Patent ID: 8680288

Claim:
A compound of general formula 1 wherein R 1 =H, R 2 ═COOMe, R 3 ═(CH 2 ) n COOR 4 , R 4 ═C 2 H 5 , C 3 H 7 , C 4 H 9 , C 5 H 11 , or C 6 H 11 , and n=1-7; or wherein the compound is selected from the group consisting of 3-(2-pyridylthio) propionic acid butyl ester (RS20), 3-(2-pyridylthio) propionic acid pentyl ester (RS Z), 7-(2-pyridylthio) heptanoic acid ethyl ester (RS 32), and 3-(2-pyridylthio) propionic acid cyclohexyl ester (RS 21).