Synthetic biologically active heterocycles, literature

Most of the synthetic routes to the compounds start from a six-membered ring heterocycle. As found in the previous review <1996CHEC-II(7)167>, the focus of many of the studies has been on the pyridine series-pyrrolo-pyridines, furopyridines, and thienopyridines. Within each of these classes of compounds, the [2,3-3] isomers have, by far, received the most attention. Also, as found in the previous review, some of the ring systems have not been investigated at all. Since that time, there has been much interest in thienopyridines because of the wide variety of biologically active compounds that originate from derivatives of thienopyridines (see Section 10.06.12.3). Much of the chemistry of furopyrans involves partially or fully reduced derivatives. There are few literature references to the parent series listed in Figure 6 however, there has been considerable activity with the reduced derivatives. 

The extraordinary diversity and multiplicity of heterocycles poses a dilemma What is to be included in an introductory book on heterocyclic chemistry which does not aim to be an encyclopaedia This difficulty had to be resolved in a somewhat arbitrary manner. We decided to treat a representative cross section of heterocyclic ring systems in a conventional arrangement. For these heterocycles, structural, physical and spectroscopic features are described, and important chemical properties, reactions and syntheses are discussed. Synthesis is consequently approached as a retrosynthetic problem for each heterocycle, and is followed by selected derivatives, natural products, pharmaceuticals and other biologically active compounds of related structure type, and is concluded by aspects of the use in synthesis and in selected synthetic transformations. The informations given are supported by references to recent primary literature, reviews and books on experimental chemistry. Finally, a section of problems and their solutions - selected in a broad variety and taken mainly from the current literature - intends to deepen and to extend the topics of heterocyclic chemistry presented in this book. 

Benzo-annelated nitrogen heterocycles (indoles, quinolines, isoquinolines, etc.) are often found to be a part of biologically active compounds of both natural and synthetic origin. In a considerable body of data on the syntheses of these compounds, which have so far been documented in the literature, the crucial step is vicarious nucleophilic substitution of hydrogen in nitroarenes. Good examples are presented by the synthesis of nordehydrobufotenine [49], eupolauramine [50, 51], damirone [52], and aklavinone [53]. 

The recent discovery of different types of biological activity in spiro-fused heterocyclic compounds has generated considerable interest among synthetic and medicinal organic chemists [124], The synthesis and chemistry of spiro-fused P-lactams have also developed steadily. Most of the methods apphcable to the synthesis of monocychc fS-lactams are apphcable with certain hmitations to the synthesis of spiro-fused 2-azetidinones [125]. The literature survey reveals the synthesis of several natural products inspired spiro-2-azetidinones having antimicrobial activity, cholesterol absorption inhibition activity, antiviral activity, and fS-lactamase inhibition activity [126]. 

---