Effect of iron (III) hydroxide sol as a support for oligomerization of l-phenylalanine in aqueous solution

An oligomerization of l-phenylalanine in aqueous solution was studied in the presence of iron (III) hydroxide sols. To an aqueous solution of the iron hydroxide sols prepared from iron (III) chloride,l-phenylalanine with 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride was added. After stirring for 48 h at 0 °C, 3 M HCl solution was added to the reaction mixture to decompose the colloidal iron hydroxide. Oligo (l-phenylalanine) was isolated by centrifugation and washed with acidic water. The maximum yield of 15% was obtained at around pH 6.3. This value was 2.5 times higher than that obtained without the iron hydroxide sols at the same pH. Adsorption study of l-phenylalanine indicated that assemblies of l-phenylalanine onto the iron hydroxide sols were predominant factor to improve the yield of the oligomerization product. The presence of nitrate anions changes the pattern of the yield of oligo (l-phenylalanine) against pH values. The maximum yield of 20% was obtained at around pH 3. This value was four times higher than that obtained without the iron hydroxide sols at the same pH. Effect of NaCl for the oligomerization of l-phenylalanine in an aqueous solution was also studied.