A Mini-Review on the Synthesis of Pyrazinoindole: Recent Progress and Perspectives

The diverse library of biologically active organic compounds is composed majorly of heterocyclic compounds. Nature provides a variety of pharmacologically active compounds consisting of N-heterocycle motif, such as Noscapine (anti-cancer), Morphine (analgesic), Chelerythrine (antibacterial), etc. which are the elementary structural units of marketed drugs in the present era. One such "N-heterocyclic" promising building block which has gained the attention of chemists is Pyrazinoindoles and the inflating interest in this moiety is a result of the three-fused heterocyclic ring structure subsuming an indolic nucleus in it. Fused-polycyclic structural core is necessary to synthesize potential multi-functional drugs, which is evident from indole (an example of fused five and six-membered ring structure) being an exemplary and established privileged template in medicinal chemistry. In the literature, Pyrazino-fused indoles have been found documented regarding their biological activities and therapeutic uses, particularly as antifungal, antibacterial, serotonergic receptor inhibitor, central nervous system depressants, anticonvulsants, antihistaminic, protein kinase C inhibitors, anti-depressants and so on. Although various synthesis strategies are available in the literature, yet the medical relevance of the Pyrazinoindoles demands the development of versatile and simple novel methodologies. This review features a comprehensive overview of the recent developments in synthetic approaches and therapeutic applications of Pyrazinoindoles based scaffolds.