Phosphoramidates (sometimes also called amidophosphates) are a class of phosphorus compounds structurally related to phosphates (or organophosphates) via the substitution of an OR for a NR2. They are derivatives of phosphoramidic acids P(=O)(OH)(NR2)2, P(=O)(OH)2(NR2).
A phosphorodiamidate (or diamidophosphate) is a phosphate that has two of its OH groups substituted by NR2 groups to give a species with the general formula HOPO(NH)2. The substitution of all three OH groups gives the phosphoric triamides (P(=O)(NR2)3), which are commonly referred to as phosphoramides.
Two examples of natural phosphoramidates are phosphocreatine and the phosphoramidate formed when histidine residues in histidine kinases are phosphorylated. An example of a phosphorodiamidate is Morpholino which is used in molecular biology.