1 ASF 3-(butylsulphonyl)-propanoic acid 1.000 2 X1R 3-(propylsulfonyl)propanoic acid 0.917 3 BBC 3-[(4-aminobutyl)sulfinyl]-2-iminopropan-1-ol 0.714 4 CY4 S-butyryl-cystein 0.714