"Old friends in new guise": exploiting privileged structures for scaffold re-evolution/refining.

The attempts to increase novel drug productivity through creative discovery technologies have fallen short of producing the satisfactory results. For these reasons, evolved from the concept of drug repositioning, "privileged structure"-guided scaffold re-evolution/refining is a primary strategy to identify structurally novel chemotypes by modifying the central core structure and the side-chain of the existing active compounds, or to exploit undescribed bioactivites by making full use of readily derivatized motifs with well-established synthetic protocols. Herein, we review the basic tricks of exploiting privileged structures for scaffold re-evolution/refining. The power of this strategy is exemplified in the discovery of other new therapeutic applications by refining privileged structures in anti-viral agents.