Compounds selected from: where DRUG-OH, DRUG-COOH and DRUG-NH2 are biologically active compounds; each X is independently selected from —CH2COO-(glycolic acid moiety), —CH(CH3)COO-(lactic acid moiety), —CH2CH2OCH2COO-(dioxanone moiety), —CH2CH2CH2CH2CH2COO-(caprolactone moiety), —(CH2)yCOO—, where y is 2-4 or 6-24 and —(CH2CH2O)zCH2COO—, where z is 2-24; each Y is independently selected from —COCH2O-(glycolic ester moiety), —COCH(CH3)O-(lactic ester moiety), —COCH2OCH2CH2O-(dioxanone ester moiety), —COCH2CH2CH2CH2CH2O-(caprolactone ester moiety), —CO(CH2)mO—, where m is 2-4 or 6-24 and —COCH2O(CH2CH2O)n-where n is between 2-24; R′ is hydrogen, benzyl or an alkyl group, the alkyl group being either straight-chained or branched; and p is 1-6. Multi-functional compounds and drug dimers, oligomers and polymers are also disclosed.