α-N-Heterocyclic Thiosemicarbazone Derivatives as Potential Antitumor Agents: A Structure-Activity Relationships Approach

α-N-Heterocyclic thiosemicarbazones, (N)-TSCs, are potent inhibitors of ribonucleotide reductase (RR). This enzyme plays a critical role in DNA synthesis and repair, and is a well-recognized target for cancer chemotherapeutic agents. In this review the structural features of (N)-TSCs, required for maximum antitumour activity have been explored. Special attention is given to the mechanisms of action and structure-activity relationships.