Library Synthesis Using 5,6,7,8-Tetrahydro-1,6-naphthyridines as Scaffolds

Rh(III)-Catalyzed Dual C-H Functionalization and C-O/C-N Annulations of Monoamide Fumarates

Pyrano[4,3-c]pyridine-diones, which are the key skeleton of bioactive compounds and functional materials, are usually prepared via a multistep synthesis using expensive substrates. This work demonstrates that Rh(III)-catalyzed dual C(sp²)-H functionalization and C-O/C-N annulation of monoamide fumarates can produce pyrano[4,3-c]pyridine-1,5(6H)-diones in high yield (up to 82%) in a single step. The substrates of monoamide fumarates and acetylenes are structurally simple, readily available, and inexpensive. The additive AgSbF₆ effectively raised the yields. On account of easier dehydrogenation of OH in the COOH group than NH in the amide group in the reaction, the process first undergoes C-O annulation and then is succeeded by C-N annulation.

Synthesis and Anticancer Properties of Functionalized 1,6-Naphthyridines

The burgeoning interest in synthesis and biological applications of 1,6-naphthyridines reflects the importance of 1,6-naphthyridines in the synthetic as well as medicinal chemistry fields. Specially, 1,6-naphthyridines are pharmacologically active, with variety of applications such as anticancer, anti-human immunodeficiency virus (HIV), anti-microbial, analgesic, anti-inflammatory and anti-oxidant activities. Although collective recent synthetic developments have paved a path to a wide range of functionalized 1,6-naphthyridines, a complete correlation of synthesis with biological activity remains elusive. The current review focuses on recent synthetic developments from the last decade and a thorough study of the anticancer activity of 1,6-naphthyridines on different cancer cell lines. Anticancer activity has been correlated to 1,6-naphthyridines using the literature on the structure-activity relationship (SAR) along with molecular modeling studies. Exceptionally, at the end of this review, the utility of 1,6-naphthyridines displaying activities other than anticancer has also been included as a glimmering extension.

Domino synthesis of functionalized 1,6-naphthyridines and their in vitro anti-inflammatory and anti-oxidant efficacies

One-pot and multicomponent reaction of ketones with malononitrile and pyrrolidine in ethanol affords 1,6-naphthyridines.

Syntheses of new tuberculosis inhibitors promoted by microwave irradiation

Tuberculosis (TB) represents a major public health problem. The growing number of (extensively) multi-drug resistance cases indicates that there is an urgent need for discovery of new anti-TB entities, addressed towards new and specific targets, and continuous development of fast and efficient synthetic strategies to access them easily. Microwave-assisted chemistry is well suited for small-scale laboratory synthetic work, allowing full control of reaction conditions, such as temperature, pressure, and time. Microwave-assisted high-speed organic synthesis is especially useful in the lead optimization phase of drug discovery. To illustrate the advantages of modern microwave heating technology, we herein describe applications and approaches that have been useful for the synthesis of new drug-like anti-TB compounds.

Microwave-assisted synthesis of small molecules targeting the infectious diseases tuberculosis, HIV/AIDS, malaria and hepatitis C

The unique properties of microwave in situ heating offer unparalleled opportunities for medicinal chemists to speed up lead optimisation processes in early drug discovery. The technology is ideal for small-scale discovery chemistry because it allows full reaction control, short reaction times, high safety and rapid feedback. To illustrate these advantages, we herein describe applications and approaches in the synthesis of small molecules to combat four of the most prevalent infectious diseases; tuberculosis, HIV/AIDS, malaria and hepatitis C, using dedicated microwave instrumentation.

Diversity through phosphine catalysis identifies octahydro-1,6-naphthyridin-4-ones as activators of endothelium-driven immunity

The endothelium plays a critical role in promoting inflammation in cardiovascular disease and other chronic inflammatory conditions, and many small-molecule screens have sought to identify agents that prevent endothelial cell activation. Conversely, an augmented immune response can be protective against microbial pathogens and in cancer immunotherapy. Yet, small-molecule screens to identify agents that induce endothelial cell activation have not been reported. In this regard, a bioassay was developed that identifies activated endothelium by its capacity to trigger macrophage inflammatory protein 1 beta from primary monocytes. Subsequently, a 642-compound library of 39 distinctive scaffolds generated by a diversity-oriented synthesis based on the nucleophilic phosphine catalysis was screened for small molecules that activated the endothelium. Among the active compounds identified, the major classes were synthesized through the sequence of phosphine-catalyzed annulation, Tebbe reaction, Diels-Alder reaction, and in some cases, hydrolysis. Ninety-six analogs of one particular class of compounds, octahydro-1,6-naphthyridin-4-ones, were efficiently prepared by a solid-phase split-and-pool technique and by solution phase analog synthesis. Structure-function analysis combined with transcriptional profiling of active and inactive octahydro-1,6-naphthyridin-4-one analogs identified inflammatory gene networks induced exclusively by the active compound. The identification of a family of chemical probes that augment innate immunity through endothelial cell activation provides a framework for understanding gene networks involved in endothelial inflammation as well as the development of novel endothelium-driven immunotherapeutic agents.

A time-resolved fluorescence-resonance energy transfer assay for identifying inhibitors of hepatitis C virus core dimerization

Binding of hepatitis C virus (HCV) RNA to core, the capsid protein, results in the formation of the nucleocapsid, the first step in the assembly of the viral particle. A novel assay was developed to discover small molecule inhibitors of core dimerization. This assay is based on time-resolved fluorescence resonance energy transfer (TR-FRET) between anti-tag antibodies labeled with either europium cryptate (Eu) or allophycocyanin (XL-665). The N-terminal 106-residue portion of core protein (core106) was tagged with either glutathione-S-transferase (GST) or a Flag peptide. Tag-free core106 was selected as the reference inhibitor. The assay was used to screen the library of pharmacologically active compounds (LOPAC) consisting of 1,280 compounds and a 2,240-compound library from the Center for Chemical Methodology and Library Development at Boston University (CMLD-BU). Ten of the 28 hits from the primary TR-FRET run were confirmed in a secondary amplified luminescent proximity homogeneous assay (ALPHA screen). One hit was further characterized by dose-response analysis yielding an IC(50) of 9.3 microM. This 513 Da compound was shown to inhibit HCV production in cultured hepatoma cells.

Cross-cyclotrimerization with two nitriles as a synthetic pathway to unsymmetrically 3,3'-disubstituted bis(tetrahydroisoquinolines)

Microwave assisted CpCo(CO)(2) catalyzed cross-cyclotrimerizations of 1,7,9,15-hexadecatetrayne with two different nitriles to give unsymmetrically substituted bis(tetrahydroisoquinolines) was studied. The reaction proceeded with a range of alkyl and aryl nitriles with reasonable isolated yields.

Intramolecular rhodium-catalyzed [2+2+2] cyclizations of diynes with enones

The Rh(I)-catalyzed inter- and intramolecular [2+2+2] cyclization of diynes with alpha,beta-unsaturated enones proceeds with microwave promotion in good yields. This chemistry was applied to the synthesis of (-)-alcyopterosin I.