N[C@H:2]([C:10]([OH:12])=[O:11])[CH2:3][C:4]1[CH:9]=[CH:8][CH:7]=[CH:6][CH:5]=1.[Br-:13].[K+].N([O-])=O.[Na+].C1(C)C=CC=CC=1>S(=O)(=O)(O)O.C(O)(=O)C>[Br:13][C@@H:2]([CH2:3][C:4]1[CH:9]=[CH:8][CH:7]=[CH:6][CH:5]=1)[C:10]([OH:12])=[O:11]A solution of L-phenylalanine (30.0 g., 0.175 mole) and potassium bromide (73.5 g., 0.618 mole) in 2.5N sulfuric acid (365 ml.) was cooled down to 0° (ice-salt bath) and treated portionwise with sodium nitrite (19.3 g., 0.28 mole) over a period of 1.0 hour. Stirring was continued for 1.0 hour at 0° and at room temperature for 1.0 hour after which the reaction mixture was extracted with ether (3×250 ml.). The combined organic extracts were washed with water (100 ml.) and brine (50 ml.), dried (anhydrous magnesium sulfate), filtered, evaporated to dryness and dried in vacuo to give 34.46 g., of product; Rf =0.45 (toluene:acetic acid, 95:5).
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