Synthesis and free radical scavenging properties of the enantiomers of erdosteine.

The synthesis of enantiomers R and S of erdosteine, a derivative of homocysteine-gamma-thiolactone, and the NMR studies for the determination of the enantiomeric excess with chiral shift reagent on the more soluble ethyl esters, are described. Pharmacological data relative to the free radical scavenging properties of the R and S enantiomers are reported. In particular, it has been documented that the S isomer is more effective than R isomer in protecting mice against lethal doses of paraquat (substance able to form free radicals when administered by i.p. route).