Copper-Catalyzed Intramolecular Cyclization of N-Propargyl-Adenine: Synthesis of Purine-Fused Tricyclics

Rogersonins C-F, 9H-Imidazo[2,1-i]purine-Incorporating Adenine-Polyketide Hybrids from an Ophiocordyceps-Associated Clonostachys rogersoniana

Rogersonins C-F (1-4), four unprecedented adenine-polyketide hybrids featuring a rare 9H-imidazo[2,1-i]purine (1,N6-ethenoadenine) moiety, were isolated from an Ophiocordyceps-associated fungus, Clonostachys rogersoniana. Their structures were elucidated primarily by NMR experiments. The absolute configurations of 1-4 were assigned by a combination of the modified Mosher method, chemical degradation, electronic circular dichroism (ECD) calculations, and X-ray crystallography using Cu Kα radiation. Compound 3 downregulated the expression of PD-L1 protein in MDA-MB-231 and A549 cells, but did not show detectable effect on mRNA transcription of the PD-L1-encoding gene CD274.

Pyrido[1,2-e]purine: Design and Synthesis of Appropriate Inhibitory Candidates against the Main Protease of COVID-19

A series of tricyclic and polycyclic pyrido[1,2-e]purine derivatives were designed and synthesized via a two-step, one-pot reaction of 2,4-dichloro-5-amino-6-methylpyrimidine with pyridine under reflux conditions. Various derivatives of pyrido[1,2-e]purine were also synthesized by substituting the chlorine atom with secondary amines. After careful physiochemical and pharmacokinetic predictions, the inhibitory effects of the synthesized compounds against the main protease of SARS-CoV-2 have been evaluated by molecular docking and molecular dynamics approaches. The in silico results revealed that among all of the studied compounds, the morpholine/piperidine-substituted pyrido[1,2-e]purine derivatives are the best candidates as effective inhibitors of SARS-CoV-2.

Heteroarene-tethered Functionalized Alkyne Metamorphosis

Heteroarene-tethered functionalized alkynes are multipotent synthons in organic chemistry. This detailed Review described herein offers a thorough discussion of the metamorphosis of heteroarene-tethered functionalized alkynes, an area which has earned much attention over the past decade in the straightforward synthesis of architecturally complex heterocyclic scaffolds in atom and step economic manner. Depending upon the variety of functionalized alkynes, this Review is divided into multiple sections. Amongst the vast array of synthetic transformations covered, dearomatizing spirocyclizations and cascade spirocyclization/rearrangement are of great interest. Synthetic transformations involving the heteroarene-tethered functionalized alkynes with scope, challenges, limitations, mechanism, their application in the total synthesis of natural products and future perceptions are surveyed.

Metal-free synthesis of 1,N6-ethenoadenines from N6-propargyl-adenines via NIS mediated radical cascade reaction

In the present paper, an efficient approach for the construction of 1,N⁶-ethenoadenines from conveniently prepared N⁶-propargyl-adenines is developed. This reaction merges N-iodosuccinimide radical initiation and aerobic aminooxygenation in dioxane. This mild, 5-exo-dig, and metal-free cascade reaction could be applied to a wide substrate scope to provide 1,N⁶-ethenoadenines in moderate to good yields. The reaction mechanism was proposed and tested using radical inhibitor (butylated hydroxytoluene) and isotopic labelling (¹⁸O₂) experiments.

An efficient approach for the construction of 1,N⁶-ethenoadenines is developed through the metal-free mediated radical cascade cyclization of conveniently prepared N⁶-propargyl-adenines.

Synthesis and Reactivity of Propargylamines in Organic Chemistry

Propargylamines are a versatile class of compounds which find broad application in many fields of chemistry. This review aims to describe the different strategies developed so far for the synthesis of propargylamines and their derivatives as well as to highlight their reactivity and use as building blocks in the synthesis of chemically relevant organic compounds. In the first part of the review, the different synthetic approaches to synthesize propargylamines, such as A³ couplings and C-H functionalization of alkynes, have been described and organized on the basis of the catalysts employed in the syntheses. Both racemic and enantioselective approaches have been reported. In the second part, an overview of the transformations of propargylamines into heterocyclic compounds such as pyrroles, pyridines, thiazoles, and oxazoles, as well as other relevant organic derivatives, is presented.

Directed adenine functionalization for creating complex architectures for material and biological applications

In this feature article, targeted design strategies are outlined for modified adenine nucleobase derivatives in order to construct metal-mediated discrete complexes, ring-expanded purine skeletons, linear and catenated coordination polymers, shape-selective MOFs, and purine-capped nanoparticles, with a wide range of applications from gas and solvent adsorption to bioimaging agents and anticancer metallodrugs. The success of such design strategies could be ascribed to the rich chemistry of purine and pyrimidine derivatives, versatile coordination behavior, ability to bind a host of metal ions, which could be further tuned by the introduction of additional functionalities, and their inherent propensity to hydrogen bond and exhibit π-π interactions. These noncovalent interactions produce stable frameworks and network solids that are useful as advanced materials, and the biocompatibility of these ligand complexes provides an impetus for assessing novel biological applications.

New protocols to access imidazoles and their ring fused analogues: synthesis from N-propargylamines

Imidazole and its derivatives are privileged N-heterocyclic structures present in various natural products and synthetic pharmaceuticals.

6-(Aryldiazenyl)pyrazolo[1,5-a]pyrimidines as Strategic Intermediates for the Synthesis of Pyrazolo[5,1-b]purines

A microwave-assisted approach for the regioselective synthesis of functionalized 6-(aryldiazenyl)pyrazolo[1,5-a]pyrimidin-7-amines from the cyclization of 3-oxo-2-(2-arylhydrazinylidene)butanenitriles with 5-amino-1H-pyrazoles under solvent-free conditions has been developed. This methodology was distinguished by its broad substrate scope, operational simplicity, high atom economy, and high-yielding without requiring chromatographic purification. In addition, an efficient and versatile palladium-catalyzed reductive azo cleavage is disclosed for the synthesis of diverse heteroaromatic 1,2-diamines, a valuable synthetic building block to develop new fused heteroaromatic systems. As synthetic example, several substituted pyrazolo[5,1-b]purines were synthesized in yields up to 96% by using microwave irradiation in the cyclocondensation of these 1,2-diamines with orthoesters.