The delivery of drug species to the brain and other organs is often seriously limited by transport and metabolism factors, including biological membranes; specifically, in the case of the brain, the functional barrier of the endothelial brain capillary wall, i.e. BBB, limits delivery. Site-specific and sustained delivery of drugs to the brain or other organs, i.e. targeted drug delivery, is even more difficult. Phosphorus compounds, are readily penetrates biological membranes such as the BBB and enters the target organ. According, phosphate esters are frequently used as a prodrug strategy,...