formic acid (52 mL) cooled in an ice bath was added acetic anhydride (20 mL) and stirred at room temperature for 3 h. After addition of ethanol (40 mL) the mixture was stirred at room temperature for an additional 3 h and evaporated. The residue was dissolved in ethyl acetate, filtered and the insoluble material was washed with, ethyl acetate. The combined filtrates were washed successively with aqueous 10% HCl, saturated aqueous NaHCO3 and saturated aqueous NaCl. The organic extract was dried over anhydrous MgSO4 and concentrated under reduced pressure to a yellow syrup. Crystallization of the syrup from ethyl acetate-petroleum ether give a white solid 2 (3.1 g, 61%); m.p. 102°-103° C.

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