tert-Butyl (1-(5-Fluoro-4-oxo-3-phenyl-3,4-dihydroquinazolin-2(1H)-ylidene)propyl)carbamate is a reagent used in the discovery of a phosphoinositide 3-kinase (PI3K) b/d inhibitor for treatment of phosphatase and tensin homolog (PTEN) deficient tumors.