A-Bromopropionic acid

TAPA has been prepared only as described in this procedure.5 a-(Isopropylideneaminooxy)propionic acid has been prepared and resolved by the present procedure 6 and has been prepared directly from a-bromopropionic acid and resolved as the (—)-ephedrine salt by crystallization from hydrocarbon mixtures.5... 

Bromophenylurea, 31, 10 f)-Bromopheny] urea, 31, 8, 9 a-Bromopropionic acid, ethyl ester,... 

Hydrogen selenide converts a-bromopropionic acid in the presence of alkali into selenodilactylic acid, (C2H4.COOH)2Se. 

Diphenyl-a-propionyl-telluretin bromide, (C6H5)2Te(Br). CH(CH3)COOH, from a-bromopropionic acid and diphenyl telluride, is an amorphous powder, sintering at 50° C. and melting at 98° C. The analysis of this product does not give good results. 

The benzylbromomalonic acid containing water is now heated in an oil bath to 125°—130°, and the fused mass evolves carbon dioxide and a certain amount of hydrobromic acid. The reaction is complete in the course of 30—45 minutes. The residue is a yellow oil, which even at a low temperature does not crystallise, and which in the main consists of phenyl-a-bromopropionic acid. For the purpose of purification it is washed with water, taken up in ether, and dried with anhydrous sodium sulphate the ether is then distilled off. The mobile, almost colourless oil remaining is dissolved in 5 times its volume (excess) of 25% aqueous ammonia, and either heated for 3 hours to 100° in a sealed tube or allowed to stand for 3 to 4 days at ordinary temperature. On evaporation of the ammo-niacal solution an almost colourless residue is left, and this chiefly consists of ammonium bromide and phenylalanine. On boiling with absolute alcohol the amino-acid is left undissolved and is recrystallised from hot water. 

Thiones 349 react with chloroacetic acid, a-bromopropionic acid, or their esters to give cyclized products for which structure 350 was assigned (78MI1 81ACH197 83MI2) (Scheme 81). The cyclized product could also be represented by alternate structure 351. Data are inadequate to decide in favor of either. 

Racemic mixtures of carboxylic adds can be resolved by esterification using lipases in organic media. Figure 21 illustrates such a process when racemic a-bromopropionic acid is stereoselectively esterified with n-buta-nol using a lipase from the yeast Candida a/lindraceae (68). This reaction was carried out in virtually anhydrous hexane. 

B) Preparation of a-Bromopropionic Acid (M.). Arrange a 500-ml Florence flask as shown in Figure 46, without the dropping funnel the absorption train is the same as used in the preparation of chloroacetic acid (page 225). The rubber stopper which connects the reflux condenser to the flask is painted with sodium silicate twice, and allowed to dry each time. 

C) Preparation of Alanine (Sm.). Place in an eight-inch test tube 11 ml of concentrated aqueous ammonia and 5.5 g of powdered ammonium carbonate. Place the tube in a water bath and warm at 40° for 15 to 20 minutes. Cool to 25° and then add 3 g (0.2 moles) of a-bromopropionic acid (obtained in Experiment 44). Stopper, and place the tube aside for 24 hours at room temperature. Remove the stopper, place in a water bath, and heat gradually to expel the ammonia and carbon dioxide (use hood). Con-... 

A number of syntheses of (V-hydroxy-a-amino acids and derivatives thereof have been reported. a-Bromocarboxylic acids or their r-butyl esters can be treated with hydroxylamine or 0-alkylated hydroxylamines to give the corresponding hydroxylamine derivatives. yV-Benzyloxy-t-alanine has been obtained by reaction of (/ )-a-bromopropionic acid with O-benzylhydroxylamine. But due to bromide exchange the optical yield was low. Anchimeric assistance of a suitable attached thio group can bring... 

Zelinsky, N. A convenient preparation of a-bromopropionic acid ester. Ber. 1887, 20, 2026. 

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