The invention provides novel chemical entities based on sugar alcohols. These new chemical entities are biocompatible and biodegradable. The molecules can be made in a single and pure form. The molecular weights of these molecules range from small (<；1000 Da) to large (1000-120,000 Da). The sugar alcohol-based molecules can have functional groups throughout the molecule for crosslinking compounds, such as the preparation of antibody-drug conjugates, or to facilitate the delivery of therapeutic proteins, peptides, siRNA, and chemotherapeutic drugs. Also provided are new conjugate entities prepared through sugar alcohol molecules. Methods of synthesizing sugar alcohol-based molecules and conjugates are also within the scope of the invention.
