Work documented here is about the synthesis and biological activities evaluation of Quinazolin-4(3H)-one based heterocyclic compounds. Chapter 1 provides detail introduction of Quinazolin-4(3H)-one alkaloids. Chapter 2 & 3 describe synthetic approaches for the synthesis and functionalization of Quinazolin-4(3H)-ones, while chapter 4 explains the biological activities evaluation of Quinazolin-4(3H)-ones and their analogs.