The present invention provides a method for forming compounds of Formula
HO—C(═O)R
1
—X—R
2
—X—R
1
—C(═O)—O—H
wherein compound (I) can be polymerized to provide a polymer that contains therapeutically active compounds. In the compounds of the invention, each R
1
is group that will provide the therapeutically active compound upon hydrolysis of the polymer; each X is independently an ester linkage or an amide linkage; and R
2
is a linking group.