Novel lactones of polysaccharide carboxylic acids, and methods for the preparation of a variety of conjugates therefrom, as well as the novel conjugates, are provided. Conjugates include metallo-coordinated cisplatin (and carboplatin), as well as conjugates of ellipticinium, aminoglutethimide, mitoxantrone, mitoguazone, cis 3-hexen-1-ol, and other nucleophilic biologically effective agents. Also provided are conjugates via a coupling agent of biologically effective agents, such as Vitamin E, DTPA, TAXOL and TAXOTERE.