Phosphatidylinositol diC4 (PI diC4) is a synthetic, purified dibutanoyl PI. Phosphoinositides (PIPns) are minor components of cellular membranes but are integral signaling molecules for cellular communication. Phosphatidylinositol (PI or PtdIns) is biosynthesized from CDP-diacylglycerol and inositol by phosphatidylinositol synthase. PI is the building block for phosphoinositide polyphosphates through phosphorylation by PI-kinases and is a substrate for PI-PLC yielding diacylgelycerol.