Bivalent linkers and conjugates therof

Abstract

Bivalent linkers to be included in or for preparing vitamin, drug, diagnostic agent, and/or imaging agent conjugates are described.

1 . A compound of the formula 
       
         
           
           
               
               
           
         
         wherein
 n is an integer from 1 to about 4; 
 R a  and R b  are each independently selected from the group consisting of hydrogen and alkyl, including lower alkyl such as C 1 -C 4  alkyl that are optionally branched; or R a  and R b  are taken together with the attached carbon atom to form a carbocyclic ring; and 
 X 1  and X 2  are each independently selected leaving groups, where each of said leaving groups is displaceable by an independently selected nucleophile. 
 
       
     
     
         2 .- 6 . (canceled)