Abstract: Resolution of synthomycin (racemic-I_a) via its esters has been described. Racemic- I_a was dissolved in anhydrous pyridine and treated with D (-) -acetylmandelyl chloride. D (-) -Acetylmandelate of L(+)-I_a was separated by fractional crystallization from 95% ethyl alcohol. The ester was shown to be identical in melting point and specific rotation to a sample prepared from L-(+)-I_a of known purity and D (-) -acetylmandelyl chloride. L(+)-I_a of good quality was obtained by mild alkaline treatment of the ester. On the other hand, racemic threo-1-p-nitrophenyl-2-amino-1,3-propanediol (racemic-II) was re- solved with methyl hydrogen (+) -tartrate. The salt of L(+)-II was less soluble in 95% ethyl alcohol, from which optically pure L(+)-II was isolated; while only impure samples containing D(-)-II could be recovered from the mother liquor.