L-Phenylalanine, methyl ester → 33605-76-4

Participants

Reaction Conditions

Reaction Steps

The resin used carries sulphonic acid groups on a polystyrene matrix and has an exchange capacity of 5 meq. per gram of dry resin. Consequently the ratio of the acid equivalents of the resin acid groups to the moles of N-formyl-L-aspartic anhydride is 0.1. The mass is agitated in the flask to obtain a suspension. The solution of L-phenylalanine methyl ester in ethyl acetate is added to this agitated suspension by means of the dropping funnel over a time of about 8 minutes, while maintaining the temperature of the mass at about 25° C. At the end of this time a solution is obtained from which the cation exchange resin is separated by filtration. The solution is then cooled to 0° C. and a crystalline precipitate is obtained constituted by a mixture of the α and β isomers of N-formyl-L-aspartyl-L-phenylalanine methyl ester (14.1 g, yield 87%). This precipitate is subjected to HPLC analysis in order to check the ratio of the α to the β by comparison with known samples. The HPLC determinations are carried out using a Perkin-Elmer chromatograph, series 3, with a 7 micron RP8 column, 250×4 mm; eluent used: continuous gradient between solvents: (A) 65 parts of monobasic potassium phosphate 0.07 molar at pH 4+35 parts of methanol; and (B) 65 parts of water +35 parts of methanol; flow rate 1 ml per minute.

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