The reaction of (S)(-)-lactic acid methyl ester (I) with Ts-Cl and TEA in dichloromethane gives the corresponding tosylate (II), which is condensed with 4-(benzyloxy)phenol (III) by means of NaH in DMF to yield (R)(+)-2-[4-(benzyloxy)phenoxy]propionic acid methyl ester (IV). The hydrogenolysis of the benzyl group of (IV) with H2 over Pd/C in ethyl acetate affords the 4-hydroxyphenoxy compound (V), which is condensed with 2,7-dichloroquinoxaline (VI) by means of K2CO3 in refluxing acetone, provides the ester precursor (VII). The hydrolysis of (VII) with KOH in THF/water, followed by acidification with HCl, gives the chiral propionic acid (VIII), which is finally converted into its sodium salt with NaOH in water.

The cyclization of 4-chlorophenylene-1,2-diamine (I) with glyoxylic acid (II) in isopropanol gives a mixture of 7-chloroquinoxalin-2-ol (III) and 6-chloroquinoxalin-2-ol (IV), which, without isolation is treated with refluxing POCl3, and the resulting mixture of dichloro compounds is submitted to flash chromatography to obtain the desired 2,7-dichloroquinoxaline (V). The condensation of (V) with 2-(4-hydroxyphenoxy)propionic acid methyl ester (VI) by means of K2CO3 in refluxing acetone affords the ester precursor (VII), which is hydrolyzed with KOH in THF/water and acidified with HCl to provide the racemic 2-[4-(7-chloroquinoxalin-2-yloxy)phenoxy]propionic acid (VIII). Finally, this compound is converted into its sodium salt with NaOH in water.