abstract |
Compounds useful as biologically active compounds are disclosed. The compounds have the following structure (I): n n n n n n n n n n or a stereoisomer, tautomer or salt thereof, wherein R 1 , R 2 , R 3 , L, L 1 , L 2 , L 3 , M and n are as defined herein. Methods associated with preparation and use of such compounds is also provided. |