(sī'ti-dēn-dī-fos'fō-kō'lēn), An intermediate in the formation of phosphatidylcholine (lecithin) and sphingomyelins; formed by the action of cytidine 5'-triphosphate on phosphocholine, linking the choline phosphate group to the α-phosphate of the cytidine 5'-triphosphate to give a pyrophosphate. Synonym(s): cytidine diphosphate choline