| abstract |
Conjugation agents of the formula: n n nare described, wherein S x is —S—, —SO— or —SO 2 —; R s is a carbon-containing substituent that does not include a cyano group; each R is a substituent, with at least one R having a reaction site that is not a carboxylic acid; n is 0-5; each A is carbon or nitrogen, with the proviso that no more than three A can be nitrogen; and S x —R s is a leaving group. The conjugation agents have good thiol reactivity and selectivity, and good stability with regard to hydrolysis. |