Compounds that inhibit PI3Kδ activity, including compounds that selectively inhibit PI3Kδ activity, are disclosed. Methods of preparing such compounds are also disclosed, including the preparation and use of the compound tert-butyl (S)-(1-(5-fluoro-4-oxo-3-phenyl-3,4-dihydroquinazolin-2-yl)propyl)carbamate of formula (110) as a precursor to synthesize an exemplary compound disclosed in this application, (S)-2-(1-((9H-purin-6-yl)amino)propyl)-5-fluoro-3-phenylquinazolin-4(3H)-one. Methods of inhibiting phosphatidylinositol 3-kinase delta isoform (PI3Kδ) activity, and methods of treating diseases, such as disorders of immunity and inflammation in which PI3Kδ plays a role in leukocyte function, using the compounds also are disclosed.